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

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.

Historical and Contemporary Diversity of Galaxiids in South America: Biogeographic and Phylogenetic Perspectives

“…Phylogenetic studies based on DNA sequences (e.g., mtDNA and nDNA) can give insights on the long-term processes, which for galaxiids include processes such as the fragmentation of Gondwana and the appearance of mountain chains as a barrier for species dispersal [41,42]. DNA sequences have also been used to study phylogeographic patterns over shorter time scales in galaxiids (e.g., [34][35][36]47,48,50,53]). The information obtained using mtDNA sequences has more recently been complemented with studies based on nuclear microsatellite markers (e.g., [32,38,43]) and Single Nucleotide Polymorphisms (SNPs, [5]), which tend to focus on processes that take place over relatively short historical and contemporary time scales (thousands of years to a few generations ago).…”

Contrasting Patterns of Genetic Diversity and Divergence Between Landlocked and Migratory Populations of Fish Galaxias maculatus, Evaluated Through Mitochondrial DNA Sequencing and Nuclear DNA Microsatellites

“…Moreover, migratory populations showed higher levels of gene flow and absence of site fidelity, while landlocked populations showed evidence of different colonization events with relatively low genetic diversity and varying levels of gene flow. Victoriano et al (2020) , using mtDNA sequences, observed that G. maculatus showed higher levels of genetic diversity and structure than the species G. platei, in the same river basin on both sides of the Andes. This result was explained by the different migratory and non-migratory behaviour of the two species.…”

“…In addition, the presence of resident or landlocked populations has been observed in lakes and rivers, as well as migratory populations that maintain amphidromous behaviour ( Delgado et al, 2019 ). This species is therefore considered an interesting model for historical biogeographic studies due to its particular distribution ( Waters and Burridge, 1999 ; Waters et al, 2000 ; Zattara et al, 2005 ; Burridge et al, 2012 ; Waters et al, 2020 ), its response to glacial events ( Zemlak et al, 2010 ; Zemlak et al, 2011 ; Carrea et al, 2012 , 2013 ; González-Wevar et al, 2015a ; González-Wevar et al, 2015b ; Victoriano et al, 2020 ), and its migratory and non-migratory behaviour in the same habitat ( Delgado et al, 2019 ; Delgado and Ruzzante, 2020 ). This variability makes G. maculatus a suitable model for evaluating genetic indicators associated with these unique characteristics, as this species has been considered to represent an intermediate evolutionary step between migratory behaviours of marine and freshwater organisms ( Corush, 2019 ).…”

Does migration promote or inhibit diversification? A case study involving the dominant radiation of temperate Southern Hemisphere freshwater fishes

“…Concomitantly, higher levels of population genetic differentiation appear linked to high diversification rates (Harvey et al 2017). However, diversification rates also depend on extinction, with lower extinction rates expected for migratory versus resident taxa because of their broader distributions, larger population sizes (McDowall 2007;Bloom and Lovejoy 2014), and higher genetic diversity (Allibone and Wallis 1993;Ward et al 1994;McDowall 1999;Victoriano et al 2020). Therefore, the broad relationship between migratory status and diversification remains unclear, and the few detailed analyses conducted to date suggest either higher (Rolland et al 2014;Fuchs et al 2015;Corush 2019;Gómez-Bahamón et al 2020) or lower (Tedesco et al 2017) diversification in migratory lineages, or no relationship with migratory status (Kennedy et al 2016).…”