Susan M. Tsang

RESEARCH and related projects

Pteropus alecto colony in Central Sulawesi
Biogeography and evolution of Pteropus
I am broadly interested in the phylogeography of Southeast Asian animals, particularly that of flying foxes (Chiroptera: Pteropodidae: Pteropus). Pteropus is an ideal focal taxon for Southeast Asian biogeographic studies because it is: 1) found everywhere in the region; 2) species-rich with several widespread species and many island endemics; and 3) relatively easy to sample. The species richness of Pteropus, their unique distributions, and their distinct life histories make them well-suited to investigating mechanisms of divergence using genetic data among populations or between species. My interest lies in addressing questions of how the complex nature of Southeast Asian geography and ecological niche affects distributions and speciation. Pteropusand Acerodon also consist of the world's largest bat species, yet this evolutionary departure in size from other chiropterans is not well-understood due to the lack of resolved phylogenies for use in trait evolution studies. Ultimately, findings related to population and species dynamics can be used for studying disease ecology of pathogens naturally hosted by flying foxes. These findings will also allow for a better understanding of species boundaries necessary for conservation management decisions. My work on this genus primarily focuses on the poorly known taxa from Southeast Asia, though I am open to collaboration regarding any aspect of Pteropus biogeography and evolution or pteropodid systematics.
Pteropus vampyrus on sale in the market in Lampung, Sumatra
Bat conservation
Logging and agricultural conversion of natural habitats are two of the leading factors causing biodiversity loss in Southeast Asia. In addition to anthropogenic development, large bats, such as Pteropusand Acerodon, face intense hunting pressure throughout their ranges. These fruit bats are often also targeted as agricultural pests and some species are hunted for sport. Mangrove loss has also led to a lack of undisturbed roosting sites for large colonies and increased the use of suboptimal roosting sites and smaller colony sizes. My conservation work primarily focuses on hunting of fruit bats in Sulawesi, Indonesia, but I have documented patterns of bat consumption throughout my research sites. In collaboration with local researchers, we seek to create grassroots initiatives to decrease demand for bat bushmeat and educate locals about the importance of bats for forest ecosystem services that they value. For more on other issues affecting bats, please visit the Southeast Asian Bat Conservation Research Unit website.

Additionally, I am working with Dr. Emily Rollinson on building models and spatial tools that would help better designate threat statuses, better identify species ranges, and study habitat requirements for species-area relationships. Ultimately, this would help provide tools for addressing questions of areas of endemism and species diversity using this group as a case study.
Schematic diagram of transmission of bats to other mammals
Diversity and dispersal potential of bat-borne zoonotic viruses in the Indo-Australian Archipelago (NIH 1R21AI105050)
In recent years, Asia has been the source of several emerging infectious diseases with high levels of mortality, including the SARS virus, H1N1 influenza virus, and Nipah virus. The severity of outbreaks can be mitigated when animal reservoirs are readily identified and their movements restricted, but when pathogens are vectored by flying organisms, containment can be difficult. The recent recognition of bats as putative sources of pathogens and the discovery of novel viruses has spurred research on their role as reservoir hosts. This is the case with large fruit bats known as flying foxes (Chiroptera: Pteropodidae: Pteropus), where there is evidence of infections from at least six virus families, including the highly pathogenic Paramyxoviridae. Colonial roosting, high vagility, and long lifespans provide the opportunity for viral persistence and intra- and inter-colony transmission. A single Pteropus bat can fly over 50 km in a single night, making these animals important long-range vectors for pathogens across. The large geographic range of Pteropus species further underlines the geographic extent and costs that bat-borne zoonoses might have on global health.

We are currently sampling Pteropus and their viruses throughout Indonesia to determine the presence and prevalence of zoonotic pathogens in relation to evolutionary history and ecological traits. Our collaborators in the Emerging Infectious Disease Program at Duke-NUS Medical School in Singapore, Drs. Vijaykrishna Dhanasekaran, Gavin Smith, and Ian Mendenhall will use RNA-based assays to detect the presence of any viruses, and subsequently clone and sequence them for comparison with other mammalian viruses. Nascent phylogeographic and network analyses will allow us to model the population structure of the host species and their dispersal routes, allowing containment efforts to focus on crucial dispersal corridors. We will then infer where viral hotspots may occur by using ecological niche modeling.