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The Wrinkled Snail, Xeroplexa intersecta, has been introduced and has spread in the Pacific Northwest of North America, with established populations now documented in Oregon, Washington, and British Columbia.
Severe storms have the potential to disperse land snails carried by strong winds between islands and archipelagos or to drown endemic fauna in storm surges. We compared land snail assemblages collected from Ngcheangel atoll (Kayangel State, Republic of Palau, Oceania) before and after the passage of Typhoon Haiyan in 2013. Most land snail species, including two species endemic to the atoll, remained present after the storm. Three species were not recovered post-Haiyan, and three species were reported for the first time after the storm. We conclude that the atoll's land snail fauna is fairly resilient to the impacts of severe storms. This finding raises the hope that at least one harbinger of climate change – increased prevalence and severity of storms – may pose minimal risk to certain imperiled and endemic Pacific Island land snails.
The next century will be a time of rapid change for freshwater mussel populations, which will be threatened by climate change, biological invasions, new pollutants, land-use change, habitat fragmentation, and many other causes. At the same time, habitat restoration and mussel propagation will offer opportunities to improve the size and viability of mussel populations. Mussel conservationists will be challenged to document, understand, and manage these changes to mussel populations and their habitats. Here, I focus on two scientific problems central to future mussel conservation: population monitoring and dynamic lags that affect mussel populations. Although mussel population monitoring has advanced greatly in recent decades, existing programs have important shortcomings: data are hard to find, data from different monitoring programs often are incompatible, many data sets are subject to permanent loss, and monitoring programs may be ill–suited to answer the questions facing us in coming decades. Monitoring programs can be improved by posting more data in public repositories, better coordinating existing monitoring programs, designing monitoring programs to answer specific questions, and better integrating monitoring into broader programs of research and management. Many drivers that affect mussel populations take decades to play out, so that mussel populations often are not in equilibrium with their current environments, leading to extinction debts and colonization credits. Delayed inputs of sediments, nutrients, and pollutants from the catchment, long intervals between extreme events, delays in biological invasions, and the demographic structure of the mussel population itself all may cause dynamic lags. Lagged systems can be difficult to understand and manage. Increased awareness of lags, model building, model application and testing, and adaptive monitoring and management may help mussel conservationists deal with lags.
Population genetics research is often a foundation of effective conservation efforts. Yet, such research is often missing for critically imperiled freshwater gastropods. Recently, several population genomic studies revealed that populations of Pleuroceridae species often harbor high amounts of genomic diversity, even when the species has undergone severe range contraction. To test for this pattern in additional species, we generated genomic data for Elimia crenatella (Lea, 1860) and Elimia capillaris (Lea, 1861). Both species have undergone greater than 95% range reduction and only one population of each species remains. We found that both species harbor relatively high amounts of genetic diversity in their remaining populations. Furthermore, genomic data do not indicate that remaining populations have undergone severe bottlenecks as might be expected given such drastic species-wide range contraction. By comparing these data to past studies, we developed a broad hypothesis to explain how pleurocerid species respond to habitat degradation: The Rapid Localized Extirpation Hypothesis. This hypothesis postulates that pleurocerid populations will persist without showing evidence of decline until a critical threshold in habitat quality is met. Crossing the threshold then results in rapid and complete extirpation. Future work should test and possibly expand on this hypothesis, which will likely include examining habitat requirements for pleurocerids, as basic toxicology and critical thermal limits are unknown for most species. Conservation efforts for pleurocerids should prepare for rapid extirpation of populations if habitat degradation occurs. However, high genetic diversity of remaining populations offers promise for management actions like captive propagation and reintroduction.
The Wichita Mountains pillsnail, Euchemotrema wichitorum (Branson, 1972), was originally described in 1972, when it was reported in two counties in southwest Oklahoma. All that was previously known about this species was from this one publication, which included no information on the species' ecology or distribution. The goal of this study was to investigate this snail's range, habitat use, and aspects of its natural history so that we may better understand and conserve this restricted-range endemic species. We located E. wichitorum in 68 of 114 survey sites across six of the sixteen counties surveyed in western Oklahoma and expanded the species' known range to approximately 4400 km2 and a total of eight counties. General Additive Models of multiple microhabitat conditions explained up to 55.6% of the variation in live snail abundance and indicated that this species is positively associated with the number of available shelter logs and canopy density, while being negatively associated with the number of boulders at a site. Interestingly, E. wichitorum also had positive associations with fire; survey sites with recent fire evidence had significantly more live snails than did unburned sites, and charred logs harbored significantly more live snails than unburned logs. Fire may increase E. wichitorum abundance through a combination of increased soil pH and nutrient bioavailability (particularly of calcium) in charred or burned plant matter. However, surveys of recently burned sites also revealed that fire can lead to significant mortality in local snail populations when fire severity was high and sheltering logs burned. We also observed that E. wichitorum breeds readily and successfully in captivity. Given our findings, E. wichitorum's conservation outlook is promising.
It came as a surprise when I realized I have been working with freshwater bivalves for 50 years. This work has spanned the transition from analyses focused initially on shells, both modern and archaeological, to collaborations using an integrative approach. These 50 years have been broken into four separate periods, each focused on different aspects of freshwater bivalves: Graduate School, University of Tennessee, Knoxville [1973–1980]; Academy of Natural Sciences of Philadelphia [1980–1992]; Consultant [1992–1996]; and North Carolina Museum of Natural Sciences [1996–present]. Starting out, historical literature forced me to pay closer attention to basic taxonomy of the families Unionidae Rafinesque, 1820 and Margaritiferidae Henderson, 1929. When I began, freshwater bivalve research was focused primarily on shell morphology, and with time more comparative anatomy was added along with host fish and behavior to form an integrative approach. The next major shift was the use of starch gel electrophoresis, followed by Sanger sequencing of mitochondrial and nuclear DNA. The introduction of anchored hybrid enrichment using nuclear DNA with an integrative approach is the latest major step forward in the understanding of unionoid evolution. Intensive fieldwork and applying modern techniques in Asia and Southeast Asia has allowed the development of a more robust phylogenetic understanding of the Unionida Rafinesque, 1820. This is a tour of my development as a malacologist and the changing technology applied to taxonomy and systematics, data management, museum collections, and tools to understand this very imperiled group of animals.
Freshwater mussels are declining globally, experiencing both species losses and declines in the abundance of common species. Because mussels often have strong effects on ecosystem processes, these declines may lead to losses in mussel-generated ecosystem functions such as biofiltration and nutrient recycling and storage. Our understanding of mussel declines, the causes underlying declines, and the consequences of decline for species success and ecosystem health are limited by the lack of long-term data. We used long-term data from the Kiamichi River, Oklahoma to examine changes in abundance, species composition, and nitrogen and phosphorus nutrient recycling over a 30-year period that included two multi-year severe droughts. Overall mussel abundance declined during drought periods, and the relative abundance of drought-tolerant mussel species increased in proportion to drought sensitive species. Since 2016, mussel populations have begun to recover, and drought-sensitive species are increasing in relative abundance. Mussel declines led to large decreases in areal nitrogen and phosphorus excretion, however these rates are increasing as mussel abundance rebounds. Long-term monitoring is often essential for documenting the response of biodiversity and key ecological processes to environmental change.
Campeloma decisum (family Viviparidae), Pointed Campeloma, is a common and widely distributed freshwater gastropod found in varied habitats across the eastern United States and southeastern Canada. Substantial conchological variation is known to be present in the species, but this variation and what it corresponds to has not been quantified. Our study sought to use geometric morphometric analyses to test which environmental factors may be driving shell shape variation in C. decisum. Campeloma decisum specimens (n = 458) and environmental data were collected from 22 sites in six lakes in central and northern Michigan. Specimens were photographed with apertures orthogonal to the camera lens and 26 landmarks were digitized onto each shell image to estimate shell and aperture shape. A Procrustes superimposition was performed to scale and rotate the shells to focus analyses solely on shape. A linear discriminant analysis of principal components (PCA-LDA) was run to quantify shape variation among the sites and lakes sampled. Correlations were tested for among environmental variables and PCA-LDA axes that defined shell shape. The PCA-LDA assigned 46.6% of snails to their site of origin and 86.9% to their lake of origin. Shell shapes of C. decisum were most strongly correlated with Secchi depth, ammonia concentration, pH, alkalinity, phosphate concentration, magnesium concentration, and percent sand substrate. Higher ammonia and phosphate concentrations often correlated with more elongate shapes (i.e., taller spire). The pH at sites and lakes appeared to be a strong driver of spire decollation with more acidic conditions likely breaking down calcium carbonate in shells. In contrast to a previous study on the often sympatric freshwater gastropod Elimia livescens (Menke, 1830) (family Pleuroceridae), our study did not find lake fetch (driving wave energy) to be major a driver of shell shape in C. decisum. However, to better test this, we recommend collecting additional C. decisum specimens from lakes with longer fetch to expand the dataset and further effects of lake morphometry on shell shape.
Fieldwork is an essential aspect of much research within malacology. However, not all fieldwork is inclusive to researchers with a diversity of needs and experiences. In this paper, we propose ways that malacological fieldwork can become more just, equitable, and inclusive for all scientists. We draw upon personal experiences, discussions at the Inclusive Fieldwork Panel at the American Malacological Society Annual Meeting in 2023, and insights from the literature. Rather than relying on “common sense” to guide field practices and avoid environmental hazards, we encourage senior malacologists to approach fieldwork as a teaching and learning experience for emerging young researchers. Conducting an inclusive field excursion requires substantial planning before fieldwork begins, including building comradery within a diverse field team, identifying and mitigating risk factors unique to each field season, and drafting day-to-day schedules that accommodate field team members' individual and personal needs. Before entering the field, team members should be familiar with logistical requirements of fieldwork, emergency protocols, and procedures for responding to discriminatory actions that may occur in a field setting. Clear communication within the field team is critical for establishing interpersonal interaction norms and addressing mental health needs. Effective communication with members of the local community can be a tool for establishing human resource networks and de-escalating potential conflicts. Reflection on past field seasons is a key method for improving inclusivity, safety, and effectiveness for future fieldwork. Inclusive fieldwork practices not only advance researcher diversity within malacology but also increase the effectiveness of our field research by minimizing risks that distract from the science at hand. We hope that this paper encourages field malacologists to incorporate inclusive practices and provides resources for those seeking to expand their approach to fieldwork.
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