Brown marmorated stink bug, Halyomorpha halys Stål, is an invasive, herbivorous insect species that was accidentally introduced to the United States from Asia. First discovered in Allentown, PA, in 1996, H. halys has now been reported from at least 40 states in the United States. Additional invasions have been detected in Canada, Switzerland, France, Germany, Italy, and Lichtenstein, suggesting this invasive species could emerge as a cosmopolitan pest species. In its native range, H. halys is classified as an outbreak pest; however, in North America, H. halys has become a major agricultural pest across a wide range of commodities. H. halys is a generalist herbivore, capable of consuming Ͼ100 different species of host plants, often resulting in substantial economic damage; its feeding damage resulted in US$37 million of losses in apple in 2010, but this stink bug species also attacks other fruit, vegetable, field crop, and ornamental plant species. H. halys has disrupted integrated pest management programs for multiple cropping systems. Pesticide applications, including broad-spectrum insecticides, have increased in response to H. halys infestations, potentially negatively influencing populations of beneficial arthropods and increasing secondary pest outbreaks. H. halys is also challenging because it affects homeowners as a nuisance pest; the bug tends to overwinter in homes and outbuildings. Although more research is required to better understand the ecology and biology of H. halys, we present its life history, host plant damage, and the management options available for this invasive pest species.

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...

We tested five mechanisms of coexistence in a community of three common rodent species (two gerbils, Gerbillus allenbyi and G. pyramidum, and one jerboa, Jaculus jaculus) inhabiting sand dunes in the Negev Desert, Israel. The five mechanisms, based on foraging theory, considered various forms of habitat selection in time and space. From November 1986 until January 1988, we live—trapped to census rodent populations, counted rodent spoor in tracking plots to quantify activity, and measured the rodents' giving—up densities (GUDs: the amount of food remaining within a resource patch following exploitation by a forager) in seed trays to determine relative foraging efficiencies. The population sizes of the two gerbil species tended to fluctuate synchronously (unfortunately, we could not live—trap any jerboas). G. allenbyi biased its activity towards the stabilized sand habitat and towards the bush microhabitat. In contrast, G. pyramidum and J. jaculus biased their activity towards semistabilized sand habitats, and J. jaculus also biased its activity towards the open microhabitat. Despite divergent patterns of habitat use among species, G. allenbyi tended to be the most efficient forager and J. jaculus the least efficient forager regardless of microhabitat, sand habitat, or month. G. allenbyi's presence in the community may be assured by its higher foraging efficiency. J. jaculus's presence in the community may either result from its ability to travel greater distances and utilize rare, rich resource patches, or result from an herbivorous diet. G. pyramidum's presence with G. allenbyi in the community appears to require the less stabilized sand habitats and the ability of G. pyramidum to dominate rich patches by interference or nightly temporal partitioning.

Many classical models of food patch use under predation risk assume that predators impose patch‐specific predation risks independent of prey behavior. These models predict that prey should leave a chosen patch only if and when the food depletes below some critical level. In nature, however, prey individuals may regularly move among food patches, even in the apparent absence of food depletion. We suggest that such prey movement is part of a predator‐prey “shell game”, in which predators attempt to learn prey location, and the prey attempt to be unpredictable in space. We investigate this shell game using an individual‐based model that allows predators to update information about prey location, and permits prey to move with some random component among patches, but with reduced energy intake. Our results show the best prey strategy depends on what the predator does. A non‐learning (randomly moving) predator favors non‐moving prey – moving prey suffer higher starvation and predation. However, a learning predator favors prey movement. In general, the best prey strategy involves movement biased toward, but not completely committed to, the richer food patch. The strategy of prey movement remains beneficial even in combination with other anti‐predator defenses, such as prey vigilance.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. A graphical model describing the optimal choices of two species competing for resources in two types of habitats is tested with hummingbirds in the field. In this model, both species prefer taking resources from one of the habitat types. However, one of the species (the dominant), by virtue of interference competition, can gain access to the better patch more readily than the other (the subordinate). The model begins with the result of single-species optimal foraging models: at low densities of birds, only the better patch type should be selected, but as density increases, both should be used. Interspecific competition should not lead to qualitatively different behaviors for the dominant species because the effects of the subordinate are weak. For the subordinate, however, there is a third class of behaviors: under the pressure of high densities of the dominant, the subordinate may totally avoid the better patch and use only the poorer.We tested the validity of the modeFs predictions using three species of hummingbirds: Bluethroated {Lampornis clemenciae), Rivoli's {Eugenes fulgens), and Black-chinned {Archilochus alexandri) coming to feeders containing 1.2 mol/L or 0.35 mol/L sucrose solution. There were no detectable effects of Rivoli's on Black-chinned or vice-versa. This allowed us to test the model's predictions about the interactions between the other two pairs of species. Blue-throateds were dominant in both cases. The amount of time birds spent feeding (or in the case of Blue-throateds, feeding and defending) was analyzed, rather than actual densities. Wide ranges of feeding and defending times were obtained using species removals and natural seasonal changes in densities. These two pairs of species exhibited all the model's features. In particular, the dominant's aggressive behavior forced the subordinate to restrict itself to a patch type known to be inferior.

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We provide experimental evidence for the isoleg theory of habitat selection in a pair of psammophilic gerbil species. Gerbillus allenbyi (mean mass: 26 g) and G. pyramidum (mean mass: 40 g) coexist in Israel's Negev desert in areas that may contain three distinct sandy habitats: stabilized sand fields, semistabilized dunes, and drifting dunes. When all three habitat types are available, coexistence between the two species has been explained by a centrifugal model of community organization that has been untested until now. To begin testing it, we conducted a field experiment in six 1 ha enclosures, each containing similar proportions of two of the sandy—habitat types (stabilized sand and semi—stabilized dune). This experiment tested the following hypotheses concerning the coexistence of the two species: (1) both species prefer the same primary habitat type; (2) G. allenbyi and G. pyramidum exhibit intraspecific density—dependent habitat selection; (3) habitat preference of both G. allenbyi and G. pyramidum is affected by the interspecific density of the other species; and (4) in the presence of the two habits of our experiment, the theory predicts that the habitat preferences of the two gerbil species should collapse from a centrifugal to a shared—preference model of habitat selection. We tested these hypotheses during two summers by measuring activity of the two species after introducing predetermined and different densities of gerbils into the enclosures during eight 3—4 wk long temporal replicates. During each temporal replicate, we further manipulated the density of G. allenbyi. Activity and habitat utilization of the rodents was measured by tracks left in the sand. Results of the experiments supported all four of our hypotheses and allowed the construction of their isoleg graph.

We studied, both theoretically and empirically, the effect of intra— and interspecific competition on the foraging effort of individuals. We considered two models, one for a time—minimizer satisfying an energy requirement, the other for an animal maximizing fitness as a function of multiple inputs subject to a time constraint. The goal of satisfying an energy constraint predicts that foraging effort should increase with increased competition. The goal of maximizing fitness subject to a time constraint on multiple inputs may also predict that foraging effort should increase with increased competition because of the missed opportunity cost that results when different inputs are complementary. However, if the fitness—maximizer with multiple inputs incurs an energy cost of foraging (in addition to missed opportunity costs), then it should often reduce foraging effort in response to an increase in competition. We experimentally tested the foraging response to increased competition by two species of gerbils, Gerbillus allenbyi and G. pyramidum, over a range of manipulated population densities in field enclosures located in the Negev Desert of Israel. Our results support the cost—benefit model when the additional energy cost of foraging is important. Per capita activity (as measured by spoor) declined as a function of intraspecific density for each species and as a function of interspecific density for G. allenbyi. We detected no interspecific effect, however, on G. pyramidum.