Phylogenie und Phylogeographie von Brutbeutel tragenden Süßwasser-Gastropoden (Thiaridae in Australien: Implikationen für die Biogeographie und die evolutionäre Rolle viviparer Reproduktionsstrategien
Zusammenfassung der Projektergebnisse
Due to their limited potential of dispersal in combination with their habitat fidelity, limnic gastropods tend to preserve distribution patterns over long periods of time. Thus they are suitable organisms in biogeographical research and the study of the relations between colonization events and speciation. In this study intensive investigations into the phylogeography and phylogeny of Australian freshwater snails are provided, presenting the first molecular study of the Thiaridae (Caenogastropoda: Cerithioidea) based on four DNA sequence markers (COI, 16S, H3, 28S) and amplified fragment length polymorphisms (AFLPs). The aim of this study is to determine the historical events that may have influenced the phylogeography of these taxa and their presence on the Australian continent. In general, the origin of Australian freshwater faunal elements and the directionality and timing of colonizations are still controversial. Conventionally, many biotic elements found in Australia today are considered to be recent invaders from the Indo-Malay archipelago but more and more cases have become known that deviate from this standard scenario. In order to test whether the thiarids represent recent invaders from the north or if they originated on the Australian continent, the evolutionary relationships within the family as well as its phylogenetic position in the superfamily Cerithioidea are analysed. A molecular clock approach is applied subsequently to date the origins of the Thiaridae and their sister families so that the dispersal events can be related to historical tectonical changes. A prerequisite for the reconstruction of past distribution patterns is the delimitation of the Australian species and the analyses of their current distributions. For this purpose, preceding investigations to characterize individual taxa by morphology are complemented with molecular analyses and additional sampling with the objective to obtain confirmation of the differentiated species and the detailed analysis of their present distribution patterns. By comparison of the molecular phylogenies, as well as the distributional data, the fossil record and divergence date estimates in conjunction with the excellent record of Earth history the long-held view that the thiarid fauna is an appendage to the Southeast Asian biota can be rejected. Instead, an Australian continental, i.e. East-Gondwanian origin is found to be the most parsimonious explanation of the present distribution. The age of the thiarids dates back to about 50 Ma and coincides with (although not necessarily causally linked to) the separation of Australia from Antarctica. With an ancestral thiarid lineage that originated in Australia, Asia seems to have been colonized a number of times within the period of the collision of the Australian plate with Southeast Asia during the past 20-30 Ma. With their now assumed long history on the continent, Australian thiarids represent an important and realistic model system in speciation research which provides details of the dynamics of the underlying mechanisms of speciation under the influence of climate change. Although there are still ambiguities to be resolved which concern the relationships among the thiarid taxa, the comparison of the extensive molecular datasets and their resultant phylogenies offer considerable insight into this enigmatic group. It is demonstrated that extreme caution must be used when inferring phylogeny from mtDNA loci in the absence of corresponding multi-locus nuclear data. Nevertheless, the mtDNA data corroborates almost all morphologically described species. In regard to the delimitation of the Australian species, a total of eleven distinct clades confirmed by morphology and molecular data are identified. Furthermore with the compilation of recent distribution maps on drainage based scales, extensive data on extant species is now available which gives new insights into the current dispersion and the degree of endemism. Besides, even a new species, that is Thiara rudis, is for the first time recorded and verified as taxa with occurrences in Australia. Moreover, the AFLP analysis reveals a recent diversification between the two endemic species “Thiara” australis and Plotiopsis balonnensis with possible hybridisation in the newly detected zone of overlap. Within the scope of this study a procedure is developed that makes it possible to contextualize old museum material within biosystematics research in a reliable way. It is based on ancient DNA techniques and comprises the amplification of short DNA fragments which are analysed in phylogenetic analyses. In this context this procedure’s application to historic specimens collected over a century ago in Papua New Guinea is relevant. The historical mini-barcodes cluster with Ripalania queenslandica sequences from Australia indicating that this thiarid is actually not endemic to the continent. In the face of the increasing biodiversity crisis, the study of the biological diversity on all levels is becoming ever more urgent. The possibility of obtaining sequence data from untapped genetic data within archived museum specimens opens up vast new reservoirs of information for future research.
Projektbezogene Publikationen (Auswahl)
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2010. Freshwater gastropods from early voyages into the Indo-West Pacific: The ‘melaniids’ (Cerithioidea, Thiaridae) from the French ‘La Coquille’ circumnavigation, 1822-1825. - Zoosystematics and Evolution, 86(2): 185-211
Glaubrecht, M. & Podlacha, K.
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2011. Focus on freshwater snails: Thiaridae and other freshwater snails. – In: Bouchet, P., Le Guyader, H. & Pascal, Olivier (eds.), The Natural History of Santo, pp. 257-264. Patrimoines Naturels (Museum National d’Histoire Naturelle), Paris
Kano, Y., Strong, E.E., Fontaine, B., Gargominy, O., Glaubrecht, M. & Bouchet, P.
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2011. Phylogeny of the gastropod superfamily Cerithioidea using morphology and molecules. - Zoological Journal Linnean Society London, 162: 43-89
Strong, E.E., Colgan, D.J., Healy, J.M., Lydeard, C., Ponder, W.F. & Glaubrecht, M.
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2011. Toward solving Darwin’s “mystery”: speciation and radiation in freshwater gastropods. - American Malacological Bulletin, 29: 187-216
Glaubrecht, M.
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2012. Comparing the reproductive biology of three “marsupial”, eu-viviparous gastropods (Cerithioidea, Thiaridae) from drainages of Australia´s monsoonal north. - Zoosystematics and Evolution, 88(2): 293-315
Maaß, N. & Glaubrecht, M.
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2019. Freshwater Cerithioidea. Family accounts Pachychilidae, Hemisinidae, Paludomidae, Melanopsidae, Thiaridae. – In: Lydeard, C. & Cummings, K. (eds.), Freshwater Mollusks of the World : an Distribution Atlas. Johns Hopkins University Press
Glaubrecht, M. & Neiber, M. T.
