Variation and Genetic Structure in Platanus mexicana (Platanaceae) along Riparian Altitudinal Gradient

Abstract

Platanus mexicana is a dominant arboreal species of riparian ecosystems. These ecosystems are associated with altitudinal gradients that can generate genetic differences in the species, especially in the extremes of the distribution. However, studies on the altitudinal effect on genetic variation to riparian species are scarce. In Mexico, the population of P. mexicana along the Colipa River (Veracruz State) grows below its reported minimum altitude range, possibly the lowest where this tree grows. This suggests that altitude might be an important factor in population genetics differentiation. We examined the genetic variation and population structuring at four sites with different altitudes (70, 200, 600 and 1700 m a.s.l.) using ten inter-simple sequence repeats (ISSR) markers. The highest value for Shannon index and Nei’s gene diversity was obtained at 1700 m a.s.l. (He = 0.27, Ne = 1.47, I = 0.42) and polymorphism reached the top value at the middle altitude (% p = 88.57). Analysis of molecular variance (AMOVA) and STRUCTURE analysis indicated intrapopulation genetic differentiation. The arithmetic average (UPGMA) dendrogram identified 70 m a.s.l. as the most genetically distant site. The genetic structuring resulted from limited gene flow and genetic drift. This is the first report of genetic variation in populations of P. mexicana in Mexico. This research highlights its importance as a dominant species, and its ecological and evolutionary implications in altitudinal gradients of riparian ecosystems.

High Genetic Diversity and Connectivity Among Populations of Quercus candicans, Quercus crassifolia, and Quercus castanea in a Heterogeneous Landscape in Mexico

“…The population genetic diversity of temperate forest species is spatially structured at different scales, from local (Holderegger & Wagner, 2008) to landscape (Ashley, Abraham, Backs, & Koenig, 2015; Sork et al., 2010) and continental (Petit et al., 2002; Wang et al., 2014; Wang, Zhang, Liu, Xu, & Liu, 2015) scales. At each scale, the ecological and genetic factors that structure the genetic diversity operate through environmental heterogeneity, species life history traits, and interactions with other organisms (Bacles, Lowe, & Ennos, 2004; Galván-Hernández, Lozada-García, Flores-Estévez, Galindo-González, & Vázquez-Torres, 2015; Honnay & Jacquemyn, 2007) determining the contemporary geographic distribution of the species.…”

“…The genetic connectivity among populations of a single species can be explained as a result of historical processes and physical barriers (e.g., mountain chains, large watercourses, or valleys) that influenced the dispersal routes (Manel & Holderegger, 2013; Sork & Waits, 2010) and the disruption of gene flow between populations at a regional scale (Galván-Hernández et al., 2015; Wang et al., 2015). Ecological traits, such as population density, pollen movement, and seed dispersal, determine the capacity of individuals to move through different environments and affect the reproductive success and population size (Breed et al., 2012; Craft & Ashley, 2010; O'Connell, Mosseler, & Rajora, 2006; Sagnard, Pichot, Vendramin, & Fady, 2011).…”

Morphological and genetic variations of Sophora davidii populations originating from different altitudes in the mountains of southwestern China

“…These mountainous ecosystems are associated with altitudinal gradients that can provide significant environmental variations (Galván-Hernández et al, 2015). Since mountainous regions exhibit a rugged topography and a complex pattern of vegetation, the migration of plants between populations can be hampered (Christoph et al, 2005).…”