Biogeographical analysis of the flea beetle genus Chaetocnema in the Afrotropical Region: distribution patterns and areas of endemism


*Maurizio Biondi, Dipartimento di Scienze Ambientali, University of L'Aquila, Coppito-L'Aquila 67010, Italy.


Aim  The areal distributions of Chaetocnema species in the Afrotropical Region have been analysed with the aims of determining the distribution patterns (chorotypes) and identifying the most important areas of endemism for this flea beetle genus in sub-Saharan Africa.

Location  Data were collected in sub-Saharan Africa, including Madagascar.

Methods  The Afrotropical Region was divided into 103 5° quadrats (operative geographical units, or OGUs). A presence–absence matrix of the Afrotropical Chaetocnema species in the OGUs was analysed by cluster analysis (Baroni Urbani & Buser index and the WPGMA clustering method) to generate distribution pattern data based on similarity of distribution. The most important areas of endemism were identified by parsimony analysis of endemicity.

Results  The general distribution of Chaetocnema in the Afrotropical Region was found to be associated with moist environments and montane grasslands. Most species exhibit restricted geographical ranges. Cluster analysis revealed 120 spatial distributions that can be grouped into 13 distinct distribution patterns (chorotypes). The most important areas of endemism for Chaetocnema in sub-Saharan Africa according to the present parsimony analysis of endemicity are: (1) central and eastern Madagascar [endemicity rate (ER) = 61.1%], (2) Western Cape Province (ER = 36.4%), (3) southern Drakensberg (ER = 26.7%), (4) the Shaba Region (ER = 16.7%), and (5) the North-Kivu Region (ER = 5.0%).

Main conclusions  There are 123 known species of Chaetocnema in the Afrotropical Region, more than in any other zoogeographical region. About 91% of the species are endemic and they generally exhibit a restricted and often very localized geographical range. The remaining 9% of the species are represented by seven species that also inhabit northern Africa and/or the Arabian peninsula (C. bilunulata Demaison, C. ganganensis Bechyné, C. ljuba Bechyné, C. pulla Chapuis, C. tarsalis Wollaston, and C. wollastoni Baly), three species that widely inhabit the Palaearctic Region (C. conducta (Motschulsky), C. schlaeflini (Stierlin), and C. tibialis (Illiger)), and two species that were introduced (C. confinis Crotch, and C. picipes Stephens).