Morphological diversity and discrimination tools of the non-marine ostracod Cypridopsis silvestrii across temporal and spatial scales from Patagonia.

Geometric morphometric methods are powerful tools to discriminate between closely related ostracods taxa as well as to study the relationship between their morphological variations, taxonomy and paleoecology. In this study, valve outline analysis allows the discrimination between the non-marine ostracod C. silvestrii and R. whatleyi juveniles, pointing out differences in the posterior valve area and surface ornamentation. Modern female specimens of C. silvestrii from 23 sites located in a spatial transect (41 to 51 °S) exhibited extensive morphological variability, on the basis of which three morphotypes (acuminated, transitional, subtruncated) were determined. Multivariate analyses showed that acuminated and transitional shapes are not arranged in groups but the subtruncated morphotype, previously described as E. cecryphalium, seems to be associated with low water conductivity (372 µS cm-1), dominant cold (5 ºC) and windy (8.6 m s-1) climatic conditions. The fossil cluster which included nine cores spanning the last 15.6 kyr, only covered acuminated and transitional shapes, which may indicate that these lineages might be older than the subtruncated morphotype. In addition, morphological differences between reproduction modes suggested that parthenogenetic females exhibit de posterior margin more acuminate than sexual females. These results set the ground for more precise ecological and paleoenvironmental studies in Patagonia.

Characterizing ecoregions in Argentinian Patagonia using extant continental ostracods.

In order to characterize Patagonian (Argentina) ecoregions using non-marine ostracods, their associations in 69 environments were assessed. Twenty eight taxa were recorded, including 12 endemic of the Neotropical region. Our results indicate that Patagonian ostracods are mainly influenced by electrical conductivity (EC), altitude, pH, and temperature; and shows a correlation with Argentinian ecoregions. Assemblage I is composed of sites located at high altitude in the Andean Patagonian forest ecoregion. Host waters have low temperature, EC and pH, and support as representative species Cypris pubera, Eucypris virens, Bradleystrandesia fuscata, Tonacypris lutaria and Amphicypris nobilis. Assemblage II, related to mid-altitude environments in the Patagonian Steppe ecoregion, thrived in waters with moderate to high EC, and alkaline pH values. Dominant species includes Limnocythere rionegroensis, L. patagonica, E. virgata, Riocypris whatleyi, Riocypris sarsi, Newnhamia patagonica, Kapcypridopsis megapodus, Ilyocypris ramirezi and Penthesinelula incae. Assemblage III inhabited environments within Monte and Espinal ecoregions, situated in the eastern part of the study area at low altitude, EC moderate and temperate waters, supporting Heterocypris hyalinus, Amphicypris argentinensis, Sarscypridopsis aculeata, Cypridopsis vidua, Herpetocypris intermedia and Chlamidotheca incisa. Our results indicates that Argentinian Patagonia hosts a diverse ostracod fauna and highlights their capacity as proxies in ecological and palaeoenvironmental studies.

Taxonomic revision of Cypridopsis silvestrii comb. nov. (Ostracoda, Crustacea) from Patagonia, Argentina with morphometric analysis of their intraspecific shape variability and sexual dimorphism.

In this study we redescribe an ostracod species belonging to the subfamily Cypridopsinae Kaufmann, 1900, sampled in seven localities of northern and southern Patagonia, Argentina. A new taxonomical combination is proposed, Cypridopsis silvestrii comb. nov., based on detailed description of females and the first descriptions of males. Cypridopsis silvestrii occurred on a wide geographical distribution range, from 40º to 48º S latitude, as well as broad environmental tolerance ranges. We evaluated morphological variations in two populations of C. silvestrii from northern (El Toro lake) and southern (El Sello lake) Patagonia, with contrasting limnological conditions. El Toro is a small shallow lake with high salinity waters and El Sello is a large deep lake with lower salinity. Based on morphometric analysis, our results showed intraspecific variation in valve shape and size between populations. Sexual dimorphism in El Toro population was identified through morphometric analyses. Additionally, comparison of valve outlines in living and subfossil individuals from El Toro lake allowed specimens previously described as juveniles of Eucypris fontana (Graf, 1931) to be identified as adults of C. silvestrii comb. nov. The present contribution increases knowledge of the taxonomic identity, the ecological requirements and the geographical distribution of C. silvestrii, and shows that morphometric analyses are a feasible and useful tool for exploring intraspecific shape differences and assisting in taxonomic identification. Furthermore, the results presented herein provide tools for C. silvestrii identification in paleolimnological studies, and emphasize the usefulness of studying living representatives for clarification of the taxonomic status of species widely distributed in Quaternary sediments.