Abstract
The last decades have shown a surge in studies focusing on the interplay between fragmented habitats, genetic variation, and conservation. In the present study, we consider the case of a temperate pond‐breeding anuran (the common toad Bufo bufo) inhabiting a naturally strongly fragmented habitat at the Northern fringe of the species’ range: islands offshore the Norwegian coast. A total of 475 individuals from 19 populations (three mainland populations and 16 populations on seven adjacent islands) were genetically characterized using nine microsatellite markers. As expected for a highly fragmented habitat, genetic distances between populations were high (pairwise F st values ranging between 0.06 and 0.33), with however little differences between populations separated by ocean and populations separated by terrestrial habitat (mainland and on islands). Despite a distinct cline in genetic variation from mainland populations to peripheral islands, the study populations were characterized by overall high genetic variation, in line with effective population sizes derived from single‐sample estimators which were on average about 20 individuals. Taken together, our results reinforce the notion that spatial and temporal scales of fragmentation need to be considered when studying the interplay between landscape fragmentation and genetic erosion.
Highlights
In ecological and evolutionary research, populations with pronounced spatial structure are often the focus of genetic investigations
The three mainland populations were characterized by higher overall measures of genetic variation than island populations, bearing 25 alleles (17.2% of the overall allelic diversity represented with 145 alleles across loci) which were absent on islands as well as high overall levels of allelic richness (Table 1)
The main findings from our study on genetic variation of anuran populations strongly subdivided across a Northern European archipelago are twofold
Summary
In ecological and evolutionary research, populations with pronounced spatial structure are often the focus of genetic investigations. Couvet 2002; Manel and Holdegger 2013; Balkenhol et al 2015) Despite these clear causal relationships, it is often notoriously difficult to discern between population declines which are purely caused by habitat reduction and declines which are accelerated by genetic erosion (Bijlsma and Loeschcke 2012; Fraser et al 2014). This poses a general problem in conservation biology, which can, at least in part, be attributed to overgeneralizations across spatial and temporal scales.
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