Phylogeography of the Komodo monitor <em>Varanus komodoensis </em>(Reptilia: Varanidae) inferred from mitochondrial DNA Control Region I and the implications for <em>in situ </em>management plans

Abstract

The Komodo monitor (<i>Varanus</i> <i>komodoensis</i>) is the largest living lizard in the world, which was discovered by scientists only about one hundred years ago. The wild populations of the Komodo monitor are restricted to five islands in the Lesser Sunda Islands, in southern Wallacea. The total population size is currently estimated to be just over 2,300 individuals, while habitat degradation that is associated with human activities seems to have accelerated the decrease in the population size over time. The Komodo monitor is now vulnerable to extinction in the near future. In order to help design conservation programmes for the Komodo monitor, I investigated the population genetic structure across the distribution range by applying a molecular phylogeographic approach. Eleven haplotypes were determined from a dataset of three hundred and sixty six mitochondrial DNA Control Region I sequences and the phylogenetic relationships among these maternal lineages formed two major clades, i.e. Western-Central and Eastern. On the other hand, the non-random geographic distribution of these haplotypes is consistent with the molecular partitioning among three regions, which I referred to as Western, Central, and Eastern. The Western region includes the island of Komodo and the Central region is composed of populations distributed on the islands of Rinca, Gili Motang, and Nusa Kode, as well as a population on the western coast of Flores. The Eastern region consists in a population on the northern coast of Flores. The level of genetic differentiation among these regions is relatively high and it seems to be maintained by a process of isolation. Geographic distance and seawater seem to be the barriers for the dispersal of the terrestrial Komodo monitor. In particular, an increased distance between islands may become a more effective barrier adding to the isolation of those populations in three regions. Nevertheless, there seems to be some signatures of dispersal among islands during the periods of low sea level in the Pleistocene. A few haplotypes are shared among islands, and genetic divergence analyses indicated a time frame within the mid-Pleistocene, about 1.3 million years ago. Based on the genetic structure of three regions revealed in this study, I proposed three Management Units for conservation. These units may be applied to identify a population source for an augmentation programme, while they are aimed at maintaining the level of genetic diversity and the associated evolutionary history that have shaped the current population structure in the Lesser Sunda Islands.