Abstract
Understanding the processes underlying spatial patterns of genetic diversity and structure of natural populations is a central topic in evolutionary biogeography. In this study, we combine data on ancient and contemporary landscape composition to get a comprehensive view of the factors shaping genetic variation across the populations of the scrub‐legume grasshopper (Chorthippus binotatus binotatus) from the biogeographically complex region of southeast Iberia. First, we examined geographical patterns of genetic structure and employed an approximate Bayesian computation (ABC) approach to compare different plausible scenarios of population divergence. Second, we used a landscape genetic framework to test for the effects of (1) Late Miocene paleogeography, (2) Pleistocene climate fluctuations, and (3) contemporary topographic complexity on the spatial patterns of population genetic differentiation. Genetic structure and ABC analyses supported the presence of three genetic clusters and a sequential west‐to‐east splitting model that predated the last glacial maximum (LGM, c. 21 Kya). Landscape genetic analyses revealed that population genetic differentiation was primarily shaped by contemporary topographic complexity, but was not explained by any paleogeographic scenario or resistance distances based on climate suitability in the present or during the LGM. Overall, this study emphasizes the need of integrating information on ancient and contemporary landscape composition to get a comprehensive view of their relative importance to explain spatial patterns of genetic variation in organisms inhabiting regions with complex biogeographical histories.
Highlights
Understanding the mechanisms that shape spatial patterns of genetic diversity and structure is a central topic in evolutionary biogeography (Habel et al, 2015; Peterman, Connette, Semlitsch, & Eggert, 2014; Yannic et al, 2014)
Ancient geological changes are known to underlie the spatial patterns of genetic divergence found in several organisms (Abellán, Arribas, & Svenning, 2012; Cheng et al, 2016; Opell, Helweg, & Kiser, 2016; Ortego, Bonal, Cordero, & Aparicio, 2009), in many other cases the genetic signals left by paleogeological events are expected to have been totally or partially eroded as a result of gene flow promoted by subsequent landscape changes (Graham, Hendrixson, Hamilton, & Bond, 2015; Pepper et al, 2008)
topographic complexity (TC) resistance distance indicated that the potential distribution of the species is more fragmented in the present than during the LGM, a pattern congruent with the increased population connectivity during glacial periods inferred for many other montane species from temperate regions (Blanco- Pastor, Fernández-Mazuecos, & Vargas, 2013; Velo-Antón et al, 2013)
Summary
Understanding the mechanisms that shape spatial patterns of genetic diversity and structure is a central topic in evolutionary biogeography (Habel et al, 2015; Peterman, Connette, Semlitsch, & Eggert, 2014; Yannic et al, 2014). The magnitude and complexity of these paleogeological and climate events are considered the most important engines of diversification and genetic structuring of many taxa in the region (Andújar, Gómez-Zurita, Rasplus, & Serrano, 2012; Faille, Andujar, Fadrique, & Ribera, 2014; Fromhage, Vences, & Veith, 2004) For all these reasons, southeast Iberia is an ideal template for testing the combined effects of ancient and more contemporary climate and landscape changes on spatial patterns of genetic diversity and structure of local populations (Faille et al, 2014). In southeast Iberia, the host plants (primarily Erinacea anthyllis and, more occasionally, Echinospartum boissieri, Genista versicolor, and Ulex parviflorus) form scattered vegetation patches located at moderate to high elevations (>1,200 m.a.s.l.) This fact restricts the distribution of the scrub-legume grasshopper to the different mountain ranges of the region (Prebetic, Penibetic and Subbetic systems) (Defaut, 2011; FIGURE 1 Scrub-legume grasshopper (Chorthippus binotatus binotatus), the study organism. We (3) tested the hypothesis predicting more genetic diversity in populations from areas with high past and present climate suitability and stability since the LGM
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