Testing biogeographic hypotheses in Wallacea using freshwater molluscs
Final Report Abstract
This project aimed at elucidating dispersal patterns in comparable freshwater mollusc taxa within Wallacea in order to dissect the complex mixture of vicariance and predominant dispersal events that led to subsequent diversification of these groups on respective islands in the Moluccas. To this purpose, tasks comprised the completion and extension of the Wallacea-wide picture and the conduction of comparative in-depth phylogeographical analyses of four selected model-taxa (Planorbidae/Lymnaeidae, Bithyniidae, Sphaeriidae) in order to assess both iInter-island biogeographical patterns and the correlation of intra-island population structure with island parameters as well as habitat diversities and availabilities to evaluate their effects on diversification patterns and population dynamics and structures. Extensive sampling on almost all of the designated target islands yielded good samples for the inter-island comparison for all but one taxon, and the Bithyniidae were consequently swapped with the Neritidae, an equally well suited group. Intra-island studies were (re-)focused on the most important Wallacean island Sulawesi, Sphaeriidae and Protancylus spp. The data generated for these freshwater mollusc taxa were subjected to phylogenetic, phylogeographic and historic biogeography analyses based on multi-marker gene phylogenies. The first molecular phylogeny of the planorbid group Miratestinae uncovered a high level of phylogenetic diversity. Most estimates of divergence times postdate major tectonic events in the archipelago, suggesting long-distance dispersal from Australia. However, vicariance events and/or stepping-stone dispersal via the Australian margin promontory that moved northward to the Asian plate and progressively got fragmented by extension from the Miocene to the Pliocene also enjoys some support. Lymnaeidae occur broadly in Southeast Asia (SEA), in the IAA and in Australia. The dated phylogeny and estimates of ancestral areas revealed several independent colonization events from both Asia and Australia into Wallacea, Phillippines and Papua New Guinea occurring during the Miocene. While the timing of colonization events from SEA suggests dispersal across Wallace’s Line, the Sulawesian lineages originating in Australia may provide another example of an "out-of-Australia" vicariance event into Wallacea. For bivalves, the project yielded the first ever records of Sphaeriidae from Sulawesi from field surveys at the Malili lakes. Analyses with samples from other Asian sites and with world-wide data from previous studies based on shell morphological variation and mitochondrial and nuclear sequences suggest the existence of a new species in addition to a record of a species known only from other parts of Indonesia. The work on intra-island diversification study focused on the lacustrine genus Protancylus on Sulawesi. Initial diversification in Protancylus started considerably earlier than in the pachychilid snail Tylomelania, on whose shells Protancylus exclusively dwells. Gene flow analyses reveal a strong signal of isolation by distance, and we also found evidence for allopatric speciation with two putative new species characterized by low morphological variation and a specific life-history. A drift-based speciation mode is most likely. No ecological divergence has been found in our studies, in contrast to Tylomelania and most other cases studied so far in the ancient lakes of Sulawesi. We also studied the phylogeography and both inter- and intra-island population structure of another selected planorbid snail species, Indoplanorbis exustus. We found a single clade throughout the IAA and contrary to expectations, no population genetic structure among islands or across the Wallace line was found, suggesting a recent colonization. Our data also suggest a sudden demographic and spatial population expansion that could have occurred naturally in the Pleistocene or may possibly be the result of a modern colonization triggered by anthropogenic activities. Finally, the extraction of island parameters from the literature and databases for a total of 85 islands yielded data for the analysis of freshwater molluscs biodiversity patterns among these islands. Potential geographic and bioclimatic predictor variables were created and their influence on the detected species settlements were analyzed by utilizing an analytical approach with generalized linear models. Important variables with a positive effect on species richness in the different categories of molluscs such as annual mean temperature were identified. Overall our results indicate that abiotic factors, which are responsible for the successful colonization of the IAA and the preservation of species richness, may have a greater impact than previously anticipated. Finally, congruence in the biogeographic patterns of the Planorbidae and the Lymnaeidae, and to a lesser extent the Sphaeriidae was found. Freshwater snails occurring in Wallacea but also throughout the IAA have both Australian and Asian origins. A combination of active dispersal (due to e.g. lowering of sea level in phases), passive dispersal (transmarine transportation depending on differential survival) and vicariance events (continental islands, mountain formation) contribute to the current distribution and diversification evidenced in the phylogenetic patterns obtained. Dispersal events and intra-island diversification comparatively are more important in the generation of current biodiversity on the studied islands. For evaluation of the importance and explanatory power of vicariance vs. dispersal hypotheses it appears that intrinsic dispersal capacity determines predominantly the current underlying distribution patterns of these taxa in this region.
Publications
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(2013): Time and space in biogeography: response to Parenti & Ebach (2013). Journal of Biogeography, 40, 2204-2206
Bruyn, M.; Stelbrink, B.; Page, T.J.; Phillips, M.J.; Lohman, D.J.; Albrecht, C.; Hall, R., Rintelen, K. von; Ng, P.K.L.; Shih, H.-T.; Carvalho, G.R. & Rintelen, T. von
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(2014). Borneo and Indochina are major evolutionary hotspots for Southeast Asian biodiversity. Systematic Biology, 63, 879-901
De Bruyn, M.; Stelbrink, B.; Morley, R. J.; Hall, R.; Carvalho, G. R.; Cannon, C. H.; van den Bergh, G.; Meijaard, E.; Metcalfe, I.; Boitani, L.; Maiorano, L.; Shoup, R.; Rintelen, T. von
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(2014). Colonization of the Indo-Australian Archipelago (IAA): Phylogeography of the freshwater snail Indoplanorbis exustus (Gastropoda: Planorbidae). Island Biology 2014 conference abstracts, University of Hawaiʻi at Mānoa, 7‐11 July 2014, p. 60-61
Gauffre Autelin, P., Stelbrink, B., Albrecht, C. & Rintelen, T. von
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(2014). Crossing Lines - Biogeographic patterns in Sulawesi. Island Biology 2014 conference abstracts, University of Hawaiʻi at Mānoa, 7‐11 July 2014, p. 133
Stelbrink, B., de Bruyn, M., Albrecht, C., Hall, R. & Rintelen, T. von
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2014. A snail perspective on the biogeography of Sulawesi, Indonesia: origin and intra-island dispersal of the viviparous freshwater gastropod Tylomelania. PLoS ONE, 9, e98917
Rintelen, T. von; Stelbrink, B.; Marwoto, R.M. & Glaubrecht, M.
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(2017): Recent range expansion of an intermediate host for animal schistosome parasites in the Indo-Australian Archipelago: Phylogeography of the freshwater gastropod Indoplanorbis exustus in South and Southeast Asia. Parasites & Vectors, 10, 126-141
Gauffre Autelin, P.; Rintelen, T. von; Stelbrink, B. & Albrecht, C.
