Rhytididae
Rhytididae are carnivores restricted to New Zealand, eastern and south-western Australia, Indonesia, Melanesia, the Caroline Islands, Samoa, Tonga, Fiji, southern Africa, Madagascar, and the Seychelles. They are most common and species-rich in New Zealand and eastern Australia.
Among New Zeqaland representatives, species of Delouagapia Powell, 1952, Amborhytida Climo, 1974 and Rhytidarex Powell, 1948 are confined to the Three Kings Islands and northern North Island, Paryphanta Albers, 1850 to the northern North Island, Delos Hutton, 1904 to the Three kings to northern South Island, Schizoglossa Hedley, 1892 to the North Island and adjacent smaller islands, Wainuia Powell, 1930 to the southern North Island and northern South Island, Rhytida von Martens, 1860 to North, South and Stewart islands and some adjacent smaller islands, and Powelliphanta O’Connor, 1945 to the southern North Island and extensively in the South Island. Thus rhytidids are notably absent from the Kermadec Islands, Chatham Islands and the subantarctic islands.
All members of the family in New Zealand are dependent upon high humidity and natural plant covival. Delos and Delouagapia are normal components of moderately deep forest litter, although Delouagapia cordelia (Hutton) is primarily arboreal in forest, yet terrestrial in low scrubland. Schizoglossa species are most common under logs in rainforest, Rhytida and Wainuia under deep litter and rock rubble in forest and shrublands, while the sole Paryphanta species is found under larger than average accumulations of litter in forest. Paryphanta b. busbyi Gray and Rhytida greenwoodi (Gray) are known to occur arboreally in the leaf debris that accumulates in epiphytic plants, while Schizoglossa novoseelandica (Pfeiffer) will occasionally search for prey several metres up trees. Most species of Powelliphanta are found in deep accumulations of forest leaf litter, but two species are restricted to alpine tussock grassland.
Several Rhytididae are identified of conservation concern in the New Zealand Threat Classification System Lists (Hitchmough et al. 2007). In particular species and subspecies in the genera Powelliphanta and Paryphanta are considered particularly vulnerable to extinction and are the subject of conservation recovery plans (Parrish et al. 1995; Walker 2003) and active management by the Department of Conservation. These conservation activities have been underpinned by research on the ecology of the animals and methods for monitoring populations (e.g. Stringer et al. 2002, 2003).
The family Rhytididae have long been of interest to New Zealand biogeographers. In recent years phylogenetic analyses have been supported by molecular genetic data (e.g. Walker 2003; Spencer et al. 2006; Trewick et al. in press). This work is ongoing.
Suggested further reading:
Barker GM 2005. The character of the New Zealand land snail fauna and communities: some evolutionary and ecological perspectives. Records of the Western Australian Museum, Supplement 68: 53–102.
Barker GM, Efford M 2004. Predatory gastropods as natural enemies of terrestrial gastropods and other invertebrates. In: Barker GM ed. Natural enemies of terrestrial molluscs. Wallingford, UK, CABI International. Pp. 279–403
Climo FM 1975. The land snail fauna. In: Kuschel G ed. Biogeography and ecology in New Zealand. The Hague, Junk. Pp. 459–492.
Climo FM 1978. The Powelliphanta gilliesi-traversi-hochstetteri-rossiana-lignaria-superba ring species (Mollusca: Pulmonata). New Zealand Journal of Zoology 5: 289–294.
Efford MG 1998. Distribution and status of native carnivorous land snails in the genera Wainuia and Rhytida. Science for Conservation 101. Wellington, Department of Conservation. 48 p.
Parrish R, Sherley G, Aviss M 1995. Giant land snail recovery plan Placostylus spp., Paryphanta sp. Threatened Species Recovery Plan 13. Wellington, Department of Conservation. 39 p.
Powell AWB 1979. New Zealand Mollusca. Marine, land and freshwater shells. Auckland, Collins.
Spencer HG, Brook FJ, Kennedy M 2006. Phylogeography of kauri snails and their allies from Northland, New Zealand (Mollusca: Gastropoda: Rhytididae: Paryphantinae). Molecular Phylogenetics and Evolution 38: 835–842.
Stringer IAN, McLean MJ, Arnold GC, Bassett SM, Montefiore R 2002. Growth and development of the rare land snail Paryphanta busbyi watti (Pulmonata: Rhytididae). Molluscan Research 22: 203–220.
Stringer IAN, Bassett SM, McLean MJ, McCartney J, Parrish GR 2003. Biology and conservation of the rare New Zealand land snail Paryphanta busbyi watti (Mollusca, Pulmonata). Invertebrate Biology 122: 241–251.
Trewick SA, Walker KJ, Jordan C 2008. Taxonomic and conservation status of a newly discovered giant landsnail from Mount Augustus, New Zealand. Conservation Genetics (in press).
Walker K 2003. Recovery plans for Powelliphanta land snails 2003–2013. Threatened Species Recovery Plan 49. Wellington, Department of Conservation. 208 p.