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6 April 2011 - GTI alumnius Tarombera Mwabvu obtains his PhD from the University of KwaZulu-Natal
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| Release date | 06/04/2011 |
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Today, we learned with tremendous joy that Tarombera Mwabvu, one of our ex-GTI students, has been awarded his PhD degree. Taro's (now Dr. Mwabvu; it pleases my fingers to type his title) new title showcases that the punctual support of the Belgian GTI to taxonomists in developing countries leads to effective and tangible results.
We wish Dr Mwabvu all our congratulations and also thank his taxon-specific tutor, Dr D. VandenSpiegel of the Royal Museum for Central Africa in Tervuren (Belgium), for his much appreciated guidance.
ABSTRACT
Taxonomic boundaries of many millipede genera are ambiguous. Therefore, modern systematics involves taxonomic revisions and biogeographic reviews of taxa, and phylogenetic analyses using new techniques and characters (including gene sequences). The African genera Archispirostreptus Silvestri 1895, Bicoxidens Attems 1928, Plagiotaphrus Attems 1914 and Spirostreptus Brandt 1833, which belong to the order Spirostreptida and family Spirostreptidae, were identified as problematic taxa because of the ambiguity of their generic limits and their undetermined distributions and species richness. Taxonomic revisions of the four genera were undertaken using morphological characters, mainly genitalic characters. Furthermore, genetic divergence of Archispirostreptus, Bicoxidens, Orthoporoides Krabbe 1982, Doratogonus Attems 1914, Plagiotaphrus, Cacuminostreptus Mwabvu 2010 and Spirostreptus, and intra-specific variation in Bicoxidens flavicollis Attems 1928 were assessed, and phylogenetic relationships among the genera were inferred by analyzing sequences of the mitochondrial 16S rRNA and cytochrome c oxidase 1 genes.
In addition to defining the generic boundaries using genitalic morphology and reporting new distribution records of these taxa, two new genera (Namibostreptus and Cacuminostreptus), three new species of Cacuminostreptus, five new species of Bicoxidens, a new species of Spirostreptus and three new species from Taita Hills, Kenya were described. These illustrated that in millipedes the number of known taxa increased mostly due to new discoveries in previously unsurveyed biomes.
Based on the gene sequences of these genera, the order Spirostreptida is monophyletic. High genetic distances (> 20 %) supported the taxonomic validity of the genera, including the recently described Cacuminostreptus. In addition, sequence differences between genera are congruent with taxonomies that are based on genitalic morphology. However, the high sequence divergence values also suggest slow genitalic evolution relative to molecular evolution. This supports the notion that millipede gonopod morphology underestimates species richness and suggests the presence of cryptic species. Although taxon sampling was limited, these results are largely concordant with morphologic evidence. Thus sequence data can be used in integrative taxonomy of spirostreptids to identify cryptic diversity and to re-assess genitalic morphology based taxonomies. However, until taxon sampling improves and a large database of DNA sequences is established, comparative morphology will continue to dominate millipede taxonomy.
Although the genera are widespread, many species in woodland and montane vegetation are endemic. This suggests that vegetation types and climatic factors influence the distribution patterns of millipedes and demonstrate that most species have narrow distributions. Furthermore, distribution ranges differ among taxa, with the small-bodied species having more restricted distributions.
The taxonomic revisions of Bicoxidens, Archispirostreptus, Plagiotaphrus and Spirostreptus illustrated that millipede diversity is underestimated, that generic boundaries need to be re-examined in other genera and that biogeographic data on most taxa are inaccurate. Therefore, future taxonomic research on millipedes should focus on sampling in unsurveyed localities, revising the taxonomy and distributions of more genera, increasing the pace of descriptions of new taxa and DNA sequencing, and producing identification keys to the species. This is in order to produce stable taxonomies and phylogenies which would provide reliable data for other disciplines, including biodiversity monitoring and conservation.
