Gene flow in an endangered willow Salix hukaoana (Salicaceae) in natural and fragmented riparian landscapes

Abstract

Salix hukaoana is an endangered riparian pioneer tree that is distributed within a restricted area of Japan. Microsatellite genetic variations and genetic structures were investigated in 80 subpopulations patchily distributed within five river basins with varying degrees of habitat fragmentation. The correlation between geographic distance and genetic distance based on the Bayesian assignment test was significant across relatively intact riparian habitats, with steeper slopes of regression for more densely grouped subpopulations, suggesting restricted gene flow. However, the correlation became less apparent with increasing spacing of the habitat patches. These contradictory results are attributed to the increased chance of long-distance dispersal of sexual propagules among more isolated habitat patches. The observed accumulation of genetic diversity with increasing distance downstream along a few, but not all, of the rivers and the results of assignment tests suggested a downstream directionality of gene flow. The results of this study illustrate the patterns of genetic diversity and contemporary dispersal of S. hukaoana, and provide important insights into understanding the gene dispersal of riparian trees and into the conservation of genetic resources for this species.

Reproduction and diversity of the endangered Salix lapponum L. populations in Eastern Poland

“…Although the expected heterozygosity (H e ) ranged from 0.143 (population B) to 0.187 (population M) and these values were quite similar to the results obtained in other studies using dominant markers (Smulders, 2008;Sochor et al, 2013), they were still lower in comparison to codominant markers (Kikuchi et al, 2011;Lee et al, 2011;Sochor et al, 2013). Nybom (2004) stated that H e of endemic and peripheral populations should be greater than 0.20, but at the same time she pointed out that heterozygosity is lower for species whose seeds disperse and germinate close to maternal plants, which was observed in the studied populations of S. lapponum.…”

The influence of landscape, climate and history on spatial genetic patterns in keystone plants (Azorella) on sub‐Antarctic islands

“…Consistent with this expectation, A. selago populations in the southeast of Marion Island have the highest levels of genetic diversity. Similar patterns of genetic accumulation have been reported for plants and invertebrates that are unidirectionally dispersed via waterways, with downstream populations typically containing higher genetic diversity than their upstream counterparts (Alp, Keller, Westram, & Robinson, ; Kikuchi, Suzuki, & Sashimura, ). To the best of our knowledge, this has not yet been demonstrated for wind‐dispersed species.…”

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

“…Although the influences of water-mediated downstream dispersal on genetic diversity of riparian plant species along linear habitats have been well studied (Tero et al 2003;Liu et al 2006;Kikuchi et al 2009;Mitsui et al 2010), few studies have been conducted to test whether confluence is a sink of genetic diversity from coterminous headwater populations (Baguette et al 2013). Here, we provide a unique empirical study to test the hypothesis that confluence populations harbor higher genetic diversity of riparian plants as compared to headwater (Morrissey and de Kerckhove 2009).…”