Exotic wild boars and native wild guinea pigs maintain plant diversity in Argentinean coastal grasslands by decreasing plant dominance

Abstract

Question: In productive grasslands highly dominated by a single plant species, herbi-vores can promote overall plant diversity. Wild boars (Sus scrofa) often decrease spe-cies diversity, alter regeneration and change community composition in their nativeand invader ranges while digging and uprooting vegetation for feeding. In addition,wild guinea pigs (Cavia aperea), a small vertebrate herbivore native to South America,concentrate their feeding activities in open patches where they also affect plant di-versity, biomass and composition. In this context, can wild-boar disturbances promoteplant diversity in herbaceous systems characterized by a highly dominant species? Cannative wild guinea pigs magnify these impacts?Location: Coastal grasslands and salt marshes of the northeastern part of the temper-ate Argentine pampas, that are dominated by native or exotic herbaceous species.Methods: We first analyzed alpha- and beta-diversity of plant assemblies in three nat-ural coastal herbaceous areas, invaded by wild boars, through samplings (comparingdisturbed and undisturbed areas) and experiments (using exclosures and control plots).Then, we analyzed whether wild guinea pigs could affect patch recovery (alpha- andbeta-diversity) after wild-boar disturbances in one site.Results: Wild boars enhanced alpha-diversity (compared to undisturbed areas) buthad no significant effect on beta-diversity. Nevertheless, wild guinea pigs feeding onwild-boar disturbances increased between-patch heterogeneity in species composi-tion (i.e., beta-diversity).Conclusion: Wild boars remove vegetation in patches that, without subsequent wild-guinea-pig herbivory, dominant species rapidly recover. Wild-guinea-pig herbivoryallows different subordinate species to peak at different disturbed patches, contrib-uting to larger species richness at larger scales in areas otherwise occupied by highlydominant plant species. In a wider context, these results imply that the joint action ofdifferent-sized exotic and native herbivores can help to maintain plant species diver-sity in highly plant-dominated grasslands.