Browsing by Author "Collado, Gonzalo A."

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    Coping With Dynamism: Phylogenetics and Phylogeographic Analyses Reveal Cryptic Diversity in Heleobia Snails of Atacama Saltpan, Chile
    (2022) Valladares, Moises A.; Fabres, Alejandra A.; Collado, Gonzalo A.; Saez, Paola A.; Mendez, Marco A.
    The species that inhabit systems highly affected by anthropic activities usually exhibit this external influence in their gene pool. In this study, we investigated the genetic patterns of populations of Heleobia atacamensis, a freshwater microgastropod endemic to the Atacama Saltpan, a system historically exposed to environmental changes, and currently subjected to conditions associated with metallic and non-metallic mining and other anthropic activities. Molecular analyses based on nuclear and mitochondrial sequences indicate that the saltpan populations are highly fragmented and that the genetic structure is mainly explained by historical geographic isolation, with little influence of contemporary factors. The microsatellite results suggest a moderate genetic diversity and sharp differentiation mediated by isolation by distance. Additionally, despite the high environmental heterogeneity detected and the marked historical dynamism of the region, our data reveal no signs of demographic instability. The patterns of contemporary gene flow suggest a change in the current genetic structure, based on the geographic proximity and specific environmental conditions for each population. Our results, highlight the role of fragmentation as a modulator of genetic diversity, but also suggest that the historical persistence of isolated populations in naturally dynamic environments could explain the apparent demographic stability detected.
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    Distribution, conservation assessment and management perspectives of Chilean micro-snails of the family Charopidae
    (2023) Collado, Gonzalo A.; Flores, Nataly; Vidal, Marcela A.; Torres-Diaz, Cristian; Valladares, Moises A.
    The biodiversity of molluscs is highly threatened in marine, terrestrial and freshwater ecosystems worldwide. This research aimed at studying the distribution and conservation status of eight poorly-known micro-snails of the genera Stephacharopa and Stephadiscus in Chile. We performed a comprehensive review of literature and databases to determine the occurrences of the species, which were mapped on vector layers containing protected areas and human development infrastructure to find potential threats. Conservation status assessment was performed following the criteria and tools implemented by the International Union for the Conservation of Nature (IUCN) Red List and NatureServe. We also conducted species distribution models, based on maximum entropy, to identify areas that should be prioritised for conservation. Two species meet the criteria for IUCN listing as Critically Endangered (CR), four Endangered (EN), one Vulnerable (Vu) and one Least Concern (LC). This classification is rather coincident with equivalent categories obtained under the NatureServe standard, in which two species were ranked as Critically Imperiled (N1), five Imperiled (N2) and one Vulnerable (N3). We found that Stephacharopa paposensis is the most at-risk species, with only one occurrence not included in a protected area, followed by Stephadiscus stuardoi, with two occurrences, one of them within a protected area. Stephadiscus lyratus was the species with the greatest geographic range, accounting for 17 occurrences, seven matching a protected area. We found wider potential ranges in modelled species that may be useful for prioritising conservation measures. Considering distributional data, protected areas and more than 20 plausible threats identified, we propose potential in situ and ex situ conservation actions to protect these neglected micro-snails.
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    Population structure and microscale morphological differentiation in a freshwater snail from the Chilean Altiplano
    (2024) Valladares, Moisés A.; Fabres, Alejandra A.; Sánchez-Rodríguez, Fernanda; Collado, Gonzalo A.; Méndez, Marco A.
    Background: The diversity and population genetic structure of many species have been shaped by historical and contemporary climatic changes. For the species of the South American Altiplano, the historical climatic changes are mainly related to the wet events of great magnitude and regional influence that occurred during the Pleistocene climatic oscillations (PCOs). In contrast, contemporary climate changes are associated with events of lesser magnitude and local influence related to intensifications of the South American Summer Monsoon (SASM). Although multiple studies have analyzed the effect of PCOs on the genetic patterns of highland aquatic species, little is known about the impact of contemporary climate changes in recent evolutionary history. Therefore, in this study, we investigated the change in population structure and connectivity using nuclear and mitochondrial markers throughout the distribution range of Heleobia ascotanensis, a freshwater Cochliopidae endemic to the Ascotán Saltpan. In addition, using geometric morphometric analyses, we evaluated the concomitance of genetic divergence and morphological differentiation. Results: The mitochondrial sequence analysis results revealed the presence of highly divergent co-distributed and geographically nested haplotypes. This pattern reflects an extension in the distribution of groups that previously would have differentiated allopatrically. These changes in distribution would have covered the entire saltpan and would be associated with the large-scale wet events of the PCOs. On the other hand, the microsatellite results defined five spatially isolated populations, separated primarily by geographic barriers. Contemporary gene flow analyses suggest that post-PCO, climatic events that would have connected all populations did not occur. The morphometric analyses results indicate that there is significant morphological differentiation in the populations that are more isolated and that present the greatest genetic divergence. Conclusions: The contemporary population structure and morphological variation of H. ascotanensis mainly reflect the post-PCO climatic influence. Although both markers exhibit high genetic structuring, the microsatellite and morphology results show the preponderant influence of fragmentation in recent evolutionary history. The contemporary genetic pattern shows that in species that have limited dispersal capabilities, genetic discontinuities can appear rapidly, erasing signs of historical connectivity.