Aerobic and anaerobic energy expenditure during rest and activity in montane Bufo b. boreas and Rana pipiens

The relations of standard and active aerobic and anaerobic metabolism and heart rate to body temperature ( T b ) were measured in montane groups of Bufo b. boreas and Rana pipiens maintained under field conditions. These amphibians experience daily variation of T b over 30°C and 23°C, respectively (Carey, 1978). Standard and active aerobic and anaerobic metabolism, heart rate, aerobic and anaerobic scope are markedly temperature-dependent with no broad plateaus of thermal independence. Heart rate increments provide little augmentation of oxygen transport during activity; increased extraction of oxygen from the blood probably contributes importantly to oxygen supply during activity. Development of extensive aerobic capacities in Bufo may be related to aggressive behavior of males during breeding. Standard metabolic rates of both species are more thermally dependent than comparable values for lowland relatives. Thermal sensitivity of physiological functions may have distinct advantages over thermally compensated rates in the short growing season and daily thermal fluctuations of the montane environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47726/1/442_2004_Article_BF00348070.pd

Data from: Trophic sensitivity of invasive predator and native prey interactions: integrating environmental context and climate change

Climate change is predicted to intensify the impacts of invasive species by enhancing their performance relative to their native counterparts. However, few studies have compared the performance of invasive predators and native prey, despite the fact that non-native predators are well known to disrupt native communities. The ‘trophic sensitivity hypothesis’ suggests that predators are less tolerant of increasing environmental stress than their prey, whereas the ‘tolerant invaders hypothesis’ suggests that invaders are more tolerant than native species due to selection during the introduction process. It is therefore unclear how invasive predators will respond to increasing climate stressors. We coupled physiological measurements (thermal tolerance, thermal optima, salinity tolerance, predation rate) with environmental time-series data to assess the effects of warming and extreme low salinity events on non-native predators (gastropods) and native prey (oysters) from a coastal ecosystem. In general support of the trophic sensitivity hypothesis, we found that both non-native predators exhibited lower thermal optima relative to native prey, lower salinity tolerance and one predator was less tolerant of warming. However, because warming tolerance was extremely high (i.e. habitat temperature is 7·9–21 °C below thermal tolerance), near-term warming may first increase predator performance (consumption and growth rates), with negative effects on prey. Low salinity will likely produce heterogeneous effects on predator–prey interactions due to varying watershed sizes among estuaries that control the duration of low salinity events. The trophic sensitivity hypothesis may be a useful framework for understanding community responses to extreme climate change, which portends a decoupling of predator–prey interactions. However, we conclude that this hypothesis must be evaluated in environmental context and that coupling physiological metrics with in situ environmental data offers the best predictive power of near-term climate change impacts on invaded communities. Within our study system, warming is likely to intensify the impacts of both invasive predators, which may greatly reduce the abundance of the native oyster, a species of conservation and restoration focus