Although most organisms thermoregulate behaviorally, biologists still cannot easily predict whether mobile animals will thermoregulate in natural environments. Current models fail because they ignore how the spatial distribution of thermal resources constrains thermoregulatory performance over space and time. To overcome this limitation, we modeled the spatially explicit movements of animals constrained by access to thermal resources. Our models predict that ectotherms thermoregulate more accurately when thermal resources are dispersed throughout space than when these resources are clumped. This prediction was supported by thermoregulatory behaviors of lizards in outdoor arenas with known distributions of environmental temperatures. Further, simulations showed how the spatial structure of the landscape qualitatively affects responses of animals to climate. Biologists will need spatially explicit models to predict impacts of climate change on local scales.behavioral thermoregulation | thermal heterogeneity | thermal ecology | spatial ecology | individual-based model T he rapid warming of many environments has generated great concern about the potential impacts on biodiversity (1). Genetic changes in response to anthropogenic warming seem rare (2) or limited (3), and many species have shifted habitats over space and time (4-7). Indeed, facultative behavioral strategies are the primary means by which many species cope with changing environments (8). In a warming world, behavioral thermoregulation could enable most organisms to maintain body temperatures that promote physiological performance (9-11). However, excessive warming constrains thermoregulation, potentially leading to extinction of populations. At local scales, recent warming apparently caused numerous extinctions by limiting the duration of foraging by lizards (12). According to mechanistic models, thermal constraints on activity will play a major role in biological invasions and local extinctions (13-16). Given constraints on thermoregulatory behaviors, some have predicted that global warming could eliminate more than 40% of lizard species by 2080 (12).Such projections, although dire, underestimate the impacts of climate change by failing to consider costs of thermoregulation that are imposed by environmental heterogeneity (10,17,18). Most models assume that an animal can access either unshaded michrohabitats or shaded microhabitats without using energy to search for and move between them (14, 19). As long as the animals prefers a body temperature within the range of operative environmental temperatures, an animal can thermoregulate by shuttling between microhabitats at no cost. Given this assumption, researchers combine meteorological data and biophysical equations to calculate the expected performance of an organism in specific climates. However, thermoregulatory behaviors impose costs such as energy loss, predation risk, and missed opportunities for foraging and breeding (20), which researchers have ignored when modeling the biological impacts of clim...

Aerobic anoxygenic phototrophic (AAP) bacteria are well known to be abundant in estuaries, coastal regions and in the open ocean, but little is known about their activity in any aquatic ecosystem. To explore the activity of AAP bacteria in the Delaware estuary and coastal waters, single-cell 3 H-leucine incorporation by these bacteria was examined with a new approach that combines infrared epifluorescence microscopy and microautoradiography. The approach was used on samples from the Delaware coast from August through December and on transects through the Delaware estuary in August and November 2011. The percent of active AAP bacteria was up to twofold higher than the percentage of active cells in the rest of the bacterial community in the estuary. Likewise, the silver grain area around active AAP bacteria in microautoradiography preparations was larger than the area around cells in the rest of the bacterial community, indicating higher rates of leucine consumption by AAP bacteria. The cell size of AAP bacteria was 50% bigger than the size of other bacteria, about the same difference on average as measured for activity. The abundance of AAP bacteria was negatively correlated and their activity positively correlated with light availability in the water column, although light did not affect 3 H-leucine incorporation in light-dark experiments. Our results suggest that AAP bacteria are bigger and more active than other bacteria, and likely contribute more to organic carbon fluxes than indicated by their abundance.

The objective of this study was to examine the abundance, size, and single-cell activity of aerobic anoxygenic phototrophic (AAP) bacteria in summer and fall over 2 yr in coastal waters of the West Antarctic Peninsula. Single-cell incorporation of 3 H-leucine was measured using a new microautoradiography approach coupled to infrared epifluorescence microscopy. The relative abundance of these photoheterotrophic bacteria was higher in January (1 to 8%) than in May (0.3 to 1%) but differed greatly between the 2 yr we sampled, as did several biogeochemical properties. The biovolume of AAP bacteria was nearly 3-fold larger than that of cells in the total bacterial community and ca. 2-fold larger than AAP bacterial biovolumes in low latitude coastal waters. A large fraction of AAP bacteria and of the total community incorporated 3 H-leucine in January (ca. 48% for both communities), which then decreased by 4-fold in May. The area of silver grains formed around active cells in microautoradiography preparations decreased nearly 5-fold from January to May. Silver grain area data indicated that AAP bacteria were about 40% more active than the total community in January but there was no difference in May, probably because of the nearly 20-fold decrease in light availability from January to May. These data suggest that AAP bacteria contribute more to biomass production in these polar waters than suggested by their abundance, but only in the austral summer.