Mexico is a center of diversification for the genus Quercus, with an important number of taxa occurring along the Trans-Mexican Volcanic Belt (TMVB). However, the impact of the interaction between historical and current climatic variation and geological heterogeneity in the TMVB on the genetic and phenotypic diversification within oak species has been scarcely investigated. We used chloroplast DNA microsatellites and a geometric morphometrics analysis of leaf shape to understand differentiation between populations of Quercus deserticola, which inhabits dry highlands along the TMVB.Ecological niche modeling (ENM) for present-day conditions and projections into past scenarios were performed to evaluate the influence of environmental variables on the evolutionary history of the species. Results showed high genetic diversity (h S =0.774) and high genetic structure (R ST =0.75) and the morphological subdivision of populations into two clusters, corresponding to the west/south and east/north sectors of the Q. deserticola geographic distribution. ENM indicated that the potential distribution of the species has remained similar from the late Pleistocene to the present. Seemingly, the phylogeographic structure of the species has been shaped by low seed-mediated gene flow and mostly local migration patterns. In turn, leaf shape is responding to climate differences either through phenotypic plasticity or local adaptation. is a volcanic mountain chain with nearly 8000 volcanic structures, extending about 1200 km west to east through central Mexico, from the Pacific coast to the Gulf of Mexico coast. Furthermore, the TMVB has a large environmental heterogeneity and has experienced important climatic changes from the Pliocene and Pleistocene to the present (Gómez-Tuena et al. 2007; Ferrari et al. 2012). Based on age, orogeny and tectonic features, the TMVB has been divided into four sectors (western, central, eastern and easternmost), each with its own characteristics (Gómez-Tuena et al. 2005; Ferrari et al. 2012). The TMVB has also been considered as a complex biogeographic unit (i. e. it shows a high degree of species endemism and diversity), with two sectors, west and east (Gámez et al. 2012;Torres-Miranda et al. 2013). Four main episodes of volcanic activity of the TMVB have occurred during different periods from the early Miocene to the present, affecting this region asynchronously, first the western and later the eastern sectors (Gómez-Tuena et al. 2005; Gámez et al. 2012; Ferrari et al. 2012).Several studies have found that the physiographic context of the TMVB has been important in the genetic structuring and phenotypic divergence of different species and how climatic and geologic events have modified their distributions in various time periods (Jaramillo-Correa et al. 2008; Gámez et al. 2012;Ruiz-Sánchez and Specht 2013;Torres-Miranda et al. 2013; Mastretta-Yanes et al. 2015; Rodríguez-Gómez and Ornelas . The TMVB has been shown to be a geographic barrier that limits the dispersion of plants and animals tha...
Aim:The extent of genetic diversity and its distribution among populations have been associated with species attributes such as mating system, dispersal ability and geographic range size. Another attribute that could contribute to intraspecific phylogeographic patterns is niche breadth, but this has rarely been tested. Here, we ask whether a Mexican oak with a comparatively narrow climatic niche breadth has distinct genetic diversity patterns compared to other codistributed oaks with a broader climatic niche. Location: Mexico.Taxon: Quercus glaucoides M. Martens & Galeotti (Fagaceae).Methods: Descriptors of genetic diversity and structure were calculated for 21 Q. glaucoides populations using chloroplast DNA (cpDNA) and nuclear microsatellites (nSSRs).Historical demographic dynamics were inferred with approximate Bayesian computation (ABC) and past potential distribution models. To test for an association between niche breadth and phylogeographic patterns, we used genetic diversity and differentiation values of Q. glaucoides plus those previously published for 10 other Mexican oak taxa. Niche breadth was estimated for all taxa and linear regressions were performed.Results: Genetic diversity calculated from nSSRs (H O = 0.539; H E = 0.714) was among the lowest and cpDNA differentiation (N ST = 0.88) was the highest so far obtained for comparable Mexican oaks. Moderate changes in demographic size and distribution shifts throughout the last glacial cycle were inferred, explaining some of the observed genetic patterns. A positive correlation of H O and a negative correlation of N ST with niche breadth were detected across taxa.Main Conclusions: Distinct phylogeographic patterns in Q. glaucoides could be explained because a narrower niche may cause lower historical effective population sizes and more fragmented distributions in comparison to species with a wider niche breadth, even with similar range sizes. Our results indicate that niche breadth would be an interesting ecological attribute to be included in future comparative phylogeographic studies.
Background: Glacial periods during the Pleistocene have been hypothesized to have greatly influenced geographical patterns of genetic structure and demography of many tropical species. The Glacial Refugium Hypothesis proposes that, during cold, dry glacial periods, populations of moisture-affinities tropical species were restricted to sheltered, humid areas and that, during warmer and more humid interglacial periods, these populations expanded. Some mountain regions in the tropics acted as refugia during the cold, dry periods of the Pleistocene for several temperate forest taxa, which recolonized the humid areas farther north during the interglacial periods.Questions: (1) Did Late Pleistocene-Holocene climate changes affect the historical demophraphy of Zamia prasina? (2) Does the historical distribution of Zamia prasina agree with the Glacial Refugium Hypothesis?Study species: Zamia prasina W.Bull. (Zamiaceae), the only cycad native to the Yucatan Peninsula Biotic Province (YPBP). Methods: Five individuals were collected in 23 populations and characterized using two DNA regions: plastid atpF-atpH, and nuclear ITS2. Genetic diversity, phylogeographic structure, historical demography, and potential distributions were assessed. Results: Our results showed moderately high genetic diversity and low, but significant, phylogeographic structure. Two genetic groups were identified, one in the eastern part of the Peninsula, the other in the western. The changes in historical demography suggest that Z. prasina experienced a population expansion following the warm conditions of the Holocene.Conclusions: The population dynamics of Zamia prasina are in accordance with the Glacial Refugium Hypothesis.
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