Fauna ofMe Aure Cave (WMD007), Moindou, : Human Introductions and Faunal Changel

Robert H. Cowie 2 andJ. A. Grant-Mackie 3

Abstract: The land snail fauna excavated from a cave at Me Aure on the central southwestern coast ofNew Caledonia represents a period of over 3000 yr, from before human arrival in the island to the present. The material excavated rep­ resents 20 terrestrial in nine families. The fauna reflects the overall land snail fauna of New Caledonia in being dominated by small snails in the families Charopidae and Rhytididae, with large Placostylus species (Bulimulidae) present and minor representation of other families. Two alien species are present: Allo­ peas gracile, probably introduced before European arrival, and fulica, introduced in 1972. There are suggestions of change in the composition of the fauna, perhaps associated with the arrival of Europeans and the replacement of native by alien vegetation, with Andrefrancia vetula and possibly A. saisseti declining and Rhytida aulacospira increasing.

DATING OF archaeological material is funda­ change. Land snails can be used as material mental to interpreting prehistoric events, and for radiocarbon dating (e.g., Goodfriend assessment of environmental change, includ­ and Mitterer 1993), with the proviso that ing human-induced change, is a major part of in limestone areas age anomalies may occur archaeological research. Radiocarbon dating (Goodfriend 1987). And if certain species and pollen analysis (e.g., Athens et al. 1992, known to be nonnative human introductions Athens and Ward 1993, Allen 1994), among are found only above a particular horizon, a range of methods, are some of the most then inferences can be drawn regarding the important tools available to the prehistoric date of arrival of humans in the locality, or if archaeologist. Often, however, analysis of the that date is known from other evidence the land snail fauna can be of additional value, snails offer corroborating evidence. providing corroborating evidence or allowing In the Pacific, land snails recovered in ar­ additional inferences regarding both dating chaeological excavations have been analyzed and environmental change (Evans 1972, from all these perspectives, notably in Hawai'i David and Stanisic 1991, Goodfriend et al. (Christensen and Kirch 1986, Dixon et al. 1994). For instance, if the habitat or micro­ 1997), the Solomon Islands (Christensen and habitat preferences of the species recovered Kirch 1981), American Samoa (Kirch 1993), are known, changes in faunal composition the Pitcairn Islands (Preece 1998), and the through the layers of an archaeological exca­ Cook Islands (Allen 1992). Despite possible vation can inform us about environmental problems associated with taphonomic pro­ cesses, especially mixing of soil layers result­ 1 Manuscript accepted 30 September 2003. ing from various disturbance factors (Carter 2 Center for Conservation Research and Training, 1990, David and Stanisic 1991, Goodfriend University of Hawai'i at Manoa, 3050 Maile Way, Gil­ and Mitterer 1993), important inferences more 408, Honolulu, Hawai'i 96822 (e-mail: cowie@ hawaii.edu). have been made. In particular, because cer­ 3 Department of Geology, University of Auckland, tain nonnative species are known to have Private Bag 92019, Auckland, (e-mail: been introduced widely by prehistoric people [email protected]). as they colonized the islands of the Pacific, and because others have only been introduced Pacific Science (2004), vol. 58, no. 3:447-460 since Western discovery of the islands, the © 2004 by University of Hawai'j Press composition of the snail faunas has been All rights reserved used to corroborate the timing of prehistoric

447 448 PACIFIC SCIENCE· July 2004

lFOnll d. N~re

21'41'760:r---'---' -----.f.------

. .- km .c...lL..zea__~:='----l.'~_~~ ~~?!.L."~="'~

FIGURE 1. Map showing the location ofMe Aure cave, archaeological site WMD007.

human colonization and the dating of partic­ est. More details are given by Grant-Mackie ular archaeological horizons. Nevertheless, et al. (2004). although a useful method, land snail analysis For excavation, the floor was divided into remains relatively little used in the Pacific an irregular grid (Figure 2). Only areas 1 and (with the above notable exceptions), and no 3 were investigated for snails. The top 5 cm such analysis has been reported from New of unconsolidated material was cleared from Caledonian deposits. each area and removed for sorting. Plant The land snail faunas of cave deposits debris, limestone fragments, and material have attracted particular interest (Evans 1972, cemented by modern bird feces were dis­ David and Stanisic 1991, Goodfriend and carded. The underlying areas were excavated Mitterer 1993) because they are often well by trowel and material was removed for lab­ preserved, having been protected from expo­ oratory analysis. More details of the excava­ sure. In this study we analyzed the land snail tion methods are given by Grant-Mackie et al. fauna of a cave deposit in New Caledonia to (2004). Area 3 was mostly sampled at regu­ investigate environmental change over time lar depth intervals of 10 cm, but this was not and human colonization of the region. possible in area 1 because of the irregular scatter of larger limestone clasts through the sequence. This also meant that the volume of MATERIALS AND METHODS spoil processed for snails varied considerably Location, Excavation, Sampling, Dating among collections. The following are indica­ tive: for NC/f1246 (Figure 3), ca. 0.025 m\ J Figure 1 shows the location of the cave (des­ for NC!fl247, ca. 0.05 m ; for NC!fl248, ignated YVMD007 in the catalog of the De­ ca. 0.125 m\ and for NC!fl249, ca. 0.15 m J partement Archeologie, Service des Musees (for explanation of sample numbers, see un­ et du Patrimoine de Nouvelle-Caledonie) on der next subheading). Snails were sorted from the central southwestern coast of New Cale­ other material by handpicking under a low­ donia. It lies ca. 13 Ian west of Moindou, power microscope or mounted lens or, for 500 m east of Me Aure, and 750 m north larger fractions, with the naked eye. Despite of the coast at grid reference 5563.6004 on the fact that the <3-mm fraction was checked Sheet SF-58-X-4a (no. 4824, Moindou) of for material before being discarded, and no the 1: 50,000 Serie Orange, Institut Geo­ notable organic remains seen, it is likely that graphique National de France (1991). The some juvenile and very small adult shells cave is situated on the northeastern flank of a were overlooked and thus not included in the low hill ca. 30 m below the summit and 50 m analysis. above high-tide mark in mixed broadleaf for- Two samples were submitted to the Uni- Land Snails from an Archaeological Site in New Caledonia . Cowie and Grant-Mackie 449

@ ~ \- \ - m 0 \ @ \ 1.0 ~ G) \.-/' \ 0.5 \ @ \ \ 0

Foot of scree slope leading uphill to ground surface -J \ )

FIGURE 2. Plan ofcave floor, with entrance at the bottom ofthe diagram, showing larger fallen blocks of limestone, the grid system used for collection and excavation purposes (straight dashed lines), and the numbered collection areas. versity of Waikato Radiocarbon Dating Lab­ various other publications (Pilsbry 1906­ oratory, New Zealand. One was a land snail 1907, Solem 1959, Mordan and Tillier 1986, shell, Placostylus duplex (Gassies 1871), from a Tillier and Mordan 1995). depth of 75 em, the other a sliver of human Because of the poor knowledge of the tibia from a depth of 37 em, both from area 1. fauna, identification of the collected mate­ rial was difficult in some cases. A number of clearly recognizable species could not be Snail Identification, Preservation, Faunal Trends readily referred to named species (they may Snail species were identified by reference to be undescribed) and are hence referred to the literature and in some cases by compari­ "Pleuropoma sp.," "Pararhytida sp.," "?Micro­ son with previously identified specimens in cystis sp.," and "Rhytida cf. aulacospira." the Bishop Museum (Honolulu). The litera­ All material is deposited in the collections ture used included the monograph of Franc of the Department of Geology, University (1957), the checklist of Solem (1961), and of Auckland, under both AU (Auckland Uni- Area 3 Area 1 Radiocarbon cm at wall ages O-+------I...---'-'-::-~-=---'c...... =:..:-.:..:....::.:..:..:...-+_---=----- B bones P potsherds -10 S marine shells

-20 c2 larger clasts ~ limitof . excavation -30~e 2300 ± 50 BP (WK 4521) -40

-50

-60

-70

~ f1250 3240 ± 60 BP ~ (WK 4195) -80

FIGURE 3. Stratigraphic columns for areas 1 and 3 showing the collection sites (f1242, etc., which should be prefixed by NC/ to give the full reference number), the distribution ofvarious materials, and the horizons of two radiocarbon dates (BP, years before present; WK ... , sample number in the University of Waikato Radiocarbon Laboratory records). The lozengelike background pattern over much of the diagram denotes finely interbedded lenses of gray ash and charcoal, reddish soil, and shell and/or bone debris; the deepest part of area 1 (NC/f1250) consisted of strllctureless reddish spoil with rock clasts and Placostylus shells; the top 5 em of the cave floor likewise showed no discernible bedding. Land Snails from an Archaeological Site in New Caledonia . Cowie and Grant-Mackie 451 versity) and NCff (New Zealand national matrix was almost entirely dry, very fine catalog of New Caledonian fossil localities) wood ash and small charcoal fragments in catalog numbers. Only the NCffnumbers are thin (up to 20 mm) lenses of dark and light referred to herein. gray and reddish brown color, and including Changes in relative abundance of individ­ charred or burnt bone and shell. Interfinger­ ual species with stratigraphic depth were ing with these were structureless concentra­ analyzed statistically using log likelihood G tions ofsmall bones (rodent, bird, lizard, frog, tests (Sokal and Rohlf 1981). bat, and fish), crab claws, marine mollusks, pottery shards, and human bone fragments. Land snails were present throughout. Bed­ RESULTS ding contacts were mostly sharp and clearly Stratigraphy, Dating distinct as a result of color contrasts, with no indication of digging, burrowing, or other Figure 3 shows the stratigraphy for areas 1 disturbance. The only intrusions were root and 3, with the snail sample numbers in­ penetration. The top 5 cm of the cave floor dicated. The human bone, from a depth of 37 was incoherent and showed no discernable cm, was dated (uncalibrated) at 2,300 ± 50 yr bedding. B.P., with a J13C value of -13.6 ± 0.2%0. The Placostylus duplex shell that was used for ra­ diocarbon dating, from a depth of 75 cm, Snail Taxa Recovered returned an uncalibrated age of 3,240 ± 60 The species recorded in each sample are yr B.P., with a J13C value of -9.97 ± 0.2%0. listed in Table 1. In total, 225 intact non­ These conventional dates may not be very marine snail shell specimens were collected. accurate for a number of reasons, including In addition, about 20 shells of Achatina Julica possible uptake of old carbonate from lime­ were recorded but not collected, and numer­ stone substrates by snails (Goodfriend 1987), ous fragments of Placostylus sp(p). shells were an unknown marine contribution to the ver­ collected. These records represent 20 terres­ tebrate diet, contaminants remaining in the trial species in nine families, and one fresh­ samples as a result ofthe limited pretreatment water species (probably a contaminant [see process, and limited isotopic data; for a fuller under Family Planorbidae]). The fauna re­ discussion see Grant-Mackie et al. (2004). flects the overall land snail fauna of New Cal­ Nevertheless, the dates accord with the stra­ edonia in being dominated by small snails tigraphy and human history of the cave in the families Charopidae and Rhytididae, (Grant-Mackie et al. 2004). Depths below with large Placostylus species present and 70 cm predate human colonization ofthe area minor representation of other families. Two (ca. 3,000-3,500 yr ago for New Caledonia as species are known human introductions. The a whole: Frimigacci 1980, Morat 1993, Gar­ following paragraphs provide brief informa­ gominy et al. 1996); the 20-cm depth repre­ tion about the species recovered, treating the sents the end of the Lapita cultural period families in the taxonomic sequence of Solem (cessation ofpottery production), estimated as (1961). about 1,700 yr B.P. (Kirch 1985); and the 15­ FAMILY HELICINIDAE. Pacific island heli­ cm depth represents the arrival ofEuropeans, cinids are poorly understood taxonomically. in 1774 (Gargominy et al. 1996). Despite the Franc's (1957) treatment followed Wagner problems mentioned here we therefore accept (1905,1907-1911), but Solem (1961) consid­ these dates as approximately correct. ered Wagner's works to be full of errors and, pending further study, placed all the New Caledonian helicinids in Pleuropoma, which Postdepositional Disturbance we follow here. Our material includes a large On the basis of its appearance during excava­ species, tentatively identified as Pleuropoma tion the sequence seen was essentially un­ primeana, and a smaller species that we refer disturbed by postdepositional processes. The to as Pleuropoma sp. The former was found in TABLE 1 Land Snail Species and Number of Specimens Recorded, by Sample and Depth, with Their Status as Native or Introduced to New Caledonia

Depth No. of Native/ Sample (cm) Family Species Specimens Introduced

NCIf1242 0-5 Subulinidae gracile (Hutton, 1834) 2 Introduced Achatina fitlica (Bowdich, 1822) ~20 Introduced Charopidae Andrefrancia dispersa (Gassies, 1863) 1 Native Charopidae Andrefrancia ventla (Gassies, 1858) 1 Native Helicarionidae ?Microcystis sp. 6 ? Native Rhytididae Rhytida (Pythorhytida) aulacospira 18 Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) cf. aulacospira 5 Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) inaequalis 5 Native (Pfeiffer, 1854) NCIf1243 5-15 Helicinidae Pleuropoma sp. 1 Native Subulinidae (Hutton, 1834) 1 Introduced Charopidae Andrefrancia vetula (Gassies, 1858) 12 Native Rhytididae Rhytida (Ptychorhytida) cf. aulacospira 1 Native (Pfeiffer, 1846) NCIf125I 5-15 Charopidae Andrefrancia vetula (Gassies, 1858) 7 Native NCIf1247 5-15 Helicinidae Pleuropoma sp. 1 Native Charopidae Andrefrancia dispersa (Gassies, 1863) 4 Native Charopidae Andrefrancia taslei (Crosse, 1874) 3 Native Charopidae Andrefrancia vetula (Gassies, 1858) 4 Native Helicarionidae ?Microcystis sp. 6 ? Native Bulimulidae Placostylus (Placostylus) porphyrostomus 1 Native (Pfeiffer, 1851) Rhytididae Rhytida (Ptychorhytida) aulacospira 24 Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) cf. aulacospira 11 Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) inaequalis 7 Native (Pfeiffer, 1854) Rhytididae Rhytida (Ptychorhytida) gassiesiana Native (Preston, 1907) NCIf1244 15-25 Planorbidae Physastra sarasini (Dautzenberg, 1923) 1 Native Charopidae Andrefrancia vetula (Gassies, 1858) 6 Native Helicarionidae ?Microcystis sp. I ? Native Bulimulidae Placostylus sp. Fragments Native Rhytididae Rhytida (Ptychorhytida) inaequalis 2 Native (Pfeiffer, 1854) NC/fI252 15-40 Helicinidae PleU1"opoma sp. 1 Native Helicarionidae ?Microcystis sp. 4 ? Native Bulimulidae Placostylus (Placostylus) porphyrostomus I Native (Pfeiffer, 1851) Rhytididae Rhytida (Ptychorhytida) inaequalis Native (Pfeiffer, 1854) NCIf1248 15-40 N eocyclotidae Gassiesa guesterianus (Gassies, 1866) 1 Native Subulinidae Allopeas gracile (Hutton, 1834) 1 Introduced Charopidae Andrefrancia vetula (Gassies, 1858) 9 Native Charopidae Tropidotropis trichocoma (Crosse, 1868) 1 Native Helicarionidae ?Microcystis sp. 4 ? Native Bulimulidae Placostylus (Placostylus) pOrphy1"ostomus 2 Native (Pfeiffer, 1851) Rhytididae Rhytida (Ptychorhytida) inaequalis 9 Native (Pfeiffer, 1854) Land Snails from an Archaeological Site in New Caledonia . Cowie and Grant-Mackie 453

TABLE 1 (continued)

Depth No. of Nativel Sample (cm) Family Species Specimens Introduced

Rhytididae Rhytida (Ptychorhytida) cf. aulacospim Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) aulacospi1'a 2 Native (Pfeiffer, 1846) NC/fl245 25-40 Charopidae Andrefrancia vetula (Gassies, 1858) 5 Native Charopidae Pararhytida sp. 1 Native Orthurethra Draparnaudia walkeri (Sykes, 1903) 1 Native Bulimulidae Placostylus sp. Fragments Native Rhytididae Rhytida (Ptychorhytida) aulacospira 1 Native (Pfeiffer, 1846) NCIfl246 35-45 Bulimulidae Placostylus sp. Fragments Native NCIfl249 40-72 Helicinidae Pleuropoma primeana (Gassies, 1863) 2 Native Helicinidae Pleuropoma sp. I Native N eoeyclotidae Gassiesa guesterianus (Gassies, 1866) 6 Native Charopidae Andrefrancia venda (Gassies, 1858) 16 Native Charopidae Monomphalus bavayi (Crosse & Marie, 1 Native 1868) Charopidae Platyrhytida saisseti (Gassies, 1871) 15 Native Helicarionidae ?Microcystis sp. 1 ? Native Rhytididae Rhytida (Ptychorhytida) aulacospira 2 Native (Pfeiffer, 1846) Rhytididae Rhytida (Ptychorhytida) inaequalis Native (Pfeiffer, 1854) NC/fl250 72-81 Bulimulidae Placostylus duplex (Gassies, 1871) 3 Native

sample NC!fl249 (pre-European); the latter and translucent. It appears recently dead and in NC!fl243, £1247, £1252, and £1249 (pre­ is probably a contaminant introduced to and post-European). the cave accidentally, although by unknown FAMILY NEOCYCLOTIDAE. Franc (1957) means. and Solem (1961,1964) used the family name FAMILY SUBULINIDAE. A number of sub­ Poteriidae, but this is a junior synonym ulinid species have been reported from New ofNeocyclotidae (Cowie 1998). All New Cal­ Caledonia, some described as endemic (Franc edonian species currently are placed in the 1957, Solem 1961, 1964). These supposed endemic Gassiesa. Only seven speci­ endemics are poorly known and probably can mens were found, one in sample NC/£1248 be referred to one of the introduced species and six in NC/£1249, both pre-European. All (Solem 1961, 1964). Our material is all iden­ were identified as Gassiesa guesterianus. tified as Allopeas gracile. This species is prob­ FAMILY PLANORBIDAE. Planorbids are ably of Neotropical origin (Solem 1964) but freshwater snails. The species are difficult to has been considered "probably the most distinguish and a number have been widely widely distributed land snail in the world" introduced around the world by people, add­ (Pilsbry 1906-1907:124). It was first reported ing to the confusion. The single specimen from New Caledonia in 1859 (Solem 1964), found (NC!fl244), however, is identified as but elsewhere in the Pacific (that is, in the the relatively distinct Physastra sarasini, a spe­ Hawaiian, Samoan, and Solomon Islands cies unique to New Caledonia. We follow [Christensen and Kirch 1981, 1986, Kirch Solem (1961) in placing it in Physastra rather 1993]) it has been shown to be of prehistoric than Franc (1957), who placed it in Isidora. origin. It may be declining in some loca­ The specimen is small, thin-shelled, shiny, tions (e.g., the Hawaiian and Samoan Is- 454 PACIFIC SCIENCE· July 2004 lands), although for unknown reasons (Cowie and fl250 (that is, at all depths except below 2001, 2002, Cowie and Robinson 2003). It 72 cm). was found in samples NC1fl242, fl243 (both Monomphalus bavayi is readily identified by post-European), and fl248 (pre-European). its depressed spire, large size, and dark and FAMILY ACHATINIDAE. Achatinafulica, the mottled coloration, which remained visible giant African snail, was first collected in New on the single specimen found, in sample NC/ Caledonia in 1972 (Tillier 1982, Gargominy fl249 (pre-European). et al. 1996). It has been widely introduced Pararhytida sp. The single, small, poorly throughout the Tropics and subtropics, in­ preserved specimen, found in sample NC/ cluding to many Pacific islands (Cowie 2002), fl245 (pre-European), could not be identi­ during the twentieth century. It was found fied. Its occurrence at the cave site does not only on the surface of the cave floor; no agree with the distributions of any of the six specimens were collected and retained. species of Pararhytida recognized by Mordan FAMILY CHAROPIDAE. All New Caledo­ and Tillier (1986). nian endodontoids were placed by Franc Platyrhytida saisseti is fairly easily identi­ (1957) and Solem (1961) in the Endodonti­ fied, although the umbilicus of our specimens dae. However, Solem (1976, 1983) restricted appears narrower than in the illustration of the Endodontidae to Polynesian species, with Franc (1957), suggesting that they might be­ all the New Caledonian species being placed long to a different, possibly undescribed spe­ in the Charopidae. Solem et al. (1984) and cies. It was found in large numbers but only Mordan and Tillier (1986) followed this fam­ in sample NCIfl249 (pre-European). ily assignment. The genus Andrefrancia was Tropidotropis trichocoma has a distinctively established by Solem (1960) but may not keeled, flat shell. Only one specimen was be valid (Pawlowska 2002). However, in the found, in sample NCIfl248 (pre-European). absence of a more recent revision of the New SUPERFAMILY LIMACOIDEA, INCERTAE Caledonian charopids, we adopt the classifi­ SEDIS. With the exception of a number of cation of Solem (1961), acknowledging the known modern introductions, the native New changes in Pararhytida of Mordan and Tillier Caledonian limacoid snails are extremely (1986). The fauna consisted of seven species. poorly known, to the extent that Solem Andrefrancia dispersa is distinguished by (1961) declined to place them in any family its strong, widely spaced transverse sculpture and was not even sure whether they are native and by almost imperceptible spiral sculpture or introduced. Franc (1957) placed the five on the protoconch, visible on only some of supposedly endemic species in the Helicar­ our specimens. It was found in only two ionidae. Solem (1961) tentatively placed three samples, NCIfl242 and fl247 (both post­ of these five in the genus Orpiella, with the European). remaining two as " incertae sedis." Andrefrancia taslei also has strong, widely Orpiella has been placed in the Helicar­ spaced transverse sculpture, but its umbilicus ionidae (e.g., Vaught 1989), although Solem is especially wide and deep and the shell is flat (1959:298) considered the Helicarionidae to with a nonprotruding spire. It was found only be absent from New Caledonia. The helicar­ in NCIfl247 (post-European). ionid subfamily Microeystinae was shown by Andrefrancia vetula was the most common Solem (1959:269) as absent from New Cale­ charopid and one of the most common spe­ donia although present to the north in Van­ cies in the overall fauna. The small shells are uatu and to the south on Norfolk Island. distinct in morphology; the transverse sculp­ Possibly, these New Caledonian species are ture is finer than that of A. rhizophorarum indeed helicarionids related to those of Van­ (Gassies 1865), the only species with which uatu and elsewhere in Melanesia. Only a it might be confused but which was not re­ single species was recorded. We tentatively corded in this study. Andrefrancia vetula was list it under Helicarionidae in Table 1 and found in all samples except NC1f1246, fl252, tentatively identify it as a species of Micro- Land Snails from an Archaeological Site in New Caledonia . Cowie and Grant-Mackie 455 cystis. It was recorded in all samples except is identified as Draparnaudia walkeri and is NC1f1245, £1246, and £1250, suggesting that in close agreement with photographs of the although its true identity is not certain it is lectotype (Solem 1959, Tillier and Mordan indeed a native New Caledonian species. 1995). FAMILY BULIMULIDAE. Bulimulids are FAMILY RHYTIDIDAE. Franc (1957) and represented in New Caledonia by the single Solem (1960, 1961, 1962, 1964) used the genus Placostylus. Conchological variation in faInily name Paryphantidae, which is a ju­ Placostylus has resulted in a plethora ofspecific nior synonym of Rhytididae (Cowie 1998). names; see, for example, the synonymy under Rhytidids are sometimes difficult to distin­ P. fibratus (Martyn 1789) given by Solem guish from charopids on the basis of the (1961). The range of variation within P. salo­ shells alone, although the two faInilies are not monis (Pfeiffer 1852) from Vanuatu, especially closely related. Solem (1961) changed some regarding the elongation of the shell spire, of the faInily assignments of Franc (1957); we is particularly noteworthy. Two species were follow Solem (1961). The fauna consisted of recorded, P. porphyrostomus and P. duplex. The four species. specimens of P. porphyrostomus are in good Specimens identified as Rhytida aulacospira agreement with the illustration of Franc are in close agreement with photographs of a (1957), but the specimens of P. duplex have a syntype given by Solem (1959). This species noticeably shorter spire than in his illustra­ was one of the most common species re­ tion. However, P. duplex is the closest match corded from the cave, being found in samples ofall those treated by Franc (1957), and given NCIf1242, £1245, £1247, £1248, and £1249, the variation in spire elongation just men­ which cover the entire depth range with the tioned for P. salomonis, the identification is exception of the deepest horizon (below probably correct. Placostylus porphyrostomus 72 cm). was present in samples NC/£1247 (post­ Other specimens, siInilar to R. aulacospira European) and NCIf1248 and £1252 (pre­ but differing from it in the rate of whorl ex­ European). Placostylus duplex was found in pansion and the wider spacing of the spiral sample NC1f1250, which is before human sculpture (especially on the underside of colonization. In addition, unidentifiable shell the shell), cannot be identified as a described fragments, referable only to Placostylus sp. but species and are referred to Rhytida (Ptycho­ probably belonging to one of the two men­ rhytida) cf. aulacospira. Franc's (1957) illustra­ tioned species, were found in samples NC/ tion of "R. aulacospira" resembles this species £1244, £124, and £1245 (all pre-European). in terms ofwhorl expansion more than it does ORDER ORTHURETHRA, INCERTAE SEDIS. Solem's (1959) illustration of a syntype of Tillier and Mordan (1995) revised New Cal­ R. aulacospira, suggesting that Franc (1957) edonian Draparnaudia, recognizing six spe­ Inisidentified his material. It was found in cies. They refuted Solem's (1962) placement samples NCIf1242, £1243, £1247, and £1248 of Draparnaudia (as the single genus in the (0-40 cm depth). subfamily Draparnaudiinae) in the faInily A single specimen, probably juvenile, Enidae (which is a junior synonym of Buli­ found in sample NC/£1247 (post-European), Ininidae [Vaught 1989]). However, although was identified as Rhytida (Ptychorhytida) gassi­ they then considered Draparnaudia as the esiana. It matches the description given by probable sister group to the family Partulidae, Franc (1957) as well as his photograph of they did not raise Draparnaudiinae to faInily the "type." In describing this species, Pres­ status, nor did they refer the group to another ton (1907) did not designate a holotype, orthurethran faInily. There is now molecular so Franc's (1957) figuring of the "type" evidence that Draparnaudia is the sister probably constitutes a lectotype designation. group to Gastrocopta (P. B. Mordan and C. M. Although Franc (1957) included it in the Wade, unpubl. data). The single specimen, Charopidae, Solem (1961), followed here, found in sample NCIf1245 (pre-European), considered it a rhytidid. 456 PACIFIC SCIENCE· July 2004

TABLE 2 Numbers of Specimens ofAndrefrancia vent/a, ?Microrystis sp., Rhytida alllacospi1-a, Rhytida cf. alllacospira, and Rhytida inaequalis CoUected from Different Depth Horizons

Species 0-5 em 5-15 em 15-40 em 40-72 em

Andl-efrancia vent/a 1 23 20 16 ?Microrystis sp. 6 6 9 1 Rhytida aulacospira 18 24 3 2 Rhytida cf. aulacospira 5 12 1 Rhytida inaequalis 5 7 12

Rhytida (Ptychorhytida) inaequalis is a rela­ cluded a decline of A. vetula and an increase tively large rhytidid, readily distinguished by of R. aulacospira. its distinct and regular transverse shell sculp­ ture. It was one of the more common species, found in samples NCIf1242 , £1244, £1247, DISCUSSION £1248, £1249, and £1252, which cover the en­ The native land snail fauna of New Caledonia tire depth range with the exception of the numbers about 110-160 known species (153: deepest horizon (below 72 cm). It has been Solem 1959; 135: Solem 1961; 110: Solem reported from Vanuatu, but according to et a1. 1984). However, many groups within Solem (1959) probably incorrectly. the fauna have been inadequately studied and the true number has been suggested as 300­ Trends in Faunal Composition 400 with many of these species locally re­ stricted (Tillier and Clarke 1983, Solem et a1. Trends in relative abundance ofnative species 1984). Thus, field collections are likely to were analyzed with contingency tables. Spe­ include undescribed species. In addition, in cies for which the expected value in any cell many groups, intraspecific variation in shell of the contingency table was <3 or for which morphology has not been adequately char­ the observed value in any cell was 0 were acterized, so that some species, currently excluded. Because only Placostylus duplex oc­ treated as valid, will probably in the future be curred (three specimens only) in the 72- to synonymized. This scenario of many species 81-cm depth horizon, this horizon was ex­ being undescribed but other species having cluded. Only three species occurred in suffi­ been described more than once is common in cient numbers to permit analysis of all other diverse tropical land snail faunas (Cowie et a1. depth ranges separately: Andrefrancia vetula, 1995, Emberton 1995). In many cases, rigor­ Rhytida aulacospira, and R. inaequalis (Table ous characterization of species will require 2). Significant trends were detected (G = study of internal anatomy and analysis of 53.2, df = 6, P < 0.001), with A. vetula molecular characters, but for most species declining and R. aulacospira increasing (R. in­ such studies have not been done. Of course, aequalis showed no clear trend and made the our samples consisted only of shells. Because smallest contribution to the value of G). By ofthese problems, some ofour material could combining all depth ranges >15 cm, corre­ not be definitively identified. sponding to arrival of Europeans, more Two of the species recorded are well­ species could be included in the analysis: An­ known aliens (Achatina fulica, Allopeas gracile), drefrancia vetula, ?Microcystis sp., Rhytida au­ introduced to Pacific islands by people. Acha­ lacospi1'a, R. cf. aulacospira, R. inaequalis (Table tina fulica was found only on the surface of 2). Again, significant trends were detected the cave floor; it is a twentieth-century intro­ (G = 58.7, df = 8, P < 0.001), and again the duction. Allopeas gracile was found in both major contributions to the value of G in- pre- and post-European horizons, confirming Land Snails from an Archaeological Site in New Caledonia . Cowie and Grant-Mackie 457 its prehistoric introduction to the islands of and Rhytida aulacospira increased. There is the Pacific (Christensen and Kirch 1981, no clear trend among the other three species 1986, Kirch 1993), with the caveat that mix­ analyzed statistically. Platyrhytida saisseti may ing of stratigraphic layers to some extent may also have declined, but its presence in only have led to it being found lower than in the one sample (albeit in large numbers) suggests absence of mixing (Carter 1990, Goodfriend that this could be a result of chance sampling. and Mitterer 1993), although Grant-Mackie Whether these changes in relative abun­ et ai. (2004) found no evidence for such mix­ dance have anything to do with human activ­ ing in this deposit. ities, especially arrival of Europeans, or with Only one sample, containing only Placosty­ changing habitat or climatic conditions is Ius duplex, was obtained from a prehuman not certain. However, vegetational changes, colonization stratum, so it is not strictly pos­ especially in lowland areas (such as the cave sible to be certain that any of the other spe­ site), have been dramatic since European cies is native, rather than prehistorically colonization, with extensive replacement of introduced. If any of these species are indeed native forest by alien vegetation (Gargominy alien (e.g., the species referred to as "?Micro­ et ai. 1996). At the time of excavation the hill cystis sp."), they were probably introduced on which the cave is located was at least partly from elsewhere in Melanesia or from farther fenced off from stock intrusion and clothed west in Australasia and southern Asia. They in sclerophyll forest, possibly little different all belong to groups that are native to this from what it was in prehuman times, but the overall region, but no phylogenetic analyses surrounding area is farmed and utterly modi­ have been undertaken that would permit their fied from what it would have been before precise geographic origins (and hence their European arrival (see Grant-Mackie et ai. native or alien status in New Caledonia) to 2004: pI. 1). Most native New Caledonian be ascertained. We interpret them all as na­ land snails are found only in native habitats tive (Table 1), as, implicitly, previous authors (Mordan and Tillier 1986, Tillier and Mor­ have done (e.g., Franc 1957, Solem 1961). dan 1995), so the decline of A. vetula and For most species, this interpretation is al­ perhaps of P. saisseti may have resulted from most certainly correct. Three species (Andre­ the modification of native habitat. Similarly, franchia dispersa, A. taslei, Rhytida gassiesiana), the presence of Pararhytida sp. in the cave although only recorded from post-European but the apparent modern absence of any spe­ strata, are very rare. This stratigraphic distri­ cies of Pararhytida from the region (Mordan bution is explained as an artifact of sampling and Tillier 1986) may also reflect habitat because, as abundance decreases, occurrence change. The increase of Rhytida aulacospira of species in samples becomes more sporadic is unexplained, unless, because it is a preda­ (ef. Goodfriend and Mitterer 1993). We tory species, it is related to availability of alien consider them native. snail prey (e.g., Allopeas gracile), but this is In addition to the introduction of alien conjecture. species (Allopeas gracile, Achatina fitlica), there Little other information has been reported are some suggestions offaunal change among regarding the ecological preferences of New the native species over the last ca. 3,500 yr. Caledonian snails. Draparnaudia walkeri is Placostylus duplex occurs only in a prehuman found only in relatively dry environments, sample. Possibly it was subsequently replaced with rainfall <2,100 mm per year (Tillier and by P. porphyrostomus, which occurs in later Mordan 1995), and the rainfall ranges for the horizons, but the small sample sizes do not six species of Pararhytida have been docu­ permit this to be determined, especially be­ mented (Mordan and Tillier 1986). No in­ cause unidentified fragments of Placostylus formation is available regarding other species. sp(p). occurred at shallower depths. Of the Because the distributions of many native spe­ five native species for which sufficient data are cies have probably contracted as native vege­ available to assess changes in their abun­ tation has been replaced by aliens, current dances over time, Andrefrancia vetula declined distribution records, such as those ofMordan 458 PACIFIC SCIENCE· July 2004 and Tillier (1986) and Tillier and Mordan ---. 1986. Nonmarine mollusks and eco­ (1995), may not reflect the natural tolerance logical change at Barbers Point, Oahu, ranges and even less the natural distribution Hawaii. Bishop Mus. Occas. Pap. 26:52­ of these species. It is therefore not possible 80. to assess changes in the fauna in the light of Cowie, R. H. 1998. Catalog of the nonmarine possible climatic change. snails and of the Samoan Islands. Bishop Museum Press, Honolulu. ---.2001. Decline and homogenization of ACKNOWLEDGMENTS Pacific faunas: The land snails ofAmerican We are grateful to Franc;oise Chavrot, pres­ Samoa. BioI. Conserv. 99:207-222. ident of the Cultural Commission of the ---. 2002. Invertebrate invasions on Pa­ Southern Province, for approval for the ex­ cific islands and the replacement ofunique cavation of the site; Jaques Leguen~ (l'Agence native faunas: A synthesis of the land and pour l'Eau et l'Environement du Pacifique, freshwater snails. BioI. Invas. 3 (3) [2001]: Noumea) for the use offield equipment; Pat­ 119-136. rick Laigret and his family for the use of their Cowie, R. H., and A. C. Robinson. 2003. The Moindou farm as a field base; Ghislain San­ decline of native Pacific island faunas: tacroce, Moindou, for permitting access to Changes in status of the land snails of the cave on what was then his farm; Peter Samoa through the 20th century. BioI. 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