Norine W. Yeung

Extinction in a hyperdiverse endemic Hawaiian land snail family and implications for the underestimation of invertebrate extinction

The International Union for Conservation of Nature (IUCN) Red List includes 832 species listed as extinct since 1600, a minuscule fraction of total biodiversity. This extinction rate is of the same order of magnitude as the background rate and has been used to downplay the biodiversity crisis. Invertebrates comprise 99% of biodiversity, yet the status of a negligible number has been assessed. We assessed extinction in the Hawaiian land snail family Amastridae (325 species, IUCN lists 33 as extinct). We did not use the stringent IUCN criteria, by which most invertebrates would be considered data deficient, but a more realistic approach comparing historical collections with modern surveys and expert knowledge. Of the 325 Amastridae species, 43 were originally described as fossil or subfossil and were assumed to be extinct. Of the remaining 282, we evaluated 88 as extinct and 15 as extant and determined that 179 species had insufficient evidence of extinction (though most are probably extinct). Results of statistical assessment of extinction probabilities were consistent with our expert evaluations of levels of extinction. Modeling various extinction scenarios yielded extinction rates of 0.4-14.0% of the amastrid fauna per decade. The true rate of amastrid extinction has not been constant; generally, it has increased over time. We estimated a realistic average extinction rate as approximately 5%/decade since the first half of the nineteenth century. In general, oceanic island biotas are especially susceptible to extinction and global rate generalizations do not reflect this. Our approach could be used for other invertebrates, especially those with restricted ranges (e.g., islands), and such an approach may be the only way to evaluate invertebrates rapidly enough to keep up with ongoing extinction.

Predation on endemic Hawaiian land snails by the invasive snail Oxychilus alliarius.

The native land snails of the Hawaiian Islands have suffered numerous extinctions and continue to decline rapidly. A leading cause of these extinctions has been the impact of non-native predators. Oxychilus alliarius is a European predatory snail that has been in Hawaii since at least 1937 and has become one of the most abundant invasive snails in the islands. It is a facultative carnivore and will also consume non-animal food. However, this species has been mostly ignored as a threat and the majority of conservation attention has been focused on Euglandina rosea, the Rosy Wolf Snail. Here we report predation by O. alliarius on two rare and endemic Hawaiian snail species: Kaala subrutila (Helicarionidae) and Pleuropoma cf. sandwichiensis (Helicinidae). The wide distribution of O. alliarius in Hawaii, its high abundance, and now compelling evidence that it preys on native (and probably endangered) snails, indicate that it could be a much greater threat than previously thought.

Two for one: inadvertent introduction of Euglandina species during failed bio-control efforts in Hawaii

The introduction of the predatory land snail, Euglandina rosea (Férrusac, 1821) from Florida to Hawaii to control the giant African snail, Lissachatina fulica (Bowdich, 1822) is among the most publicized biological control cases gone awry. Following preliminary genetic analyses that revealed a second, possibly undescribed Euglandina species was probably introduced to Hawaii, we used an integrative systematic approach combining both genetic and morphological assessments to examine the taxonomic status of the snail referred to as E. rosea in Hawaii. Genetic and morphological analyses support the interpretation that two Euglandina species were introduced to and have become established in Hawaii and can be readily distinguished based on morphological differences. This finding has significant ramifications for understanding both historical and contemporary biocontrol as it suggests that: (1) other species may have been inadvertently introduced through bio-control programs, (2) inadequate understanding of the taxonomy of bio-control agents has obscured our ability to effectively study their ecological impacts, and (3) while the US has no comprehensive regulatory framework for importing biological control agents, one is urgently needed. This also has wide-ranging implications for conservation efforts throughout the tropics because Euglandina from Oahu, Hawaii were released on other Hawaiian Islands, New Guinea, Okinawa, Palau Islands, Philippines, India, Bonin Islands and Bermuda for use in biological control programs that led to catastrophic loss of endemic land snail diversity.

Identity and Distribution of Introduced Slugs (Veronicellidae) in the Hawaiian and Samoan Islands

Abstract: The Veronicellidae include some of the most widespread and agriculturally damaging invasive slugs. However, they are difficult to distinguish and identify accurately based on external morphology because of their great intraspecific variability, especially in body color and pigmentation pattern. Based on the published accounts, museum collections, and recent surveys, four species had been recorded previously from the Hawaiian Islands: Diplosolenodes occidentalis, Laevicaulis alte, Sarasinula plebeia, and Veronicella cubensis; and the latter three plus an additional species, Semperula wallacei, were known from the Samoan Islands. We reexamined these identifications using external morphology, internal anatomy, and/or DNA sequences. Both L. alte and V. cubensis are present on all six of the largest Hawaiian Islands. Sarasinula plebeia, although recorded previously, was not present in the museum collections and was found in only one of our recent survey samples, on O‘ahu. It may in fact never have been present in the Islands previously, the earlier records being misidentifications; or it may have been present but highly localized and was not collected and deposited in the Bishop Museum (Honolulu). Unfortunately, the single Diplosolenodes occidentalis specimen was not found in the usnm collections. Molecular analyses of specimens from American Samoa, previously identified as L. alte and S. plebeia, showed them to be primarily V. cubensis, with a few Semperula wallacei and Laevicaulis sp., and a single L. alte and S. plebeia, and all specimens sequenced from independent Samoa were S. wallacei.