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 a-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 Communicated by Kwek Yan Chong.Electronic supplementary material The online version of this article (forest but still harbor a considerable number of species, particularly if canopy cover is present.

Geometrid moth assemblages reflect high conservation value of naturally regenerated secondary forests in temperate China

“…Mature forests are crucial for global biodiversity conservation, as they harbour a unique and often highly specialized fauna and flora (Gibson et al, 2011;Ruiz-Benito et al, 2012;Adams and Fiedler, 2015). At the same time, the potential of both plantation and secondary forests to contribute towards ecosystem service provision and conservation of diverse species assemblages is being increasingly recognized (Brockerhoff et al, 2008;Chazdon et al, 2009;Bremer and Farley, 2010;Martin and Blackburn, 2014;Zou et al, 2015).…”

Low Herbivory among Targeted Reforestation Sites in the Andean Highlands of Southern Ecuador

“…Likewise contrary to our initial assumption, leaf damage was highest in undisturbed forest as opposed to reforestation sites. This discrepancy between expectations and observed pattern was mirrored by a parallel increase in abundance and diversity of phytophagous insects [ 63 ]. This corresponds to findings in tropical forests [ 43 ] and temperate-zone grassland systems [ 83 , 84 , 85 , 86 ], which likewise demonstrated higher density and diversity of herbivores with greater plant species richness, accompanied by a concurrent increase in herbivory.…”

“…We distinguished between herbivory in the strict sense (i.e. primarily caused by Lepidoptera larvae and Coleoptera; [ 63 ]) and foraging activity of leafcutter ants, which represent key herbivores and significant pests in Neotropical ecosystems [ 64 , 65 ].…”

“…While such chemical countermeasures may have limited effect on host-specialists, they can be expected to repel a substantial number of generalist or accidental consumers. In the present study, assemblages of chewing herbivores were mostly dominated by a large number of species with low individual abundance [ 63 ], suggesting that prolific specialists were rare (except in pine sites; see below).…”

“…At first glance, reforestation sites seem to adhere to the abovementioned reduction of herbivory with increased stand diversity: the successional shrub site was characterized by substantially higher plant species richness than either pasture or pine habitat ([ 87 ]; J. Gawlik, unpublished data), and showed correspondingly lower levels of foliar damage. An overall sparsity of insects and arachnids on the shrub habitat [ 63 , 88 ], however, suggests that the observed pattern in herbivore damage is at least partly a function of microclimate, rather than of floristic diversity or increased activity of natural enemies. Folivory has been shown to decrease at high levels of insolation due to alterations in host-plant phytochemistry and physiology [ 89 , 90 , 91 ].…”