A decision-making framework to maximize the evolutionary potential of populations: Genetic and genomic insights from the common midwife toad (Alytes obstetricans) at its range limits

Anthropogenic habitat modification and climate change are fundamental
drivers of biodiversity declines, reducing the evolutionary potential of
species, particularly at their distributional limits. Supportive breeding
or reintroductions of individuals are often made to replenish declining
populations, sometimes informed by genetic analysis. However, most
approaches utilised (i.e. single locus markers) do not have the resolution
to account for local adaptation to environmental conditions, a crucial
aspect to consider when selecting donor and recipient populations. Here,
we incorporate genetic (microsatellite) and genome-wide SNP (ddRAD-seq)
markers, accounting for both neutral and putative adaptive genetic
diversity, to inform the conservation management of the threatened common
midwife toad, Alytes obstetricans at the northern and eastern edges of its
range in Europe. We find geographically structured populations (n=4), weak
genetic differentiation and fairly consistent levels of genetic diversity
across localities (observed heterozygosity and allelic richness).
Categorising individuals based on putatively adaptive regions of the
genome showed that the majority of localities are not strongly locally
adapted. However, several localities present high numbers of private
alleles in tandem with local adaptation to warmer conditions and rough
topography. Combining genetic diversity and local adaptations with
estimates of migration rates, we develop a decision-making framework for
selecting donor and recipient populations which maximises the geographic
dispersal of neutral and putatively adaptive genetic diversity.
Our framework is generally applicable to any species, but especially to
amphibians, so armed with this information, conservationists may avoid the
reintroduction of unsuitable/maladapted individuals to new sites and
increase the evolutionary potential of populations within species.