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Biogeography of Tasmanian native land snails


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Bonham, Kevin James 2003 , 'Biogeography of Tasmanian native land snails', PhD thesis, University of Tasmania.

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The Australian island state of Tasmania has a well-sampled land snail fauna
consisting mostly of endemic species, mostly confined to particular portions of the
state. This thesis analyses the known distribution of different species within the state
with the aims of: (i) describing and summarising these distributions, (ii) examining
the applicability of models used for other Tasmanian taxa to land snail distributions,
(iii) categorising and tentatively explaining snail distributions where possible, and (iv)
assessing some ramifications of snail distributions for conservation planning.
One hundred and six species/morphospecies are discussed, of which approximately 39
were not formally or informally recognised before this project commenced.
Undescribed species (and genuine species incorrectly synonymised) are here
identified chiefly through qualitatively significant shell-feature distinctions, or
through reliable quantitative differences. Species distribution is analysed primarily at
a resolution of 10x10km grid squares, at which level 4272 records (including project specific
fieldwork aimed at improving the representativeness of sampling) are used.
Discussion is chiefly inferential in the absence of adequate statistical models, but
overall database statistics are used to comment on whether apparent gaps in species
ranges are likely to be meaningful. The single most significant pattern in the Tasmanian mainland snail fauna
distributions separates the west and far south from the remainder, a pattern to which
geology, rainfall, vegetation and substrate may all contribute. The manifestation of
this pattern varies between different contributing species. This result is practically
identical to results previously obtained for other invertebrates, but another broad-scale
pattern, the influence of the face of the Great Western Tiers in the central north, is
not. Congruence with bioregional models based on trees and vertebrates is only
approximate and piecemeal, showing potential limitations for conservation planning
of models that do not include poorly dispersing taxa (such as non-flying invertebrates)
in their source data. Known facets of local endemism such as island endemism, karst endemism,
parapatric species mosaics, alpine endemism, "toeholding" and glacial refuge
endemism are all reflected in the fauna to some degree. The value of these for
predicting the likely locations of undescribed or as yet undifferentiated twha is,
however, undermined by the frequency of distributions not explicable by any known
direct cause, and by the relatively small and spatially variable contribution of each
specific known cause. The potential merits of limiting the spatial scale of
comprehensive habitat loss, especially in poorly-surveyed areas, are therefore

Item Type: Thesis - PhD
Authors/Creators:Bonham, Kevin James
Keywords: Snails
Copyright Holders: The Author
Copyright Information:

Copyright 2003 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2003. Includes bibliographical references

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