Data from: Invasive species and postglacial colonization: their effects on the genetic diversity of a Patagonian fish

The present distribution of Patagonian species is the result of a complex
history involving Quaternary refugial populations, Holocene range
expansions, and demographic changes occurring during the Anthropocene.
Invasive salmonids were introduced in Patagonia during the last century,
occupying most rivers and lakes, preying on, and competing with native
species, including the fish Galaxias platei. Here we used G. platei as a
case study to understand how long-term (i.e. population differentiation
during the Holocene) and short-term historical processes (salmonid
introductions) affect genetic diversity. Using a suite of microsatellite
markers, we found that the number of alleles is negatively correlated with
presence of salmonids (short-term processes), with G. platei populations
from lakes with salmonids exhibiting significantly lower genetic diversity
than populations from lakes without salmonids. Simulations (100 years
backwards) showed that this difference in genetic diversity can be
explained by a 99% reduction in population size. Allelic richness and
observed heterozygosities were also negatively correlated with the
presence of salmonids, but also positively correlated with long-term
processes linked to Quaternary glaciations. Our results show how different
genetic parameters can help identify processes taking place at different
scales and their importance in terms of conservation.