Effects of Land Use and Climate Change on Gene Flow of Taxus wallichiana Zucc. (Taxaceae) in Nepal

Abstract

This research work was carried out in three regions and six valleys with different precipitation regimes in the southern slope of Nepal that included Manaslu Conservation Area, Sagarmatha National Park and buffer zone and Kanchenjunga Conservation Area. The extensive field work from 2011 to 2013 helped to record and collect herbarium specimens of Taxus wallichiana, with more than 812 individuals from six valleys (2200 m asl to 3450 m asl). The 454 pyro sequencing technique helped in development of ten microsatellite markers in a short period of time and was economic. The genetic diversity and differentiation were studied with the help of FSTAT, Arlequin, GenAlex and STRUCTURE software. The historic gene flow was studied in GeneClass software while the contemporary gene flow was studied with the help of Migrate-n software for the first time using adult as well as seed data. The anthropogenic, geographic (altitude and latitude) as well as climatic variables (temperature, precipitation and humidity) have played an important role in genetic divergence among population of Taxus wallichiana in the study area within the Nepal Himalaya. This study determined a high genetic diversity in one of the study sites and regional differentiation among the study sites. The overall pairwise FST showed a high level of population differentiation. The gene pools (clusters) inferred in the study has different patterns with respect to latitude, FST, altitudinal distribution and allelic richness, temperature, precipitation and humidity. Population subdivision in Taxus wallichiana in the study area was shaped by altitude and land-use types. The distribution of gene pools was influenced by altitude, land-use type, bioclim variables (annual temperature, precipitation), as well as air humidity. These information revealed from data suggested the gene flow in Taxus wallichiana will be influenced by climate change, land-use change, altitude and precipitation. Species distribution model predicted a relatively large area of occupancy despite of the low population density of Taxus wallichiana which was encountered in the field. It was found that the livelihood of people was related with this species in the study sites. This study will help to develop strategies for the conservation and management of Taxus wallichiana in the Nepal Himalaya.