John B. Burch

Prehistoric inter-archipelago trading of Polynesian tree snails leaves a conservation legacy

Inter-archipelago exchange networks were an important aspect of prehistoric Polynesian societies. We report here a novel genetic characterization of a prehistoric exchange network involving an endemic Pacific island tree snail, Partula hyalina. It occurs in the Society (Tahiti only), Austral and Southern Cook Islands. Our genetic data, based on museum, captive and wild-caught samples, establish Tahiti as the source island. The source lineage is polymorphic in shell coloration and contains a second nominal species, the dark-shelled Partula clara, in addition to the white-shelled P. hyalina. Prehistoric inter-island introductions were non-random: they involved white-shelled snails only and were exclusively inter-archipelago in scope. Partulid shells were commonly used in regional Polynesian jewellery, and we propose that the white-shelled P. hyalina, originally restricted to Tahiti, had aesthetic value throughout these archipelagoes. Demand within the Society Islands could be best met by trading dead shells, but a low rate of inter-archipelago exchange may have prompted the establishment of multiple founder populations in the Australs and Southern Cooks. The alien carnivorous land snail Euglandina rosea has recently devastated populations of all 61 endemic species of Society Island partulid snails. Southern Cooks and Australs P. hyalina now represent the only unscathed wild populations remaining of this once spectacular land snail radiation.

Moorean tree snail survival revisited: a multi-island genealogical perspective.

BackgroundThe mass extirpation of the island of Mooreas endemic partulid tree snail fauna, following the deliberate introduction of the alien predator Euglandina rosea, represents one of the highest profile conservation crises of the past thirty years. All of the islands partulids were thought to be extirpated by 1987, with five species persisting in zoos, but intensive field surveys have recently detected a number of surviving wild populations. We report here a mitochondrial (mt) phylogenetic estimate of Moorean partulid wild and captive lineage survival calibrated with a reference museum collection that pre-dates the predators introduction and that also includes a parallel dataset from the neighboring island of Tahiti.ResultsAlthough severe winnowing of Mooreas mt lineage diversity has occurred, seven of eight (six Partula; two Samoana) partulid tip clades remain extant. The extinct mt clade occurred predominantly in the P. suturalis species complex and it represented a major component of Mooreas endemic partulid treespace. Extant Moorean mt clades exhibited a complex spectrum of persistence on Moorea, in captivity, and (in the form of five phylogenetically distinct sister lineages) on Tahiti. Most notably, three Partula taxa, bearing two multi-island mt lineages, have survived decades of E. rosea predation on Moorea (P. taeniata) and in the valleys of Tahiti (P. hyalina and P. clara). Their differential persistence was correlated with intrinsic attributes, such as taxonomy and mt lineages, rather than with their respective within-island distribution patterns.ConclusionConservation efforts directed toward Moorean and Tahitian partulids have typically operated within a single island frame of reference, but our discovery of robust genealogical ties among survivors on both islands implies that a multi-island perspective is required. Understanding what genetic and/or ecological factors have enabled Partula taeniata, P. hyalina and P. clara to differentially survive long-term direct exposure to the predator may provide important clues toward developing a viable long term conservation plan for Society Island partulid tree snails.

Tahitian tree snail mitochondrial clades survived recent mass extirpation.

Oceanic islands frequently support endemic faunal radiations that are highly vulnerable to introduced predators [1]. This vulnerability is epitomized by the rapid extinction in the wild of all but five of 61 described Society Islands partulid tree snails [2], following the deliberate introduction of an alien biological control agent: the carnivorous snail Euglandina rosea[3]. Tahitis tree snail populations have been almost completely extirpated and three of the islands eight endemic Partula species are officially extinct, a fourth persisting only in captivity [2]. We report a molecular phylogenetic estimate of Tahitian Partula mitochondrial lineage survival calibrated with a 1970 reference museum collection that pre-dates the predators 1974 introduction to the island [4]. Although severe winnowing of lineage diversity has occurred, none of the five primary Tahitian Partula clades present in the museum samples is extinct. Targeted conservation measures, especially of montane refuge populations, may yet preserve a representative sub-sample of Tahitis endemic tree snail genetic diversity in the wild.

Molecular Phylogenetic Revision of the Freshwater Limpet Genus Ferrissia (Planorbidae: Ancylinae) in North America Yields Two Species: Ferrissia (Ferrissia) Rivularis and Ferrissia (Kincaidilla) Fragilis

ABSTRACT Members of the gastropod genus Ferrissia Walker, 1903, have a near-cosmopolitan distribution in freshwater ecosystems. Five North American species, distinguished by conchological, habitat, and distributional details, are generally recognized. However, they can be difficult to diagnose in practice, and we aimed to comprehensively revisit their systematics and taxonomy using molecular phylogenies. Our primary result was congruent for all three genetic markers: two highly distinctive Ferrissia clades, each encompassing multiple nominal species, were widely distributed across North American watersheds in both lentic and in lotic habitats. One clade was restricted to North America and was exclusively composed of lotic F. rivularis (Say, 1817) and lentic F. parallela (Haldemann, 1841). These two taxa exhibited geographic, rather than taxonomic, genetic structuring, strongly implying that they are conspecific and that F. parallela is a junior synonym of F. (Ferrissia) rivularis. The other clade contained three North American taxa, F. fragilis (Tryon, 1863) and putative specimens of F. mcneilli Walker, 1925, and F. walkeri (Pilsbry & Ferriss, 1907), in addition to the Hawaiian F. sharpi (Sykes, 1900), as well as multiple invasive Eurasian founder populations. All four taxa shared overlapping genotypes and shell phenotypes, prompting us to conclude that they are conspecific with F. fragilis having taxonomic priority. This New World species had robust phylogenetic links to Old World congeners, thereby enabling us to unite global septum-forming Ferrissia species under the subgenus Kincaidilla Hannibal, 1912. Ferrissia rivularis and F. fragilis differed in a number of conchological traits, including maximum body size, details of apex positioning and orientation, and the ability to form a septum. The two former traits were sufficient to distinguish sympatric populations.

Not completely lost: two partulid tree snail species persist on the highest peak of Raiatea, French Polynesia

The spectacular partulid tree snail fauna of the Society Islands has been almost completely extirpated in recent decades following the deliberate introduction of the alien carnivorous snail Euglandina rosea . The greatest loss has occurred on the island of Raiatea, French Polynesia, home to an estimated 34 species (including 33 single-island endemics), all of which have been deemed extirpated in the wild. However, we report here the February 2006 discovery of two surviving Raiatean partulid lineages on the upper slopes of Mount Tefatua, the highest peak on the island. They have been identified using morphological and molecular phylogenetic analyses, the latter approach employing available museum and captive reference samples. One population, at 750 m elevation, consisted of Samoana attenuata . It has a multi-island distribution within the archipelago and surviving populations persist also on Tahiti and Moorea. A second population, present just below the summit at 950 m, consisted of a previously unstudied morphospecies and it has been formally described as Partula meyeri . It is unclear if a stable altitudinal refuge from E. rosea predation exists on Mount Tefatua but the unexpected discovery of these two surviving montane populations raises the possibility of preserving some fraction of Raiateas endemic tree snail diversity in the wild.

Conservation Genetics of a Critically Endangered Limpet Genus and Rediscovery of an Extinct Species

Background A third of all known freshwater mollusk extinctions worldwide have occurred within a single medium-sized American drainage. The Mobile River Basin (MRB) of Alabama, a global hotspot of temperate freshwater biodiversity, was intensively industrialized during the 20th century, driving 47 of its 139 endemic mollusk species to extinction. These include the ancylinid limpet Rhodacmea filosa, currently classified as extinct (IUCN Red List), a member of a critically endangered southeastern North American genus reduced to a single known extant population (of R. elatior) in the MRB. Methodology/Principal Findings We document here the tripling of known extant populations of this North American limpet genus with the rediscovery of enduring Rhodacmea filosa in a MRB tributary and of R. elatior in its type locality: the Green River, Kentucky, an Ohio River Basin (ORB) tributary. Rhodacmea species are diagnosed using untested conchological traits and we reassessed their systematic and conservation status across both basins using morphometric and genetic characters. Our data corroborated the taxonomic validity of Rhodacmea filosa and we inferred a within-MRB cladogenic origin from a common ancestor bearing the R. elatior shell phenotype. The geographically-isolated MRB and ORB R. elatior populations formed a cryptic species complex: although overlapping morphometrically, they exhibited a pronounced phylogenetic disjunction that greatly exceeded that of within-MRB R. elatior and R. filosa sister species. Conclusions/Significance Rhodacmea filosa, the type species of the genus, is not extinct. It persists in a Coosa River tributary and morphometric and phylogenetic analyses confirm its taxonomic validity. All three surviving populations of the genus Rhodacmea merit specific status. They collectively contain all known survivors of a phylogenetically highly distinctive North American endemic genus and therefore represent a concentrated fraction of continental freshwater gastropod biodiversity. We recommend the establishment of a proactive targeted conservation program that may include their captive propagation and reintroduction.

Recognition of a highly restricted freshwater snail lineage (Physidae: Physella) in southeastern Oregon: convergent evolution, historical context, and conservation considerations

Non-marine mollusks have the highest number of documented extinctions of any major taxonomic group. Given their conservation status and the numerous cases of taxonomic uncertainty concerning freshwater mollusks in particular, the recognition of potentially endangered species is critically important. Here, we evaluate the genetic distinctiveness and phylogenetic position of a freshwater snail restricted to a series of geothermal springs within the Owyhee River drainage in Oregon (the ‘Owyhee wet-rock physa’). Because these snails closely resemble Physella (Petrophysa) zionis, a wet-rock physa that occurs in a small area in Zion National Park (Utah), the Owyhee wet-rock physa is presumably either closely related to or represents a disjunct population of P. zionis. However, phylogenetic analyses of sequences of mitochondrial cytochrome oxidase I and nuclear first and second internal transcribed spacer gene regions indicate that the Owyhee wet-rock physa is genetically distinct from other physid species. Despite exhibiting similar morphologies, the Owyhee wet-rock physa and P. zionis are distantly related physids; instead, the Owyhee wet-rock physa is most closely related to a population of physids from central California. These results suggest that convergent evolution may be responsible for the similar shell morphologies of the Owyhee wet-rock physa and P. zionis. Furthermore, the close relationship between physid populations in southeastern Oregon and central California suggests a historical connection between the Owyhee River and river drainages to the south. Finally, we recommend that the Owyhee wet-rock physa be considered critically endangered based on its extremely limited distribution.