RESUMO
Land-cover and climate change are both expected to alter species distributions and contribute to future biodiversity loss. However, the combined effects of land-cover and climate change on assemblages, especially at the landscape scale, remain understudied. Lowland tropical amphibians may be particularly susceptible to changes in land cover and climate warming because many species have narrow thermal safety margins resulting from air and body temperatures that are close to their critical thermal maxima (CTmax ). We examined how changing thermal landscapes may alter the area of thermally suitable habitat (TSH) for tropical amphibians. We measured microclimates in 6 land-cover types and CTmax of 16 frog species in lowland northeastern Costa Rica. We used a biophysical model to estimate core body temperatures of frogs exposed to habitat-specific microclimates while accounting for evaporative cooling and behavior. Thermally suitable habitat area was estimated as the portion of the landscape where species CTmax exceeded their habitat-specific maximum body temperatures. We projected changes in TSH area 80 years into the future as a function of land-cover change only, climate change only, and combinations of land-cover and climate-change scenarios representing low and moderate rates of change. Projected decreases in TSH area ranged from 16% under low emissions and reduced forest loss to 30% under moderate emissions and business-as-usual land-cover change. Under a moderate emissions scenario (A1B), climate change alone contributed to 1.7- to 4.5-fold greater losses in TSH area than land-cover change only, suggesting that future decreases in TSH from climate change may outpace structural habitat loss. Forest-restricted species had lower mean CTmax than species that occurred in altered habitats, indicating that thermal tolerances will likely shape assemblages in changing thermal landscapes. In the face of ongoing land-cover and climate change, it will be critical to consider changing thermal landscapes in strategies to conserve ectotherm species.
Assuntos
Biodiversidade , Mudança Climática , Conservação dos Recursos Naturais , Animais , Costa Rica , Ecossistema , Clima TropicalRESUMO
Agricultural expansion continues to drive forest loss in species-rich tropical systems and often disrupts movement and distributions of organisms. The ability of species to occupy and move through altered habitats likely depends on the level of contrast between natural forest and surrounding land uses. Connectivity models, such as circuit theory models, are widely used in conservation biology, and their primary input consists of resistance surfaces representing movement costs associated with landscape features. Cost values are most frequently determined by expert opinion, which may not capture relevant levels of contrast among features. We developed resistance surfaces using experiments that represent different local mechanisms hypothesized to affect connectivity for two Neotropical amphibian species. Response ratios were calculated to translate experimental results to cost values used in connectivity modeling. We used relative abundance data in three land-cover types to generate resistance surfaces for evaluating independent support of models derived from experiments. Finally, we analyzed agreement among movement pathways predicted for each species and among three commonly used connectivity measures: Euclidean, least cost, and resistance distances. Experiments showed that extreme microclimates associated with altered habitats significantly increased desiccation and mortality risk for both species. Resistances estimated from microclimate experiments were concordant with those from survey data for both species. For one focal species, resistance estimates derived from predator encounter rates were also highly correlated with abundance-derived resistances. There was generally low agreement among the three alternative distance measures, which underscores the importance of choosing connectivity models that are most appropriate for the study objectives. Overall, similarity among linkages modeled for each species was high, but decreased with declining forest cover. Our results highlight the value of experiments for drawing inferences about processes in resistance modeling, as well as the need to consider model differences and species-specific responses when developing strategies to maintain connectivity.
Assuntos
Distribuição Animal , Anuros/fisiologia , Ecossistema , Animais , Anuros/classificação , Comportamento Animal , Costa Rica , Especificidade da Espécie , Clima TropicalRESUMO
OBJECTIVE: To examine relative contributions of functional parenchymal preservation and renal ischemia following nephron-sparing surgery (NSS). While residual functional parenchymal volume (FPV) is proposed as the key factor in predicting functional outcomes following NSS, efforts to curtail ischemia time continue to add technical complexity to partial nephrectomy. METHODS: Our kidney cancer database was queried for patients who underwent NSS with warm ischemia time (WIT). Patients with cross-sectional imaging for FPV calculation were included. Cylindrical volume approximation methodology was used to calculate FPV, accounting for the volume of tumor's endophytic component. Percent estimated glomerular filtration rate (eGFR) preservation, perioperatively and at 6 months, was the outcome metric. Spearman correlation and linear regression analyses were used to evaluate associations of WIT and %FPV preservation with renal function preservation. RESULTS: Of the 179 patients included, median preoperative eGFR was 88.4 (9.5% chronic kidney disease III or IV), tumor size was 2.7 cm (interquartile range [IQR] 2.0-3.6 cm), and R.E.N.A.L. nephrometry was low in 34%, intermediate in 57%, and high in 9%. Median WIT was 30 minutes (IQR 24-36), resulting in 97.4% FPV preservation. Median postoperative eGFR at 6.4 months was 80.5 (19.1% chronic kidney disease III or IV), a median of 93.1% eGFR preservation (IQR 85.1-101.7). At discharge, WIT (P <.001), not %FPV (P = .112), was associated with %eGFR preservation. However, 6 months following surgery, on multivariable analysis, both preoperative eGFR (linear regression coefficient = -0.208, P = .006) and %FPV preservation (linear regression coefficient = 0.491, P = .001), but not WIT (P = .946), demonstrated statistically significant association with %eGFR preservation. CONCLUSION: Residual FPV, and not WIT, appears to be the main predictor of ultimate renal function following NSS.