Project Details
Projekt
New Caledonian biogeography from the perspective of snails from springs and groundwater
Subject Area
Systematics and Morphology (Zoology)
Term
since 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 531482467
Due to its unique biota consisting of a large proportion of endemics, a mix of old Gondwanan and young lineages, New Caledonia is considered one of the hotspots of biodiversity. New Caledonia is part of the continental fragment Zealandia, which separated from Australia about 80 Mya and largely subsided. However, the question, whether New Caledonia was entirely submerged or if some subaerial land supported the survival of Gondwanan biota in situ, has sparked a vivid debate. If there was permanently land available, vicariance should explain the presence of old lineages. Otherwise, all biota would have had arrived via long distance dispersal. According to the latest review of the geological history, the entire area had been submerged until 60 Mya leaving no space for vicariance. However, in the absence of evidence for terrestrial erosion between 34 and 25 Mya, the big, open question from the geological point of view remains whether there was land subaerial throughout the Oligocene, hence, whether organisms could have survived in situ. Thus, the question about the origin and evolution of the New Caledonian biota has slightly changed and shifted regarding the critical period of time. Biological evidence for in situ survival requires phylogenetic analysis of extant endemic lineages whose origin predates the Oligocene. Only clades that have persisted and diversified in New Caledonia for over 34 My can reject the hypothesis of complete submergence. Such evidence is scarce. In order to make robust inferences about the origin and evolution of the biota of New Caledonia, additional evidence should be sought and may best be provided by taxa which are micro-endemics, i.e. weakly dispersing organisms. Preliminary analyses based on limited data have now suggested that tateid gastropods, a group of small-sized freshwater snails with mostly very narrow ranges and largely restricted to springs and the groundwater, may provide such evidence. During three expeditions organized by Philippe Bouchet (Paris) between 2016 and 2018 about 50 undescribed species, most of them in the size range of 1-2 mm, have been discovered. This size range is challenging for taxonomic and systematic analyses based on morphology, anatomy and genomic data. In preparation, we have established the necessary approaches and resources in our labs including micro-computer tomography for anatomical investigations and a draft genome of one species as basis for phylogenomic analyses. Equipped in this way, we will describe the new species integrating morphology, anatomy and genetics and analyze their relationships. This will allow to reconstruct the biogeographic history of tateids of New Caledonia and the SW-Pacific and to answer questions about the number of colonization events, adaptation to different types of geology, and how often ground waters were accessed. The ultimate goal is to test the hypothesis of Oligocene submersion of New Caledonia as suggested by the geological record.
DFG Programme
Research Grants
Co-Investigators
Dr. Carola Greve; Dr. Ira Richling
