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1. Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina ‘rosea’ and the flatworm Platydemus manokwari

   https://doi.org/10.1007/s10530-020-02436-w  

   Gerlach, Justin; Barker, Gary M.; Bick, Cindy S.; Bouchet, Philippe; Brodie, Gilianne; Christensen, Carl C.; Collins, Timothy; Coote, Trevor; Cowie, Robert H.; Fiedler, G. Curt; et al (April 2021, Biological Invasions)

   null (Ed.)

   Abstract Since 1955 snails of the Euglandina rosea species complex and Platydemus manokwari flatworms were widely introduced in attempted biological control of giant African snails ( Lissachatina fulica ) but have been implicated in the mass extinction of Pacific island snails. We review the histories of the 60 introductions and their impacts on L. fulica and native snails. Since 1993 there have been unofficial releases of Euglandina within island groups. Only three official P. manokwari releases took place, but new populations are being recorded at an increasing rate, probably because of accidental introduction. Claims that these predators controlled L. fulica cannot be substantiated; in some cases pest snail declines coincided with predator arrival but concomitant declines occurred elsewhere in the absence of the predator and the declines in some cases were only temporary. In the Hawaiian Islands, although there had been some earlier declines of native snails, the Euglandina impacts on native snails are clear with rapid decline of many endemic Hawaiian Achatinellinae following predator arrival. In the Society Islands, Partulidae tree snail populations remained stable until Euglandina introduction, when declines were extremely rapid with an exact correspondence between predator arrival and tree snail decline. Platydemus manokwari invasion coincides with native snail declines on some islands, notably the Ogasawara Islands of Japan, and its invasion of Florida has led to mass mortality of Liguus spp. tree snails. We conclude that Euglandina and P. manokwari are not effective biocontrol agents, but do have major negative effects on native snail faunas. These predatory snails and flatworms are generalist predators and as such are not suitable for biological control. 

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2. Plants critical for Hawaiian land snail conservation: arboreal snail plant preferences in Puʻu Kukui Watershed, Maui

   https://doi.org/10.1017/S0030605320000873  

   Meyer, Wallace M.; Evans, Lily M.; Kalahiki, Connor J.K.; Slapcinsky, John; Goulding, Tricia C.; Robinson, David G.; Kaniaupo-Crozier, D. Pomaikaʻi; Kim, Jaynee R.; Hayes, Kenneth A.; Yeung, Norine W. (May 2021, Oryx)

   null (Ed.)

   Abstract The Hawaiian archipelago was formerly home to one of the most species-rich land snail faunas (> 752 species), with levels of endemism > 99%. Many native Hawaiian land snail species are now extinct, and the remaining fauna is vulnerable. Unfortunately, lack of information on critical habitat requirements for Hawaiian land snails limits the development of effective conservation strategies. The purpose of this study was to examine the plant host preferences of native arboreal land snails in Puʻu Kukui Watershed, West Maui, Hawaiʻi, and compare these patterns to those from similar studies on the islands of Oʻahu and Hawaiʻi. Concordant with studies on other islands, we found that four species from three diverse families of snails in Puʻu Kukui Watershed had preferences for a few species of understorey plants. These were not the most abundant canopy or mid canopy species, indicating that forests without key understorey plants may not support the few remaining lineages of native snails. Preference for Broussaisia arguta among various island endemic snails across all studies indicates that this species is important for restoration to improve snail habitat. As studies examining host plant preferences are often incongruent with studies examining snail feeding, we suggest that we are in the infancy of defining what constitutes critical habitat for most Hawaiian arboreal snails. However, our results indicate that preserving diverse native plant assemblages, particularly understorey plant species, which facilitate key interactions, is critical to the goal of conserving the remaining threatened snail fauna. 

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3. Tiny Snails With Large Distributions: Systematics and Delimitation of the Pacific Land Snails Pacificella and Lamellidea (Stylommatophora: Achatinellidae: Pacificellinae)

   https://doi.org/10.18061/bssb.v2i2.8873  

   Goulding, Tricia C.; Yeung, Norine W.; Slapcinsky, John; Strong, Ellen E.; Kim, Jaynee R.; Brook, Fred J.; Hayes, Kenneth A. (July 2023, Bulletin of the Society of Systematic Biologists)

   The Pacificellinae are a group of small, high-spired land snails distributed on islands across the Pacific. Some species are endemic to particular island groups, but others have wide geographic distributions, several of which have been attributed to anthropogenic transport between islands before western contact. We used DNA sequence data (COI, 16S, ITS2, 28S) from recently collected and historical specimens to estimate a phylogeny of the Pacificellinae, with a focus on Hawaiian species. Phylogenetic analyses support recognizing Lamellidea and Pacificella as distinct genera and indicate that the genus group Tornatellinops should be regarded as a synonym of Lamellidea. The number of taxa defined by species delimitation analyses (ASAP, bPTP, mPTP) varies widely, with between 6 and 42 species estimated in the Hawaiian Islands. These candidate species hypotheses were evaluated in an integrative framework, including shell morphology, geography, and a multilocus phylogeny, to revise the taxonomy of Hawaiian pacificellines. Four Lamellidea species and two Pacificella species are recognized from the Hawaiian Islands, including two widespread species introduced to Hawaiʻi from the South Pacific. Lamellidea peponum in Hawaiʻi shows little genetic divergence from Polynesian specimens previously referred to L. oblonga, and the name L. oblonga is now regarded as a junior synonym. Lamellidea polygnampta is recognized here from across the Hawaiian Islands, L. cylindrica from the island of O‘ahu, and the lowland species, L. extincta, from the main Hawaiian Islands and the Northwestern Islands. The only Pacificella specimens found in Hawai‘i in modern surveys are more closely related to specimens of P. variabilis from Polynesia than to historical specimens of P. baldwini, indicating that the only Pacificella species now found in the main Hawaiian Islands appears to be introduced. Pacificellines have declined in abundance in Hawai‘i over the last century and the two species L. extincta and P. baldwini, formerly present across the Hawaiian Islands, are now either critically endangered or extinct. 

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4. Increasing grazer density leads to linear decreases in Spartina alterniflora biomass and exponential increases in grazing pressure across a barrier island

   https://doi.org/10.3354/meps13569  

   Renzi, JJ; Silliman, BR (February 2021, Marine Ecology Progress Series)

   Researchers now recognize that top-down as well as bottom-up forces regulate salt marsh primary production. However, how top-down forces vary with grazer density is still poorly resolved. To begin to address this void, we (1) surveyed grazing intensity in short-form Spartina alterniflora across Sapelo Island, Georgia (USA), and (2) removed varying densities of grazers from 13 sites over 2 yr. Our survey revealed a non-linear relationship between snail abundance and grazing intensity, with grazing scars per stem increasing exponentially with snail density. Further, there appeared to be a threshold at ~80 snails m -2 , below which increasing snail density did not significantly increase grazing scars—potentially because snails target dead grass rather than live grass when competition with other snails is low. Increasing snail densities also exponentially reduced stem density within a plot, but only over 80 snails m -2 . Our removal experiment showed that snails linearly decreased S. alterniflora biomass across a naturally representative range of snails (0-586 snails m -2 ) and that top-down control of short-form S. alterniflora was important at multiple sites across an island, with snail removal on average increasing primary production by 164%. Our results reveal that top-down control of short-form S. alterniflora is a common process across this intensively studied island, and that grazing scars increase non-linearly with snail density, while consumer effects on biomass increase linearly. Future models based on marsh plant growth (e.g. geomorphic evolution, primary production) should incorporate both the importance and functional form of grazer control to create more accurate carbon budgets and to better understand marsh network dynamics. 

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5. The Invasion of Megachile policaris (Hymenoptera: Megachilidae) to Hawai‘i

   https://doi.org/10.1093/jisesa/ieab065  

   Koch, Jonathan Berenguer; Tabor, Jesse Anjin; Montoya-Aiona, Kristina; Eiben, Jesse A (September 2021, Journal of Insect Science)

   Godfrey, Kris (Ed.)

   Abstract Islands are insular environments that are negatively impacted by invasive species. In Hawai‘i, at least 21 non-native bees have been documented to date, joining the diversity of >9,000 non-native and invasive species to the archipelago. The goal of this study is to describe the persistence, genetic diversity, and natural history of the most recently established bee to Hawai‘i, Megachile policaris Say, 1831 (Hymenoptera: Megachilidae). Contemporary surveys identify that M. policaris is present on at least O‘ahu, Maui, and Hawai‘i Island, with the earliest detection of the species in 2017. Furthermore, repeated surveys and observations by community members support the hypothesis that M. policaris has been established on Hawai‘i Island from 2017 to 2020. DNA sequenced fragments of the cytochrome oxidase I locus identify two distinct haplotypes on Hawai‘i Island, suggesting that at least two founders have colonized the island. In their native range, M. policaris is documented to forage on at least 21 different plant families, which are represented in Hawai‘i. Finally, ensemble species distribution models (SDMs) constructed with four bioclimatic variables and occurrence data from the native range of M. policaris predicts high habitat suitability on the leeward side of islands throughout the archipelago and at high elevation habitats. While many of the observations presented in our study fall within the predicted habitat suitability on Hawai‘i, we also detected the M. policaris on the windward side of Hawai‘i Island suggesting that the SDMs we constructed likely do not capture the bioclimatic niche flexibility of the species. 

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