Multiple-scaled spatial genetic structures of Fraxinus mandshurica over a riparian–mountain landscape in Northeast China

Abstract

Landscape genetics increasingly focuses on the way in which landscape features cause the fragmentation of lineages of terrestrial organisms. However, landscape features can also provide functional connectivity or corridors, enhancing the dispersal of plant populations, particularly the case in riparian habitat. Unfortunately, recent research in tree genetics has paid little attention to this role. To examine the possible effects of landscape connectivity on the current population genetic distribution of Fraxinus mandshurica and to provide insights into conserving the local genetic diversity for this endangered tree species, we used nine nuclear microsatellite loci to examine the spatial genetic structure of F. mandshurica at multiple-scales over a riparian-mountain landscape in Northeast China. F-statistics indicated that the magnitude of among-population genetic differentiation was significantly higher between the riparian and mountain habitats than within the riparian habitat. Spatial analysis of molecular variance and principal coordinate analysis consistently revealed that this species exhibited a clear landscape genetic structure between the riparian and mountain habitats, despite no significant isolation by distance pattern being identified by the Mantel test. Spatial autocorrelation analysis further demonstrated significant, positive fine-scale spatial genetic structure among individuals over short distances (\80 m) in each mountain population. Conversely, no spatial genetic structures were identified within and among the riparian populations. Overall, the results suggest that seed dispersal is very low among mountain populations; however seed transport is probably enhanced by a secondary phase of hydrochory (water-dispersal) among riparian populations during flooding. Despite this, there was no significant accumulation of genetic diversity in downstream populations along the main channel. This result suggests that hydrochory is not sufficient to produce a clear unidirectional gene flow along the water course, although it may impede the development of spatial genetic structuring within and among riparian populations.

Gene Flow within and between Catchments in the Threatened Riparian Plant Myricaria germanica

“…We found substantial population subdivision between and within rivers; this result is similar to what was found in other studies of riparian and aquatic shrubs or herbs [7], [24], [27], [38]–[40]. Our study species exhibited far more population subdivision than two wind-pollinated riparian tree species [34], [41]. We attribute this difference partly to efficient pollen dispersal by wind in these trees, increasing gene flow between populations.…”

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

“…By studying an aquatic plant (e.g., Nuphar lutea), Fér and Hroudová (2008) Fig. 3 Unrooted neighbor-joining tree based on Nei's genetic distance (Nei et al 1983) (Hu et al 2010). This indicates that upstream dispersal can offset the potential water-mediated downstream dispersal.…”

Landscape-Scale Genetic Structure of Wild Rice Zizania latifolia: The Roles of Rivers, Mountains and Fragmentation

“…In this situation, it is difficult to predict the genetic structure of riparian species when the competing factors (rivers, mountains and fragmentation) might work together on historical or current dispersal of seeds or vegetative propagules. The consequences of fragmentation in riparian-mountain habitats are less well understood, though previous researches are available for a few streamside tree species (Hu et al, 2010;Wei et al, 2013). In the example of the streamside tree, Euptelea pleiospermum Hook.…”