Individuals that disperse farther than other individuals are more likely to be on the frontlines of spreading populations and may be more likely to mate with one another as a consequence of their spatial proximity. Over generations, this process—known as spatial sorting—can produce patterns of increasing dispersal ability from a population's core towards the spreading front. By contrast, when the spread of a population is limited by the availability of suitable habitat, theory predicts that range boundaries can select against more dispersive phenotypes and produce patterns of decreasing dispersal capacity towards population margins. In a common garden study of invasive kudzu bugs ( Megacopta cribraria )—which are limited by the availability of hostplants in their southern and western margins—I show that midrange individuals fly 49% farther than individuals in the core and 37% farther than individuals at margins. This result highlights that other processes, such as maternal effects or selection at range boundaries, may create more complicated patterns of dispersal ability across landscapes than predicted by models of spatial sorting alone.

An individual's susceptibility to attack can be influenced by conspecific and heterospecifics neighbors. Predicting how these neighborhood effects contribute to population-level processes such as competition and evolution requires an understanding of how the strength of neighborhood effects is modified by changes in the abundances of both consumers and neighboring resource species. We show for the first time that consumer density can interact with the density and frequency of neighboring organisms to determine the magnitude of neighborhood effects. We used the bean beetle, Callosobruchus maculatus, and two of its host beans, Vigna unguiculata and V. radiata, to perform a response-surface experiment with a range of resource densities and three consumer densities. At low beetle density, damage to beans was reduced with increasing conspecific density (i.e., resource dilution) and damage to the less preferred host, V. unguiculata, was reduced with increasing V. radiata frequency (i.e., frequency-dependent associational resistance). As beetle density increased, however, neighborhood effects were reduced; at the highest beetle densities neither focal nor neighboring resource density nor frequency influenced damage. These findings illustrate the importance of consumer density in mediating indirect effects among resources, and suggest that accounting for consumer density may improve our ability to predict population-level outcomes of neighborhood effects and our use of them in applications such as mixed-crop pest management.

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Maintaining fire-dependent habitat for species of conservation concern often requires a balancing act between the short-term costs of direct mortality caused by fires and the long-term benefits of ensuring high-quality habitat. To reduce risk to threatened populations, land managers may need to adjust the frequency with which they burn sites and, likely, mitigate the short-term costs of prescribed fires by not burning during a species' life stages that may be especially sensitive to fires. Few, if any, studies have investigated burn regimes for butterflies in longleaf pine forests-a once dominant habitat in the southeast United States-despite a long history and frequent usage of prescribed burns in these ecosystems. We surveyed a recently discovered metapopulation of frosted elfin (Callophrys irus) butterflies residing in longleaf pine forest over seven years at sites across nine management units with differing fire return intervals and fire seasonalities. We observed dramatic population declines after burns, with no adults observed at some sites in subsequent years. Our analyses demonstrate that populations may need at least three to 4 years to recover, and that burns in the spring, when frosted elfin eggs and larvae are found on hostplants, should be avoided if possible. In fact, our model suggests that the largest spring-burned sites have fewer than 20% of the adult elfins the year following a fire than do sites burned in other seasons. Land managers seeking to conserve frosted elfins and other butterflies with similar life histories may need to burn at times of the year that reduce direct mortality and with fire return intervals that are longer than the one-to two-year intervals recommended by some for maximizing the diversity of the herbaceous understory in longleaf pine forests.

Within an animal species, the body sizes of individuals at higher latitudes are often different from individuals at lower latitudes. For homeothermic species that maintain a relatively constant body temperature, such as mammals and birds, individuals at higher latitudes tend to be larger. For ectothermic species, such as insects, that do not retain their own body heat and which often do not maintain a relatively constant body temperature, patterns of body size with latitude are highly variable. This has led some authors to contend that patterns in even closely related species cannot be expected to be similar. Indeed, to our knowledge, no studies of invertebrates have found that more closely related species have more similar relationships between body size and latitude. Further, no studies have investigated the potential influence of diet quality on interspecific differences in these clines. We measured wing lengths of specimens (N = 1753) in eight lycaenid butterfly species and one species of the sister family, Riodinidae to determine if more closely related species have similar latitudinal trends. We also estimated the mean nitrogen content of caterpillars’ hosts to investigate whether this often‐limiting nutrient influences the strength and direction of latitudinal clines in body size. We found that four species are significantly smaller at higher latitudes, an additional species is marginally smaller at higher latitudes (p < .06), and four species had no significant relationship with latitude. We also found a strong phylogenetic signal for latitudinal clines in body size among our species, which indicates that some closely related species may have similar clines. However, the strength and direction of these clines did not depend on the estimated nitrogen content of caterpillars’ hosts. Our results indicate that mean nitrogen content of hosts may not be an important driver in latitudinal clines but that phylogenetic relationships among species should be accounted for when exploring other potential drivers of body‐size clines in invertebrate species.