Contrasting evolutionary responses in two co-distributed species of Galaxias (Pisces, Galaxiidae) in a river from the glaciated range in Southern Chile.

P F Victoriano,C B Canales-Aguirre,C Muñoz-Mendoza,C P Muñoz-Ramírez,E M Habit,T Burgos-Careaga,I Vera-Escalona,A Jara

doi:10.1098/rsos.200632

Abstract

Life-history traits are among the most important factors affecting population abundance and genetic diversity of species. Here, we analysed the genetic patterns of two Galaxias species with different life-history traits to investigate how these biological differences impacted their evolution in the Valdivia River basin, Southern Chile. We analysed mitochondrial DNA (mtDNA) sequences from 225 individuals of Galaxias maculatus and 136 of G. platei to compare patterns of genetic diversity, structure and demographic growth across the basin. Galaxias maculatus presented higher genetic diversity and higher genetic structure than G. platei. Demographic analyses showed G. maculatus kept a higher population size over time, with a signal of demographic expansion in the last 250 kyr. Whereas Galaxias platei, exhibited lower, but constant population size over time. Furthermore, haplotype networks revealed higher lineage diversity in G. maculatus with a tendency to occupy different areas of the basin. Coalescent simulations ruled out that genetic differences between species could be explained by stochastic processes (genetic drift), suggesting species-specific biological differences as responsible for the observed genetic differences. We discuss how differences in life-history traits and past glaciations interact to shape the evolutionary history of the two Galaxias species.

Highlights

Phylogeographic studies in freshwater fish have recently increased our understanding on the relevant processes shaping biodiversity in southern South America [1,2]
Genetic diversity and structure were lower in the freshwater strict G. platei than in the diadromous G. maculatus
We found strong differences in the patterns of genetic diversity and structure between Galaxias maculatus and Galaxias platei in the Valdivia River basin

Summary

Introduction

Phylogeographic studies in freshwater fish have recently increased our understanding on the relevant processes shaping biodiversity in southern South America [1,2]. Zemlak et al [9] found close relationships between some geographically close (i.e. similar latitude) trans-Andean populations of Galaxias platei, suggesting a complex Patagonian history of drainage translocations across the Andes, triggered by transitions between glacial and interglacial periods. It is not yet clear though how strong or consistent these patterns are across taxa, as freshwater phylogeography in Patagonian systems is still in an early stage. Some of these studies, such as Ruzzante et al [8], have emphasized the relevance of comparing patterns across species to understand how biological differences may influence species’ demographic responses to shared historical events

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Conclusion