Extent and pattern of genetic differentiation within and between phenotypic populations of Leymus chinensis (Poaceae) revealed by AFLP analysis

The extent and pattern of genetic differentiation between two naturally occurring phenotypes, grey-green leaf (GGL) and yellow-green leaf (YGL), of Leymus chinensis (Trin.) Tzvel., which colonize distinct habitats in the Songnen Prairie in northeast China, were investigated by amplified fragment length polymorphism (AFLP) analysis. Twelve selected AFLP primer pairs amplified 593 reproducible hands, of which 148 (24.96%) were polymorphic among 69 individuals taken from three populations: two natural ones (YGL and GGL1) and one transplanted (GGL2). Cluster analysis based on the AFLP data categorized the plants into distinct groups that are in line with their phenotypes and population origins, thus denoting clear genetic differentiation between the two phenotypes. This, together with their adaptation to contrasting natural habitats, suggests that the two phenotypes probably represent stabilized ecotypes. The grouping was supported by multiple statistical analyses including Mantel's test, principal coordinate analysis (PCOORDA), and analysis of molecular variance (AMOVA). The GGL phenotype harbors a higher level of within-population genetic diversity than YGL, possibly reflecting selection by habitat heterogeneity. Although GGL2 is largely similar to its original population (GGL1), further diversification since transplantation was evident. Sequence analysis of a subset of phenotype-specific or phenotype-enriched AFLP hands implicated diverse biological functions being involved in ecological adaptation and formation of the two phenotypes.