Gene flow and genetic structure of a mountain riparian tree species, Euptelea pleiospermum (Eupteleaceae): how important is the stream dendritic network?

Abstract

Riparian landscapes are dendritic in nature. However, much attention on genetic structure of riparian plants has been paid to linear models of connectivity while studies that investigate the influence of dendritic landscape are scarce. In this study, we used nuclear microsatellite markers to investigate genetic diversity, gene flow, and genetic structure of a streamside tree species (Euptelea pleiospermum) in a natural stream dendritic network in the Shennongjia Mountains, central China. We tested the following hypotheses: (1) genetic diversity is higher at confluence than that at headwater populations and (2) genetic structure within the stream dendritic network was determined by in-stream dispersal or out-of-stream dispersal. Contrary to our prediction, we found that both genetic diversity and effective population size are congruent at headwater and confluence populations. We found symmetrical gene flow in most (four out of six) headwater-confluence pairs and asymmetrically downstream gene flow in the other two headwater-confluence pairs. Analysis of molecular variance (AMOVA) detected significant differentiation at two scales (among streams within catchments, among populations within stream) and did not reveal significant structure among catchments. STRU CTURE analysis clustered individuals from different catchments into the same genetically homogeneous group. There was no significant isolation by distance (IBD) with Euclidean, stream, or overland distance. Our results suggest that E. pleiospermum populations within the stream dendritic network did not present a hierarchical genetic structure probably because of extensive out-of-stream dispersal.

Tangled banks: A landscape genomic evaluation of Wallace's Riverine barrier hypothesis for three Amazon plant species

“…Animal‐mediated seed dispersal is considered the most prevalent dispersal syndrome for lowland rain forest tree plant species (Howe & Smallwood, ; Willson, Irvine, & Walsh, ). Although correlations of dispersal mode with levels of genetic structure for riverine plant species are weak (e.g., Fér & Hroudová, ; Nazareno, Dick, et al., ; Wei, Meng, Bao, & Jiang, ; Zellmer, Hanes, Hird, & Carstens, ), plant species that are animal‐dispersed tend to have lower levels of genetic structure than species dispersed by other syndromes (Collevatti et al., ; Fér & Hroudová, , ; Hamrick & Godt, ; Ray & Excoffier, ), slowing down population differentiation (Linhart & Grant, ).…”

Gene flow and genetic structure in Acacia stenophylla (Fabaceae): Effects of hydrological connectivity

“…In addition, most of these methods do not assess levels of effective dispersal, so inferences about gene flow cannot be confidently made. Numerous studies have used genetic markers such as microsatellites, demonstrating their effectiveness for examining genetic structure, dispersal and gene flow in riparian and aquatic plants of riverine ecosystems (Jacquemyn, Honnay, Looy, & Breyne, 2006;Wei, Meng, Bao, & Jiang, 2015).…”

“…Gornall, Hollingsworth, & Preston, 1998;Love, Maggs, Murray, & Provana, 2013), several have not (e.g. Markwith & Scanlon, 2007;Ritland, 1989;Wei et al, 2015), often citing sporadic upstream dispersal via anemochory or zoochory as the reason downstream increases in diversity are absent (Honnay, Jacquemyn, Nackaerts, Breyne, & van Looy, 2010). Several alternative models depict linear patterns of gene flow and dispersal in plants of riverine systems (e.g.…”

Genetic analysis suggests extensive gene flow within and between catchments in a common and ecologically significant dryland river shrub species; Duma florulenta (Polygonaceae)

“…However, while rivers can generally be considered linear at a reach scale, at catchment and basin scales, rivers are a hierarchical network of tributaries and main river channels (Fagan, ). Recent research regarding the genetics of riparian plant populations reflects this by investigating nonlinear patterns that occur within river networks (Cushman et al, ; Prentis & Mather, ; Wei, Meng, Bao, & Jiang, ).…”

“…However, while rivers can generally be considered linear at a reach scale, at catchment and basin scales, rivers are a hierarchical network of tributaries and main river channels (Fagan, 2002). Recent research regarding the genetics of riparian plant populations reflects this by investigating nonlinear patterns that occur within river networks (Cushman et al, 2014;Prentis & Mather, 2008;Wei, Meng, Bao, & Jiang, 2015). The stream hierarchy model (SHM) was originally developed to describe patterns of genetic structure in desert fishes and describes a situation in which an organism is restricted to dispersal within the river corridor (Meffe & Vrijenhoek, 1988).…”