Various foraging modes are employed by predators in nature, ranging from ambush to active predation. Although the foraging mode may be limited by physiological constraints, other factors, such as prey behavior and distribution, may come into play. Using a simulation model, we tested to what extent the relative success of an ambush and an active predator changes as a function of the relative velocity and movement directionality of prey and active predator. In accordance with previous studies, we found that when both active predator and prey use nondirectional movement, the active mode is advantageous. However, as movement becomes more directional, this advantage diminishes gradually to 0. Previous theoretical studies assumed that animal movement is nondirectional; however, recent field observations show that in fact animal movement usually has some component of directionality. We therefore suggest that our simulation is a better predictor of encounter rates than previous studies. Furthermore, we show that as long as the active predator cannot move faster than its prey, it has little or no advantage over the ambush predator. However, as the active predator's velocity increases, its advantage increases sharply.
Much recent literature is concerned with how variation among individuals (e.g., variability in their traits and fates) translates into higher-level (i.e., population and community) dynamics. Although several theoretical frameworks have been devised to deal with the effects of individual variation on population dynamics, there are very few reports of empirically based estimates of the sign and magnitude of these effects. Here we describe an analytical model for sizedependent, seasonal life cycles and evaluate the effect of individual size variation on population dynamics and stability. We demonstrate that the effect of size variation on the population net reproductive rate varies in both magnitude and sign, depending on season length. We calibrate our model with field data on size-and density-dependent growth and survival of the generalist grasshopper Melanoplus femurrubrum. Under deterministic dynamics (fixed season length), size variation impairs population stability, given naturally occurring densities. However, in the stochastic case, where season length exhibits yearly fluctuations, size variation reduces the variance in population growth rates, thus enhancing stability. This occurs because the effect of size variation on net reproductive rate is dependent on season length. We discuss several limitations of the current model and outline possible routes for future model development.Keywords: body size, individual variation, population stability, seasonal environment, univoltine lifecycle. Ecological entities are organized hierarchically into different levels of organization, such as the individual, the population, and the community (MacMahon et al. 1987;Allen and Hoekstra 1992;Pickett et al. 1994). The way in which these different organizational levels combine to influence the dynamics of natural systems remains a fundamental research topic in ecology (Lomnicki 1988;Nisbet et al. 1989; Abrams 1995;Levin et al. 1997;. Such research is motivated by the need to understand the level of mechanistic biological detail that must be included in ecological theory as well as how much can be safely abstracted while still achieving biologically faithful and quantitatively accurate descriptions of population and community dynamics.In the past 30 years, ecologists have become increasingly interested in linking individual phenotypic variation (in behavior, morphology, physiology, and life history) to population and community dynamics (e.g., Lomnicki 1978;Metz and Diekmann 1986;Begon and Wall 1987;Ebenman and Persson 1988;Nisbet et al. 1989;Bjørnstad and Hansen 1994;Uchmanski 1999;Schmitz 2000;de Roos et al. 2003). Specifically, many theoretical studies have demonstrated how age, stage, and size structure; cohort effects; and other forms of individual variation (e.g., in developmental and growth rates or in competitive ability) have important consequences for population dynamics, stability, and persistence (e.g., Bellows 1986aBellows , 1986bLomnicki 1988;Bjørnstad and Hansen 1994;de Roos 1997;Uchmanski 2000;Kendall ...
6Fire effects on ecosystems range from destruction of aboveground vegetation 2 7 to direct and indirect effects on belowground microorganisms. Although variation in 2 8 such effects is expected to be related to fire severity, another potentially important and 2 9 poorly understood factor is the effects of fire seasonality on soil microorganisms. We 3 0 carried out a large-scale field experiment examining the effects of spring versus 3 1 autumn burns on the community composition of soil fungi in a typical Mediterranean 3 2woodland. Although the intensity and severity of our prescribed burns were largely 3 3 consistent between the two burning seasons, we detected differential fire season 3 4
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.