Genetic diversity of Kobresia pygmaea populations along a grazing gradient.

Abstract

Aims Our objective was to explore differences in genetic diversity of Kobresia pygmaea populations related to grazing intensity to help prevent grassland degradation and contribute to ecology,genetics and evolutionary ecology. Methods We randomly selected tender leaves from 25 K. pygmaea individuals from four populations along a gradient of grazing intensity,used SRAP (Sequence-related amplified polymorphism) molecular markers,and examined the genetic diversity of the populations to determine the effect of grazing disturbance. Important findings We used 20 primers and produced 448 clear bands,376 (83.93%) of which were polymorphic. With increased grazing intensity,the percentage of polymorphic loci,Nei's genetic diversity index and Shannon information index of the K. pygmaea populations decreased. Total genetic diversity (Ht) of the four populations under different grazing intensities was 0.276 6,genetic diversity within the four populations (Hs) was 0.243 6,genetic differentiation coefficient among populations (Gst) was 0.119 4 and gene flow (Nm*) was 1.843 4. With increased grazing intensity,Gst increased and gene flow decreased. Therefore,grazing increased genetic the differentiation coefficient among populations,restrained gene transfer among populations and promoted population gene differentiation. The genetic distance of the four populations with different grazing intensities was small; however,with increased grazing intensity,genetic distance slowly increased and genetic consistency among populations decreased. The UPGMA dendrogram constructed by genetic distance arrayed the four populations in order of increasing grazing pressure.