Present and past climatic effects on the current distribution and genetic diversity of the Iberian spadefoot toad (Pelobates cultripes): an integrative approach

Abstract

Aim Predicting species responses to global change is one of the most pressing issues in conservation biogeography. A key part of the problem is understanding how organisms have reacted to climatic changes in the past. Here, we use species distribution modelling to infer the effects of climate changes since the Last Interglacial (LIG, c. 130,000 yr bp) on patterns of genetic structure and diversity in the western spadefoot toad (Pelobates cultripes) in combination with spatially explicit phylogeographical analyses.Location Iberian Peninsula and mainland France.Methods Five hundred and twenty-four individuals from 54 populations across the species range were sampled to document patterns of genetic diversity and infer their evolutionary history based on data from mtDNA and 14 polymorphic microsatellites. Generalized linear models based on distribution data were used to infer climatic favourability for the species in the present and in palaeoclimatic simulations for the LIG, the mid-Holocene and the Last Glacial Maximum (LGM).Results Estimates of genetic diversity show a decreasing trend from south to north, suggesting persistence of high historical population sizes in the southern Iberian Peninsula. Species distribution models show differences in climatic favourability through time, with significant correlations between historically stable favourable areas and current patterns of genetic diversity. These results are corroborated by Bayesian skyline plots and continuous diffusion phylogeographical analyses. Main conclusionsThe results indicate the presence of southern refugia, with moderate recent expansions at the northern end of the species' range. Toads at the northern range margin exhibit the lowest genetic diversity and occupy areas of high past climate variability, classified as marginal in terms of favourability, rendering these populations most vulnerable to climate-mediated changes in the long term.

Mountains as barriers to gene flow in amphibians: Quantifying the differential effect of a major mountain ridge on the genetic structure of four sympatric species with different life history traits

“…The strong barrier effect exerted by Sierra de Guadarrama on P. cultripes is well supported based on high overall population differentiation (Table S1.4) and results of the clustering and causal modelling approaches (Table , Figures and S2.9–S2.11). This barrier effect is consistent with the absence or rarity of this species above 1,500 m (Cejudo, ) and the strong phylogeographical break at the Central System (Gutiérrez‐Rodríguez, Barbosa, et al., ). Mountain passes in Sierra de Guadarrama are above the higher reported altitudes for this species except at Somosierra and Alto del León (Figure ).…”

“…If this effect is significant in the present interglacial period, it is safe to assume that it was probably stronger during the Pleistocene, when glaciers covered large areas in Sierra de Guadarrama (Domínguez‐Villar et al., ). This long‐term effect could explain the phylogeographical breaks found in P. cultripes (Gutiérrez‐Rodríguez, Barbosa, et al., ) and H. molleri (Sánchez‐Montes & Martínez‐Solano, unpublished), two species showing a clear north–south subdivision in the Iberian Peninsula and meeting at the Central System mountains.…”

“…Among these, the Central System mountains are thought to represent a historical barrier to gene flow across diverse taxonomic groups. The ranges of several amphibian species find their distributional limit in the Iberian Central System (Arntzen & Espregueira Themudo, ; Reino et al., ), and these mountains separate well‐differentiated intraspecific clades in other species (Gutiérrez‐Rodríguez, Barbosa, & Martínez‐Solano, ).…”

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

“…Restrictions to population connectivity imposed by elevation and slope probably operate on deeper timescales than those related to land use/cover. Recent phylogeographic studies have shown that the Iberian Central System has acted as an historical barrier to gene flow in the two species, separating different evolutionary groups north and south of this mountain range (Gutiérrez‐Rodríguez, Barbosa, & Martínez‐Solano, ,b). These groups would have experienced limited connectivity during the Last Glacial Maximum (21 ka), as glacial areas occupied lower altitudes around 1,350 m in the study area (Bullón, ).…”

Geology and paleontology of Tresjuncos (Cuenca, Spain), a new diatomaceous deposit with Konservat-Lagerstätte characteristics from the European late Miocene

“…Their Quaternary changes and climatic favorability have recently been analyzed, particularly for Pelobates cultripes (Lobo et al 2016;Gutiérrez-Rodríguez et al 2017). …”