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Desiccation Risk (desiccation + risk)
Selected AbstractsAquatic herbicide exposure increases salamander desiccation risk eight months later in a terrestrial environmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Jason R. Rohr Abstract Contaminants and climate change may be factors in amphibian declines. However, few studies have explored their joint impacts on postmetamorphic amphibians, a life stage of great importance to amphibian population dynamics. Here, we examine the effects of premetamorphic exposure (mean exposure of 64 d) to ecologically relevant concentrations of the globally common herbicide atrazine (0, 4, 40, 400 ,g/L) on the behavior and water retention of lone and grouped postmetamorphic, streamside salamanders, Ambystoma barbouri. Salamanders exposed to ,40 ,g/L of atrazine exhibited greater activity, fewer water-conserving behaviors, and accelerated water loss four and eight months after exposure compared to controls. No recovery from atrazine exposure was detected and its effects were independent of the presence of conspecifics. These results are consistent with the hypothesis that adverse climatic conditions and contaminants can interact to harm post-metamorphic amphibians; however, they suggest that these two stressors need not be experienced simultaneously to do so. These results emphasize the importance of considering both latent and cumulative effects of temporally linked stressors in ecotoxicology. [source] The interaction of multiple environmental stressors affects adaptation to a novel habitat in the natterjack toad Bufo calamitaJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 11 2009B. ROGELL Abstract The potential to adapt to novel environmental conditions is a key area of interest for evolutionary biology. However, the role of multiple selection pressures on adaptive responses has rarely been investigated in natural populations. In Sweden, the natterjack toad Bufo calamita inhabits two separate distribution areas, one in southernmost Sweden and one on the west coast. We characterized the larval habitat in terms of pond size and salinity in the two areas, and found that the western populations are more affected by both desiccation risk and pond salinity than the southern populations. In a common garden experiment manipulating salinity and temperature, we found that toads from the west coast populations were locally adapted to shorter pond duration as indicated by their higher development and growth rates. However, despite being subjected to higher salinity stress in nature, west coast toads had a poorer performance in saline treatments. We found that survival in the saline treatments in the west coast populations was positively affected by larger body mass and longer larval period. Furthermore, we found negative genetic correlations between body mass and growth rate and their plastic responses to salinity. These results implicate that the occurrence of multiple environmental stressors needs to be accounted for when assessing the adaptive potential of organisms and suggest that genetic correlations may play a role in constraining adaptation of natural populations. [source] Variation in the degree and costs of adaptive phenotypic plasticity among Rana temporaria populationsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2004J. Merilä Abstract Adaptive phenotypic plasticity in the form of capacity to accelerate development as a response to pond drying risk is known from many amphibian species. However, very little is known about factors that might constrain the evolution of this type of plasticity, and few studies have explored to what degree plasticity might be constrained by trade-offs dictated by adaptation to different environmental conditions. We compared the ability of southern and northern Scandinavian common frog (Rana temporaria) larvae originating from 10 different populations to accelerate their development in response to simulated pond drying risk and the resulting costs in metamorphic size in a factorial laboratory experiment. We found that (i) northern larvae developed faster than the southern larvae in all treatments, (ii) a capacity to accelerate the response was present in all five southern and all five northern populations tested, but that the magnitude of the response was much larger (and less variable) in the southern than in the northern populations, and that (iii) significant plasticity costs in metamorphic size were present in the southern populations, the plastic genotypes having smaller metamorphic size in the absence of desiccation risk, but no evidence for plasticity costs was found in the northern populations. We suggest that the weaker response to pond drying risk in the northern populations is due to stronger selection on large metamorphic size as compared with southern populations. In other words, seasonal time constraints that have selected the northern larvae to be fast growing and developing, may also constrain their innate ability for adaptive phenotypic plasticity. [source] Ant Activity along Moisture Gradients in a Neotropical Forest,BIOTROPICA, Issue 4a 2000Michael Kaspari ABSTRACT Insect activity often tracks moisture gradients. We studied ant activity, size, and diversity along three moisture gradients in a Panamanian rain forest. Ant activity at baits increased by 25 percent from the dry to the wet season, and > 200 percent on a topographical gradient from a ravine to an exposed plateau. Activity varied little from day to night. Three microhabitats,tree trunk, shrub, and litter,showed different responses to these three gradients. The size distribution of the species pool (N= 63) was right skewed, but the average size of ants at a bait was strongly bimodal. Ants active in moister times and places were not significantly smaller. We suggest that gradients of desiccation risk and food availability were the two most likely causes of these patterns. Two temporal niche axes (daily and seasonal) showed little species specialization, but half of the common species could be categorized as litter or plant microhabitat specialists. RESUMEN Nosotros estudiamos actividad de hormiga, tamaño, y diversidad en 4 microhabitats a lo largo de tres gradientes de humedad en un bosque Panameño. La actividad de hormiga aumentada por 25 percent desde la seca a la temporada mojada, y > 200 percent sobre un gradiente topográfico desde un barranco a una meseta expuesta. La actividad varió poco desde el día a la noche. Tres microhabitats,tronco de árbol, arbusto, y la hojarasca-mostró respuestas diferentes a estos tres de gradientes. El tamaño la distribución de las especies combina (N= 63) tuvo razón skewed, pero el tamaño promedio de hormigas a una carnada era fuertemente bimodal. Las hormigas activas en los lugares y veces más húmedas no eran significativamente menores. Nosotros sugerimos que los gradientes de desecamiento arriesgan y la disponibilidad alimentaria son los dos muy probables ocasiona de estos modelos. Dos temporal los nichos (diarios y estacionales) mostraron poca especialización de especies. La mitad de las especies comunes podría categorizarse como hojarasca o plantada microhabitat especialistas. [source] | ||||||||||