High interpopulation genetic differentiation and unidirectional linear migration patterns in Myricaria laxiflora (Tamaricaceae), an endemic riparian plant in the Three Gorges Valley of the Yangtze River

Abstract

Myricaria laxiflora is restricted to the riverbanks of the Yangtze River valley and will be completely lost owing to the construction of the Three Gorges Dam. Genetic diversity and structure of nine natural and one ex situ populations were investigated using amplified fragment length polymorphisms (AFLPs). A moderate level of gene diversity was found in natural populations, while the ex situ population had the highest. The F statistics calculated by different approaches consistently revealed a high genetic differentiation among natural populations, contributing >45% of the total gene diversity. The Bayesian-based analysis differentiated nine independent populations in accordance with the sites sampled. Estimates of gene flow by F(ST) and coalescent-based simulation analysis indicated a restricted recurrent gene exchange among populations (Nm = 0.290-0.401), whereas genetic distance-based clustering and coalescent-based assignment analyses revealed significant genetic isolation among populations. The migration pattern in M. laxiflora is best explained by a classical metapopulation model, but with a unique unidirectional direction underlined by hydrochoric force that drove dispersal of seeds and propagules from upstream toward downstream populations. Previous efforts in preserving genomic integrity in ex situ conservation were evaluated, and the results provide valuable information to formulate conservation guidelines for successfully reintroducing M. laxiflora to the wild.

Rivers shape population genetic structure in Mauritia flexuosa (Arecaceae)

“…Rivers influence animal distributions such as birds (e.g., Fernandes, Wink, & Aleixo, 2012), frogs (Gascon, Lougheed, & Bogart, 1998), and mammals (e.g., Patton, Da Silva, & Malcolm, 2000) that disperse the seeds of palms and other plants. The impact of rivers on the genetic structure of other plants such as Myricaria laxiflora (Tamaricaceae; Liu, Wang, & Huang, 2006) has shown that water flow is a major driver of seed and propagule dispersal, and that migration patterns among populations can form along rivers, similar to what we found here in M. flexuosa . Other Amazonian studies have shown that the fruiting of tropical wetland plants occurs in the rainy season when rivers and other bodies of water are overflowed, enabling long‐distance fruit dispersal (De Campos, De Cedro, Tejerina‐Garro, Bayer, & Carneiro, 2013).…”

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

“…In contrast, riparian woody species that rely primarily on hydrochory for seed dispersal may exhibit significant accumulation of genetic diversity in downstream areas, reflecting clear unidirectional gene flow along the water course (e.g. Myricaria laxiflora in Yangtze River valley, China, Liu et al 2006). Thus, the contrasting results suggest that more empirical data are required to appreciate the extent to which dispersal by hydrochory affects the dynamics of gene flow and the genetic distribution of riparian woody species with different dispersal patterns along diverse river systems.…”

Diversity of endophytic fungi of Myricaria laxiflora grown under pre- and post-flooding conditions

“…Myricaria laxiflora is an endangered evergreen shrub that is distributed in the lowaltitude region of the Yangtze River valley (Liu et al, 2006;Wang et al, 2009). Due to longterm evolutionary adaptation to the natural dynamics of seasonally fluctuating water levels, M. laxiflorais capable of surviving prolonged immersion in water, for 3 to 5 months in summer Chen and Xie, 2009).…”

“…It was predicted that M. laxiflora would completely disappear following construction of the dam, as this would elevate water levels and cause year-round submergence of plants, and the entire natural habitat (Liu et al, 2006). For this reason, a number of studies were carried out to better understand morphological characteristics; natural distribution and habitat; coexisting plant community structure; ecological adaptability; and propagation methods, for the ex situ conservation for M. laxiflora (Wu et al, 1998;Wang et al, 2003).…”