Comparative landscape genetics of pond‐breeding amphibians in Mediterranean temporal wetlands: The positive role of structural heterogeneity in promoting gene flow

Abstract

Comparative landscape genetics studies can provide key information to implement cost-effective conservation measures favouring a broad set of taxa. These studies are scarce, particularly in Mediterranean areas, which include diverse but threatened biological communities. Here, we focus on Mediterranean wetlands in central Iberia and perform a multi-level, comparative study of two endemic pond-breeding amphibians, a salamander (Pleurodeles waltl) and a toad (Pelobates cultripes). We genotyped 411 salamanders from 20 populations and 306 toads from 16 populations at 18 and 16 microsatellite loci, respectively, and identified major factors associated with population connectivity through the analysis of three sets of variables potentially affecting gene flow at increasingly finer levels of spatial resolution. Topographic, land use/cover, and remotely sensed vegetation/moisture indices were used to derive optimized resistance surfaces for the two species. We found contrasting patterns of genetic structure, with stronger, finer scale genetic differentiation in Pleurodeles waltl, and notable differences in the role of fine-scale patterns of heterogeneity in vegetation cover and water content in shaping patterns of regional genetic structure in the two species. Overall, our results suggest a positive role of structural heterogeneity in population connectivity in pond-breeding amphibians, with habitat patches of Mediterranean scrubland and open oak woodlands ("dehesas") facilitating gene flow. Our study highlights the usefulness of remotely sensed continuous variables of land cover, vegetation and water content (e.g., NDVI, NDMI) in conservation-oriented studies aimed at identifying major drivers of population connectivity.

Reconciling direct and indirect estimates of functional connectivity in a Mediterranean pond-breeding amphibian

“…An alternative explanation is that dispersal is instead shaped by topography, with animals moving preferentially downslope from Laguna to Gravera. This is consistent with landscape genetics studies showing a significant effect of slope on resistance to gene flow (Gutiérrez-Rodríguez et al 2017a).…”

“…Understanding functional connectivity among demes in population networks is thus paramount to prevent and reverse negative population trends (Petranka et al 2004;Leung et al 2017). Attempts to characterize patterns of connectivity among amphibian populations at the landscape scale have largely relied on molecular markers to identify factors that promote or restrict gene flow (Newman and Squire 2001;Wang 2009a;Gutiérrez-Rodríguez et al 2017a). However, in the absence of information on the frequencies and distances of individual displacement events, it is difficult to relate gene flow estimates with the actual dispersal capacity of individuals, which is a critical parameter to design and implement conservation actions (Sinsch et al 2012;Sinsch 2014;Trochet et al 2017).…”

“…In this study, we estimate local abundance and reconcile direct and indirect estimates of functional connectivity in a spatially structured population of the sharp-ribbed newt (Pleurodeles waltl Michahelles, 1830), a common inhabitant of Mediterranean temporary ponds, listed as Near Threatened in IUCN's Red List based on inferred population decline caused by habitat loss and the negative effects of invasive species (Beja et al 2009). Our study area is located in Sierra de Guadarrama (Madrid, Central Spain), where previous studies have reported female-biased dispersal in the species (Gutiérrez-Rodríguez et al 2017b), and showed that vegetation heterogeneity plays an important role in promoting population connectivity at the landscape level (Gutiérrez-Rodríguez et al 2017a). Here we extend previous studies and further characterize the demographic and spatial dynamics of a P. waltl metapopulation by estimating population size and assessing functional connectivity between the two main breeding ponds in the study area in relation to local abundance and sex-biased dispersal.…”

Anthropogenic pressures drive population genetic structuring across a Critically Endangered lemur species range

“…Several factors may be driving this pattern, including past episodes of forest contraction and expansion and biogeographic barriers (i.e., rivers or valleys). These landscape features are thought to operate on much deeper time scales than anthropogenic change in terms of their influence on an organism’s dispersal abilities, population connectivity, and genetic structure 89 . In an earlier study, we identified genetic clustering on either side of the Mangoro—the largest river in eastern Madagascar—lending support to these findings, and leading us to hypothesize that Madagascar’s rivers structure V .…”

Comparative landscape genetics of two endemic torrent salamander species, Rhyacotriton kezeri and R. variegatus: implications for forest management and species conservation

“…However, comparative studies can provide insights into whether relationships between landscape features and genetic distance differ among taxa, habitat types, and geographic areas. Comparative studies examining either ecologically similar or distinct species in the same landscape have become more common in recent years, providing novel perspectives on different species' relationships with the landscape (Engler et al 2014;Whiteley et al 2014;Mims et al 2015;Kierepka et al 2016;Burkhart et al 2017;Gutiérrez-Rodríguez et al 2017). In one such study, Engler et al (2014) determined that among three Hesperid butterfly species in the genus Thymelicus, recent human land conversion restricted gene flow in a poorly dispersing habitat specialist, while a generalist with moderate dispersal abilities was restricted by climate, and another generalist that was the strongest disperser exhibited IBD.…”