Tarombera Mwabvu

Is Millipede Taxonomy Based on Gonopod Morphology Too Inclusive? Observations on Genetic Variation and Cryptic Speciation in Bicoxidens flavicollis (Diplopoda: Spirostreptida: Spirostreptidae)

ABSTRACT The structure of the male gonopods of millipedes has been considered to be species-specific. As such, gonopods—which aid in copulation and sperm transfer—are used in the taxonomic diagnosis and description of species. However, it was recently demonstrated that gonopod morphology is not always characteristic of species. Diagnoses based on gonopod morphology can therefore result in underestimation of taxonomic diversity amongst millipedes. On the basis of this observation, we examined genetic variation in two populations (approximately 250 km apart) of a widely distributed and colour-polymorphic southern African millipede, namely Bicoxidens flavicollis Attems, 1928. An analysis of genetic divergence based on 520 nucleotides of the mitochondrial cytochrome oxidase 1 gene, and 684 nucleotides of the mitochondrial 16S rRNA gene, demonstrated high levels of divergence (19.09% for cytochrome oxidase 1 and 6.66% for 16S rRNA) between the two populations. These results suggest the presence of cryptic species in B. flavicollis and, furthermore, corroborate observations that taxonomy based on gonopod morphology may be too inclusive.

A Review of the Genus Obelostreptus Attems, 1909 (Diplopoda, Spirostreptida, Spirostreptidae) with the Description of a New Species from Kenya

ABSTRACT The east African millipede genus Obelostreptus Attems, 1909 is revised to include four species, new distribution records are given, and a new combination is established. In addition, the genus is removed from the family Harpagophoridae and placed in the Spirostreptidae. A new species, O. bilamellatus VandenSpiegel sp. n. from Kenya is described, and Mardonius nakitawa (Silvestri 1907) is removed from the genus Mardonius Attems, 1914 to become the fourth known species, O. nakitawa comb. n., in Obelostreptus. An identification key to the species of Obelostreptus based on male gonopod structure is also presented.

Do cytochrome c oxidase 1 Gene Sequences Differentiate Species of Spirostreptid Millipedes (Diplopoda: Spirostreptida: Spirostreptidae)?

ABSTRACT The aim of this study was to use cytochrome c oxidase 1 (CO1) sequences to recover a phylogeny for seven morphologically described spirostreptid millipede taxa from southern Africa, and to evaluate the correspondence between morphological and molecular phylogenies. Genetic p-distance generally increased with taxonomic divergence: inter-specific mean 15.33 % (14.09 % –17.02 %), inter-generic mean 18.43 % (6.83 %–26.81 %) and inter-order mean 24.16 % (range 18.56 %–30.77 %). Congruent Bayesian, maximum parsimony and neighbour-joining analyses of 520 nucleotides of the CO1 gene resolved the orders Spirostreptida, Julida and Callipodida. Members of genera within the Spirostreptidae (Archispirostreptus, Bicoxidens, Cacuminostreptus, Doratogonus, Orthoporoides, Plagiotaphrus and Spirostreptus) formed a single clade within which a sample of Thyropygus (family Harpagophoridae) was paraphyletically nested. Phylogenetic analyses failed to recover support for the genera Doratogonus, Bicoxidens, Archispirostreptus and Spirostreptus, as representatives of these genera were not monophyletic. Samples morphologically identified as the same species (Bicoxidens flavicollis) were part of two different clades, one of which was well supported and otherwise contained members of Doratogonus. This high level of divergence (mean 12.64 %) between morphologically identified spirostreptid millipede sister species could indicate that changes in genital morphology occur rather slowly relative to CO1 sequence substitution, and may underestimate species diversity.