Island Land Snail Research Articles

Flying snails: immigrant selection and the taxon cycle in Pacific Island land snails

Flying snails: immigrant selection and the taxon cycle in Pacific Island land snails

Evolutionary history of inshore oceanic island land snails diversified in shell colour

AbstractAimOceanic islands provide an excellent opportunity to study the mode and tempo of phenotypic evolution of terrestrial organisms. Many studies have focused on oceanic islands far from the mainland. Oceanic islands near the mainland may provide distinct perspectives on phenotypic evolution, but a comprehensive understanding is still lacking. To address this gap, this study aimed to reveal when a land snail species inhabiting a volcanic archipelago within 40 km of the mainland diverged and how their shell colours evolved.LocationSouthern Izu Peninsula and five Izu Islands (Oshima, Toshima, Niijima, Shikine and Kozu), Japan.Taxon Euhadra peliomphala simodae. MethodsDouble‐digest restriction site‐associated DNA sequencing (ddRAD‐seq) was conducted using 117 individual snails. Molecular phylogenetic and population genomic analyses were performed, including approximation Bayesian computation (ABC). We then examined whether the island area, elevation, distance from the surrounding landmasses and historical event (bottleneck) explain the shell colour diversity on each island using a phylogenetic generalised linear mixed model (PGLMM).ResultsSnails could be genetically categorised according to the island they inhabited, and on Niijima, their genetic structure was further divided within the island. The divergence times among the extant populations of the snail dated back to 2.1 million years ago (Ma), which is older than that of other animals occurring in this region. Additionally, island elevation positively affected shell colour diversity, and populations with similar shell colour profiles were phylogenetically different.Main conclusionsIsland land snails diversified early in the ecosystem of the Izu Islands. This suggests that proximity to the mainland, immobility and the physiological tolerance of passive dispersal in land snails were the main causes of early diversification. Moreover, our study proposes that environments covarying with elevation would determine shell colour diversity on each island through natural selection.

Mollusk loves: Becoming with native and introduced land snails in the Hawaiian Islands

Hawaiian island land snails once represented one of the most diverse archipelagic evolutionary radiations. Historically, indigenous Hawaiians (Kānaka maoli) and Westerners also heard some snails (kāhuli) sing. Today, most of these species are extinct or endangered. One major cause has been the intentional mid-20th century introduction of a land snail, Euglandina rosea, for the biological control of another mollusk, Lissachatina fulica. In this article, I join efforts of noticing and engaging landscapes of the situated Anthropocene with the goal of demonstrating the potential for mollusks to be dynamic alliance-forming companions. In articulating methods of becoming with snails, I pass kāhuli through Western and Kānaka maoli knowledge-making projects. First considering the evolutionary biological work of John Gulick and his counterparts to genealogize contemporary snail-love, I then elaborate on what care and hope might mean with Pacific Island land snails living through ongoing environmental dispossession and alteration. I then reconsider Euglandina on parallel conceptual terms, engaging natural historical and laboratory accounts to think with the introduced mollusk beyond its categorization as ‘alien invader’. Loving Euglandina as well as kāhuli may help realize livable futures for indigenous and introduced Hawaiian island mollusks alike, in a world hopefully full of snail-song.

Historical DNA from Museum Shell Collections: Evaluating the Suitability of Dried Micromollusks for Molecular Systematics

Natural history collections are an invaluable resource that can inform systematic studies and biodiversity discovery, and also contribute to understanding changes in species abundance and distributions over time. The decline in abundance and diversity of Pacific Island land snails has been a major conservation concern for more than six decades, but only the largest and most colorful snails are protected under the US Endangered Species act, and few are listed as critically endangered on the IUCN Red List. Like most invertebrates, the conservation status of many Hawaiian land snails still need assessment. Molecular data are highly informative for revising species limits and understanding evolutionary patterns and processes, but with as much as 70% of Hawaiian land snails already extinct, few fresh samples are available from which to extract DNA. To overcome the lack of material suitable for DNA barcoding, we test whether short DNA fragments of 225 to 355 bp can be sequenced from museum snail shells containing dried tissues collected more than 50 years ago. Short DNA sequences (225 bp) were obtained from 66.7% of lots, while longer DNA sequences (355 bp) were successfully sequenced from 24.2% of lots. Snail specimens stored in natural history cabinets for more than 100 years were successfully sequenced, supporting the inclusion of these materials for modern biodiversity studies. Molecular data from this study represents a small proportion of Hawaiian microsnail species housed among the millions of specimens in the Bishop Museum in Hawaii and other natural history collections. Additional resources and focused efforts are needed to scale this approach to incorporate many more of the hundreds of snail species in need of assessment in Hawaii. More broadly, there are large representative collections of endangered Pacific Island non-marine snails in many natural history museums that may be suitable for molecular work, either with DNA barcoding or other genomic approaches.

Millimeter-sized smart sensors reveal that a solar refuge protects tree snail Partula hyalina from extirpation

Pacific Island land snails are highly endangered due in part to misguided biological control programs employing the alien predator Euglandina rosea. Its victims include the fabled Society Island partulid tree snail fauna, but a few members have avoided extirpation in the wild, including the distinctly white-shelled Partula hyalina. High albedo shell coloration can facilitate land snail survival in open, sunlit environments and we hypothesized that P. hyalina has a solar refuge from the predator. We developed a 2.2 × 4.8 × 2.4 mm smart solar sensor to test this hypothesis and found that extant P. hyalina populations on Tahiti are restricted to forest edge habitats, where they are routinely exposed to significantly higher solar radiation levels than those endured by the predator. Long-term survival of this species on Tahiti may require proactive conservation of its forest edge solar refugia and our study demonstrates the utility of miniaturized smart sensors in invertebrate ecology and conservation.

Molecular phylogenetics and premating isolation in the punctoid land snails of Belau (Republic of Palau, Oceania)

AbstractPacific island land snails exhibit exceptionally high species diversity, morphological diversity, and endemism. Species within superfamily Punctoidea, which contains the Charopidae and Pacific‐endemic family Endodontidae, are among the most morphologically spectacular Pacific endemic land snails. The evolution of Pacific island punctoids remains poorly known, due in part to rampant human‐induced extinction within this group of minute ground‐dwellers. The Belau archipelago (Republic of Palau) with its relatively intact lowland rainforest and limestone karst Rock Islands, is home to many endemic punctoids and presents a unique opportunity to better understand the diversification of one of the most diverse but also imperiled land snail lineages on Pacific islands. For the first time, the diversification of the endemic Pacific punctoid fauna of Belau was studied using Bayesian Inference (BI) and Maximum Likelihood (ML) methods applied to sequences from mitochondrial (COI) and nuclear (ITS2) gene regions. Evolutionary relationships, molecular divergence, disjunct or complex geographic ranges, and ecological similarity among Belau punctoid species, likely reflect species’ long evolutionary history and diversification through geographic isolation. We find no evidence for adaptation in species‐level shifts in spire height within Aaadonta endodontids. We also find preliminary evidence for the evolution of premating reproductive isolation in Semperdon species in sympatry, through the study of apertural teeth. In addition, we report the first new endodontid species from living individuals as well the first new genus record from the Belau archipelago in nearly half a century.

Biodiversity and Extinction of Hawaiian Land Snails: How Many Are Left Now and What Must We Do To Conserve Them-A Reply to.

Pacific islands, with their incredible biodiversity, are our finest natural laboratories for evolutionary, ecological, and cultural studies. Nowhere, in relation to land area, does land snail diversity reach that of the Pacific islands, with more than 6000 species, most of which are single island endemics. Unfortunately, land snails are the most imperiled group with the most recorded extinctions since the 1500s, and Pacific island snails make up the majority of those extinctions. In 1990, Dr. Alan Solem, a well renowned malacologist, with expertise in Pacific island land snails, posthumously published a plea to save the remaining Hawaiian land snails before they vanish forever. Now, more than 25 years later, we have finally begun to make inroads into answering the questions "How many Hawaiian land snails remain?" and "What will we need to save them?". Here we provide a belated reply to Solem (1990) and address these questions about Hawaiian land snails. We conclude by building on the actions suggested by Solem and that we feel are still needed to realize his hope of conserving Hawaii's remaining land snails specifically, but also our hope of conserving invertebrates more broadly.

A checklist of land snails from the west coast islands of Sabah, Borneo (Mollusca, Gastropoda).

Sabah, situated in one of the world’s biodiversity hotspots, has the largest number of islands in Malaysia with more than 500 of various sizes and degrees of isolation. However, information on the islands’ biodiversity is limited. This study provides an up-to-date checklist of land snail species found on 24 west coast islands in Sabah. A total of 67 species (nearly 20% of the total number of land snail species in the state) representing 37 genera and 19 families is enumerated based on systematic field surveys of 133 sampling plots, BORNEENSIS database records and species checklists published between 2000 and 2016. The number of species on the islands ranges from four to 29. Labuan Island has the highest number of species (29), followed by Tiga Island (25), Mantanani Besar Island (24) and Gaya Island (23). However, the populations of some land snail species may have declined as several previously recorded species on the islands were not found in a recent systematic field sampling. This checklist is provided as a baseline inventory for future island land snail studies and to better inform biodiversity conservation plans of marine parks and other islands on the Sabah west coast.

Type Specimens of Hawaiian Land Snails in the Smithsonian Institution, National Museum of Natural History, with Lectotype Designations

Pacific island land snail faunas are among the most threatened faunas in the world, having suffered a higher rate of extinction than any other major animal group. The Hawaiian land snails are among the most species-rich and most severely effected of these faunas, yet the current status of most of the Hawaiian species is unknown. Most of the major taxonomic studies on the fauna were undertaken 50–100 years ago and only certain groups were comprehensively studied. New research is uncovering undescribed species, both extant and extinct. The need for rigorous taxonomic treatment of the group is acute if the taxonomic and conservation status of the many species is to be ascertained, and the basis for such research is comprehensive study of type material. The Smithsonian's National Museum of Natural History holds type material of 39 nominal species-group taxa of Hawaiian land snails belonging to eight families; this annotated catalog provides details of this material. Of these taxa, 29 were described by Augustus Addison Gould from material collected by the U.S. Exploring Expedition of 1838–1842. For completeness, we also provide details for one lot of purported paralectotypes that are here inferred not to have been syntypes and one lot representing an unavailable infrasubspecific name. We designate lectotypes for 12 species-group taxa . Yeung, Norine W., Robert H. Cowie, Kenneth A. Hayes, and Ellen E. Strong. Type Specimens of Hawaiian Land Snails in the Smithsonian Institution, National Museum of Natural History, with Lectotype Designations. Smithsonian Contributions to Zoology, number 647 , vi + 34 pages, 11 figures, 2017.

Annotated catalogue of types of Hawaiian land and freshwater snails (Mollusca: Gastropoda) in the Muséum national d'Histoire naturelle, Paris, with lectotype designations

ABSTRACT Pacific island land snail faunas are among the most threatened faunas in the world, having suffered a higher rate of extinction than any other major animal group. The Hawaiian land snails are among the most species rich and most severely impacted of these faunas, yet the current status of most of the Hawaiian species is unknown. Most of the major taxonomic studies on the fauna were under-taken 50–100 years ago and only certain groups were comprehensively revised. New research is uncovering undescribed species, both extant and extinct. The need for rigorous taxonomic treatment of the group is acute if the validity and conservation status of the many species is to be ascertained, and the basis for such research is comprehensive study of type material. The Museum national d'Histoire naturelle, Paris, holds type material of 38 nominal species-group taxa of Hawaiian land and freshwater snails belonging to six families, overwhelmingly the Achatinellidae Gulick, 1873 and Amastridae Pilsbry, 1910; this a...

Evaluating the efficacy of land snail survey techniques in Hawaii: implications for conservation throughout the Pacific

Terrestrial micromolluscs (snails with an adult maximum shell dimension <5 mm) constitute a considerable proportion of the land snail fauna of the Pacific. However, micromolluscs are often underestimated in biological surveys because of size bias. It has been argued that visual searches are preferable on Pacific islands because: (1) size biases are limited based on the understanding that most native Pacific island land snails are very small, and (2) amount of labor is less than other methods such as soil surveys and adequate for inventory purposes (though not for abundance assessments). To test whether visual surveys and soil surveys were accurately recording all taxa, land snail inventories were completed in three forest reserves (5 sampling sites in each) on the island of Oahu, Hawaii. Visual surveys involved 30-min visual search in a 10 m2 site; soil surveys involved sieving leaf litter and topsoil from four 0.3 m2 quadrats and extracting snails with the aid of a microscope. The data indicate a size and microhabitat bias associated with both techniques. Visual surveys consistently collected large arboreal and litter-dwelling species but missed a significant portion of micromolluscs, while soil surveys collected micromolluscs but missed larger snails. Because of such biases, employing both methods is critical for collecting all taxa at a survey location. As such, we recommend that future land snail surveys on Pacific Islands incorporate both survey techniques. Obtaining a complete inventory is critical if we are to understand species distributions and patterns of diversity and make well-informed conservation recommendations.

Distribution, movement, and microhabitat use of the introduced predatory snailEuglandina roseain Hawaii: implications for management

The purposeful introduction of the land snail Euglandina rosea, which feeds exclusively on snails and slugs, has been implicated as a major factor in the decline of diverse Pacific island land snail faunas. We report on the distribution, movement patterns, and microhabitat preferences of E. rosea in a gulch in the Waianae Mountains, Oahu, Hawaii, because such data will help focus management actions at a local scale to protect native snail populations in areas where E. rosea is established. The Waianae Mountains harbor many endangered or threatened snails, most currently found in isolated habitat patches near the ridges. Conversely, most living individuals (28/29) and shells (46/56) of E. rosea were collected within the gulch, which supported higher densities of other native and non-native snails, and was cooler and more moist than the ridges. Thirteen individuals of E. rosea were tracked (eight directly using a bobbin and thread method, and five indirectly by mark–recapture); most (10/13) moved on average <2.5 m per week (range 0.1–25.21 m), and all stayed within the gulch. Members of E. rosea preferred leaf litter over open, fern/shrub, or wood microhabitats. There were large differences in the population density of E. rosea over small spatial scales, indicating that there may be places where native snail populations could persist even in areas where populations of E. rosea are established. Identifying areas with differing population densities of E. rosea is critical for not only understanding why some native snail species may be more vulnerable to extinction, but also to locate areas where predation pressure is low and conservation efforts will be most likely to succeed.

Pleistocene–Holocene environmental change in the Canary Archipelago as inferred from the stable isotope composition of land snail shells

The isotopic composition of land snail shells was analyzed to investigate environmental changes in the eastern Canary Islands (28–29°N) over the last ~ 50 ka. Shell δ 13C values range from −8.9‰ to 3.8‰. At various times during the glacial interval (~ 15 to ~ 50 ka), moving average shell δ 13C values were 3‰ higher than today, suggesting a larger proportion of C 4 plants at those periods. Shell δ 18O values range from −1.9‰ to 4.5‰, with moving average δ 18O values exhibiting a noisy but long-term increase from 0.1‰ at ~ 50 ka to 1.6–1.8‰ during the LGM (~ 15–22 ka). Subsequently, the moving average δ 18O values range from 0.0‰ at ~ 12 ka to 0.9‰ at present. Calculations using a published snail flux balance model for δ 18O, constrained by regional temperatures and ocean δ 18O values, suggest that relative humidity at the times of snail activity fluctuated but exhibited a long-term decline over the last ~ 50 ka, eventually resulting in the current semiarid conditions of the eastern Canary Islands (consistent with the aridification process in the nearby Sahara). Thus, low-latitude oceanic island land snail shells may be isotopic archives of glacial to interglacial and tropical/subtropical environmental change.

Feeding Preferences of Two Predatory Snails Introduced to Hawaii and Their Conservation Implications

Two introduced predatory land snails, Euglandina rosea and Oxychilus alliarius, have been implicated in the decline of native Hawaiian and Pacific island land snails. We examined the feeding ecology of E. rosea and O. alliarius, focusing first on prey size and species preferences, and second on quantifying consumption rates, which is necessary to address the possible levels of impact on natural populations. In prey-size preference experiments, E. rosea always consumed more snails in the smaller size class. In prey-species preference experiments, E. rosea preferred snails to slugs but showed no preference among snail species. Size preference experiments indicated that O. alliarius will only consume prey less than 3 mm in shell length. In prey species preference experiments O. alliarius consumed every snail species offered but did not consume either of the slug species. Consumption rates were positively related to the size of the predator, with the larger predator, E. rosea, having a much higher consumption rate than O. alliarius, and with larger E. rosea consuming more than smaller E. rosea. These results have unfortunate conservation ramifications, because since they indicate that both E. rosea and O. alliarius are generalist snail predators feeding preferentially on the smallest snails, although they rarely eat slugs. Since many extant Hawaiian and Pacific island snail species are small, they are at risk of predation by these two introduced predators, while invasive slugs — there are no native slugs in Hawaii — may not be impacted by them.

Effects of habitat history and extinction selectivity on species-richness patterns of an island land snail fauna

Aim Local-scale diversity patterns are not necessarily regulated by contemporary processes, but may be the result of historical events such as habitat changes and selective extinctions that occurred in the past. We test this hypothesis by examining species-richness patterns of the land snail fauna on an oceanic island where forest was once destroyed but subsequently recovered. Location Hahajima Island of the Ogasawara Islands in the western Pacific. Methods Species richness of land snails was examined in 217 0.25 × 0.25 km squares during 1990–91 and 2005–07. Associations of species richness with elevation, current habitat quality (proportion of habitat composed of indigenous trees and uncultivated areas), number of alien snail species, and proportion of forest loss before 1945 in each area were examined using a randomization test and simultaneous autoregressive (SAR) models. Extinctions in each area and on the entire island were detected by comparing 2005–07 records with 1990–91 records and previously published records from surveys in 1987–91 and 1901–07. The association of species extinction with snail ecotype and the above environmental factors was examined using a spatial generalized linear mixed model (GLMM). Results The level of habitat loss before 1945 explained the greatest proportion of variation in the geographical patterns of species richness. Current species richness was positively correlated with elevation in the arboreal species, whereas it was negatively correlated with elevation in the ground-dwelling species. However, no or a positive correlation was found between elevation and richness of the ground-dwelling species in 1987–91. The change of the association with elevation in the ground-dwelling species was caused by greater recent extinction at higher elevation, possibly as a result of predation by malacophagous flatworms. In contrast, very minor extinction levels have occurred in arboreal species since 1987–91, and their original patterns have remained unaltered, mainly because flatworms do not climb trees. Main conclusions The species-richness patterns of the land snails on Hahajima Island are mosaics shaped by extinction resulting from habitat loss more than 60 years ago, recent selective extinction, and original faunal patterns. The effects of habitat destruction have remained long after habitat recovery. Different factors have operated during different periods and at different time-scales. These findings suggest that historical processes should be taken into account when considering local-scale diversity patterns.

Taxonomic revision of the fossil land snail species of the genus Mandarina in the Ogasawara Islands

The taxonomy of extant animal species is often based on biological information that is not normally preserved in fossils. Reducing discrepancies between taxonomy based only on hard tissues and that based on other biological information to a minimal level is crucial in studies focusing on species diversity that integrate extant and fossil material. In the present study, I address this issue using morphological analysis of the endemic Ogasawara Island land snails in the genus Mandarina. I first examine pairwise differences in shell morphology among 39 populations of 15 extant species that were discriminated by differences in their reproductive organs and their phylogenetic relationships. A classification model to assess whether the observed differences in fossil shell characters were inter- or intra-specific was developed by training an artificial neural network (ANN) with the patterns of differences in shell characters among the extant species. The average probability that the trained ANN misclassifies extant forms was 1.4%. The trained ANN was applied to discriminate morphological differences among the Pleistocene-Holocene fossil samples of Mandarina luhuana that occurred in Chichijima and Minamijima. As a result, three species were identified in the samples previously referred to M. luhuana. Mandarina pallasiana, previously treated as a synonym of M. luhuana, is separated, and one new species and one new subspecies are described.

Speciation: Marathon mollusc migrations

Speciation: Marathon mollusc migrations

Charopid land snails (Gastropoda Pulmonata Charopidae) from Mayotte, Comores: alive and well

The land snail fauna of Mayotte, the oldest of the Comores Islands, has been resurveyed for the first time since the pioneering work of Morelet in the 19th century. All historically recorded species in the family Charopidae are now documented based on live-taken specimens or fresh shells. In contrast with many other radiations of tropical island land snails, the Mayotte faunule appears to be exempt from extinctions. The family Charopidae is represented in Mayotte by 10 species of Psichion Gude 1911, five of them new, and one new species of Phaulocystis H. Watson 1934. All species are endemic to the Comores, and all except two may be restricted to Mayotte. Helix mica Morelet 1879 is treated as a senior synonym of Helix miliaris Morelet 1887, the type species of Psichion. Helix mutica and H. radiolata, both Morelet 1882 (earlier classified in the family Hygromiidae), H. homalospira Morelet 1883 (earlier classified in the Punctidae) and Helix arachne Morelet 1877 are transferred to Psichion. key words: land snails, Psichion, Phaulocystis, new species, Comores, Mayotte, extinction.

Area and habitat relationships in island land snail faunas: an Aegean case study exploring the choros model

In the present paper we study the biogeography of land snails in the Skyros archipelago (central Aegean) using both conventional species-area analysis and the newly-developed choros model. The choros model is a simple mathematical relationship, which analyses species richness as a function of area and of environmental heterogeneity, quantified by assessing the number of defined habitats present on each island. We surveyed land snails on 12 islands of the archipelago of Skyros in the central Aegean Sea (Greece). The different types of habitats were defined based on the ecology and biology of each species distributed in the archipelago. Forty-two land snail species were recorded living in 11 different habitat types. The z-values from both models, the choros and the classic species-area relationship, place the archipelago in the within biogeographic province category, mainly due to the recent formation of the archipelago. This recent formation resulted in a group of small islands still behaving as parts of a continuous landmass. The recorded extinction of land snails in the archipelago follows the general pattern of extinctions of this animal group in the Aegean area. The choros model gave a better fit to the data than the classic species-area model, indicating that the range of habitats available plays a significant role in determining faunal diversity independently of area. The availability of knowledge on the ecology of each species in most islands of the Aegean enabled us to recognise the key environmental features on which we based the definition of the habitat types. Such background knowledge is essential if island studies are to progress beyond the simple demonstration of a species! area relationship.

STEPHEN J. GOULD (1941–2002): A personal reflection on his life and work

In his memorial for George Gaylord Simpson, Steve Gould quoted Cassius' assessment of Julius Caesar: “Why, man, he doth bestride the narrow world like a Colossus; and we petty men walk under his huge legs, and peep about” (1985a). These were the first words that occurred to me when I learned of Steve's death on May 20, 2002. Steve was indeed a Colossus. He accomplished the equivalent of several normal lifetimes of work; had he only been a popular writer and lecturer or only worked on island landsnails or only written Ontogeny and Phylogeny or only co-authored the theory of punctuated equilibrium, he would have been considered to have had a very successful career. But he did all of these and much more. One hardly knows how to begin to assess such a legacy. Since his death, many commentators have focused on Steve the essayist. Certainly, his 27-year run with Natural History magazine is one of the most remarkable literary achievements of recent times in any discipline. These essays exposed thousands, perhaps millions, of people to paleontology and evolutionary biology who would otherwise probably not have given these subjects much thought. He once said that he thought there were a lot of people who subscribed to Natural History just so they could say they read it; perhaps, but his achievement of making paleontology a cocktail party subject was nevertheless remarkable. Yet I believe that history will conclude that Steve Gould's greatest accomplishment was not popular, but technical. I believe he will be remembered most for what he did to the sciences of paleontology and evolutionary biology, not mostly for explaining these subjects to the lay reader. Although many other workers contributed to the rebirth of paleontology in the 1970s, it was clearly Steve who led the charge and served as …