Population genetics and structure of the Sumatran tiger

Abstract

The two key determinants of population persistence in fragmented landscapes are population size and connectivity. Populations with high levels of genetic variation and large population size are expected to have a lower risk of extinction. Similarly, populations with high rates of connectivity are expected to persist long-term. For many elusive landscape species it is difficult to obtain direct estimates of these parameters, but genetic sampling can offer powerful indirect assessments. Whilst these techniques have been applied to the study of many wide-ranging carnivores, this study represents the first example in the Sumatran tiger (Panthera tigris sumatrae). Extensive field surveys were conducted to collect faecal samples from several Tiger Conservation Landscapes and protected areas on Sumatra. Samples were then processed according to optimised protocols to obtain reliable results. In order to quantify extinction risk I first estimated genetic variation and effective population size using microsatellite loci. I also determined relative levels of connectivity using estimates of differentiation (FST), gene flow and genetic clustering. Results indicate that Sumatran tigers have high levels of genetic variation and that their effective population size is within the expected range. There is very little population structure and there is no obvious evidence for barriers to dispersal. The Batang Hari/Kerinci Seblat ecosystem emerged as a potential source population and in contrast there was some evidence of isolation affecting the population of Way Kambas NP in the extreme south of the island. Overall, despite high levels of human land cover conversion over the past 20-30 years, few genetic changes have been expressed in the Sumatran tiger. The immediate threat to tigers is not the loss of genetic diversity, but the rapidly declining area of suitable habitat in which they can survive.