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Marion, AL, United States

Niraula B.B.,Troy University | Hyde J.M.,Troy University | Miller J.M.,Troy University | Johnson P.D.,Alabama Aquatic Biodiversity Center | Stewart P.M.,Troy University
American Malacological Bulletin | Year: 2015

Although habitat alteration and degradation in riverine systems are the major threats to overall mussel assemblages to date, no or few studies have been able to document significant differences in habitat variables between species. The purpose of this study was to evaluate microhabitat associations of three federally threatened freshwater mussel species, Fusconaia burkei (Walker, 1922) (Tapered Pigtoe), Hamiota australis (Simpson, 1900) (Southern Sandshell), and Pleurobema strodeanum (Wright, 1898) (Fuzzy Pigtoe), and a common mussel species, Elliptio pullata (Lea, 1856) (Gulf Spike), at 3 localities in the Choctawhatchee River watershed in southeast Alabama and northwest Florida. Depth, current velocity, and compaction were measured, and a sediment core sample was collected for each individual mussel encountered. The Kruskal-Wallis H-test was performed to determine differences in each variable measured and each sediment size class among the mussel species at each site, followed by the Mann-Whitney U-test after applying Bonferroni's correction if significant. Six out of nine times, current velocity (3 times), depth (twice), and compaction (once) were significantly higher for the threatened species compared to E. pullata, whereas there were no differences in these variables between a set of any two threatened species within a site. This study suggests that E. pullata was associated with shallow and slow flowing water and loose sediment (usually stream banks), while the threatened species used deeper and relatively faster flowing water with more compact sediment. Anthropogenic disturbances are causing Coastal Plain streams to become more sand-bottomed and shallower, which is suited to species such as E. pullata and/or its host fishes, while the species in this study preferring deeper and faster flowing water and more compact sediments are in decline. © 2015 American Malacological Bulletin Advanced Access. Source


Foighil D.O.,University of Michigan | Li J.,University of Michigan | Lee T.,University of Michigan | Johnson P.,Alabama Aquatic Biodiversity Center | And 2 more authors.
PLoS ONE | Year: 2011

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. © 2011 Ó Foighil et al. Source


Johnson P.D.,Alabama Aquatic Biodiversity Center | Bogan A.E.,North Carolina State Museum of Natural science | Brown K.M.,Louisiana State University | Burkhead N.M.,U.S. Geological Survey | And 9 more authors.
Fisheries | Year: 2013

This is the first American Fisheries Society conservation assessment of freshwater gastropods (snails) from Canada and the United States by the Gastropod Subcommittee (Endangered Species Committee). This review covers 703 species representing 16 families and 93 genera, of which 67 species are considered extinct, or possibly extinct, 278 are endangered, 102 are threatened, 73 are vulnerable, 157 are currently stable, and 26 species have uncertain taxonomic status. Of the entire fauna, 74% of gastropods are imperiled (vulnerable, threatened, endangered) or extinct, which exceeds imperilment levels in fishes (39%) and crayfishes (48%) but is similar to that of mussels (72%). Comparison of modern to background extinction rates reveals that gastropods have the highest modern extinction rate yet observed, 9,539 times greater than background rates. Gastropods are highly susceptible to habitat loss and degradation, particularly narrow endemics restricted to a single spring or short stream reaches. Compilation of this review was hampered by a paucity of current distributional information and taxonomic uncertainties. Although research on several fronts including basic biology, physiology, conservation strategies, life history, and ecology are needed, systematics and curation of museum collections and databases coupled with comprehensive status surveys (geographic limits, threat identification) are priorities. Source


Whelan N.V.,University of Alabama | Whelan N.V.,Auburn University | Johnson P.D.,Alabama Aquatic Biodiversity Center | Harris P.M.,University of Alabama
Journal of Molluscan Studies | Year: 2015

Life histories of the imperilled freshwater gastropod genus Leptoxis are poorly known, and this information is required to achieve a basic understanding of the evolution of this diverse group and to develop management strategies for species conservation and recovery. We describe egg-laying behaviours and associated traits for all 13 extant Leptoxis species. We also explore patterns of shell growth and assess the extent to which intraspecific shell variation is a result of phenotypic plasticity or genetic differences. Each Leptoxis species exhibits one of three distinct oviposition strategies: deposition of single eggs, deposition of eggs in a single line or deposition in circular clutches. Temperature cues for initiating egg laying varied from 12 to 26 °C depending on the species. There were significant differences in clutch size among species and between populations of L. ampla and L. taeniata. Furthermore, 1- and 2-year-old female L. foremani laid significantly fewer eggs per clutch than females 4 years or older. Finally, discrete shell morphologies that are characteristic of any given species are genetically controlled and not an ecophenotypic response. Clutch egg laying likely represents increased parental investment compared with other behaviours and clutches may provide individual eggs protection from predation or passive dislodgement. Data from this study, including necessary conditions for successful culturing and period of oviposition for each species, can inform captive propagation efforts for imperilled Leptoxis species and aid in predicting how they will respond to future habitat alteration and climate change. © 2014 © The Author 2014. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved. Source


Whelan N.V.,University of Alabama | Johnson P.D.,Alabama Aquatic Biodiversity Center | Harris P.M.,University of Alabama
PLoS ONE | Year: 2012

The Mobile River Basin is a hotspot of molluscan endemism, but anthropogenic activities have caused at least 47 molluscan extinctions, 37 of which were gastropods, in the last century. Nine of these suspected extinctions were in the freshwater gastropod genus Leptoxis (Cerithioidea: Pleuroceridae). Leptoxis compacta, a Cahaba River endemic, has not been collected for >70 years and was formally declared extinct in 2000. Such gastropod extinctions underscore the imperilment of freshwater resources and the current biodiversity crisis in the Mobile River Basin. During a May 2011 gastropod survey of the Cahaba River in central Alabama, USA, L. compacta was rediscovered. The identification of snails collected was confirmed through conchological comparisons to the L. compacta lectotype, museum records, and radulae morphology of historically collected L. compacta. Through observations of L. compacta in captivity, we document for the first time that the species lays eggs in short, single lines. Leptoxis compacta is restricted to a single location in the Cahaba River, and is highly susceptible to a single catastrophic extinction event. As such, the species deserves immediate conservation attention. Artificial propagation and reintroduction of L. compacta into its native range may be a viable recovery strategy to prevent extinction from a single perturbation event. © 2012 Whelan et al. Source

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