The Stegana undulata species group is revised and eight new species described: S. (Steganina) flaviclypeata Chen & Chen, sp. n., S. (S.) flavipalpata Chen & Chen, sp. n., S. (S.) leucothorax Chen & Chen, sp. n., S. (S.) melanocheilota Chen & Chen, sp. n. and S. (S.) melanothorax Chen & Chen, sp. n. from southern China, and S. (S.) flaviscutellata Chen & Chen, sp. n., S. (S.) nigriclypeata Chen & Chen, sp. n. and S. (S.) nigripalpata Chen & Chen, sp. n. from eastern Malaysia. A key to all the species examined based on morphological data is provided. Based on DNA sequence data of the mitochondrial ND2 and COI genes, the relationship among six Chinese species of the undulata group and that of the S. coleoptrata and S. nigrolimbata species groups of the same subgenus is investigated, using S. emeiensis of the subgenus Stegana s. str. as an out-group. and Jin-Ming LU, Jian-Jun GAO, Xi-Peng CHEN, Hong-Wei CHEN.
Understanding the genetic mechanisms of morphological evolution is one of the greatest challenges in evolutionary biology and for such studies sexually dimorphic traits in closely related species are of prime interest. In the Drosophila bipectinata species complex, which consists of four closely related species, namely D. bipectinata, D. parabipectinata, D. malerkotliana and D. pseudoananassae, the pattern of sex combs (a sexually dimorphic trait) is found to be highly diversified. The present investigation documents some unique and new sex comb phenotypes and demarcates intra- and interspecific variations in the sex comb pattern among the four species and their hybrids. There is remarkable similarity in sex comb pattern of D. bipectinata and D. parabipectinata but it differs from that of D. malerkotliana and D. pseudoananassae, which is in consistent with the phylogenetic relationships among the four species traced out by cytological, biochemical and molecular studies. The genetic basis of inheritance of sex comb patterns, its plausible implication with biogeographical distribution of species and the relationship between degree of hybridization and phylogenetic proximity have been addressed.
Wolbachia pipientis (Hertig) (Rickettsiaceae) is an endocellular bacterium infecting numerous species of arthropods. The bacterium is harboured by males and females but is only transmitted maternally because spermatocytes shed their Wolbachia during maturation. The presence of this endosymbiont can lead to feminisation of the host, parthenogenesis, male-killing or reproductive incompatibility called cytoplasmic incompatibility (CI). Although Wolbachia transmission is exclusively maternal, phylogenetic evidence indicates that very rare inter-species transmission events have taken place. Horizontal transmission is possible in the laboratory by transferring cytoplasm from infected to uninfected eggs. Using this technique, we have artificially infected lines of the fruit fly Drosophila simulans Sturtevant (Drosophilidae). Recipient lines came from two different D. simulans populations. One ("naive" host) is not infected in the wild. The other ("usual" host) is a population naturally carrying Wolbachia in the wild. In this second case, recipient flies used in the experiment came from a stock culture that had been cured off its infection beforehand by an antibiotic treatment. Infected D. simulans laboratory stocks were used as donors. We assessed the three following parameters: (i) trans-infection success rate (ratio of infected over total female zygote having survived the injection), (ii) level of cytoplasmic incompatibility expressed by trans-infected males three generations post-trans-infection, and (iii) infection loss rate over time in trans-infected lines (percentage of lines having lost the infection after 20 to 40 generations). We observed that parameter (i) did not differ significantly whether the recipient line came from a "naive" or a "usual" host population. However, both (ii) and (iii) were significantly higher in the "naive" trans-infected stock, which is in agreement with earlier theoretical considerations.