TANE 20 1974

LAND SNAILS FROM SHOE AND MIDDLE ISLANDS, NORTH-EAST NEW ZEALAND.

by P.G. Parkinson* and P.R. Moore f

SUMMARY

Seventy-two specimens representing seventeen species of land snails are recorded from Middle (Aldermen Group) and Shoe Island off the east coast of Coromandel Peninsula. The largest and most diverse faunule occurs beneath a canopy of Metrosideros excelsa (pohutukawa). The islands do not appear to possess any distinctive faunule elements as far as are concerned.

INTRODUCTION

During a visit to the Aldermen Islands in May 1972, samples were collected (by PRM) of shell midden on Middle Island, from which a small faunule was later extracted. Samples of leaf-mould were collected on Shoe Island during August 1973 (Fig. 1). The faunulae from the two islands have been examined and determined by the senior author (PGP) and are described herein. Middle Island is one of the four main islands of the Aldermen group and lies about 20km offshore. The effects of burning and previous Maori occupation on the islands' vegetation have been discussed.5' The vegetation of Shoe Island, 3-4km offshore, is described by Court.6 Collection numbers are those of the Auckland University Geology Department, in which the faunulae have been deposited.

THE FAUNULAE

The faunulae collected from Middle and Shoe Islands is listed in Table 1. Endodontid snails have been identified largely from the revision by Climo.1'2 Punctids and others have been identified largely from the account in Suter's "Manual"10. Endodontid nomenclature follows that of Climo; Punctid (Laomid) nomenclature follows that of Powell9, save that Phrixignathus Hutton is considered a subgenus of Laoma, not a distinct .

*c/- 16 Liston Cres, HUlcrest, Hamilton, fc/- N.Z. Geological Survey, Lower Hutt.

25 TABLE I: Land snail faunulae from Middle and Shoe Islands

Species/ Middle Island Shoe Island Total Specimens Collection number 1981 1982 1983 1984 1985 1986 1987 1988 1989 Cytora aff. torquilla (Suter) (?) 3 2 5 Cytora sp. (destroyed) 1 1 Therasia decidua (Pfeiffer) 1 7 8 Phenacohelix ponsonbyi (Suter) 1 1 Charopa caputspinulae (Reeve) 2 2 2 6 Charopa bianca (Hutton)* 3 3 Charopa eta (Pfeiffer) 10 10 Charopa reeftonensis (Suter) i 2 2 Charopa buccinella (Reeve) (?) 1 1 Flammocharopa costulata (Hutton) 1 1 Laoma (Phrixignathus) celia (Hutton) 7 7 Laoma (Phrixignathus) ariel (Hutton) 2 2 Laoma (Phrixignathus) sublucida (Suter) 1 1 2 Laoma (Phrixignathus) fulgurata (Suter) 1 1 10 12 Paralaoma aff. raricostata (Reeve) 1 1 Paralaoma sericata (Suter) 3 2 3 8 Delos coresia (Gray) 1 1 2

Number of specimens 2 1 17 3 1 1 4 34 9 72

*These specimens agree well with C. bianca except in their having a very distinctly spirally striate protoconch This specimen is juvenile but seems distinct from C. reeftonensis in riblet frequency Fig. 1. Shoe & Middle Islands showing collection points.

27 Description of Habitats

Sample number Location, and vegetation. Middle Island 1981 Open valley with large pohutukawa; little ground cover. 1982 small boulder-strewn terrace covered with kawakawa and Paratrophis banksii.

1983 near cliff top; canopy of pohutukawa. Shoe Island (all leaf mould) 1984 fairly open area beneath a canopy of pohutukawa and subcanopy of mahoe and kanuka; few Asplenium lucidum provide ground cover. 1985 under low canopy of kanuka and pohutukawa with ground cover of bracken and few Asplenium lucidum.

1986 gully with fairly open pohutukawa (4-5m high), flax and Astelia.

1987 ridge with canopy of large (10m +) pohutukawa and subcanopy of mahoe; sparse undergrowth of bracken and Asplenium lucidum.

1988 Slopes beneath large pohutukawa and mahoe with scattered flax clumps and Asplenium lucidum.

1989 valley with very open canopy of mahoe and kawa• kawa; few ferns.

DISCUSSION

Land snail faunulae have been sampled from several offshore islands of the east coast of the North Island. Climo3 has summarised the studies of the land snail population of the Poor Knights Islands, and finds that the faunule (ten species so far recorded) shows 50% endemism. The Three Kings Islands (the land snail literature of which has been reviewed by Climo4) and the Cape Maria van Diemen-Te Paki block also have conspicuous endemic elements in their faunulae. In contrast, the faunule of Mayor Island (investigated by Milligan7 and Easterbrook-Smith (pers. comm.)) shows no endemism. The same is the case with the faunule recorded here. The most interesting find from a systematic point of view is the Charopa aff. bianca with its pronounced spiral striae on the protoconch. Climo2 describes the protoconch of thu species as "of 1 lA — VA smooth or weakly radially costate whorls." However a spirally striate protoconch has been observed in other

28 species of the subgenus Champa e.g. anguicula, pilsburyi, transenna. A spirally striate protoconch has formerly been considered typical of the genus of subgenus Mocella. Climo2 (page 286) states "The constantly sparse spiral lirae on the protoconch of Mocella Iredale in combination with a fairly constant shell form enables this group of species to be retained at the subgeneric level." Charopa (Ptychodon j seems poorly represented in the faunulae, only Charopa (Ptychodon) reeftonensis and the doubtful juvenile possibly of C. (P.) buccinella being referable to this subgenus. Punctid genera (Phrixignathus and Paralaoma j are comparatively well represented although there are none of the punctids with lamellae in the aperture {Laoma (Laoma) sensu Powell.) The scarcity of Flammulininae is also interesting, the only species being Therasia decidua and Phenacohelix ponsonbyi, the latter often an abundant species but here repre• sented by a single specimen. A solitary Paryphantid, Delos coresia is recorded. The absence of Liarea (Liareidae) is not unusual. Two apparent Cytoras were collected but one of these, represented by a single broken specimen, was accidentally destroyed. The species of Cytora are not well understood and the identification of the other specimens is C. torquilla is tentative. None of the species has its range extended remarkably by these collections. As is usual with collections from leaf Utter the snail samples from Shoe Island show no significant correlation with microhabitat. Correlations may sometimes be found when living snails are collected from foliage. Probably the dispersal of dead shells by wind and water disturbing leaf litter accounts for this lack of correlation where dead shells are involved.

REFERENCES

1. Climo, F.M. 1969: Classification of New Zealand Arionacea (Mollusca: ) II, A Revision of Charopa subgenus Ptychodon Ancey 1888. Records of the Dominion Museum 6 (14): 175-258. 2. Climo, F.M. 1970: Classification of New Zealand Arionacea (Mollusca: Pulmonata) III. A Revision of the genera Charopa Albers 1860 (excluding subgenus Ptychodon Ancey 1888), Phenacharopa Pilsbury, 1893 and Flammocharopa n. gen. (Endodontinae). Records of the Dominion Museum 6 (18): 285-366. 3. Climo, F.M. 1971: Additions to the Land Snail Fauna of the Poor Knights Islands, New Zealand. Joum. Roy. Soc. N.Z. 1 (1): 65-9. 4. Climo, F.M. 1973: The systematics, biology and zoogeography of the land small snail fauna of Great Island, Three Kings Group, New Zealand. Journ. Roy. Soc. N.Z. 3(4): 565-628. 5. Court, D.J. Hardacre, A.K.; Lynch, P.A. 1973: The vegetation of the Aldermen Islands; A Reappraisal, Tane 19: 41-60. 6. Court, D.J. 1974: Vegetation of Shoe Island. Tane 20: (this issue). 7. Milligan, E.N. 1956: Land molluscs of some offshore islands Tane 7: 56-7. 8. Moore, P.R. 1973: Evidence of former Maori occupation of the Aldermen Island Tane 19: 21-29. 9. Powell, A.W.B. 1967: "Shells of New Zealand". Whitcombe & Tombs. 10. Suter, H. 1913: "Manual of the New Zealand Mollusca". Govt. Printer Wellington.

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