title: Positive and negative effects of mesograzers on early-colonizing species in an intertidal rocky-shore community.
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.
authors.affiliation: Doctorado en Ciencias, mención en Ecología y Evolución Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile; Instituto de Ciencias Ambientales y Evolutivas Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile.
authors.forename: Daniela
authors.initials: D
authors.lastname: Tejada-Martinez
authors.affiliation: Doctorado en Ciencias, mención en Ecología y Evolución Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile; Instituto de Ciencias Ambientales y Evolutivas Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile.
authors.forename: Daniela N
authors.initials: DN
authors.lastname: López
authors.affiliation: Instituto de Ciencias Marinas y Limnológicas Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile.
authors.forename: César C
authors.initials: CC
authors.lastname: Bonta
authors.affiliation: Instituto de Ciencias Ambientales y Evolutivas Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile; South American Research Group on Coastal Ecosystems (SARCE) Universidad Simón Bolivar Caracas Venezuela.
authors.forename: Roger D
authors.initials: RD
authors.lastname: Sepúlveda
authors.affiliation: Instituto de Ciencias Marinas y Limnológicas Facultad de Ciencias Universidad Austral de Chile Campus Isla Teja Valdivia Chile; Centro FONDAP de Investigación en Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL) Valdivia Chile.
authors.forename: Nelson
authors.initials: N
authors.lastname: Valdivia
keywords: Community structure; Southern Chile; consumers; disturbance; intertidal; top‐down