Molluscs from underwater meadows - on the Miocene diversification of Indo-Pacific molluscan faunas associated to seagrass

Molluscs from underwater meadows – on the Miocene diversification of Indo-Pacific mollusc faunas associated to seagrass Reich, Sonja, Wesselingh, Frank P., Renema, Willem NCB Naturalis, P.O. box 9517, 2300 RA Leiden, the Netherlands sonja.reich@ncb.naturalis.nl Numerous shallow marine biota reach their global peak diversity in the Indo-Malayan region broadly covering Malaysia, the Philippines, Indonesia, and Papua New Guinea. The Indo-Malayan biodiversity hotspot developed in the middle Cenozoic (~25 Ma). In Miocene times many of the shallow marine habitats reached diversity levels similar or even exceeding those of today’s. However, the exact timing of diversification as well as the driving processes are still incompletely understood and there is only sparse fossil data to investigate diversification patterns. The THROUGHFLOW-Project, a Marie-Curie Initial Training Network, aims to fulfill the crucial need for new fossil data in the region and investigates the history of the marine biodiversity hotspot in Indonesia. One of the fossil groups, the molluscs associated to seagrass meadows, is subject of this study. These faunas are used as a model group to reconstruct the development of shallow marine molluscan biotas during the Miocene in Indonesia. The research in this project aims to elucidate how ancient seagrass faunas can be identified, how and when such faunas developed, and when modern type of shallow marine assemblages became in place. Furthermore, we study how such shallow marine ecosystems and their inhabitants reacted to regional expression of global change, and on the tectonic shaping of the regional paleogeography and oceanographic conditions. Steps in the research are the taxonomical, ecological, sedimentological and taphonomical characterization of sea grass mollusc faunas and their distinction from biotas from other shallow water habitats such as reef associated communities. Furthermore, the composition and diversity in stratigraphic successive sea grass habitats will be assessed. The research is based on museum collections and newly collected fossil molluscan material from East Kalimantan and Java (Indonesia) covering the Early Miocene to the present. Extensive taxonomic work and counting of specimens had been carried out. First results in the research reveal the possibility for the characterization of seagrass associated mollusc faunas by the abundance and diversity of gastropod feeding guilds. Furthermore, preliminary results show an increase of species diversity in seagrass associated molluscs through the Miocene in Indonesia, and a distinctive higher diversity in the Miocene of Indonesia than in modern biotas from temperate regions.