Systematic review of the land snails of the Pitcairn Islands

The land snails (and semi-terrestrial molluscs) of the four islands that comprise the Pitcairn group are reviewed and the indigenous species illustrated. The strictly terrestrial molluscan faunas from the two atolls (Oeno and Ducie) are poor, like many other atolls in the Pacific. Each supports less than six species with wide geographical ranges. In contrast, the terrestrial molluscan fauna from Henderson Island, an uplifted atoll, is more diverse with at least 16 species belonging to seven families. Over half these taxa appear to be endemic, at least at the level of sub-species. Two species of semi-terrestrial molluscs have also been found on Henderson. Analyses of archaeological deposits in caves near the North Beach have revealed that at least a further six species of land snail formerly occurred on Henderson. The volcanic island of Pitcairn, the only island in the group still inhabited, supports the greatest number of terrestrial molluscs. Twenty-six species of land snail (and one semi-terrestrial pulmonate) were found living there during the recent expedition and a further three taxa were recognized amongst museum material. At least seven of these species are thought to be recent adventives and a further three are likely to have been prehistoric introductions. One Henderson (Georissa hendersoni) and three Pitcairn endemics (Pacificella filica, Sinployea pitcaimensis and Diastole tenuistriata) are formally described as new species. Some of the Pitcairn endemics occur in very restricted areas (less than a hectare) and it is important that measures should be taken to prevent the spread of invasive plants, such as rose-apple, that would threaten their survival.     

The composition and relationships of the marine molluscan fauna of the Pitcairn Islands

The recent expedition has doubled the number of marine molluscs known from the Pitcairn Islands. Over 80 taxa are recorded from Ducie and Pitcairn (both still poorly known), 240 from Oeno and 320 from Henderson. A total exceeding 400 taxa is now known from the group as a whole. Most of this increase results from a vastly improved knowledge of the small taxa that had been neglected in earlier surveys. Important faunal differences exist between the four islands in the group which are related to the different character of each island. These totals still underestimate the true diversities, but they provide data that are comparable in quality to those from adjacent regions. In this context the molluscan fauna from the Pitcairn Islands is seen to be impoverished when compared to those from islands further west. Most of the fauna is composed of widespread Indo-West Pacific species, but there are several taxa that have more restricted ranges centred on S.E. Polynesia. A few, including some undescribed taxa discovered on the expedition, appear to be endemic. Significantly, many of these are characterized by non-planktotrophic larval development. Comparison of the modern fauna from Henderson with the fossil fauna from the Pleistocene reef on its plateau reveals important differences. About 25% of the fossil molluscs are currently unknown from the group and about 5% appear to be undescribed. These high rates of turnover demonstrate that the faunas are temporally unstable.     

The Pitcairn Islands, South Pacific Ocean: plate tectonic and climatic contexts

The remote Pitcairn Group in the South Pacific Ocean comprises a volcanic island (Pitcairn Island), two low coral atolls (Oeno, Ducie) and a raised coralline island (Henderson Island). The geological history of these islands, on anomalously thin oceanic lithosphere, is related to the development of two subparallel island chains (Oeno-Henderson-Ducie; Pitcairn) associated with intra-Pacific plate 'hotspot' activity; the surface manifestation of this activity has been partly determined by structural lineations in the plate inherited from past plate history. The climate of the Pitcairn Islands is determined by the position of the subtropical high pressure system and the South Pacific Convergence Zone. Variations in the strength of this atmospheric circulation system, measured by changes in the Southern Oscillation index of pressure difference, provide a partial explanation of the long-term variability of mean annual rainfall at Pitcairn Island. Knowledge of past climates in the Pitcairn Group remains speculative. Maps of the Pitcairn Islands and a report of climate at Henderson Island (2/91-1/92) are included in the paper.     

The phytogeographical affinities of the Pitcairn Islands – a model for south‐eastern Polynesia?

Aim To identify how the Pitcairn group relates biogeographically to the south‐eastern Polynesian region and if, as a subset of the regions flora, it can then be used as a model for biogeographical analyses. Location The Pitcairn group (25°4′ S, 130°06′ W) comprises four islands: Pitcairn, a relatively young, high volcanic Island; Henderson, an uplifted atoll, the uplift caused by the eruption of Pitcairn; and two atolls, Ducie and Oeno. The remote location, young age and range of island types found in the Pitcairn Island group makes the group ideal for the study of island biogeography and evolution. Methods A detailed literature survey was carried out and several data sets were compiled. Dispersal method, propagule number and range data were collected for each of the 114 species that occurs in the Pitcairn group, and environmental data was also gathered for islands in Polynesia. Analyses were carried out using non‐metric multidimensional scaling and clustering techniques. Results The flora of the Pitcairn Islands is derived from the flora of other island groups in the south‐eastern Polynesian region, notably those of the Austral, Society and Cook Islands. Species with a Pacific‐wide distribution dominate the overall Pitcairn group flora. However, each of the islands show different patterns; Pitcairn is dominated by species with Pacific, Polynesian and endemic distributions, with anemochory as the dominant dispersal method (39.5%); Henderson is also dominated by species with Pacific, Polynesian and endemic distributions, but zoochory is the dominant dispersal method (59.4); Oeno and Ducie are dominated by Pantropic species with hydrochory as the most common dispersal method (52.9% and 100%, respectively). Main conclusions ? Habitat availability is the most significant factor determining the composition and size of the flora. ? South‐east Polynesia is a valid biogeographical unit, and should include the Cook, Austral, Society, Marquesas, Gambier, Tuamotu and Pitcairn Islands with Rapa, but should exclude Easter Island, Tonga and Samoa. ? Regionalization schemes should take island type into consideration. ? The Pitcairn Island group can serve as a useful model for Pacific biogeographical analyses.     

The flora of the Pitcairn Islands: a review

vascular plant flora of the Pitcairn Islands, south-central Pacific Ocean, is described based on extensive new collections made in 1991 and previously published records. Two vascular plants occur on Ducie Atoll; one (Pemphis acidula) is a new record. Sixty-three native vascular plants occur on Henderson, of which nine are endemic; Canavalia rosea, Operculina lurpethum, Psilotum nudum and Solanum americanum are new records for the island. Oeno Atoll has 16 native vascular plants; the single endemic (Bidens hendersonensis var. oenoensis) was not found in 1991 despite careful searches. Triumfetta procumbens was new for Oeno. Sixty-six native vascular plants have now been recorded from Pitcairn Island, there are two endemic ferns and seven endemic angiosperms in this number. A number of non-native taxa were new to Pitcairn. Some of the previously described taxa could not be found on Pitcairn, probably because they are very rare and only a small amount of time was spent collecting on Pitcairn. Many of the Pitcairn taxa are threatened by the spread of introduced species, especially Syzygium jambos.     

Geomorphology of the uplifted Pleistocene atoll at Henderson Island, Pitcairn Group

Henderson Island, in the Pitcairn Group, preserves a Pleistocene atoll physiography with the rim of the raised reef structure, supporting spur and groove topography, enclosing a central lagoon. Excellent preservation of coral reef communities occurs along the ancient atoll rim and within the central lagoon. The previously interpreted depositional nature of the fossil atoll structure is herein corroborated with geomorphologic and stratigraphic evidence from previously un-visited portions of the island. Stratigraphic and lateral facies relationships indicate a physiographic zonation which includes spur and grooves, outer reef flat, lagoon margin, and an interior lagoon with patch reefs. The in situ occurrence and zonation of reef coral communities around the periphery and within the interior of the island appear to reflect the original physiography of the atoll lagoon, with the most pronounced reef development on the SE side of the original atoll. Stratigraphic units which comprise the raised atoll lagoon structure represent different time intervals, so the atoll lagoon structure formed during various sea level fluctuations. The modern atolls of the Pitcairn Group, Oeno and Ducie, provide some comparisons (similarities and differences) with the fossil lagoon on top of Henderson Island.     

The breeding biology of the gadfly petrels Pterodroma spp. of the Pitcairn Islands: characteristics, population sizes and controls

This paper reports the breeding biology and nesting seasons of the gadfly petrels which nest on the four islands of the Pitcairn group, Pitcairn, Henderson, Oeno and Ducie. The species currently breeding are Murphy's petrel Pterodroma ultima , Kermadec petrel P. neglecta , Herald petrel P. heraldica and Henderson petrel P. atrata. Of these, Murphy's petrel is the most numerous; an estimated 250000 pairs bred on Ducie, which is probably the major breeding station of the species. Novel basic breeding data for Murphy's petrel are presented. Incubation spells, averaging 19.3 days, are exceptionally long for a petrel. Phoenix petrel P. alba appears to have ceased to breed on the Pitcairn Islands since the 1922 surveys of the Whitney Expedition. Nesting success was low on Henderson Island during the study. For all four breeding species, less than 20% of eggs laid yielded fledglings. Failure occurred at the early chick stage and observations indicated that it was due to predation by Pacific rats Rattus exulans. Although rats are present on Ducie, predation was apparently less severe there. The situation on Oeno may be intermediate. I consider how the populations of Henderson are maintained in the face of this intense predation. The Murphy's petrel population may be sustained by immigration from Ducie while the Herald and Henderson petrel populations could be undergoing a long-term decline on Henderson. It is not clear how the Kermadec petrel population is maintained. The conservation implications of these findings are discussed.     

Naïve birds and noble savages - a review of man-caused prehistoric extinctions of island birds

Many bird species were extirpated or became extinct when prehistoric man reached oceanic islands We list > 200 species of extinct island birds only recorded as sub-fossils and which probably vanished due to prehistoric man In addition we list c 160 cases where an extant species has been found as subfossil on islands where it no longer occurs Several species today considered endemic to single islands of island groups had a much wider distribution in the past Biogeographic analyses of insular avifaunas are almost meaningless it the extensive prehistoric extinctions are not taken into account
Most extinct species belong to Anatidae Rallidae and Drcpanididae while local extirpations are numerous among doves and seabirds Smaller birds are rare mainly due to sampling bias and taphonomic factors The bird populations were depleted mainly by overhunting predation by introduced vertebrates and alteration of the original vegetation
Prehistoric humans on islands although dependent on limited animal resources regularly failed to exploit these in a sustainable way Several cases where human populations disappeared from islands in the Pacific may have been due to over-exploitation of native animals
Prehistoric man reached most tropical and temperate islands and most of the few remaining island faunas have been severely depleted in historic times The prehistoric extinctions emphasize the extreme vulnerability and value of the very few pristine island faunas that still remain     

The fossil birds of Henderson Island, Pitcairn Group: natural turnover and human impact, a synopsis

Recent studies of island biotas have suggested that the impact of man on indigenous flora and fauna is much greater than previously suspected. This impact resulted in the introduction of many new species and the extinction of many unique life-forms. Henderson Island, in the Pitcairn Group, has been found to be an excellent laboratory for the study of natural faunal turnover and the impact of people on the natural environment. This was principally due to the island's remote location and its limestone structure, which resulted in the excellent preservation of fossil remains. During the Sir Peter Scott Commemorative Expedition to the Pitcairn Islands, extensive excavations were undertaken resulting in the collection of 42213 bird bones. It was possible to identify 31%. Of the 31 taxa identified, four seabirds appear to be vagrants, a surprisingly high number illustrating that the uncritical evaluation of fossil bird lists from other islands risks over-estimating the number of indigenous species. As a result of the arrival of Polynesian people during the first half of this millennium, half of Henderson's endemic landbirds became extinct, as did most of the small ground-nesting seabirds. The lower sea level during cold stages creates many temporary limestone 'high' islands. This results in many 'former-atolls' developing geological and ecological similarity to Henderson. Hence lower sea-level greatly facilitates the movement of flora and fauna between currently isolated oceanic 'high' islands.     

Seasonality and numbers of green turtles Chelonia mydas nesting on the Pitcairn Islands

During 1991 and 1992 the first regular field observations of green turtles, Chelonia mydas , on the Pitcairn Islands (South Pacific) revealed that nesting occurs only on Henderson where about 10 females laid eggs (c. 1% of the French Polynesian population). Substrates on Pitcairn and Ducie Atoll are unsuitable for nesting and no signs of nesting were found on Oeno Atoll where the terrain appears suitable.     

On the urgency of conservation on Guadalupe Island, Mexico: is it a lost paradise?

Guadalupe is an oceanic island located in the Pacific Ocean off Mexico's northwest coast. Its flora is composed of many plant species with more northern affinities and disjunctions from the California Floristic Province. Almost 16% of the native plant species are endemic, including two monospecific genera. However, the activities of feral goats released in the early 19th century have devastated most of the island. At present, at least 26 native plant species have disappeared from Guadalupe and many more seem to be on the threshold. To add to the problem, 61 exotic plant species have been documented on the island, many of which are aggressive weeds. In this paper, we propose eight types of environmental conditions for the island where different species assemblages of the pristine flora probably existed before their demise. It is of obvious urgency that the island needs a recovery plan and the first step should include the eradication of the feral goats. Only after this process can subsequent conservation measures be applied to ensure any restoration of this natural heritage. The recovery plan will need to address both spontaneous and human-induced plant repopulation processes from the main island's three southern islets, which have never been impacted by goats. Also, it may be necessary to reintroduce non-endemic, native plant taxa from the nearest Californian islands and the Mexican coast in order to reestablish some of the island's original diversity of plant species and communities. However, it should be noted that the forested communities do not have great hopes of recovering in the short term, since the ground water and soil conditions have been significantly altered. Furthermore, the eradication of an estimated 4000 goats still living on the island (year 2000) depends upon the vacillating motivation and will of Mexican authorities.     

The modern avifauna of the Pitcairn Islands

Excluding the gadfly petrels Pterodroma spp. and the resident landbirds, this paper details the present status of bird species seen during an expedition to the Pitcairn Islands (Ducie, Henderson, Oeno and Pitcairn) in 1991 and early 1992. Ten species were recorded in the Islands for the first time. Several Southern Ocean petrels were recorded, most in the midwinter period of June and July. The populations of Christmas Island shearwaters breeding on Oeno and Ducie laid in synchrony every 9–10 months. The species is one of few with such a sub-annual, synchronized regime. The majority of other seabirds had an annual breeding cycle, laying between May and October. Around one percent of the world population of the bristle-thighed curlew passes the non-breeding season in the Pitcairn Islands.     

Near-shore bathymetry and reef biotopes of Henderson Island, Pitcairn Group

The coral reef which surrounds two thirds of Henderson Island, Pitcairn Group, consists of a reef flat, reef margin and fore-reef which slopes gradually into deeper water. The range of sublittoral habitats provided by this topography is limited, reflecting a low level of coral diversity. Spur and groove formations of the fore-reef are present around the northern end of the island which contrasts with the south-western corner, where, in the absence of a fringing reef platform, subaerial cliff faces are fronted by a cliff foot submarine 'trench'. In general, live coral cover on the fore-reef was estimated at between 10–30%, though at sites off the east coast it reached 80%. The associated communities, particularly of sessile filter-feeding groups, were found to be impoverished. The two factors of biogeographical isolation and of local bioerosion processes are proposed as being the main reasons for the depauperate nature of the island's reef. Brief notes are included on the lagoon and fore-reef bathymetry and habitats of Ducie and Oeno Atolls for comparative purposes.     

The historic biogeography and community ecology of Polynesian pigeons and doves

The species richness, taxonomic diversity, and geographic distribution of pigeons and doves (Columbidae) have been altered irreversibly in Polynesia by 3500 years of human activity. Natural (without human influence) columbid faunas are estimated primarily by studying prehistoric bones. In all Polynesian island groups studied (except outlying Easter Island, Hawaiian Islands, or New Zealand), the prehistoric columbid faunas had more species, more genera, and more species per genus than modern faunas from the same island. Congeneric species pairs or triplets occurred on many islands for Ducula , Ptilinopus , and Gallicolumba. The losses of Polynesian columbids include the extinction of at least 9 species in the genera Ducula , Ptilinopus , Macropygia , Caloenas , Gallicolumba , and Didunculus as well as the extirpation of numerous island populations of extant species. If not for human impact, a typical East Polynesian island would support at least 5–6 species of columbids in 3–4 genera (compared to 0–3 species in 0–3 genera today). A typical West Polynesian island would support at least 6–7 species in 4–5 genera (compared to 1–6 species in 1–5 genera today). Since all Polynesian pigeons and doves are frugivorous and/or granivorous, their decline in recent millennia probably has affected the composition of Polynesian forests by limiting inter- and intra-island dispersal of plant propagules.     

The Foraminifera of the Pitcairn Islands

Foraminifera were recovered from 18 samples collected in the Pitcairn Islands, 12 from Henderson Island (including the best and most comprehensive collections) and three each from Oeno Atoll and Pitcairn Island itself. Although both algae and sediment samples were collected, the living Foraminifera came, almost exclusively, from phytal (attached or clinging) habitats. Foraminifera in the sediment samples are mainly thanatocoenoses. The fauna is an exclusively calcareous, relatively low diversity assemblage, dominated by large soritids [Marginopora, Amphisorus, Sorites) and Amphistegina , all of which are ubiquitous throughout the tropical Pacific. These larger Foraminifera are usually accompanied by small miliolids in particular, as well as by small attached Foraminifera (discorbids and the like). Typical reefal Foraminifera are generally under-represented. So far, no endemic species have been found. Of more significance, perhaps, is the apparent absence of Calcarina , small rotaliids, elphidiids and agglutinating species, so common in the western Pacific islands. One sample of fossil Foraminifera was analysed, from a shelly sand (c. 30 m above present sea-level) on Henderson Island. Though, for the most part, like the Recent assemblages, this was characterized by Archaias , a soritid which was not found in any of the modern collections made by the 1991– 92 Expedition. This could either be a sampling artifact or refer to a real environmental change since the Pleistocene.     

Rapid, independent evolution of flightlessness in four species of Pacific Island rails (Rallidae): an analysis based on mitochondrial sequence data

Flightless rails were once ubiquitous in the avifauna of Pacific oceanic islands. Most species have become extinct since human colonization of islands began about 2000 years ago. In this study, we use mitochondrial sequence data to estimate the phylogenetic relationships and ages of four species of flightless insular rails in the genus Porzana : palmeri , from Laysan Island in the Hawaiian archipelago; sandwichensis , from the island of Hawaii; monasa , from Kosrae Island in Micronesia; and atra , from Henderson Island in the Pitcairn group. Although all four species survived into historic times, all but atra are now extinct. The optimal trees show that palmeri is descended from Porzana pusilla , a volant crake distributed widely throughout the Old World. Porzana sandwichensis , P. monasa , and P. atra are each descended from the lineage leading to P. tabuensis , a volant rail widespread in northern and eastern Australia and on islands north to Micronesia and the Philippines and east through Polynesia. Loss of flight appears to have evolved rapidly in these insular rails, based on both sequence divergence values and data on the ages of the islands. In the case of the Laysan Rail ( palmeri ), divergences including loss of flight probably evolved in less than 125,000 years .     

The Patterning Cascade Model and Carabelli's trait expression in metameres of the mixed human dentition: exploring a morphogenetic model

Since ancient times the Mediterranean island of Sardinia has been known for harboring a population with an average body height shorter than almost every other ethnic group in Europe. After over a century of investigations, the cause(s) at the origin of this uniqueness are not yet clear. The shorter stature of Sardinians appears to have been documented since prehistoric times, as revealed by the analysis of skeletal remains discovered in archaeological sites on the island. Recently, a number of genetic, hormonal, environmental, infective and nutritional factors have been put forward to explain this unique anthropometric feature, which persisted for a long time, even when environmental and living conditions improved around 1960. Although some of the putative factors are supported by sound empirical evidence, weaker support is available for others. The recent advent of whole genome analysis techniques shed new light on specific variants at the origin of this short stature. However, the marked geographical variability of stature across time and space within the island, and the well‐known presence of pockets of short height in the population of the southern districts, are still puzzling findings that have attracted the interest of anthropologists and geneticists. The purpose of this review is to focus on the state‐of‐the‐art research on stature, as well as the factors that made Sardinians the shortest among Europeans.