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201.
Dispersal can influence population dynamics, species distributions, and community assembly, but few studies have attempted
to determine the factors that affect dispersal of insects in natural populations. Consequently, little is known about how
proximate factors affect the dispersal behavior of individuals or populations, or how an organism’s behavior may change in
light of such factors. Adult predaceous diving beetles are active dispersers and are important predators in isolated aquatic
habitats. We conducted interrelated studies to determine how several factors affected dispersal in two common pond-inhabiting
species in southern Alberta, Canada: Graphoderus occidentalis and Rhantus sericans. Specifically, we (1) experimentally tested the effect of plant and beetle densities on dispersal probabilities in ponds;
(2) surveyed ponds and determined the relationships among beetle densities and plant densities and water depth; and (3) conducted
laboratory trials to determine how beetle behavior changed in response to variation in plant densities, conspecific densities,
food, and water depth. Our field experiment determined that both species exhibited density dependence, with higher beetle
densities leading to higher dispersal probabilities. Low plant density also appeared to increase beetle dispersal. Consistent
with our experimental results, densities of R. sericans in ponds were significantly related to plant density and varied also with water depth; G. occidentalis densities did not vary with either factor. In the laboratory, behavior varied with plant density only for R. sericans, which swam at low density but were sedentary at high density. Both species responded to depth, with high beetle densities
eliciting beetles to spend more time in deeper water. The presence of food caused opposite responses for G. occidentalis between experiments. Behavioral changes in response to patch-level heterogeneity likely influence dispersal in natural populations
and are expected to be important for observed patterns of individuals in nature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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