Multiple spatial scale patterns of genetic diversity in riparian populations ofAinsliaea faurieana(Asteraceae) on Yakushima Island, Japan

Abstract

Habitat and geographical features of river systems strongly influence gene flow and spatial genetic patterning in riparian plant populations. We investigated the patterns of genetic diversity within and among populations of Ainsliaea faurieana relative to different spatial conditions (along a river, among rivers, and among regions on an island), based on nuclear and chloroplast microsatellite DNA variations. Within an individual river system, we found higher haplotype diversities in downstream populations, and in a Bayesian analysis of recent migration, we detected unidirectional gene movements from upstream to downstream, indicating water-mediated dispersal along the river. Mantel tests detected no isolation-by-distance in genetic variation, suggesting the maintenance of a metapopulation with wide-range seed dispersal by water. Moreover, the observed high level of genetic differentiation, especially in the cpDNA (F(ST) = 0.539), indicated a metapopulation structure with frequent extinction and colonization. On a larger scale, we found high population differentiation and clear genetic structuring among regions, suggesting that gene flow was restricted by geographical features (mountains separating river systems) for relatively long periods. Our findings of genetic structures based on different spatial conditions elucidated patterns and ranges of historical and contemporary gene movement in a plant species that is persistent in extremely disturbed riparian environments.

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

“…4a, c). Lack of IBD is also considered as evidence for long-distance dispersal for riparian or aquatic plants (Pollux et al 2009;Mitsui et al 2010). However, at a larger scale, we showed a significant correlation between genetic distance and Euclidean distance for E. pleiospermum across the whole Shennongjia Mountains (Wei et al 2013).…”

“…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).…”

Recent origin and adaptive diversification of Ainsliaea (Asteraceae) in the Ryukyu Islands: molecular phylogenetic inference using nuclear microsatellite markers

“…In addition, the two rheophytic species, A. linearis and A. oblonga, showed lower within-population diversity compared to the inland relatives distributed on the same drift, resulting in the loss of alleles due to strong disturbances in flooded habitats (Mitsui et al 2010).…”

Population genetic diversity and structure within and among disjunct populations of Alnus maritima (seaside alder) using microsatellites

“…Alnus maritima experiences both periodic flooding and has hydrochorous seed dispersal. Several authors have reported a lack of IBD in riparian plant species (Mitsui et al 2010;Honnay et al 2010;DeWoody et al 2004). Therefore, explaining the effects of distance on genetic structure in this riparian system requires further study.…”

“…However, the data also highlight the inherent limitations of IBD analyses which are based on Euclidian distances and assumes island and stepping stone models that are too simple to account for the complexity of certain landscapes (Jenkins et al 2010). This is particularly true of dynamic riparian habitats, which can have variable geography over time, are susceptible to periodic flooding (Mitsui et al 2010), and, in species with hydrochorous seeds, long distance dispersal in a single direction away from the maternal tree (Mitsui et al 2010;Honnay et al 2010;Kudoh and Whigham 1997). Alnus maritima experiences both periodic flooding and has hydrochorous seed dispersal.…”