Quo vadis biodiversity? Species richness following twenty years of taxonomic revisions on Afrotropical Galerucinaes. str. (Coleoptera, Chrysomelidae).

Thomas Wagner

doi:10.3897/zookeys.720.14011

Abstract

Galerucinae is one of the most species-rich leaf beetle group with its greatest diversity occurring in tropical forests. There are 1680 nominal species of Afrotropical Galerucinae s. str. (without Alticini) described. Considering global diversity estimations, many unknown species can be presumed. Several taxa traditionally placed in “Monoleptites”, have been revised in the last twenty years. To date 259 species have been re-examined, revealing in 139 valid species and 120 mainly newly recognized synonyms. This large number of synonyms can mainly be ascribed to highly variable colour patterns, a typical character used for the identification of many chrysomelid species. Genitalic structures and molecular work can support a more precise allocation to species. Within around 72,000 specimens of galerucines s. str. from 48 museums and private collections, only 107 species were newly described. After revising approximately 15% of the Afrotropical galerucine fauna their species richness decreased from 259 to 246 species, a pattern that appears to be similar to that for other African galerucine groups. Since the estimation of the extent of global diversity based mainly on insect species richness in tropical forests, our current study which is based on hard data suggests a much lower diversity than previously predicted.

Highlights

Galerucinae s. str. is one of most diverse group of leaf beetles in tropical forests, including 1680 nominal species from Africa (Wagner 2006) and 7145 species worldwide (Nie et al 2017)
When a taxonomic and phylogenetic revision of Afrotropical Monolepta was started, it became clear that this genus as traditionally delimited was a non-monophyletic group (Wagner 1999, 2003, 2004)
The author’s empirical data of species revisions in a quite highly diverse tropical leaf-beetle group is used here to address the question, What is the global diversity of Galerucinae s. str.?

Summary

Introduction

Galerucinae s. str. (without Alticini) is one of most diverse group of leaf beetles in tropical forests, including 1680 nominal species from Africa (Wagner 2006) and 7145 species worldwide (Nie et al 2017). Besides redefining generic characters in the external morphology, we studied the genitalic patterns of all the examined taxa for the first time These were found to be valuable to distinguish species, and to define genera as monophyletic groups within Monolepta Global insect diversity caught the attention of entomologists, and a broader audience, in the 1980s, when data of canopy fogging in tropical forests were extrapolated to 30 million species of insects (Erwin 1982). The author’s empirical data of species revisions in a quite highly diverse tropical leaf-beetle group is used here to address the question, What is the global diversity of Galerucinae s. Quo vadis biodiversity? Species richness following twenty years of taxonomic revisions... 133

Material and methods

Results

Discussion