Sexual harassment in heterogeneous landscapes can mediate population regulation in a grasshopper

Population regulation has been related to differences in thequality among habitats, which mediate differences in vital ratessuch that in poor habitats reproductive rates are lower thanthose in high-quality habitats. The spatial distribution ofanimals in such habitats depends on their preferences and thedegree to which individuals have a free choice of a particularhabitat. The identified mechanisms that lead to a particularspatial distribution and eventually to regulation mainly includeforaging-related interference, for example, ideal free distribution,or simple selection of available high-quality habitats, thatis, site-dependent habitat selection. However, in insect speciesthese mechanisms might not be applicable, but density-dependenthabitat selection still occurs. We therefore suggest a mechanismthat refers to the nearly universal observation that matingsalso bear fitness costs. Although these costs have been investigatedon the individual level in many insect species, their consequencesfor population dynamics have not yet been addressed. In thegrasshopper species Stenobothrus lineatus, females in a nonreceptivemating status escape sexually approaching males by undirectedjumps. By including such avoidance behavior in a spatially-explicitsimulation model, we investigated its potential to result inprogressive use of low-quality habitats at increasing populationdensities. In particular, we show that (1) such behavior changeshabitat selection, (2) altered habitat selection results inpopulation regulation, and (3) the degree of habitat heterogeneityinfluences regulation such that (4) heterogeneous habitats showfine-tuned regulation and homogeneous habitats tend to supportlarge fluctuations.