Niche conservatism is the tendency of species and clades to retain their niches and related ecological characteristics over time.The degree to which ecological niches are conserved carries implications for a range of ecological and evolutionary phenomena,from the role of ecology in speciation to the expected response by species to climatic changes.Gynandropaa (Dubois,1992) occurs in southwestern China (Sichuan,Yunnan and Guizhou provinces),northern Vietnam and Myanmar and presumably in intervening Laos.It has a low dispersal capability and shows a preference for living near moss-covered rocks in cold montane streams at the elevations of 1000-2800 m.The phylogeographic analyses showed that it contained three major clades (clade east,central and west),the estimated divergence time among them was in the period of the rapidest uplift of the Qinghai-Tibet plateau,and their divergence were probably caused by the changes of the old Red River system.Based on the representative coverage of occurrence sites of Gynandropaa from extensive field expeditions and literatures,we applied a series of geographic information system-based analyses to define the patterns of environmental variation within and among the clades,to remove potentially confounding effects of spatial autocorrelation in the environmental data due to allopatric ranges,and to build ecological niche models (ENM).Substantial environmental variation were detected among the three clades with most environmental variables showing a significant clade effect.However,clades east,central and west differed significantly from each other for six out of all 14 individual variables.Principal components analysis of the environmental variables identified four components (with eigenvalue>1) that collectively explain 82% of the observed variation among the three clades.Comparisons of the observed niche overlap values to simulated null distributions indicated that the hypothesis that any clade-pair of Gynandropaa is distributed in identical environmental space should be rejected,regardless of the measure of similarity used.Furthermore,both an ENM-based background similarity test and a niche space-based multivariate test provided evidence of a distinct niche shift in Gynandropaa.