Report on a Centenary Research Grant for 2003

Taxonomy of Austropeplea tomentosa (Pfeiffer, 1855), an intermediate host of liver fluke.

Louise Puslednik, Conservation Biology University of Wollongong, NSW 2522, Australia.  lp9...@uow.edu.au

In 2003 I was awarded monies to fund some aspects of my PhD research on the systematics of the Australasian Lymnaeidae. This funding was to specifically investigate the taxonomy of Austropeplea tomentosa, in using DNA sequences of the nuclear internal transcribe spacer 2 (ITS-2) gene.

Austropeplea tomentosa was originally described from New Zealand (Pfeiffer, 1855), but has a large distribution within both Australia and New Zealand. Under the current taxonomy, Australian and New Zealand populations of A. tomentosa are considered conspecific (Smith, 1992). However, Australia and New Zealand have been separated for 85 million years by the Tasman Sea (Stevens, 1985), and it seems improbable that a freshwater gastropod would be able to maintain gene flow under these circumstances. In addition, A. tomentosa has a large distribution within Australia and is thought to display a number of different shell morphs. However, these shell morphs have never been tested.

Fig:  Austropeplea tomentosa from Australia

The aim, therefore, was to test two hypotheses:

1.     That the Australian and New Zealand populations of the taxon currently called Austropeplea tomentosa are not conspecific, and;

2.     That the Australian A. tomentosa represents more than one species.

These tests were carried out using DNA sequence comparison of the nuclear internal transcribe spacer 2 (ITS-2) gene. While this grant only funded the sequencing of eight populations, a total of 13 populations of A. tomentosa were sampled, with five populations from New Zealand, seven from mainland Australia and two from Tasmania. Sequences were aligned with Clustal W and a maximum parsimony analysis was performed in PAUP* 4.0b10 (Swofford, 2002). A bayesian analysis using MrBayes 3.04 (Huelsenbeck and Ronquiest, 2001) was conducted as another means of estimating phylogeny.

Results of these analyses are still in a preliminary stage, and further work needs to be performed before any conclusions can be drawn. However, there is one strong pattern within the group emerging. The Austropeplea tomentosa clade is divided into two separate lineages, with the New Zealand populations consistently falling out as separate taxa to the Australian populations of A. tomentosa. The New Zealand clade is further subdivided into two separate groups, which represent populations from the north and south islands of New Zealand. Within the Australian populations of A. tomentosa, relationships are less clear and there seems to be little resolution within some of the branches. At this point no inferences can be drawn as to the relationships among the Australian populations of A. tomentosa. However, it should be noted that these analyses are still in a preliminary stage and further analysis will hopefully elucidate the relationships within the Australian populations of A. tomentosa.

The results of this study could have broader implications in relation to the phylogeny of the Lymnaeidae. The current phylogeny of this family of freshwater snails is based on the assumption that Austropeplea tomentosa is a single species. These results seem to indicate that A. tomentosa under the current taxonomy, is a complex of cryptic species. If the taxonomy of the group is incorrect then the phylogeny of the group needs to be revisited. In addition, these results could change our understanding of the biogeography of the Lymnaeidae. There is much debate as to whether Austropeplea is a basal or derived group of Lymnaeids and where the group arose. The results of this study could help in our understanding of the biogeography of the group.

I would like to take this opportunity to thank the Malacological Society of London for the assistance and funding that they have provided. This research would not have been possible without this support.

Smith BJ (1992) Non-marine mollusca. Zoological Catalogue of Australia Vol. 8. Australian Governemt Publishing Service, Canberra

Stevens G (1985) Lands in collision: Discovering New Zealand's past geography. Scientific Information Publishing Centre, Wellington

Pfeiffer L (1855) Proc. Zool. Soc. Lond, 1854, 286-298.