The value of targeted reforestations for local insect diversity: a case study from the Ecuadorian Andes

Abstract

We surveyed insect communities (Coleoptera, Hemiptera, Lepidoptera) on native treelets (Cedrela montana, Heliocarpus americanus, Tabebuia chrysantha) planted among anthropogenic land cover types (pasture, secondary shrub, and a pine plantation), comparing them among one another and to those found on conspecific treelets in adjacent montane rainforest. Between 2010 and 2012, we sampled 160 treelets (Pasture: 47, Shrub: 26, Pine: 44, Forest: 43). Habitability of reforestations for forest insects was quantified by examining species richness, diversity partitioning and community composition on reforestations relative to natural forest. Species richness was high (phytophagous Coleoptera: 185 spp., predatory Coleoptera: 101 spp., phytoph. Hemiptera: 174 spp., phytoph. Lepidoptera: 147 spp.) with values being highest in natural forest, and significantly lower in all reforestations. Phytophagous Coleoptera and Lepidoptera communities showed a trend toward higher species richness in pine than in pasture or shrub. Predatory Coleoptera showed higher values in pasture and pine compared to shrub. These findings suggest that microclimatic effects of surrounding vegetation may affect species richness. Given high habitat heterogeneity and prevalence of rare species, tree-level α-diversity and turn-over between individual sample treelets emerged as the strongest contributors to overall diversity. Coleoptera community composition was mainly a function of habitat, but colonization of reforestations by forest species was restricted to phytophagous taxa and contingent on the presence of canopy cover. For Hemiptera and Lepidoptera, community composition was similar across habitats and determined mainly by host species. In summary, young reforestations maintain less diverse insect communities compared to natural forest but still harbor a considerable number of species, particularly if canopy cover is present.