High genetic diversity of common toad (Bufo bufo) populations under strong natural fragmentation on aNorthern archipelago

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.

Trapped within the city: integrating demography, time since isolation and population‐specific traits to assess the genetic effects of urbanization

“…Interestingly, though, N e exhibited by Oviedo's populations are comparable to effective sizes observed in metapopulation systems of pond-breeding amphibians outside of urban environments (e.g. Beebee 2009;Wang et al 2011;Wang 2012;Roth & Jehle 2016). On the other hand, N e in most populations is below recommended thresholds proposed in the literature to avoid inbreeding depression (N e > 50 in Jamieson & Allendorf 2012; N e > 100 in Frankham et al 2014), making them potentially vulnerable to deleterious effects of genetic drift (Frankham 2005).…”

“…Beebee ; Wang et al . ; Wang ; Roth & Jehle ). On the other hand, N e in most populations is below recommended thresholds proposed in the literature to avoid inbreeding depression ( N e > 50 in Jamieson & Allendorf ; N e > 100 in Frankham et al .…”

Linking effective population size dynamics to phenotypic traits in the common toad (Bufo bufo)

“…Life-history traits such as male-biased operational sex ratios are linked to rather low levels of genetic variation, and corresponding N e and N b values are typically below other anurans (Scribner et al 1997;Brede and Beebee 2006). The population structure of B. bufo is further shaped by human habitat alteration, with negative effects on standing levels of genetic variation (Hitchings and Beebee 1998;Scribner et al 2001;Flavenot et al 2015; see also Roth and Jehle 2016). In the present study, we employ a temporal genetic sampling regime to an intensively studied (1980-present) B. bufo population which previously underwent a decrease in individual body condition and survival linked to a local rise in spring temperature (Reading and Clarke 1995;Reading 2007).…”

An amphibian species pushed out of Britain by a moving hybrid zone

“…The populations in Norway are almost completely devoid of spinosus‐alleles, except at the loci aimp2 and med8 (Table ). Considering that genetic variation usually decreases towards a species' range edge, the standing genetic variation observed in Norway is high (Roth & Jehle, ). A pattern where alleles reappear at localities away from the admixture zone has been observed in European house mice (Teeter et al, ) and is suggestive of differential negative selection, stronger within the area of admixture than away from it.…”

“…Tissue material was obtained as toe tips from adults and the tips of tailfins from larvae for 145 individuals at 15 localities in Great Britain (Table ) and as extracted DNAs from 358 individuals from Dorset, United Kingdom (Coles, Reading, & Jehle, ) and 318 individuals at 21 localities in the southwest of Norway (Roth & Jehle, ). New material was collected in accordance with the UK's Wildlife and Countryside Act, 1981.…”