Low beta diversity of herbivorous insects in tropical forests

Abstract

Recent advances in understanding insect communities in tropical forests have contributed little to our knowledge of large-scale patterns of insect diversity, because incomplete taxonomic knowledge of many tropical species hinders the mapping of their distribution records. This impedes an understanding of global biodiversity patterns and explains why tropical insects are under-represented in conservation biology. Our study of approximately 500 species from three herbivorous guilds feeding on foliage (caterpillars, Lepidoptera), wood (ambrosia beetles, Coleoptera) and fruit (fruitflies, Diptera) found a low rate of change in species composition (beta diversity) across 75,000 square kilometres of contiguous lowland rainforest in Papua New Guinea, as most species were widely distributed. For caterpillars feeding on large plant genera, most species fed on multiple host species, so that even locally restricted plant species did not support endemic herbivores. Large plant genera represented a continuously distributed resource easily colonized by moths and butterflies over hundreds of kilometres. Low beta diversity was also documented in groups with differing host specificity (fruitflies and ambrosia beetles), suggesting that dispersal limitation does not have a substantial role in shaping the distribution of insect species in New Guinea lowland rainforests. Similar patterns of low beta diversity can be expected in other tropical lowland rainforests, as they are typically situated in the extensive low basins of major tropical rivers similar to the Sepik-Ramu region of New Guinea studied here.

Parasitism rate, parasitoid community composition and host specificity on exposed and semi-concealed caterpillars from a tropical rainforest

“…The sampling spanned 4-16 months per tree species during 2002-2004 (see Table S1 for a list of tree species and corresponding sampling effort and sampling period). The variable sampling effort is due to merging of two datasets with identical sampling methods (Novotny et al 2002(Novotny et al , 2007 to maximize overall sample size. The number of tree inspections (a particular tree sampled at a particular time) exceeded 1,000 per tree species for each 1,500 m 2 sampled.…”

Phylogenetic isolation of host trees affects assembly of local Heteroptera communities

“…Garrett & Mundt 1999;Gilbert & Webb 2007). These plant/pest-based studies demonstrate that closely related hosts should be susceptible to the same plant pests, revealing a strong phylogenetic signal in host range of pests (Novotny et al 2002;Parker & Gilbert 2004;Novotny & Basset 2005). However, the effect of intercropping may to a large extent reflect the dilution of suitable food sources among non-suitable food sources at a very fine scale, i.e.…”

No post-Cretaceous ecosystem depression in European forests? Rich insect-feeding damage on diverse middle Palaeocene plants, Menat, France

“…Species-level damage data should be less affected by the overall floral richness and by the increased spatial and temporal averaging at Menat (see Currano 2009 and also Novotny et al 2007 for limited beta diversity of herbivores over large host-plant ranges). Therefore, although we present both, we feel that species-level herbivory data are more suitable for comparison than bulk floral data.…”