Publicaciones
Mosaic Evolution of Grasping and Genital Traits in Two Sympatric Scorpion Species with Reproductive Interference Paleobiology
2024
By Oviedo-Diego M, Mattoni C, Bollati FA, Soto EM & Peretti AV
Components of the same structure or characters of the same individual might respond differently to natural and sexual selective pressures, showing complex morphological patterns. Besides, studying interactions between species plays a crucial role in understanding the diversification of sex-linked phenotypes. Specifically, when two closely related species coexist and exhibit interspecific sexual interactions (reproductive interference—IR), key traits for mating can diverge in sympatric areas to prevent interbreeding and ensure reproductive isolation (reproductive character displacement—RCD). RCD is primarily driven by natural selection, although sexual selection pressures can alter the pattern of phenotypic variation. Additionally, to gain a comprehensive understanding of the patterns of morphological diversification, it is essential to consider changes related to phenotypic plasticity across environmental gradients. To date, there are no studies evaluating this topic in scorpions, and two sympatric species (Urophonius brachycentrus and U. achalensis) with RI, provide an ideal model for evaluating phenotypic variation across environmental gradients and the presence of RCD. In this study, we compared intra-specific variation, as well as the size and shape of multiple characters involved in courtship and sperm transfer, between individuals from sympatric and allopatric populations using geometric morphometrics. Our findings revealed an increase in the size of various characters at lower temperatures (higher altitudes) for U. brachycentrus, making them more similar to heterospecifics in sympatric areas, resulting in a pattern of morphological convergence between these species. Increased similarity between species combined with a scramble competition mating system could intensify sexual selection pressures on particular characters. Furthermore, we identified asymmetric RCD in the shape of several sexual characters crucial for mating success (grasping structures) and sperm transfer (genital characters), which could potentially be significant for mechanical isolation during interspecific interactions. Our results highlight significant morphological variability in the size and shape of somatic and genital characters in two scorpion species. This variability may reflect different evolutionary responses, driven in part by natural selection pressures associated with geographic and environmental variations and species recognition mechanisms, and in part by sexual selection pressures at both the intra- and interspecific levels. This comprehensive study reveals the complexity of evolving multifunctional traits in an understudied model and offers valuable insights into traits subject to multiple selective pressures in animal systems experiencing RI.
2023
By Barbero S, Teta P & Cassini GH
The key role of the skull in food intake and processing implicates its morphology should be to some extent adapted to the functional demands present in different diets, while also showing similarities between those which are closely related. Sigmodontine
rodents, with a generalist body plan and broad dietary habits, are an interesting case study to explore these relationships. We used linear morphometrics to assess craniomandibular morphology, and explored its relationship with dietary composition
and phylogeny in a sample of sigmodontines from central-eastern Argentina, representative of this subfamily’s morphological and ecological diversity. We took 26 measurements performed on 558 specimens belonging to 22 species, and resorted to
bibliographic information for proportion of food items in their diets, dietary categories, and phylogeny. Multivariate statistical analyses revealed a strong evolutionary integration between morphological traits of crania and mandibles, and a conspicuous
relationship between them and dietary composition in our study group, independent of phylogeny. Species of larger sizes exhibited more robust skulls and a tendency towards folivorous diets, whereas smaller species had more gracile craniomandibular
apparatuses and diets richer in seeds and invertebrates. Additionally, we used the observed patterns to made predictions of dietary categories for the three species of this region with unknown diets, completing the map of feeding ecology of one of the most
researched group of sigmodontines and enabling future studies to further explore this topic. The present work contributes to understanding the link between morphology, ecology and phylogeny in small mammals.
2023
By Pérez Ben C, Lires A & Gómez R
The unique body plan of frogs (Lissamphibia: Anura) has been largely conserved from at least 200 Myr, and its evolution from a more generalized tetrapod condition is still poorly understood, in part due to the scarce early fossil record of Salientia, the anuran total-group. The origin of the anuran Bauplan has been classically explained as an adaptation to jumping, but recent studies incorporating new data in a phylogenetic context have challenged the popular jumping hypothesis. Here we revisit and test this hypothesis from a paleobiological perspective by integrating limb data from a wide range of extant and fossil frogs. We first explored the evolution of limb proportions from the Jurassic to the Paleogene to understand when the present limb diversity originated and whether, and to what extent, limb proportions have been conserved over the last 200 Myr. We then inferred the locomotor capabilities of extinct species by phylogenetic flexible discriminant analysis, and from these inferences, we studied the locomotor diversity of frogs over geological time and reconstructed the ancestral state for frog-like salientians. The evolution of limb proportions is characterized by an early diversification that was underway in the Jurassic, followed by a repeated convergence over a limited area of the morphospace that was already explored by the Early Cretaceous. In agreement with this early limb diversity, the Jurassic stem species were also locomotory diverse, and their inferred locomotor modes do not support the jumping hypothesis. We propose that the patterns found herein of repeated convergent evolution of both limb proportions and locomotor capabilities over geological time hamper any attempt to confidently infer the ancestral locomotion mode and, it therefore might be time to start focusing on other hypotheses on the origin of the anuran Bauplan that are not related to locomotion.
Ortholog genes from cactophilic Drosophila provide insight into human adaptation to hallucinogenic cacti. Scientific Reports
2022
By Padró J, De Panis DN, Luisi P, Dopazo H, Szajnman S, Hasson E & Soto IM
Cultural transformations of lifestyles and dietary practices have been key drivers of human evolution. However, while most of the evidence of genomic adaptations is related to the huntergatherer transition to agricultural societies, little is known on the influence of other major cultural
manifestations. Shamanism is considered the oldest religion that predominated throughout most of human prehistory and still prevails in many indigenous populations. Several lines of evidence from ethno-archeological studies have demonstrated the continuity and importance of psychoactive plants in South American cultures. However, despite the well-known importance of secondary metabolites in human health, little is known about its role in the evolution of ethnic differences. Herein, we identified candidate genes of adaptation to hallucinogenic cactus in Native Andean populations with a long history of shamanic practices. We used genome-wide expression data from the cactophilic fly Drosophila buzzatii exposed to a hallucinogenic columnar cactus, also consumed by humans, to identify ortholog genes exhibiting adaptive footprints of alkaloid tolerance. Genomic analyses in human populations revealed a suite of ortholog genes evolving under recent positive selection in indigenous populations of the Central Andes. Our results provide evidence of selection in genetic variants related to alkaloids toxicity, xenobiotic metabolism, and neuronal plasticity in Aymara and Quechua populations, suggesting a possible process of gene-culture coevolution driven by religious practices.
The effects of breeding resource, sex and environmental temperature on adult locomotor activity in cactophilic Drosophila.
Entomologia Experimentalis et Applicata
2022
By Crespo J, Divito F, Pueyrredón J, Hasson E & Soto EM
The evolution of insects inhabiting arid environments is heavily shaped by resource scarcity and temperature. Ecological interdependence could be tight and complex as in the model cactus–yeast–Drosophila. Cactophilic species of Drosophila (Diptera: Drosophilidae) differ in their preference for the type of breeding resources and life-history traits that respond to variation in environmental temperature. Adult flies feed and breed on rotting cacti but they are physiologically limited to cope with temperature changes. However, flies can behaviourally avoid such stressful conditions by actively seeking benign microhabitats. We investigate how alternative breeding resources (cactus species) and thermal environment affect the spontaneous adult locomotor activity in two species, Drosophila buzzatii Patterson & Wheeler and Drosophila koepferae Fontdevila & Wasserman, adapted to semi-arid environments. Locomotor activity of D. buzzatii was more affected by the breeding resource, whereas D. koepferae showed a clear ‘bell shape’ activity curve in response to a wide range of temperatures, independent of the breeding resource. These idiosyncratic responses suggest that the selective pressures that shaped life-history evolution in these Drosophila species were different, with the breeding resource and environmental temperature contributing to the development of diverging survival strategies in arid environments.
Limited behavioral flexibility in oviposition behavior for the invasive fly species Zaprionus indianus (Diptera: Drosophilidae).
Entomologia Experimentalis et Applicata
2022
By Gramenos IA; Soto EM & Lavagnino NJ.
Zaprionus indianus Gupta (Diptera: Drosophilidae) is a fly species native to the Afrotropical biogeographic region that expanded its geographical distribution to the American continent around 1999. This fly lays eggs, feeds, and develops on a wide variety of fruits colonized by yeasts and bacteria, as well as on ripe, non-damaged soft-skinned fruits. The arrival of Z. indianus to American ecosystems entails co-existence with other drosophilid species with the same resource specificity, such as the cosmopolitan human commensal Drosophila melanogaster Meigen. In this scenario, the oviposition strategy could be relevant for invasion success in terms of partitioning the utilization of resources in space or time. We investigated whether Z. indianus avoids laying eggs in resources previously used by another species (D. melanogaster), or whether oviposition is unaffected by the presence of other species’ larvae. Results show a stable oviposition behavior of Z. indianus, considering that this fly lays the same number of eggs regardless of whether the oviposition resource has larvae of other species, whereas D. melanogaster showed a flexible oviposition behavior when presented with the same oviposition resources. Zaprionus indianus being a good larval competitor against other drosophilids, this stable oviposition strategy could be positive for invasiveness as it ensures a continuous spread of eggs and subsequent larval development during invasion in new and heterogeneous ecosystems.
2021
By Milla Carmona P, Lazo DG, Soto IM
Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.
2021
By Saint Esteven A, Benedictto M, Garolla FA, Padró J, Soto IM
The Multiple Use Reserve of Valle Fértil (San Juan province, Argentina) is a protected area with particular climatic features that includes a large segment of xeric environments. It harbors numerous endemic and protected species. Despite the conspicuous presence of a cacti and succulent community in the area, a formal survey of species richness had been lacking. Moreover, as this region has been declared at risk of degradation due to soil erosion driven by high deforestation rates the importance of carrying out biodiversity surveys with interest on conservation raises. During the last decade, and product of several field trips to the Reserve, seven genera of Cactaceae were observed. Thus, we present the first formal list of cacti and succulent species in the Multiple Use Reserve of Valle Fértil gathering relevant information for scientific and conservational purposes.
The incubatory chamber of marsupial carditids (Bivalvia: Carditidae: Thecaliinae) as an exaptation.
Paleobiology.
2021
By Pérez DE, Soto IM
Marsupial carditids of the subfamily Thecaliinae are characterized by the presence of an “incubatory chamber” in female shells, where the eggs hatch and develop during their first stages. According to recent phylogenetic studies, Thecaliinae are closely related to Carditinae, a group that has a byssal gape. This structure occurs in the same area as the incubatory chamber, and both structures could be evolutionarily related. Using the newest phylogenetic context for the subfamilies, we test whether the incubatory chamber of Thecaliinae is related to characters present in Carditinae. We also provided a more precise definition of the implied structures. Two distinct morphologies for the incubatory chamber are described: one with an exteriorly opened pouch (present in the genera Powellina and Milneria) and the other with a completely internal funicular infold (present in Thecalia). The byssal gape is present in the Cardiobyssata clade (Carditamerinae + (Carditinae + Thecaliinae)), and we discuss whether the incubatory chamber could be the result of an exaptation event, and the possible evolutionary pathways implied. According to the present evidence, we propose a co-optation of the byssal gape into a new function (brooding of larvae) at some point during the transition from the Carditinae to the Thecaliinae lineages, thus determining an exaptation. Adaptative processes probably modified this structure into the incubatory chamber (an external pouch first, and a funicular infold later). We discuss alternative scenarios and implications on phylogenetic studies and the importance of considering non-adaptative evolutionary scenarios in the study of evolutionary narratives.
Specialization and performance trade-offs across hosts in cactophilic Drosophila species.
Ecological Entomology
2021
By Bouzas S, Barbarich MF, Soto EM, Padró J, Carreira VP, Soto IM
1. We assessed the host-related niche breadth for D. koepferae and D. buzzatii, a pair of sibling cactophilic species with contrasting backgrounds of host use. We tested for the ‘Jack of all trades- Master of none’ scenario predicting a more evident exhibition in D. buzzatii rather than in the supposedly specialist D. koepferae.
2. Additionally, using laboratory strains of both species selected for tolerance to extremely high concentrations of a columnar cacti's secondary metabolites, we tested whether adaptation to a high-demanding host involved the loss of performance capabilities in other hosts.
3. D. buzzatii was more affected by the artificial host shifts than D. koepferae which presented an overall better performance when rearing in novel columnar hosts.
4. Artificially selected strains of D. buzzatii performed poorer in both novel and native natural hosts compared with control strain indicating that adaptation carried associated costs regarding the potential to exploit other cacti. Conversely, artificial evolution of the D. koepferae's strains did not translate into decreased performance in other hosts.
5. D. buzzatii complied better with the predictions of the Jack of all trades-Master of none hypothesis.
6. Host specialization is a dynamic feature in the repleta group and a major driver of diversification in its evolutionary history. As the group presents an Opuntia breeder as the ancestral condition, D. buzzatii would represent not only a plesiomorphic state of host use but also the ancestral ecological strategy of specialization.
A protocol for health assessment of cacti populations: A case study from Northwestern Argentina.
Ecological Indicators
2021
By Barbarich MF, Otegui F, Saint Esteven A, Soto IM, Varone L
Argentina is considered megadiverse for Cactaceae, and Jujuy province, with a high proportion of cacti endemism, is a critical region for their preservation. Cacti deterioration is mainly associated with habitat degradation, agricultural frontier advance, urbanization, illegal collection and trade. Of the three species of columnar cacti within Trichocereus genus that are present, Trichocereus atacamensis represents a valuable species for local communities. In the last decades, detrimental effects on T. atacamensis populations increased despite the reduction in the use of timber for construction or handicrafts. Knowledge on the health of cacti populations is fundamental for conservation and resource management, therefore the objective of the present study was to develop a health status classification criterion for cacti in Quebrada de Humahuaca, Jujuy. A generic method was elaborated to assess the health of cacti populations to facilitate and speed-up the decision-making process for conservation purposes. The evaluation of factors involved in the deterioration is very complex. We designed a method considering aspects that the local residents identified as the most relevant: a) presence of air plant (genus Tillandsia), b) larvae of Cactoblastis bucyrus and c) signs of rot. Band transects were sampled in patches of T. atacamensis, surveying these aspects for each individual. A Multivariate Regression Tree analysis (MRT) was conducted. According to this clustering, an accessible assessment protocol with a 5-level health status was established to classify the cactus as optimal, suboptimal, compromised, vulnerable or critical. The general health status of the patches was highly variable. This MRT analysis is potentially applicable to any columnar cacti population and to establish the basis of a decision protocol for health status assessment. It is evident that the situation of T. atacamensis transcends as a local problem and exceeds the presence of pathogens suggesting a multifactorial causality that needs special attention.
First record of Macrocheles subbadius (Berlese) (Acari: Macrochelidae) in Argentina, associated with the cactophilic fly Drosophila koepferae Fontdevila & Wasserman (Diptera: Drosophilidae).
Revista de la Sociedad Entomológica Argentina.
2020
Porta AO, Soto IM, Soto EM, Saint Esteven A
The mite Macrocheles subbadius (Berlese) (Acari: Macrochelidae) is recorded for the first time in Argentina, associated to the cactophilic fly Drosophila koepferae Fontdevila & Wasserman (Diptera: Drosophilidae) from San Agustín de Valle Fértil, province of San Juan.
New remains of Cephalomys arcidens (Rodentia, Caviomorpha) and a redefinition of the enigmatic Cephalomyidae.
Journal of Systematic Paleontology.
2020
By Busker F, Dozo MT, Soto IM.
Cephalomys is the best-known cephalomyid, recorded in five localities in Argentina and known from well-preserved mandibles, fragments of skull, and a large number of isolated teeth, from both juveniles and adults. Despite this, a modern description is lacking and the validity of some species of Cephalomys has been questioned in the last few years. New material from the Deseadan locality of Cabeza Blanca (Chubut, Argentina), including skull fragments unknown for the species thus far, and well-preserved juvenile teeth, along with a large number of specimens from collections in Argentina, allow us to propose a more complete description of the genus and a new taxonomic arrangement for the Cephalomys species. We also analysed some dubious records of Cephalomys from Quebrada Honda and Pico Truncado and confirm that they are not part of this genus. We consider C. plexus to be a synonym of C. arcidens, we consider the combination previously proposed for C. bolivianus (as a species of Asteromys) to be valid, and we consider C. ceciae also to be a valid species. We performed a phylogenetic analysis including for the first time all cephalomyids (Cephalomys, Litodontomys, Cephalomyopsis, Soriamys and Banderomys) and possibly related genera (Perimys, Scotamys, Asteromys) to test the position of the family Cephalomyidae among the other caviomorph rodents, as well as its validity and internal relationships. The results recovered Cephalomyidae as a clade, including Cephalomys, Cephalomyopsis and Litodontomys. The monophyly of Cephalomys could not be confirmed. Soriamys and Banderomys were recovered within Cavioidea. Perimys, Scotamys and Asteromys were recovered within Chinchilloidea, and we analysed the implications of their positions within the group. The implications in terms of the biochron, distribution and evolutionary history of the Cephalomyidae, considering the new definition for the family proposed herein (including only Cephalomys, Cephalomyopsis and Litodontomys), are discussed, as well as inferences regarding caviomorph evolution at the scale of the entire group.
The grass was greener: Repeated evolution of specialized morphologies and habitat shifts in ghost spiders following grassland expansion in South America.
Systematic Biology
2019
By Ceccarelli FS, Koch NM, Soto EM, Barone ML, Arnedo MA & Ramírez MJ
While grasslands, one of Earth’s major biomes, are known for their close evolutionary ties with ungulate grazers, these habitats are also paramount to the origins and diversification of other animals. Within the primarily South American spider subfamily Amaurobioidinae (Anyphaenidae), several species are found living in the continent’s grasslands, with some displaying putative morphological adaptations to dwelling unnoticed in the grass blades. Herein, a dated molecular phylogeny provides the backbone for analyses revealing the ecological and morphological processes behind these spiders’ grassland adaptations. The multiple switches from Patagonian forests to open habitats coincide with the expansion of South America’s grasslands during the Miocene, while the specialized morphology of several grass-dwelling spiders originated at least three independent times and is best described as the result of different selective regimes operating on macroevolutionary timescales. Although grass-adapted lineages evolved towards different peaks in adaptive landscape, they all share one characteristic: an anterior narrowing of the prosoma allowing spiders to extend the first two pairs of legs, thus maintaining a slender resting posture in the grass blade. By combining phylogenetic, morphological, and biogeographic perspectives we disentangle multiple factors determining the evolution of a clade of terrestrial invertebrate predators alongside their biomes
Fat body morphology, but not body size, changes in forager bees of Scaptotrigona jujuyensis (Apidae: Meliponini) during foraging season.
Zoologischer Anzeiger
2019
By Galvani GL, Soto, EM, Canavoso LE, & Settembrini BP
The morphological variation of workers is a phenomenon related to a colony context. We have studied body size and fat body morphology in foragers of Scaptotrigona jujuyensis during different periods of the foraging season. In workers which forage at the start of season the number of oenocytes was lower than that of the remaining groups. Cytological analyses of trophocytes revealed that the granules differed in the staining pattern according to the period of sampling. The differences in the fat body of the workers may be due to the complexity and dynamic turnover of the vacuolar system of the trophocytes. Our results suggest that fat body morphology in adults of Scaptotrigona jujuyensis changes during foraging. The fat body might play a key role as an organ contributing to the success of a colony through its plastic changes in worker bees.
Protein – alkaloid interaction in larval diet affects fitness in cactophilic Drosophila (Diptera: Drosophilidae).
Biol. J. Linn. Soc
2019
By Vrdoljak J, Padró J, De Panis D, Soto IM, Carreira VP.
Drosophila koepferae and Drosophila buzzatii are closely related cactophilic species with overlapping distributions in Andean regions. Both species exploit necrotic tissues, and whereas the former breeds and feeds mostly in columnar cacti of Trichocereus and Cereus genera rich in secondary metabolites, the latter primarily exploits a less toxic host of the genus Opuntia. Although secondary metabolites have been related to the pattern of host exploitation, the microbial community associated with necrosis of cacti could also play a key role in the nutrition and/or alkaloid tolerance of the flies. We investigated the interaction between natural alkaloids and a yeast-protein supplement on both fly species raised in each type of cactus separately. We found that alkaloids reduced viability in both species, whereas a diet poor in protein reduced it only in D. buzzatii, especially when raised in Trichocereus. Concerning fitness traits that are related to adulthood, the addition of yeasts had positive effects, whereas the absence of yeasts resulted in strong detrimental effects. We present evidence of antagonistic effects on fitness and an interaction between alkaloids and proteins when these components are present in the diets of the flies.
Divergent patterns of correlated evolution in primary and secondary sexual traits of cactophilic Drosophila.
Evolutionary Ecology
2019
By Padró, J., Vrdoljak, J., Milla Carmona, P., Soto, I.M.
The rapid diversification of sexual traits is a common phenomenon accompanying the evolution of reproductive isolation, yet the evolutionary mechanisms driving such diversification are often unknown. Based on experimentally evolved strains of two sister species of cactophilic Drosophila, we investigated the correlated evolution of primary and secondary sexual traits to semi-natural environments enriched in secondary metabolites. We compared patterns of morphological evolution in the size and shape of male wing and genitalia of Drosophila buzzatii and Drosophila koepferae selected for different levels of alkaloid intensities for 20 generations. We found similar modes of selection operating among organs but not among species. The evolution of these traits in D. koepferae were compatible with patterns of stabilizing selection, while in D. buzzatii were characterized by directional changes. We also found that allometric variation was an important component of genital shape evolution, whereas changes in the wing morphology were less pronounced and mostly non-allometric. Overall, our data suggest that the diversification of sexual traits in this species pair is related to the evolution of dissimilar genetic architectures and reinforced by divergent ecological responses.
2018
By Soto, E.M., Padró, J., Milla Carmona, P., (...), Carreira, V.P., Soto, I.M.
Drosophila buzzatii and D. koepferae are sibling cactophilic species. The former breeds primarily on prickly pears (genus Opuntia) whereas the latter breeds on columnar cacti of the genera Cereus and Trichocereus, although with certain degree of niche overlapping. We examined the interspecific differences in diurnal temporal patterns of adult emergence from puparia and evaluated whether this behavior is affected by rearing in the different cactus hosts available in nature. We detected important host-dependent genetic variation for this trait differentially affecting the emergence schedule of these species. Diurnal pattern of emergence time was directly correlated with developmental time and negatively correlated with adult wing size, suggesting that early emergences are at least indirectly correlated with increased fitness. We discussed our results in terms of their putative effects on fitness and the genetic-metabolic pathways that would be presumably affected by host's nutritional-chemical differences.
The influence of developmental environment on courtship song in cactophilic Drosophila.
Journal of Evolutionary Biology
2018
By Iglesias, PP, Soto, EM., Soto, IM, Colines, B, Hasson, E.
Closely related species often differ in the signals involved in sexual communication and mate recognition. Determining the factors influencing signal quality (i.e. signal's content and conspicuousness) provides an important insight into the potential pathways by which these interspecific differences evolve. Host specificity could bias the direction of the evolution of sexual communication and the mate recognition system, favoring sensory channels that work best in the different host conditions. In this study, we focus on the cactophilic sibling species Drosophila buzzatii and D. koepferae that have diverged not only in the sensory channel used for sexual communication and mate recognition but also in the cactus species that use as primary hosts. We evaluate the role of the developmental environment in generating courtship song variation using an isofemale line design. Our results show that host environment during development induces changes in the courtship song of D. koepferae males, but not in D. buzzatii males. Moreover, we report for the first time that host rearing environment affects the conspicuousness of courtship song (i.e. song volume). Our results are mainly discussed in the context of the sensory drive hypothesis. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology
Rapid divergence of courtship song in the face of neutral genetic homogeneity in the cactophilic fly Drosophila buzzatii.
Biol. J. Linn. Soc.
2018
By Iglesias P.P., Soto, I.M., Soto, E.M., Calderon L, Hurtado J., Hasson, E.
Closely related species often differ in the signals involved in sexual communication and mate recognition. Determining the factors influencing signal quality (i.e. signal's content and conspicuousness) provides an important insight into the potential pathways by which these interspecific differences evolve. Host specificity could bias the direction of the evolution of sexual communication and the mate recognition system, favouring sensory channels that work best in the different host conditions. In this study, we focus on the cactophilic sibling species Drosophila buzzatii and D. koepferae that have diverged not only in the sensory channel used for sexual communication and mate recognition but also in the cactus species that use as primary hosts. We evaluate the role of the developmental environment in generating courtship song variation using an isofemale line design. Our results show that host environment during development induces changes in the courtship song of D. koepferae males, but not in D. buzzatii males. Moreover, we report for the first time that host rearing environment affects the conspicuousness of courtship song (i.e. song volume). Our results are mainly discussed in the context of the sensory drive hypothesis. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology
2018
By Stefanini, M.I., Milla Carmona, P., Iglesias, P.P., Soto, E.M., Soto, I.M.
Genital morphology in animals with internal fertilization is considered to be among the fastest evolving traits. Sexual selection is often proposed as the main driver of genital diversification but the exact selection mechanisms involved are usually unclear. In addition, the mechanisms operating may differ even between pairs of sibling species. We investigated patterns of male genital variation within and between natural populations of the cactophilic fly Drosophila koepferae ranging its entire geographic distribution and compared them with those previously observed in its sibling species, D. buzzatii. Using both mtDNA and nDNA markers we found that genital shape variation in D. koepferae is more restricted than expected for neutral evolution, suggesting the predominance of stabilizing selection. We also detected dissimilar patterns of divergence between populations of D. koepferae that were allopatric and sympatric with D. buzzatii. The constrained evolution inferred for D. koepferae’s genitalia clearly contrasts with the rapid divergence and higher morphological disparity observed in the populations of D. buzzatii. Finally, different possible scenarios of male genital evolution in each species and within the radiation of D. buzzatii cluster are discussed.
Experimental Evolution of Alkaloid Tolerance in Sibling Drosophila Species with Different Degrees of Specialization. Evolutionary Biology
2018
By Julián Padró, Diego N. De Panis, Juan Vrdoljak, Pablo Milla Carmona, Betina Colines, Esteban Hasson, Ignacio M. Soto.
Drosophila buzzatii and Drosophila koepferae are sibling species with marked ecological differences related to their patterns of host exploitation. D. buzzatii is a polyphagous species with a sub-cosmopolitan distribution, while D. koepferae is endemic to the mountain plateaus of the Andes, where it exploits alkaloidiferous columnar cacti as primary hosts. We use experimental evolution to study the phenotypic response of these cactophilic Drosophila when confronting directional selection to cactus chemical defenses for 20 generations. Flies adapted to cactus diets also experienced higher viability on alkaloid-enriched media, suggesting the selection of adaptive genetic variation for chemical-stress tolerance. The more generalist species D. buzzatii showed a rapid adaptive response to moderate levels of secondary metabolites, whereas the columnar cacti specialist D. koepferae tended to maximize fitness under harder conditions. The evolutionary dynamic of fitness-related traits suggested the implication of metabolic efficiency as a key mediator in the adaptive response to chemical stress. Although we found no evidence of adaptation costs accompanying specialization, our results suggest the involvement of compensatory evolution. Overall, our study proposes that differential adaptation to secondary metabolites may contribute to varying degrees of host specialization, favoring niche partitioning among these closely related species.
Morphological evolution of the bivalve Ptychomya through the Lower Cretaceous of Argentina.
Paleobiology
2018
By Carmona, P.S.M., Lazo, D.G., Soto, I.M..
The complex morphological evolution of the bivalve Ptychomya throughout the well-studied Agrio Formation in the Neuquén Basin (west-central Argentina, lower/upper Valanginian-lowest Barremian) constitutes an ideal opportunity to study evolutionary patterns and processes occurring at geological timescales. Ptychomya is represented in this unit by four species, the morphological variation of which needs to be temporally assessed to obtain a thorough picture of the evolution of the group. Here we use geometric morphometrics to measure variation in shell outline, ribbing pattern, and shell size in these species. We bracket the ages of our samples using a combination of ammonoid biostratigraphy and absolute ages and study the anagenetic pattern of evolution of each trait by means of paleontological time-series analysis and change tracking. We find that evolution in Ptychomya is mostly speciational, as the majority of traits show stasis, with the exceptions of shell size in P. coihuicoensis and shell outline in P. windhauseni, which seem to evolve directionally toward larger and higher shells, respectively. Ptychomya displays changes in its average morphology and disparity, which are the result of amixture of taxonomic turnover and mosaic evolution of traits. Pulses of speciation would have been triggered by ecological opportunity, as they occur during the recovery of shallow-burrowing bivalve faunas after dysoxic events affecting the basin. On the other hand, the presence of directional patterns of evolution in P. coihuicoensis and P. windhauseni seems to be the result of a general shallowing-upward trend observed in the basin during the upper Hauterivian-lowest Barremian, as opposed to the cyclical paleoenvironmental stability inferred for the early/late Valanginian-early Hauterivian, which would have prompted stasis in P. koeneni and P. esbelta.
Experimental hybridization in allopatric species of the Drosophila repleta group (Diptera: Drosophilidae): Implications for the mode of speciation.
Biol. J. Linn. Soc
2018
By Colines, B., Soto, I.M., De Panis, D.N., Padró, J.
The Pleistocene refugia theory proposes that recurrent expansions and contractions of xerophytic vegetation over periods of climate change affected the evolution of cactophilic Drosophila in South America. The resulting demographic fluctuations linked to the available patches of vegetation should have been prone to bottlenecks and founder events, affecting the fate of gene pool dynamics. However, these events also promoted the diversification of cacti, creating an ecological opportunity for host specialization. We tested the hypothesis of ecological speciation in the Drosophila buzzatii group. We assessed adaptive footprints and examined the genetic architecture of fitness-related traits in the sibling allopatric species D. koepferae and D. antonietae. The results are in line with the idea that these species evolved under different ecological scenarios. Joint-scaling analysis comparing both species and their hybrids revealed that additive genetic variance was the major contributor to phenotypic divergence, but dominance, epistasis and maternal effects were also important factors. Correlation analysis among functionally related traits suggested divergent selection on phenotypic integration associated with fitness. These findings support the hypothesis of adaptive evolution driving the phylogenetic radiation of the group through independent events of host shifts to chemically complex columnar cacti.
The life and adventures of an eight-legged castaway: Colonization and diversification of Philisca
ghost spiders on Robinson Crusoe Island (Araneae, Anyphaenidae)
Molecular phylogenetics and evolution
2017
By Soto EM, Labarque F.M.; Ceccarelli FS, Arnedo MA, Pizarro-Araya J &. Ramírez MJ
Oceanic archipelagoes, by their young origin and isolation, provide privileged settings to study the origin and diversification of species. Here, we study the anyphaenid spider genus Philisca, endemic to the Valdivian temperate rainforest, which includes species living both on the mainland as well as on the Robison Crusoe Island in the Juan Fernández archipelago. Anyphaenids, as many spiders, are potentially good colonizers due their ability for ballooning, an airborne dispersal mediated by strands of silk that are caught in the wind. We use a molecular approach to estimate both the phylogenetic relationships and the timeframe of species diversification of Philisca, with the aim to infer its evolutionary history. We further estimate the rates of speciation on both the insular and continental Philisca species and score the microhabitat used by each species and their sizes as a proxy to evaluate ecological niche diversification within the island. Most analyses support the monophyly of Philisca, with the exclusion of Philisca tripunctata. Our results reveal colonization from a single lineage that postdated the origin of the island, followed by rapid (ca. 2 Ma) diversification. The ancestral microhabitat was most likely leaf-dwelling but we identify two independent microhabitat shifts. Our data provides evidence that Philisca has undergone an adaptive radiation on the Robison Crusoe Island.
2017
By De los ríos-Escalante P, Pizarro-Araya J & Soto EM
The aim of the present study now is to make a morphometric description of a population of Orchestia selkirki Stebbing, 1888, found in a so-called "Claro Verde", that is a zone with Myrceugenia fernandeziana (Hook. & Arn.) Johow forest with small streams, and with many access difficulties due to a long mountain path and in addition access problems with respect to entry from the continent. This valley is located on Robinsoe Crusoe Island, one of the islands of the Juan Fernández archipelago (Pérez-González et al., 2014).
Cactus-fungi interactions mediate host preference in cactophilic Drosophila (Diptera: Drosophilidae).
Biol. J. Linn. Soc
2017
By Soto, E.M., Nicolás Mongiardino Koch, Carmona, P.M., Soto, I.M., Hasson, E.
The cactophilic flies Drosophila buzzatii and Drosophila koepferae are generally each associated with a different host cactus, although resource sharing can occur in regions of sympatry. Host choice has been shown to affect several fitness-related traits, but the mechanisms determining it are poorly understood. We investigate how alternative cacti and cactophilic fungi modulate adult host preference (olfaction preference and oviposition behaviour) in both species. All aspects of the flies' resource selection behaviour seem to be driven by both the cactus and the microorganism encountered. In the presence of some fungi, both fly species exhibit strong preferences for their respective primary hosts, while other fungi obliterate differences in preference. Similarly, oviposition behaviour is strongly modulated by particular host-fungus combinations. Overall, the observed patterns of host selection and exploitation in these flies appear to be largely determined by the interaction between the cactus species and only a subset of cactophilic fungi, including the filamentous fungus Bisifusarium lunatum and the yeast Sporopachydermia cereana 'australis'. The evolution of alternative strategies associated with the election of natural breeding resources has played a crucial role in the divergence of the D. buzzatii and D. koepferae lineages and might be based on relatively simple decision-making scenarios.
Taxonomy of the bivalve Ptychomya in the Lower Cretaceous of the Neuquén basin (west-central Argentina).
Papers in Paleontology
2017
By Milla Carmona, P.S., Lazo, D.G., Soto, I.M.
In the Lower Cretaceous Agrio Formation, Neuquén Basin (west-central Argentina), the highly variable genus Ptychomya Agassiz has challenged traditional taxonomists for over a century. Here we apply a previously outlined quantitative protocol in order to settle the taxonomy of the genus based on specimens recorded from the base to the top of the Agrio Formation. The shell outline and ribbing pattern, two prominent external features of the valves, were quantified using geometric morphometric measurements of closed and open outlines, respectively. Morphological groupings were identified using model-based clustering, and the presence of significant morphological gaps between them was statistically tested. Our results show that the variation historically attributed to a single species, namely Ptychomya koeneni Behrendsen, corresponds to intra- and interspecific variability of at least four species, one of which was previously unknown (Ptychomya esbelta sp. nov.) whereas another was regarded as a subspecies of P. koeneni, namely Ptychomya windhauseni Weaver. We were also able to confirm the specific rank of Ptychomya coihuicoensis Weaver and the presence of P. koeneni in the upper Hauterivian of the Agrio Formation. This study represents a significant improvement over the previous state of knowledge of the genus Ptychomya in the Andes of Argentina, enhancing its biostratigraphical usefulness and palaeobiogeographical significance, and may serve as a model for the study of other poorly known bivalve faunas from other Andean basins of South America.
Walk before you jump: New insights on early frog locomotion from the oldest known salientian.
Paleobiology
2016
By Lires, A.I., Soto, I.M., Gómez, R.O.
Understanding the evolution of a Bauplan starts with discriminating phylogenetic signal from adaptation and the latter from exaptation in the observed biodiversity. Whether traits have predated, accompanied, or followed evolution of particular functions is the basic inference to establish the type of explanations required to determine morphological evolution. To accomplish this, we focus in a particular group of vertebrates, the anurans. Frogs and toads have a unique Bauplan among vertebrates, with a set of postcranial features that have been considered adaptations to jumping locomotion since their evolutionary origin. This interpretation is frequently stated but rarely tested in scientific literature. We test this assumption reconstructing the locomotor capabilities of the earliest known salientian, Triadobatrachus massinoti. This extinct taxon exhibits a mosaic of features that have traditionally been considered as representing an intermediate stage in the evolution of the anuran Bauplan, some of which were also linked to jumping skills. We considered T. massinoti in an explicit evolutionary framework by means of multivariate analyses and comparative phylogenetic methods. We used length measurements of major limb bones of 188 extant limbed amphibians (frogs and salamanders) and lizards as a morphological proxy of observed locomotor behavior. Our findings show that limb data correlate with locomotion, regardless of phylogenetic relatedness, and indicate that salamander-like lateral undulatory movements were the main mode of locomotion of T. massinoti. These results contrast with recent hypotheses and indicate that derived postcranial features that T. massinoti shared with anurans might have been later co-opted as exaptations in jumping frogs.
Transcriptome modulation during host shift is driven by secondary metabolites in desert Drosophila.
Molecular Ecology
2016
By De Panis DN, J Padró, P Furió‐Tarí, S Tarazona, P Milla Carmona, IM Soto, H Dopazo, A Conesa , E Hasson
High-throughput transcriptome studies are breaking new ground to investigate the responses that organisms deploy in alternative environments. Nevertheless, much remains to be understood about the genetic basis of host plant adaptation. Here, we investigate genome-wide expression in the fly Drosophila buzzatii raised in different conditions. This species uses decaying tissues of cactus of the genus Opuntia as primary rearing substrate and secondarily, the necrotic tissues of the columnar cactus Trichocereus terscheckii. The latter constitutes a harmful host, rich in mescaline and other related phenylethylamine alkaloids. We assessed the transcriptomic responses of larvae reared in Opuntia sulphurea and T. terscheckii, with and without the addition of alkaloids extracted from the latter. Whole-genome expression profiles were massively modulated by the rearing environment, mainly by the presence of T. terscheckii alkaloids. Differentially expressed genes were mainly related to detoxification, oxidation-reduction and stress response; however, we also found genes involved in development and neurobiological processes. In conclusion, our study contributes new data onto the role of transcriptional plasticity in response to alternative rearing environments.
2016
By Muñoz‐Muñoz F, VP Carreira, N Martínez-Abadías, V Ortíz, R. González-José, IM Soto.
To predict the response of complex morphological structures to selection it is necessary to know how the covariation among its different parts is organized. Two key features of covariation are modularity and integration. The Drosophila wing is currently considered a fully integrated structure. Here, we study the patterns of integration of the Drosophilawing and test the hypothesis of the wing being divided into two modules along the proximo‐distal axis, as suggested by developmental, biomechanical, and evolutionary evidence. To achieve these goals we perform a multilevel analysis of covariation combining the techniques of geometric morphometrics and quantitative genetics. Our results indicate that the Drosophila wing is indeed organized into two main modules, the wing base and the wing blade. The patterns of integration and modularity were highly concordant at the phenotypic, genetic, environmental, and developmental levels. Besides, we found that modularity at the developmental level was considerably higher than modularity at other levels, suggesting that in the Drosophila wing direct developmental interactions are major contributors to total phenotypic shape variation. We propose that the precise time at which covariance‐generating developmental processes occur and/or the magnitude of variation that they produce favor proximo‐distal, rather than anterior‐posterior, modularity in the Drosophila wing.
Introducing Explorer of Taxon Concepts with a Case Study on Spider Measurement Matrix
Building
BMC Bioinformatics
2016
By Cui H, Su D, Chong SS, Ramirez MJ, Rodenhausen T, Macklin JA, Ludäscher B, Morris RA, Soto EM & Mongiardino Koch N
Taxonomic descriptions are traditionally composed in natural language and published in a format that cannot be directly used by computers. The Exploring Taxon Concepts (ETC) project has been developing a set of web-based software tools that convert morphological descriptions published in telegraphic style to character data that can be reused and repurposed. This paper introduces the first semi-automated pipeline, to our knowledge, that converts morphological descriptions into taxon-character matrices to support systematics and evolutionary biology research. We then demonstrate and evaluate the use of the ETC Input Creation - Text Capture - Matrix Generation pipeline to generate body part measurement matrices from a set of 188 spider morphological descriptions and report the findings.
2016
By Ceccarelli FS, Opell BD, Haddad CR, Raven RJ, Soto EM & Ramírez MJ.
Closely related organisms with transoceanic distributions have long been the focus of historical biogeography, prompting the question of whether long-distance dispersal, or tectonic-driven vicariance shaped their current distribution. Regarding the Southern Hemisphere continents, this question deals with the break-up of the Gondwanan landmass, which has also affected global wind and oceanic current patterns since the Miocene. With the advent of phylogenetic node age estimation and parametric bioinformatic advances, researchers have been able to disentangle historical evolutionary processes of taxa with greater accuracy. In this study, we used the coastal spider genus Amaurobioides to investigate the historical biogeographical and evolutionary processes that shaped the modern-day distribution of species of this exceptional genus of spiders. As the only genus of the subfamily Amaurobioidinae found on three Southern Hemisphere continents, its distribution is well-suited to study in the context of Gondwanic vicariance versus long-distance, transoceanic dispersal. Ancestral species of the genus Amaurobioides appear to have undergone several long-distance dispersal events followed by successful establishments and speciation, starting from the mid-Miocene through to the Pleistocene. The most recent common ancestor of all present-day Amaurobioides species is estimated to have originated in Africa after arriving from South America during the Miocene. From Africa the subsequent dispersals are likely to have taken place predominantly in an eastward direction. The long-distance dispersal events by Amaurobioides mostly involved transoceanic crossings, which we propose occurred by rafting, aided by the Antarctic Circumpolar Current and the West Wind Drift.
Giving taxonomic significance to morphological variability in the bivalve Ptychomya Agassiz.
Paleontology
2016
By Milla Carmona P, D Lazo, IM Soto.
The taxonomic significance of the morphological variability present in the genus Ptychomya Agassiz has remained obscure due to inadequacy of the traditional qualitative approach to account for complex patterns of variation. In this work, we focus on solving the distinction between intra‐ and interspecific variability in Ptychomya from Hauterivian marine beds of the Neuquén Basin (west‐central Argentina), a longstanding and unresolved palaeontological issue, using the quantitative framework provided by geometric morphometrics and multivariate statistics. The species Ptychomya koeneni Behrendsen and several subspecies had been recognized in the studied succession by former authors based on qualitative morphological descriptions. We tested two hypotheses: (1) that there exist morphological discontinuities between hypothesized species that mark their boundaries; and (2) that morphology follows a pattern of geographical variation, suitable for recognition of subspecies. We find two morphological groups in the studied sample, with a significant morphological gap between them, supporting the idea that there are at least two species in the studied succession, Ptychomya cf. koeneni and Ptychomya coihuicoensis Weaver. On the other hand, we found no correspondence between morphological and geographical distributions, leading to the conclusion that the named subspecies are invalid taxa. This study highlights the potential of this methodological approach for solving the taxonomy of this notorious genus of pandemic distribution during the Cretaceous.
2015
By Mongiardino Koch N, IM Soto.
Music preferences have long been studied owing to their importance in the fields of psychology and sociology. However, previous efforts seldom focused on people’s deliberate choices of music in everyday life. In this study, we aimed to analyze music listening behaviors using personal records of music listening activity. We obtained the history of songs listened to by 50 different users of the online database system Last.fm, spanning on average five years of activity. With the use of this data set, we are able to confirm that the number of songs reproduced per artist follows a truncated power-law distribution. The scaling parameter of the distribution varies considerably among users, providing a metric that characterizes the way in which different people explore music. We propose that this pattern is consistent with a preferential attachment model, according to which the probability of listening to a given artist at a given time is proportional to the frequency to which the artist was listened to in the past. These results provide new insight regarding the way in which individual music preferences are built.
Overcoming problems with the use of ratios as continuous characters for phylogenetic analyses.
Zoologica Scripta
2015
By Mongiardino Koch N, Soto IM, Ramírez MJ.
The use of quantitative morphometric information for phylogenetic inference has been an intensely debated topic for most of the history of phylogenetic systematics. Despite several drawbacks, the most common strategy to include this sort of data into phylogenetic studies is the use of ratios, that is quotients between morphometric variables. Here, we discuss one particular problem associated with such methodology: the fact that the often arbitrary election of which variable serves as numerator and which as denominator affects the phylogenetic outcome of the analysis. We describe the cause for such an effect, and study its implications with the use of several published data matrices. Alternative coding schemes for ratio characters result in very different phylogenetic hypotheses, an effect that may even be strong enough to affect studies that combine continuous and discrete morphological information. Some of the resulting incongruence is produced by the differences in magnitude of the continuous characters involved, although different rescaling techniques are shown to decrease, but not eliminate, the confounding effect. To eliminate such problematic effect, ratios should be either log-transformed before their use or replaced by more effective ways to capture morphometric information.
First phylogenetic analysis of the family Neriidae (Diptera), with a study on the issue of scaling continuous characters. Cladistics
2015
By Mongiardino Koch, IM Sito, MJ Ramírez.
Neriidae are a small family of acalyptratae flies, mostly distributed in the tropics. Very little is known about their biology, and the evolutionary relationships among species have never been evaluated. We perform the first comprehensive phylogenetic analysis of the family, including 48 species from all biogeographic regions inhabited, as well as five species of Micropezidae and one Cypselosomatidae as outgroups. We build a morphological data matrix of 194 characters, including 72 continuous characters. We first explore ways to deal with the issue of scaling continuous characters, including rescaling ranges to unity and using implied weighting. We find that both strategies result in very different phylogenetic hypotheses, and that implied weighting reduces the problem of scaling, but only partially. Furthermore, using implied weighting after rescaling characters improves the congruence between partitions and results in higher values of group support. With respect to the Neriidae, we confirm the monophyly of the family and of most its genera, although we do not obtain any of the currently accepted suprageneric groups. We propose to restrict the Eoneria and Nerius groups exclusively to the Neotropical fauna, and synonymize Glyphidops subgenus Oncopsia Enderlein with Glyphidops subgenus Glyphidops Enderlein, eliminating the subgeneric divisions. This revised phylogeny presents a striking biogeographic consistency, and shows that previous main divisions of the family were based on events of convergence.
Biodiversity of cactophilic microorganisms in western Argentina: Community structure and species composition in the necroses of two sympatric cactus hosts.
Fungal Ecology
2015
By Mongiardino Koch N, Soto IM, Galvagno M, Hasson E, Ianonne L.
The cactus-yeast-. Drosophila system is a model system in evolutionary biology, and the participating saprotrophic microorganisms represent one of the most thoroughly studied microbial communities. However, much of the cactus-dominated regions of South America, home to endemic versions of this classical system, remain understudied. A combined morpho-physiological and molecular approach was employed to identify the fungal members of the cactus-yeast-. Drosophila system in western Argentina. We identified twenty one species of saprotrophic organisms in the necroses of Opuntia sulphurea and Trichocereus terscheckii in a region of sympatry, where both cacti are exploited by cactophilic Drosophila. After excluding opportunistic isolates, we determined that the saprobe community of O. sulphurea was composed of eight species (including the first consideration of filamentous fungi as community members), whereas the community of T. terscheckii represented a subgroup of the former. We explain this nested pattern by considering the physiological and ecological attributes of both hosts and vectors involved.
Chasing ghosts: the phylogeny of Amaurobioidinae ghost spiders (Araneae, Anyphaenidae).
Zoologica Scripta
2015
By Labarque FM, Soto EM, Ramírez MJ & Arnedo MA.
The family Anyphaenidae, also known as ghost spiders, includes a diverse array of nocturnal cursorial spiders that actively hunt on vegetation. The family is mostly distributed in the Americas and has been traditionally divided into three subfamilies. The mostly tropical and North American Anyphaeninae and the Amaurobioidinae, primarily distributed in southern South America, hold the bulk of the diversity, while the Malenellininae includes a single Chilean species. Here, we use a combined morphological and molecular approach to infer the relationships of the subfamily Amaurobioidinae and examine the delimitation of contentious genera. The morphological characters include both genitalic and somatic morphology, whereas molecular data include four markers, two mitochondrial (COI, 16S) and two nuclear (28S, H3). All our analyses agree on the monophyly of Amaurobioidinae, Amaurobioidini, Gayennini, the genera Negayan, Amaurobioides, Josa, Araiya, Arachosia and Monapia, as well as the paraphyly of Anyphaeninae. The total evidence analysis supports the novel placement of Josa as the sister group of both tribes Amaurobioidini and Gayennini, most of the previously known intergeneric relationships within Gayennini, and a clade of Amaurobioidini with a projecting ocular area, including Aysenoides, Axyracrus, Amaurobioides and Aysenia. The sequence data solve the puzzling placement of Philisca puconensis, here transferred to Tomopisthes, and Tasata chiloensis, transferred to Oxysoma. The advantages of the total evidence phylogenetic approach and the evolution of the male copulatory organ are discussed.
Host alkaloids differentially affect developmental stability and wing vein canalization in cactophilic Drosophila buzzatii.
Journal of Evolutionary Biology
2014
By Padró J, Carreira VP, Corio C, Hasson E, Soto IM.
Host shifts cause drastic consequences on fitness in cactophilic species of Drosophila. It has been argued that changes in the nutritional values accompanying host shifts may elicit these fitness responses, but they may also reflect the presence of potentially toxic secondary compounds that affect resource quality. Recent studies reported that alkaloids extracted from the columnar cactus Trichocereus terscheckii are toxic for the developing larvae of Drosophila buzzatii. In this study, we tested the effect of artificial diets including increasing doses of host alkaloids on developmental stability and wing morphology in D. buzzatii. We found that alkaloids disrupt normal wing venation patterning and affect viability, wing size and fluctuating asymmetry, suggesting the involvement of stress-response mechanisms. Theoretical implications are discussed in the context of developmental stability, stress, fitness and their relationship with robustness, canalization and phenotypic plasticity.
2014
By Soto IM, VP Carreira, C Corio, J Padró, EM Soto, E Hasson.
The evolution of cactophily in the genus Drosophila was a major ecological transition involving over a hundred species in the Americas that acquired the capacity to cope with a variety of toxic metabolites evolved as feeding deterrents in Cactaceae. D. buzzatii and D. koepferae are sibling cactophilic species in the D. repleta group. The former is mainly associated with the relatively toxic-free habitat offered by prickly pears (Opuntia sulphurea) and the latter has evolved the ability to use columnar cacti of the genera Trichocereus and Cereus that contain an array of alkaloid secondary compounds. We assessed the effects of cactus alkaloids on fitness-related traits and evaluated the ability of D. buzzatii and D. koepferae to exploit an artificial novel toxic host. Larvae of both species were raised in laboratory culture media to which we added increasing doses of an alkaloid fraction extracted from the columnar cactus T. terschekii. In addition, we evaluated performance on an artificial novel host by rearing larvae in a seminatural medium that combined the nutritional quality of O. sulphurea plus amounts of alkaloids found in fresh T. terschekii. Performance scores in each rearing treatment were calculated using an index that took into account viability, developmental time, and adult body size. Only D. buzzatii suffered the effects of increasing doses of alkaloids and the artificial host impaired viability in D. koepferae, but did not affect performance in D. buzzatii. These results provide the first direct evidence that alkaloids are key determinants of host plant use in these species. However, the results regarding the artificial novel host suggest that the effects of alkaloids on performance are not straightforward as D. koepferae was heavily affected. We discuss these results in the light of patterns of host plan evolution in the Drosophila repleta group
2014
By Carreira VP, Padró J, Mongiardino Koch N, Fontanarrosa P.,Alonso I, IM Soto.
Several studies have shown the interesting properties of Opuntia spp. ("prickly pears"), although most of this knowledge is based on O. ficus-indica. O. sulphurea is a species that is largely distributed in the Monte region of Argentina, where it has been used as an edible resource, especially in periods of food shortage. This is the first report evaluating the chemical composition of O. sulphurea cladodes. Our results show that cladodes are composed primarily of water, as with most other prickly pears that have been studied, which is consistent with their expected role as water reservoir in desert communities. Ash and protein content in O. sulphurea are consistent with values found for other species of the genus, whereas carbohydrates are well below levels of other Opuntia spp. Finally, the percentage of lipids in O. sulphurea cladodes is larger than in other studied species and fatty acid composition is quite different from observations made in similar studies. These earlier studies showed that linoleic acid is the major constituent of fatty acid fractions, followed by palmitic and oleic acids. Our analyses showed that these fatty acids are also principal constituents of O. sulphurea cladodes, although linolenic acid proved to be the most abundant. Curiously, the previous works found relatively low quantities of this fatty acid. Other minor fatty acids were also detected in cladodes of O. sulphurea, although the percentages are larger than in other studies of prickly pears. We discuss our results in the context of the potential nutraceutical and economic utility of O. sulphurea cladodes as a new source of essential fatty acids, especially in semi-arid areas as the Monte region where this species represents an abundant edible resource which is available even in periods of scarcity.
Oviposition Site Preference for Natural Breeding Sites in Drosophila melanogaster (Diptera: Drosophilidae) Populations from Argentina.
Annals of the Entomological Society of America
2014
By Betti MIL, Soto EM, Hasson E.
Maternal decisions, like the choice of a site for laying eggs, have important ecological and evolutionary implications. In the current study, we investigated variation both within and between populations in oviposition site preference (OSP) in a collection of isofemale lines derived from three Drosophila melanogaster Meigen natural populations of western Argentina. In the oviposition preference assay, we used two resources that fruit flies use as egg-laying sites in nature. Results revealed 1) the distribution of eggs across the two alternative resources offered to the flies deviated from random when flies were given the chance to choose between grape and orange, 2) OSP varied within and between populations, and 3) a substantial proportion of OSP variation has a genetic basis as suggested by the signiÞcant contribution of variation among lines to total trait variance. Our survey represents an initial step in understanding patterns of natural variation in oviposition preferences for natural resources in D. melanogaster.
2014
By Pérez-González A, Ramírez MJ, Soto EM & Pizarro-Araya J.
Acropsopilio chilensis Silvestri, 1904 (Eupnoi: Caddidae: Acropsopilioninae), is recorded for Robinson Crusoe Island, Chile. This is the first harvestman species recorded for the Juan Fernández Archipelago and also the first extra-continental record for this species. During the comparison with continental co-specific specimens, some previously unknown, remarkable morphological characteristics were discovered, among them: the absence of ovipositor seminal receptacles and tracheal system, small and probably imperforate spiracles and the presence of a subdistal spiny structure, maybe a stylus, in the major branch of the penis.