Phylogeography of Sulawesi tarsier

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With luck and patience small, nocturnal primates called tarsiers can be observed in the understory of southeast Asian rainforests.Several morphological peculiarities reflect the long independent evolution of these fascinating creatures which nowadays are recognized as members of the haplorhine clade within the primate tree. Of the 14 tarsier species described so far, 12 occur on the island of Sulawesi. Their evolutionary history is closely linked to the island's complex geological past.

Sulawesi is the largest island in the Wallacea region and lies in the collision zone of two major tectonic plates. Their movements and Pleistocene sea level fluctuations implicated considerable geological changes up to the recent past. Resulting temporal water barriers, mountain ranges and land bridges have led to diversification and characteristic biogeographic patterns of the species populating Sulawesi. In fact, molecular investigations revealed that tarsier species living in close geographical proximity are not necessarily closest related. This led to the assumption that the geographic distribution of the extant tarsier species might be the result of several expansion waves of two tarsier lineages from southern to northern Sulawesi. Our research aims to further decipher the colonization of Sulawesi by tarsiers, as well as their diversification and dispersal patterns on the island, in light of the unique paleogeology of the area.

In our most recent publication, we describe the phylogenetic position of the so-called mountain tarsier (Tarsius pumilus), which has been referred to as one of the most mysterious primates on the planet. According to our analysis, it appears to be the sister taxon to all other recent Sulawesi tarsiers, with a split date long before any further known tarsier speciation events. We are currently striving to learn more about the demographic history of tarsiers using state-of-the-art sequencing techniques. Furthermore, we aim to contribute to the understanding of the morphological and genetic diversity of tarsiers on Sulawesi, focusing on Central Sulawesi. In this region the two main lineages of tarsiers may have overlapped and displaced each other leaving their imprint in the recent fauna.

All projects are in close collaboration with PD Dr. Stefan Merker (SMNS), the Primate Research Center (PSSP) in West Java and Tadulako University in Palu, Sulawesi. Other collaboration partners are Dr. Christine Driller (JGU Mainz), Dr. Nanda Grow (WSU) and Prof. Sharon Gursky (A&M University)

 

Acantocephalan evolution and control

 

Acanthocephala or thorny-headed worms are endoparasites with a complex life cycle and a worldwide distribution. Acanthocephala also parasitize human livestock and have recently gained importance as a pest in fish farming. To provide the basis for effective and specific control of these parasites, we are investigating their evolution, phylogenetic relationships and development using genomic, transcriptomic and proteomic data. Our analyses revealed that the two-host cycle of Acanthocephala living today probably evolved via a transitional stage in which they lived on mandibulate arthropods. The next steps in the evolution of Acanthocephala were the invasion of the first host (Arthropoda: Mandibulata) and upward incorporation of a second host (Vertebrata: Gnathostomata) into the life cycle (e.g., Wey-Fabrizius et al. 2014; Herlyn 2021). We were also able to show that females suffer more severe developmental impairments than males in unsuitable hosts, due to their higher female energy requirements (Schmidt et al. 2022a). Furthermore, we were able to identify acanthocephalan proteins as targets for their effective and specific control in aquaculture. This included the identification of compounds that can now be tested in the acanthocephalan model (Schmidt et al. 2022b). We are currently continuing to study the genomic architecture of Acanthocephala, the development of transcriptomes and the reproduction of Acanthocephala.