Deforestation and apparent extinctions of endemic forest beetles in Madagascar

Ilkka Hanski,Pierre Rahagalala,Alison Cameron,Helena Koivulehto

doi:10.1098/rsbl.2007.0043

Abstract

Madagascar has lost about half of its forest cover since 1953 with much regional variation, for instance most of the coastal lowland forests have been cleared. We sampled the endemic forest-dwelling Helictopleurini dung beetles across Madagascar during 2002–2006. Our samples include 29 of the 51 previously known species for which locality information is available. The most significant factor explaining apparent extinctions (species not collected by us) is forest loss within the historical range of the focal species, suggesting that deforestation has already caused the extinction, or effective extinction, of a large number of insect species with small geographical ranges, typical for many endemic taxa in Madagascar. Currently, roughly 10% of the original forest cover remains. Species–area considerations suggest that this will allow roughly half of the species to persist. Our results are consistent with this prediction.

Highlights

Two-thirds of all described species of animals and plants are insects, of which roughly 45% are beetles, but the level of threat imposed by the global environmental changes to beetle and insect diversities remains poorly documented
An good model was obtained if PC1 was dropped from the candidate variables, in which case the last year when the species had been sampled was selected at 5% level
Helictopleurini are mostly relatively large, many species have colour-patterned elytra and are diurnal and easy to sample with dung and carrion-baited traps

Summary

Introduction

Two-thirds of all described species of animals and plants are insects, of which roughly 45% are beetles, but the level of threat imposed by the global environmental changes to beetle and insect diversities remains poorly documented. Of the described species of insects and beetles, only 0.07 and 0.02% have been classified as globally extinct or threatened, respectively, compared with 24% for mammals and 12% for birds (IUCN 2004; Birdlife 2006). In Finland, with a beetle fauna of 3640 species, 12.1% of the species are classified as nationally extinct (1.6%) or threatened (10.5%), compared with 15.3% in birds, 17.0% in mammals and 15.4% in vascular plants (Rassi et al 2001). The historically documented extinction rate is 34% for birds, 43% for mammals, 26% for vascular plants and 38% for butterflies (Brook et al 2003). There is no difference between vertebrates, plants and butterflies

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Results

Conclusion