Abstract
The ecological consequences of human‐driven overexploitation and loss of keystone consumers are still unclear. In intertidal rocky shores over the world, the decrease of keystone macrograzers has resulted in an increase in the dominance of herbivores with smaller body (i.e., “mesograzers”), which could potentially alter community assembly and structure. Here, we experimentally tested whether mesograzers affect the structure of rocky intertidal communities during the period of early colonization after the occurrence of a disturbance. A manipulative field experiment was conducted to exclude mesograzers (i.e., juvenile chitons, small snails, amphipods, and juvenile limpets) from experimental areas in an ecosystem characterized by the overexploitation of keystone macrograzers and predators. The results of multivariate analyses suggest that mesograzers had significant effects on intertidal community structure through negative and positive effects on species abundances. Mesograzers had negative effects on filamentous algae, but positive effects on opportunistic foliose algae and barnacles. Probably, mesograzers indirectly favored the colonization of barnacles and foliose algae by removing preemptive competitors, as previously shown for other meso‐ and macrograzer species. These results strongly support the idea that small herbivores exert a firm controlling effect on the assembly process of natural communities. Therefore, changes in functional roles of top‐down controllers might have significant implications for the structure of intertidal communities.
Highlights
The structure of natural communities can be determined by top-down processes, in which consumers placed high in the food web modulate the patterns of relative abundance of basal species (e.g., Menge et al 1999; O’Connor et al 2013; He and Silliman 2015; He et al 2015)
Ecology and Evolution published by John Wiley & Sons Ltd
The principal coordinates analysis (PCoA) multivariate ordination, based on the area under the curve (AUC) of species abundances throughout time, showed that the grazer-excluded plots were segregated in the multivariate space from the other two treatments, especially in the first and more important axis of variation (Fig. 1)
Summary
The structure of natural communities can be determined by top-down processes, in which consumers placed high in the food web modulate the patterns of relative abundance of basal species (e.g., Menge et al 1999; O’Connor et al 2013; He and Silliman 2015; He et al 2015). As a form of consumption, plays a key role in determining the abundance, presence or absence, and distribution limits of sessile species Anthropogenic impacts on local communities have caused dramatic changes in the abundance of species and ecological interactions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
