Seven new montane species of Drosophila in the Eastern Arc mountains and Mt Kilimanjaro in Tanzania attesting to past connections between eastern and western African mountains (Diptera: Drosophilidae)

Daniel Lachaise,Marie-Therese Chassagnard

doi:10.14411/eje.2001.056

Abstract

This report describes 7 new species of Drosophila found in the Eastern Arc mountains and on Mount Kilimanjaro in Tanzania: D. baucipyga, D. gata, D. kilimanjarica, D. neogata, D. paragata, D. pilocornuta and D. usambarensis spp.n. Two new species complexes, the megapyga species complex (Sophophora subgenus, melanogaster group, montium subgroup) and the gata species complex (Drosophila subgenus) are introduced. Only one species, D. baucipyga of the montium subgroup, has a geographical range matching the whole Eastern Arc, from the Usambara Mts. in the north-east of Tanzania to Mt. Uzungwa in the south-south west of the country. Five others, including one representative of the dentissima group of the Sophophora subgenus, D. usambarensis, and four representatives of the Drosophila subgenus, D. gata, D. neogata, D. paragata and D. pilocornuta, were found only in the Usambara Mts. Two of these five, D. usambarensis and D. pilocornuta were found only in West-Usambara, while two other related species, D. gata and D. paragata, were found only in East-Usambara. Only the distribution of D. neogata covers the whole of the Usambara mountains. Outside the Eastern Arc, another representative of the dentissima group, D. kilimanjarica, was found only on Mount Kilimanjaro. This new, highly specific, montane fauna of Drosophila further contributes to the unique biological diversity of the Eastern Arc Mts. The biogeographic affinities of the new taxa suggest past connections with the Virunga and Ruwenzori ranges and further west with the Cameroon Volcanic Line. It indicates, in particular, that the Eastern Arc forests have passed through a succession of coalescence and fragmentation events.

Highlights

The Eastern Arc mountain forests of Tanzania in East Africa is a range of fragmented residual submontane rain forests extending from the Indian Ocean coast at the north-easternmost border with Kenya to the northern shore of Lake Malawi
The Eastern Arc forests harbour a range of endemics in different forest types and of different affinities and there fore it is thought that the Eastern Arc cannot have suf fered a major loss of forest or a sustantial lowering in the altitude of forest types, at least in the last 30 000 years (Lovett, 1993b)
The seven remarkable new species of Drosophila found in the Eastern Arc mountains and on Mount Kilimanjaro and described in the present work provide futher evidence that the highly fragmented montane for ests ofTanzania have long been centres of speciation

Summary

Introduction

The Eastern Arc mountain forests of Tanzania in East Africa is a range of fragmented residual submontane rain forests extending from the Indian Ocean coast at the north-easternmost border with Kenya to the northern shore of Lake Malawi. Epandrium and cercus brownish black, glossy; cap-shaped in lateral view that is very large dorsally and tapering ventrally; a fringe of long setae along the posterior edge and the lateral expansion of the epandrium; cercus not fused to epandrium and most remarkable in being made up of two lobes separated by a deep medial indentation, the ventral lobe racket-like and bearing ca.

Results

Conclusion