Diversity And Distribution Pattern Of Amphibians In Mahakali River Basin, Far-Western Nepal

Abstract

Amphibian diversity along elevation gradient in Nepal has rarely been studied. This is the first study in Mahakali River basin along elevation gradient for amphibian diversity. This study aimed to explore diversity, distribution pattern and body size variation of amphibians along elevation gradient, in Mahakali River basin. Time-constrained visual encounter survey was conducted for data collection. Different environmental variables were measured along each transects. Body size of individuals were measured on the field and released at the site of capture. A total of 17 species of amphibians belonging to six families and one order i.e., Anura were recorded and Dicroglossidae family was dominant among them. Shannon wiener diversity index of overall study area; H = 2.436 and evenness E = 0.672 was found. Study showed that amphibians were not uniformly distributed along elevation gradient. Linear regression model showed both species richness and species abundance was declined monotonically along elevation gradient. Similarly, diversity and mean abundance of different habitat was calculated. Highest species diversity was found in forest habitat. Influence of environmental variables on amphibian species distribution was examined; main factors responsible for amphibian species distribution were elevation, temperature and humidity. Body size of two families; Bufonidae and Dicroglossidae along elevation gradient increased with increasing elevation; followed Bergmann’s rule. Body size of individuals belonging to Microhylidae was decreased with increasing elevation. That means all amphibians do not follow Bergmann’s rule. It is concluded that amphibians portrayed narrow distribution range along elevation gradient and with environmental variables such as temperature and elevation.