Exploitation Competition in Mobile Grazers: Trade-offs in Use of a Limited Resource

摘要: Mechanisms underlying competitive effects between two species of marine snails (Tegula aureotincta and Tegula eiseni) were examined; results indicated that the interaction involved exploitation microalgae not interference. A behavioral exper- iment demonstrated an individual either was less likely to feed on a recently grazed patch when prior forager T. aureotincta. Both responded only amount food available patch, and, except at very low levels, likelihood snail would remain identical for across microalgal densities. Where scarce, eiseni more than in patch. Density-dependent standing stock differed snails; grazer densities, depressed levels comparatively greater degree, whereas high had relatively effect. The relative growth performance as function food: superior body resource while grew better Differences responses arose from dissimilar foraging characteristics snails. Compared with eiseni, moved rapidly feeding, harvested twice great area per unit time, but unable crop close rock surfaces. While smaller it removed grazed. These differing suites attributes may represent trade-off harvest different densities: cropping closer substratum (area intensive grazing) yields are precludes grazing larger time extensive through fast movement, which provides intake abundant. If (moves faster)-intensive (digs deeper) is common feature benthic systems, knowledge this aspect could provide predictive insight into patterns causes density dependence arising exploitation.