Forest cover drives insect guild diversity at different landscape scales in tropical dry forests

Abstract

Tropical dry forests are among the most threatened tropical ecosystems. Human-modifications to landscapes create forest patches that vary in size and shape, which in turn affects regional insect diversity. We evaluated β-diversity of insect herbivores and the effects that forest cover has on guild richness and abundance at five landscape scales (radii). We assessed insect herbivore communities in 48 plots of four dry forest sites—three in Brazil and one in Mexico—ranging in latitude from 19° south to 19° north. We collected 2893 insects representing 438 morphospecies, of which 113 were leaf-chewing, 225 sap-sucking and 100 xylophagous. β-diversity was higher in the site with the most unpredictable weather, and species turnover contributed most to β-diversity at all dry forest sites. Forest cover on a landscape scale enhanced local species richness and abundance of insects per day. Nevertheless, leaf-chewing richness was only associated with the smallest landscape scale (0.25 km radius), while sap-sucking and xylophagous insect richness and abundance were positively affected by forest cover at all spatial scales, with a higher explanatory power between scales of 1–1.5 km, which reflects potential dispersal distances. The high degree of species replacement (turnover) among plots of dry forest sites and the biological relevance of forest cover to herbivores suggest that maintaining forest areas in the surrounding landscape will contribute to dry forest insect diversity and the maintenance of their ecological services. Variation in landscape scale requirements among guilds indicates that managing landscape features is as important for the preservation of dry forest diversity as is conserving a particular forest fragment.