Journal of the Royal Society of New Zealand abstracts
Morphological variation, biogeography and local extinction of the northern
New Zealand landsnail Placostylus hongii (Gastropoda:
Bulimulidae)
F. J. Brook*, B. H. McArdle**
* Department of Conservation, P. O. Box 842, Whangarei, New Zealand
**School of Biological Sciences, University of Auckland, Private Bag 92019,
Auckland, New Zealand
Placostylus hongii (Lesson) is recorded from sites between Whangaroa and
Whangarei on the mainland Northland coast, and from the Poor Knights, Chicken,
Mokohinau and Great Barrier Islands offshore. There is considerable variation
in shell morphology between the various populations, commonly with marked
morphological divergence at a local scale but with overlapping variation
overall across all populations of the taxon. Patterns of morphological
variation show no clear geographic trends and are at least in part related to
local environmental factors. Correlations are identified between shell shape
and substratum type, and between shell size and vegetation type.
Placostylus hongii has a very restricted stratigraphic distribution in
mainland Northland, with most if not all of the few known fossil populations
post-dating Polynesian settlement at c. 900-700 years BP. We suggest that P.
hongii populations on the Poor Knights and possibly also those on the
Mokohinau Is. are endemic, whereas the mainland populations and those on Great
Barrier and the Chicken Is. have originated from anthropic redistribution of
snails in prehistoric time. A high proportion of the mainland P. hongii
populations and some offshore island populations became extinct in the last few
hundred years as a result of predation by introduced mammals and the
modification and destruction of shrubland and forest habitat.
Keywords landsnail; Placostylus hongii; biogeography;
extinction; variation
(c) Journal of The Royal Society of New Zealand,
Volume 29, Number 4, December 1999, pp 407-434
PDF file of entire paper: medium quality (2198K); (scanned from paper original: notes about this process)
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