Local Species Richness of Leaf-Chewing Insects Feeding on Woody Plants from One Hectare of a Lowland Rainforest

Local species diversity of insect herbivores feeding on rainforest vegetation remains poorly known. This ignorance limits evaluation of species extinction patterns following various deforestation scenarios. We studied leaf-chewing insects feeding on 59 species of woody plants from 39 genera and 18families in a lowland rainforest in Papua New Guinea and surveyed all plants with a stem diameter at breast height of>5 cm ina 1haplot within the same area. We used two extrapolation methods, based on randomized species-accumulation curves, to combine these two data sets and estimate the number of species of leaf-chewing herbivores feeding on woody plants from the 1-ha area. We recorded 58,483 feeding individuals from 940 species of leaf-chewing insects. The extrapolation estimated that there were 1567-2559 species of leaf-chewing herbivores feeding on the 152 plant species from 97 genera and 45 families found in 1 ha of the forest. Most of the herbivore diversity was associated with plant diversity on the familial and generic levels. We predicted that, on average, the selection of 45 plant species each representing a different family supported 39% of all herbivore species, the 52 plant species each representing a different additional genus from these families supported another 39% of herbivore species, and the remaining 55 plant species from these genera supported 22%> of herbivore species. Lepidoptera was the most speciose taxon in the local fauna, followed by Coleóptera and orthopteroids (Orthoptera and Phasmatodea). The ratio of herbivore to plant species and the estimated relative species richness of the Lepidoptera, Coleóptera, and orthopteroids remained constant on the spatial scale from 0.25 to 1 ha. Tlowever, the utility of local taxon-to-taxon species ratios for extrapolations to geographic scales requires further study. Riqueza de Especies Locales de Insectos Masticadores de Hojas en Plantas Leñosas de una Hectárea de Selva Lluviosa Resumen: Se conoce poco de la diversidad de especies locales de insectos herbívoros que se alimentan de la vegetación de selvas lluviosas. Esta escasez de información limita la evaluación de patrones de extinción de especies después de varios escenarios de deforestación. Estudiamos insectos masticadores de hojas que se alimentan de 59 especies de plantas leñosas de 39 géneros y 18 familias en vestigios de selva lluviosa en Papua Nueva Guinea y examinamos todas las plantas con un diámetro > 5 cm a la altura del pecho en una •ffAddress correspondence to S. E. Miller. Paper submitted August 14, 2002; revised manuscript accepted June 3, 2003-