Endotherms dissipate heat to the environment to maintain a stable body temperature at high ambient temperatures, which requires them to maintain a balance between heat dissipation and water conservation. Birds are relatively small, contain a large amount of metabolically expensive tissue, and are mostly diurnal, making them susceptible to physiological challenges related to water balance and heat dissipation. We compiled total evaporative water loss (TEWL) measurements for 174 species of birds exposed to different temperatures and used comparative methods to examine their relationships with body size, ambient temperature, precipitation, diet, and diel activity cycle. TEWL in the thermoneutral zone (TNZ) was associated primarily with body mass and activity phase. Larger and more active-phase birds, with their higher metabolic rates, lost more water through evaporation than smaller, resting-phase birds, particularly at higher thermal exposures. However, maximum temperature of the natural habitat became an important determinant of TEWL when birds were exposed to temperatures exceeding the TNZ. Species from hotter climates exhibited higher TEWL. Adaptation to arid climates did not restrict evaporative water loss at thermal conditions within the TNZ, but promoted evaporative water loss at exposures above the TNZ. The TEWL of granivores, which ingest food with low water content, differed little from species with other food habitats under all thermal conditions. The effects of environmental covariates of TEWL were dissimilar across thermal exposures, suggesting no evidence for a tradeoff between water conservation in the TNZ and heat dissipation at exposure to higher temperatures. Thus, birds may be able to acclimate when climate change results in the need to increase heat dissipation due to warming, except perhaps in hot, arid environments where species will need to depend heavily upon evaporative cooling to maintain homeothermy.

Palestra apresentada no âmbito do Ciclo "Árvores e seus habitats", organizado pela Fabre Actum - Associação Para a Dinamização, Defesa & Animação de Patrimónios e Artes. | info:eu-repo/semantics/draft

A partir de 18 variables características del hábitat actual de Quercus suber L. en el centro-oeste de España (Salamanca y Zamora), se ha cartografiado el área potencial climática para la especie así como los límites máximos de las áreas potenciales considerando no sólo los factores climáticos sino tres variables edafoclimáticas para dos hipótesis extremas de capacidad de retención de agua (CRA): CRA baja (50 mm) y CRA elevada (250 mm). Por último, se han tenido en cuenta las posibles limitaciones derivadas de la reacción del suelo. Los resultados obtenidos muestran la notable potencialidad climática de la zona para el alcornoque. Asimismo, se ha constatado que las áreas climática y edafoclimáticamente aptas para el alcornoque en el área española occidental de la cuenca del Duero presentan una notable dependencia de la CRA que condiciona no sólo su carácter central o marginal sino, en buena medida, su extensión. En la cuenca del Tajo, al sur de Salamanca, esta dependencia es notablemente menor.

The ecological consequences of impoundment construction on riparian systems throughout the U.S. Southwest has profoundly affected a variety of organisms, including many amphibians. To better understand the current extent of hybridization and changes in genetic composition over time in Bufo (Anaxyrus) woodhousii and Bufo microscaphus, we used microsatellite loci to evaluate 260 individuals representing 10 total populations constituting B. woodhousii, B. microscaphus, and putative hybrids along the Agua Fria River in Arizona during two time periods (1992–97 and 2009–10). Consistent with prior work with these two anurans documenting unidirectional replacement or genetic introgression, we predicted that microsatellites would provide evidence of directional introgression of B. woodhousii into B. microscaphus. The putative hybrid populations exhibited the highest number of alleles, and B. microscaphus exhibited the lowest number of alleles. Structure analysis indicated K = 2 as the best-fit population number for both time periods. All pairwise F-statistics were highly significant, corroborating differentiation among populations as inferred by structure analysis. The principal coordinates analysis demonstrated three distinct clusters of individuals that corresponded strongly with prior morphological and mitochondrial assignments within this region over both sampling periods. Our findings indicate that the genetic identity of B. microscaphus remains distinct from B. woodhousii and the hybrids, suggesting that the genetic structure of the corresponding populations has remained intact. Bufo woodhousii has not replaced B. microscaphus along the Agua Fria River beyond those habitats directly associated with impoundment construction.

Wetlands provide unique goods and services, as habitats of high biodiversity. Hydrology is the principal control on wetland functioning; hence, understanding the water source is fundamental. However, groundwater inflows may be discrete and easily missed. Research techniques are required with low cost and minimal impact in sensitive settings. In this study, the effectiveness of using a three-dimensional (3D) temperature model and botanical indicators to characterise groundwater discharge is explored at the CEH (Centre for Ecology and Hydrology) River Lambourn Observatory, Boxford, UK. This comprises a 10 ha lowland riparian wetland, designated for its scientific interest and conservation value. Temperature data were collected in winter at multiple depths down to 0.9 m over approximately 3.6 ha and transformed into a 3D model via ordinary kriging. Anomalous warm zones indicated distinct areas of groundwater upwelling which were concurrent with relic channel structures. Lateral heat propagation from the channels was minimal and restricted to within 5–10 m. Vertical temperature sections within the channels suggest varying degrees of groundwater discharge along their length. Hydrochemical analysis showed that warmer peat waters were akin to deeper aquifer waters, confirming the temperature anomalies as areas of groundwater discharge. Subsequently, a targeted vegetation survey identified Carex paniculata as an indicator of groundwater discharge. The upwelling groundwater contains high concentrations of nitrate which is considered to support the spatially restricted growth of Carex paniculata against a background of poor fen communities located in reducing higher-phosphate waters.