Powelliphanta augusta, a new species of land snail, with a description of its former habitat, Stockton coal plateau, New Zealand

Abstract

A recently discovered and threatened large land snail, Powelliphanta augusta n. sp. is described from Mt Augustus on the western scarp of the Stockton Plateau, North Westland. On shell characters it is readily distinguishable from all other Powelliphanta, with narrow red spiral lines underlying irregular and variable dark reddish-brown axial bands, a small adult size and sculptured dorsal surface. Differences in the shell morphology of P. augusta, its closest phylogenetic relative P. lignaria, and its closest geographic neighbour P. patrickensis, were investigated using principal components analysis. P. lignaria is much larger than either P. augusta or P. patrickensis, and there are significant differences in shell shape between the three taxa. Earlier mitochondrial DNA sequencing data, which supported specific status of P. augusta, is discussed. The snail's only habitat on the Mt Augustus ridgeline is described, but most has now been removed by coal mining. Snails salvaged before the destruction of their habitat have been taken into captivity or released in the wild outside their natural range.

Modelling the growth and population dynamics of the exiled Stockton coal plateau landsnail,Powelliphanta augusta

“…Subsequent measurements were taken in captivity at intervals of approximately 1Á2 months. Maximum shell height, width and diameter, as defined by Walker et al (2008), were measured to the nearest 0.01 mm using digital calipers.…”

“…Almost all Powelliphanta species have small, discrete distributions, a pattern thought to reflect New Zealand's complex bio-geographical history (Walker 2003). The restricted spatial and ecological range of most Powelliphanta makes them especially vulnerable to habitat loss and predation by introduced predators (Meads et al 1984), with most Powelliphanta taxa being classified as endangered or declining (Hitchmough et al 2007).…”

“…Powell (1946) stated (without giving evidence) that there was '15 years to a generation' and hypothesised that Powelliphanta may have 'a life span of up to 40 years'. Walker (2003) suggested an average life span of 12Á14 years, with some individuals living up to 20 years following the study of marked wild Powelliphanta hochstetteri bicolor and Powelliphanta lignaria johnstoni, and many lowland Powelliphanta species kept in captivity. Sexual maturity in captivity appeared to be around 5Á6 years (Walker 2003).…”

“…Walker (2003) suggested an average life span of 12Á14 years, with some individuals living up to 20 years following the study of marked wild Powelliphanta hochstetteri bicolor and Powelliphanta lignaria johnstoni, and many lowland Powelliphanta species kept in captivity. Sexual maturity in captivity appeared to be around 5Á6 years (Walker 2003). Powelliphanta augusta, like other Powelliphanta species, are normally crossfertilising hermaphrodites, although individuals housed apart appear capable of either sperm storage or self-fertilisation .…”

“…Powelliphanta augusta is a recently described alpine species, endemic to Mount Augustus on the Stockton Plateau (600Á1100 m asl), just north of Westport in New Zealand's South Island Walker et al 2008). …”