Management and Conservation of Freshwater Systems I
Presiding: W Hiler, Arkansas State University; S Linke, University of Canberra
NB13C-01 13:30h
Examination of the Trophic Interactions Between a Species in Decline, the Ozark Hellbender (Cryptobranchus alleganiensis bishopi), and a Prey Base Composed of Multiple Crayfish Species Using Stable Isotope Analysis
Since the early 1980's the Ozark hellbender, North America's largest salamander, has undergone a series of declines throughout its entire range. Two Arkansas rivers known to have populations of hellbenders are the Eleven Point (EP) and Spring (SR) rivers. Ozark hellbenders from the SR have undergone the most drastic population decline witnessed within their range over the past 20 years. Shifts in benthic habitat and community compositions could influence these declines, which could affect the species composition of their primary prey item, the crayfish. The objectives of our study were to use stable C and N isotope analysis to 1) determine what individual or multiple species of crayfish contribute to hellbender diets, and 2) determine if certain size classes of crayfish contribute to hellbender diets. We chose four study sites, three from the EP and one from the SR and collected tissue plugs from a total of 10 hellbenders. Tissue samples from three size classes of the crayfish known to occur in the EP and SR rivers were also collected. By linking stable C and N ratios results and relative abundances of crayfish in each of the river sites, we hope to identify species-specific trophic relationships between hellbenders and crayfish.
http://www.ozarkhellbender.com
NB13C-02 13:45h
Taxonomic and Functional Clumping of Exotic Macroinvertebrates: the Case of French Inland Waters
The introduction of exotic species and biological invasions are now considered to be a major driver of change of freshwater biodiversity. The analysis of a database allowed to review a list of 43 French freshwater exotic species, which represent 1.2 % of the French freshwater macroinvertebrates. We analysed their geographic origins, their distributions among zoological units by comparison with the native fauna and their functional characteristics according to a recent typology based on bio/ecological traits. At least six of these exotic species can be considered as invasives. An exponential trend of the cumulated number of non-indigenous species over time was evidenced, with a classical clumping of exotics within crustaceans and molluscs. Donor areas of exotic species are in majority European, and the Ponto-Caspian basin is identified as the principal one. This pattern could be explained by a spread along waterways but its origin lies in a process of recolonisation of defaunated areas following several episodes of glaciation / deglaciation in Western Europe during the last 80,000 years. Finally, from a functional point of view, exotic species exhibit a limited functional diversity, with two functional groups representing 80 % of them.
NB13C-03 14:00h
Muddy waters: Introducing systematic conservation planning to riverine landscapes
For the last 20 years, systematic conservation planning has been an invaluable tool in assigning terrestrial protected areas for biodiversity conservation. Its main goal is to represent the full variety of taxa or ecosystems in a proposed reserve design, while minimising costs and effort. We introduce this widely established technique to river systems, using fish and macroinvertebrates. Central questions in this approach include choice of targets, proper selection of algorithms and input data. Input data can range from species data to higher taxonomic levels, from predicted occurrences to GIS surrogates. Using datasets from Canada and Australia, we built and compared three sets of conservation models. All conservation plans were built using sub-watersheds as the unit of replication. The first set of models tries to assign reserve networks using real data. Using a more advanced technique recently developed for terrestrial application, the second set uses probabilities of occurrence modelled by nearest neighbour prediction to achieve reserve design targets. The third set of models assesses the representativeness of GIS surrogates alone. Possible congruence among outputs adds confidence in to the value of a single approach.
NB13C-04 14:15h
Land Use Patterns, Water Quality and Spawning Success of (Barbus) in the Mnembo River Catchment, Southern Africa
Endorheic Lake Chilwa is one of the most productive lakes in Africa. High population density and agricultural practices in the Chilwa catchment have been linked to observed declines in the number and size of the commercially fished (Barbus) species. The Mnembo River is a major inflow into Lake Chilwa which has received little scientific study to date. In 2003/04, water quality and (Barbus) spp. abundance and distribution were monitored monthly in the Mnembo River to provide data for a lake management plan. Studies on smaller inflows into Lake Chilwa have implicated sediment yield, discharge, conductivity and total suspended solids (TSS) as influences on (Barbus) migration. Conductivity, pH and discharge were the most significant influences on (Barbus) spp. catch in the Mnembo River, while rainfall and water temperature were the most influential on (Barbus) spawning condition (Gonadosomatic Index). Sediment yield and soil loss were significantly lower in the Mnembo than in other catchments of Lake Chilwa because of markedly reduced agricultural land use. These results suggest that compared to Lake Chilwa's other catchments, the Mnembo is in good condition, however unsustainable land use practices will continue to increase until a management strategy for the Lake Chilwa watershed is implemented.
NB13C-05 14:30h
Evolutionary History and Conservation Status of Cave Crayfishes Along the Cumberland Plateau
Obligate cave-dwelling crayfish species are found only in southeastern United States, Mexico, and Cuba. Most species are considered to be endangered because of surface pollution threats to groundwater and small geographic distributions. There are currently three subterranean species of the genus Orconectes found along the Cumberland Plateau, a worldwide hotspot of cave biodiversity. The objectives of my dissertation research are to: 1) delineate species' boundaries using molecular genetic data in a phylogenetic framework, 2) examine evolutionary history of each species using Nested Clade Analysis, and 3) assess conservation status of each species using measures of effective population size and genetic diversity. This research project has uncovered a new species of cave crayfish along the border of Tennessee and Kentucky, an area previously thought to have "intergrades" between two subspecies of O. australis. It appears that Cambarus gentryi, a surface-dwelling burrowing species, is the closest living ancestor to the cave Orconectes assemblage on the Plateau. The origin appears to be Eastern Kentucky, with range expansions occuring southward down the Plateau. Although controversial, these cave species exhibit high levels of genetic diversity, especially in comparison to surface-dwellers. Conservation efforts should focus on protecting `high-traffic' areas to maintain gene flow and prevent isolation.
NB13C-06 14:45h
Phylogeography of Cambarus tenebrosus: a Facultative Cave-Dwelling Freshwater Crayfish Species.
Cambarus tenebrosus is a unique freshwater crayfish species, inhabiting both subterranean and surface habitats in southeastern United States. This facultative cave-dweller is found in all aquatic karst areas within its range, including deep pits, massive underground rivers, springs, and surface streams, which makes this species ideal for a phylogeographic study. The objectives of our research are to: 1.) determine if C. tenebrosus is a single lineage or represents multiple cryptic species using phylogenetic methods, 2.) evaluate the evolutionary history and current gene flow patterns of C. tenebrosus using Nested Clade Analysis, and 3.) assess genetic diversity and conservation status of the species. We have gathered molecular genetic data from over 300 individuals from cave and surface environments across the entire range, with focus on the Cumberland Plateau from Kentucky to Alabama. Preliminary findings suggest that there are several clades of C. tenebrosus, but these clades geographically overlap in many areas. There is also no association between genetics and habitat (surface vs. subsurface), suggesting that there is gene flow between the two environment types. The origin of the species appears to be around Western Kentucky and Indiana, which then expanded southward down the Cumberland Plateau.