Population Genetic and Ecological Studies of the Bornean Endemic Cox’s Leaf-nosed Bat (Hipposideridae: Hipposideros coxi) in Sarawak

Praveena, Rajasegaran (2019) Population Genetic and Ecological Studies of the Bornean Endemic Cox’s Leaf-nosed Bat (Hipposideridae: Hipposideros coxi) in Sarawak. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

The endangered Cox’s Leaf-nosed bat, Hipposideros coxi, is known as a rare Bornean endemic species which are currently known as geographically disjunct population that are distributed in Northern region and Southwest region in Sarawak, Borneo. This study looked into the i) ecology, echolocation, physiology and dietary preferences together with ii) population genetic; gene flow and genetic structure of H. coxi in Sarawak. Little is known about the population size, abundance and trend of this endemic species; therefore, the ecological survey was conducted to study their distribution and ecological behaviour in six areas across Sarawak. Roost survey revealed an approximate of 34 individuals from three caves (Bako National Park, Gunung Mulu NP, and Wind Cave Nature Reserve). Their roost exhibit microclimate variation that influenced greatly by the number of individuals at the roosting sites, where H. coxi roost with more individuals showed higher temperature. Echolocation analysis revealed a marked difference of 5 kHz in peak frequency between the Northern region population (50.0 ± 0.18 kHz) and Southwestern region populations (45.3 ± 0.56 kHz). This variation further correlates with their morphological features, where the higher call frequency from Northern region having lighter body mass (8.75 ± 0.96 g) compared to Southwest population that exhibit lower call frequency but larger body mass (9.4 ± 0.44 g). The activity pattern recorded from three caves revealed that their emergence variation was influenced by the timing of sunsets and sunrise. Hipposideros coxi population from Northern region emerge earlier before sunsets, whereas, the population from Southwest region emerge approximately 5 to 10 minutes pass the sunsets. Analysis of diet preferences identified seven insects’ orders (Coleoptera, Lepidoptera, Hemiptera, Diptera, Hymenoptera, Trichoptera and Odonata) from the stomach content indicating that H. coxi is a generalist feeder. The gene flow and genetic structure based on 25 samples of H. coxi populations in Sarawak were revealed using concatenated mitochondrial DNA Cytochrome-b and partial D-loop gene. Phylogenetic analyses resulted in two major splits according to the sites that fall into two geographic groups (Northern regional group - Gunung Mulu NP; Southwestern regional group - Bako NP, Mount Penrissen, Tanjung Datu, Wind Cave NR) The Northern population shows a genetic divergence of 4.2% from the Southwestern population (indicating a conspecific species group). Time scale divergence analyses showed the diversification of H. coxi lineage in Borneo occur ~9.02 Mya. The diversification within Southwestern region took place during Pleistocene epoch. The repeated glacial cycle may have formed the geographical barriers among population. Thus, resulted in fragmented population and cut off the gene flow among H. coxi population within Sarawak, Borneo. The absence of gene flow contributed to a pronounced genetic structure within the population indicating this species is reproductively isolated. Partitioning of genetic diversity using AMOVA revealed a major genetic differentiation among and within the populations. Finally, the population level genetic analysis divulged a multimodal distribution curve. Thus, suggest that the population have been affected by bottleneck event which was supported by positive neutrality test of Tajima’s D (2.09). Bayesian Skyline Plot analyses further supported the population expansion hypothesis. To conclude, this study revealed that there may be multiple other sites occupied by H. coxi that yet to be discovered. Microclimate data presented in this study are crucial in identifying the hotspot for this species occurrences. All this information on this endangered bat would be fundamental insights to conserve and manage this species form further declining. Keywords: Divergence, echolocation, molecular marker, microclimate, roost ecology

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