Scientia Discipulorum vol. 2 (2006)
Variability in troglomorphic adaptations of a Mexican cavefish, Poecilia mexicana, from Tabasco, MexicoThe cavefish Poecilia mexicana, earlier known as Poecilia sphenops, is a live-bearing toothcarp or molly found only in Cueva de las Sardinas (also known as Cueva de Villa Luz or El Azufre), in Tabasco, Mexico. The cave ecosystem is based on mixed energy inputs from sulfur springs and chemolithotrophic baceteria, bats, and skylights. The rich food base supports an amazing population density of the cavefish. Earlier studies reported that the fish showed increasing troglomorphic adaptations in physical characteristics and behaviors as you went deeper into the cave. Data presented on eye size reduction show considerable variation and overlap of data by location sampled, and no statistical analyses were done. We sampled from some of the same areas as earlier studies and from the most remote sites in the cave. Our results show considerable variation in troglomorphy of eye reduction from all locations, and no statistical difference with fish from any part of the cave. Evolutionary pressure to develop troglomorphy may be reduced in this cave because of the rich food base, or hybridization with surface forms may not be limited by physical location within the cave.
Comparisons of Four Riparian Plant Communities on the Little Chazy River, Northern New YorkRiparian zones are transitional plant communities that are important for the protection of stream water quality and biota and they often have high biological diversity within small geographical areas. This study characterized the vegetation and several physical site features within four riparian zones in the Little Chazy River watershed located in Clinton County, NY. A total of 110 plant species were sampled in the overstory, understory, and groundcover at these study sites. Average species richness in the 1m2 groundcover plots ranged between 7.0 at the agricultural riparian zone to 17.8 at one of the forested riparian zones. Species diversity values ranged between 1.23 at the agricultural riparian zone to 2.32 at one of the forested riparian zones. In this study, the riparian zone with active agricultural activity had no overstory or understory and the least diverse groundcover. Ordination of groundcover data showed both between-site and within-site separations, indicating large differences in species composition can occur on a small spatial scale. No relationship was found between nutrient availability and disturbance intensity of the riparian zones. The abundance of non-indigenous plant species was directly related to disturbance history of the riparian zones. Best management practices (BMP's) for agriculture and forestry in the Lake Champlain Valley should include guidelines for the preservation of natural riparian ecosystems without producing severe economic consequences for landowners. BMP's should be specific to each type of riparian ecosystem found in northeastern New York.
Effects of land use on periphyton chlorophyll a concentrations and biomass in Adirondack Upland StreamsIn this study we examined bottom-up (light, nutrient availability) and habitat (stream velocity, stream depth) factors affecting benthic chlorophyll a and periphyton biomass in logged and Forest Preserve watershed streams located in the Adirondack Uplands. Chlorophyll a concentrations and ash-free dry mass on ambient substrate were measured in six Preserve and six logged catchments, five samples were taken per site. In a nutrient amendment experiment, porous artificial substrates containing nutrient agar treatments (agar only, N, P, N+P) were secured to the bottom of two streams (one Preserve, one logged), and chlorophyll a concentrations measured after 19 days. Biomass was significantly higher (p=0.034) in streams located in the Preserve. Chlorophyll a was marginally higher (p=0.063) in the Preserve sites. Stream velocity and depth were significant covariables for both chlorophyll a concentrations and biomass. Light, while different between lands uses (p=0.045), was not a significant covariable of periphyton standing stock. In the nutrient amendment experiment, all treatments in the Preserve stream showed higher chlorophyll a concentrations than in the logged stream (p<0.001). Treatments within the logged stream showed higher chlorophyll a concentrations for the N+P treatment only, and treatments within the Preserve stream were not different (p=0.226). Higher ambient nutrient concentrations in the Preserve stream may explain these results.
Habitat Usage by Birds at the Lake Alice Wildlife Management Area Chazy, New YorkThe Lake Alice Wildlife Management Area (LAWMA) in northern Clinton County, New York is a popular location for birding enthusiasts. However, this study is the first comprehensive survey of bird species within major habitat types at LAWMA in more than 20 years. Birds were identified by sight and sound in four habitats at LAWMA between June 2 and July 22, 2003. Relative abundance and diversity were calculated for bird species in the forest habitat, and the forest-field, forestwetland and wetland-field ecotones. Thirty-one residential species were observed during the summer, with between 14 and 21 species per habitat type. The highest diversity indices were in the forest ecotones. Recommendations were made for habitat management projects to enhance bird species richness at LAWMA and increase the populations of bird species that are either threatened or of special concern status in New York.