Comparative analysis of spatial genetic structures in sympatric populations of two riparian plants, Saxifraga acerifolia and Saxifraga fortunei

Abstract

Premise The genetic structure between plant populations is facilitated by the spatial population arrangement and limited dispersal of seed and pollen. Saxifraga acerifolia, a local endemic species in Japan, is a habitat specialist that is confined to waterfalls in riparian environments. Its sister species, Saxifraga fortunei, is a generalist that is widely distributed along riverbanks. Here, we examined sympatric populations of the two Saxifraga species to test whether the differences in habitat preference and colonization process influenced regional and local genetic structures. Methods To reveal genetic structures, we examined chloroplast microsatellite variations and genome‐wide nucleotide polymorphisms obtained by genotyping by sequencing. We also estimated the gene flow among and within populations and performed landscape genetic analyses to evaluate seed and pollen movement and the extent of genetic isolation related to geographic distance and/or habitat differences. Results We found strong genetic structure in the specialist S. acerifolia, even on a small spatial scale (<1 km part); each population on a different waterfall in one river system had a completely different predominant haplotype. By contrast, the generalist S. fortunei showed no clear genetic differentiation. Conclusions Our findings suggest that the level of genetic isolation was increased in S. acerifolia by the spatially fragmented habitat and limited seed and pollen dispersal over waterfalls. Habitat differentiation between the sister taxa could have contributed to the different patterns of gene flow and then shaped the contrasting genetic structures.

Phylogeographic analysis reveals extensive genetic variation of native grass Elymus nutans (Poaceae) on the Qinghai-Tibetan plateau

“…Nevertheless, it is imperative to acknowledge that the Shannon information index ( I ) recorded for the E. nutans population ( I = 0.46) was significantly elevated in comparison to that of E. breviaristatus ( I = 0.13), underscoring a distinctive and intriguing pattern of genetic diversity. As a species with an extensive distribution, E. nutans demonstrates a more homogeneous allele distribution, potentially attributed to its propensity to sustain larger population sizes and engage in more substantial gene flow across various populations ( Magota et al., 2021 ). Conversely, the endangered status of E. breviaristatus may exert limitations on gene flow and genetic exchange, culminating in a diminished Shannon’s information index ( I ).…”