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
