Data from: Gene flow from an adaptively divergent source causes rescue through genetic and demographic factors in two wild populations of Trinidadian guppies

Genetic rescue, an increase in population growth owing to the infusion of new alleles, can aid the persistence of small populations, but its use as a management tool is limited by poor understanding of effects of gene flow on local adaptation and demography. Experimental translocations provided an opportunity to monitor demographic consequences of gene flow. We took advantage of two experimental introductions of Trinidadian guppies to test the effects of gene flow on downstream native populations. We individually marked guppies from native populations to monitor population dynamics for 3 months before and 26 months after gene flow. We genotyped all individuals caught during the first 17 months at microsatellite loci to classify individuals by genetic ancestry: native, immigrant, F1 hybrid, F2 hybrid, or backcross. Our study documents a combination of demographic and genetic rescue over multiple generations in nature. Within both recipient populations, we found substantial and long-term increases in population size that could be attributed to high survival and recruitment caused by immigration and gene flow from introduction sites. Our results suggest that low levels of gene flow, even from a divergent ecotype, can provide substantial demographic boosts to small populations, which may allow them to withstand environmental stochasticity.