In this situation, the effective gene flow is reduced as a consequence of local adaptation, resulting in a pattern of isolation by adaptation/environment (IBA or IBE 11), or monopolization under the influence of founder effects (IBM 4, 12). When ecological characteristics of habitats are dissimilar among natural populations, the probability of successful establishment of immigrants or their offspring may reduce. It can also deepen our understanding of how landscape variables affect dispersal and gene flow and shape patterns of genetic variation in nature 5, 7.įor aquatic plants, given that they live in fragmented islands in terrestrial landscapes, severe genetic differentiation by geographic isolation may be common 8, 9, representing an increasing genetic differentiation among populations with increasing geographic distance, as a result of reduced gene flow (isolation by distance, IBD 10). Recent advances in molecular ecology and landscape genetics make it feasible to dissect the independent roles of landscape features on population genetic differentiation 4, 5, 6. Environmental variables can influence the movement of gametes, individuals and groups of individuals among natural populations to affect gene flow patterns 1, which may have a profound influence on the spatial and temporal distribution of genetic variation and further, evolutionary progress of natural populations 2, 3. Understanding how natural processes affect population genetic structures and gene flows is an important issue in evolutionary biology. spicatum under a steep environmental gradient in the alpine landscape as a result of dispersal limitation and genetic drift. Our findings suggested the dominant role of geography on the evolution of M.
Both tests and MMRR revealed a significant and strong correlation between genetic divergence and geographic isolation under the influence of environmental heterogeneity at the overall and finer spatial scales. Two genetic clusters corresponding to the QTP and YGP were identified. The genetic isolation by geographic distance (IBD) was tested by Mantel tests and the relative importance of environmental variables on population genetic differentiation was determined by a partial Mantel test and multiple matrix regression with randomization (MMRR). Bioclim layers, hydrological properties and elevation were considered as environmental variables and reduced by principal component analysis. In this study, we examined the spatial genetic variation of thirteen Myriophyllum spicatum populations from the Qinghai-Tibetan Plateau (QTP) and adjacent highlands (Yunnan-Guizhou Plateau, YGP) by using microsatellite loci and environmental and geographical factors. One effective method is to assess the relative importance of environmental and geographical factors in the genetic structure of populations. Understanding how natural processes affect population genetic structures is an important issue in evolutionary biology.
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