A survey of the amphibians and reptiles of Reserva Natural Absoluta Cabo Blanco (RNACB), Puntarenas, Costa Rica was conducted from May to August 2003. Thirteen amphibian and 19 reptile species were found within the RNACB boundaries. Twenty-two of these species were not previously recorded from the lower Nicoya Peninsula and for seven, this locality represents the southernmost extension of their range. One additional amphibian and three reptile species are known from the area based on literature review and examination of museum collections. However, interviews with locals indicate that up to nine other reptile species could be present in the reserve. I observed all but one amphibian species at Laguna Balsitas and at least eight species utilize the lagoon for reproduction. The lagoon is also notable for its population of Kinosternon scorpioides. This study will provide a baseline for further research in the reserve.
Disentangling local and historical factors that determine species diversity patterns at multiple spatial scales is fundamental to elucidating processes that govern ecological communities. Here we investigated how environmental correlates may influence diversity at local and regional scales. Primarily utilizing published species lists, amphibian and reptile alpha and beta diversity were assessed at 17 well-surveyed sites distributed among ecoregions throughout Costa Rica. The degree to which regional species diversity patterns were related to environmental variables and geographic distance was determined using Canonical Correspondence Analysis and Mantel tests. Amphibian alpha diversity was highest in lowland Pacific sites (mean = 43.3 species) and lowest at the high elevation site (9 species). Reptile alpha diversity values were high for both lowland Atlantic (mean = 69.5 species) and lowland Pacific (mean = 67 species) sites and lowest for the high elevation site (8 species). We found high species turnover between local sites and ecoregions, demonstrating the importance of beta diversity in the determination of regional diversity. For both amphibians and reptiles, beta diversity was highest between the high-elevation site and all others, and lowest among lowland sites within the same ecoregion. The effect of geographic distance on beta diversity was minor. Ecologically significant climatic variables related to rain, temperature, sunshine and insolation were found to be important determinants of local and regional diversity for both amphibians and reptiles in Costa Rica.
Amphibians inhabiting montane riparian zones in the Neotropics are particularly vulnerable to decline, but the reasons are poorly understood. Because environmental contaminants, endocrine disruption, and pathogens often figure prominently in amphibian declines it is imperative that we understand how these factors are potentially interrelated to affect montane populations. One possibility is that increased precipitation associated with global warming promotes the deposition of contaminants in montane regions. Increased exposure to contaminants, in turn, potentially elicits chronic elevations in circulating stress hormones that could contribute to montane population declines by compromising resistance to pathogens and/or production of sex steroids regulating reproduction. Here, we test this hypothesis by examining contaminant levels, stress and sex steroid levels, and nematode abundances in male drab treefrogs, Smilisca sordida, from lowland and montane populations in Costa Rica. We found no evidence that montane populations were more likely to possess contaminants (i.e., organochlorine, organophosphate and carbamate pesticides or benzidine and chlorophenoxy herbicides) than lowland populations. We also found no evidence of elevational differences in circulating levels of the stress hormone corticosterone, estradiol or progesterone. However, montane populations possessed lower androgen levels, hosted more nematode species, and had higher nematode abundances than lowland populations. Although these results suggested that nematodes contributed to lower androgens in montane populations, we were unable to detect a significant inverse relationship between nematode abundance and androgen level. Our results suggest that montane populations of this species are not at greater risk of exposure to contaminants or chronic stress, but implicate nematodes and compromised sex steroid levels as potential threats to montane populations.
Little attention has been focused on evaluating river restoration projects. Postproject assessments commonly identify improvements in biological or physical conditions, but opportunities for understanding the interactions between such processes are often missed. This study assesses the linkages between geomorphological and ecological responses in three stream channels in Austin, Texas, restored since 1998 with riffles and steps and riparian planting along graded banks. Prerestoration topographic surveys and data for habitat and macroinvertebrate characteristics enabled comparisons with postrestoration conditions in 2007. Results showed increased channel widths and depths, leading to larger cross-sectional areas and inferred lowered velocities and unit stream power. Improvements in habitats included greater bank stability, less channel alteration, and more diverse velocity-depth regimes. Changes in functional feeding groups of macroinvertebrate communities were reflected in metrics of the Benthic Index of Biotic Integrity, including greater percentages of grazers, filterers, and collector-gatherers in the restored streams. A multivariate statistical model, redundancy analysis, linked improvement in key ecological response variables (taxa richness, % EPT, % grazers, and % chironomids) to better conditions in habitats (lower embeddedness, greater epifaunal cover, greater riparian vegetative width, and more velocity-depth regimes). Key explanatory changes in physical characteristics were increased cross-sectional area and decreased average velocity, which were attributed to restoration designs. These results suggest that although the main restoration goals were to stabilize eroding channels, improvements in physical characteristics could nevertheless lead to positive ecological outcomes. These findings suggest the potential of integrated approaches to target both physical and biological improvements in future restoration projects
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