TAXONOMY AND SYSTEMATICS OF CENTIPEDES ORDER SCOLOPENDROMORPHA IN THAILAND

Abstract

Scolopendromorph centipede specimens were collected mainly in Thailand and from several other parts of mainland Southeast Asia. Taxonomic revision based on traditional morphology and molecular phylogeny from three partial gene datasets (COI, 16S rRNA and 28S rRNA) have been used to verify the taxonomic validity of this centipede group. Twenty-four described species were documented and classified into two families, Scolopendridae and Cryptopidae. Scolopendridae, the largest group, comprises nine genera: Scolopendra, Otostigmus, Rhysida, Alluropus, Cormocephalus, Asanada, Digitipes, Sterropristes and Ethmostigmus. The most aggressive and harmful group belong to the genus Scolopendra. Taxonomic revision of Scolopendra indicated 8 previously described and one new species from this region. Scolopendra pinguis, S. cataracta and S. dawydoffi were regarded as regionally endemic species according to their narrow distributions and lower population densities in natural habitats. Otostigmus, Digitipes, Rhysida and Alluropus reveal high morphological and genetic variability which is correlated with distribution patterns. Geometric-morphometric study has been implemented in Scolopendra to test the taxonomic potential of three traditional characters used for species identification in Scolopendromorpha. The result of shape variation tests by CVA indicated that the tergite of the ultimate leg-bearing segment is most powerful for species delimitation by this technique. Several scolopendrid species exhibit various kinds of colouration patterns, and light photographs of living specimens are used to document this morphological variability, which may be specific to geographical populations. The blind family Cryptopidae also occurs in this region, the two described species from the genera Cryptops and Scolopocryptops being found with their densest populations in the north of Thailand and Laos. Molecular phylogeny depicted the monophyly of two families in this order. In Scolopendridae, which divides into two subfamilies, Scolopendrinae and Otostigminae, phylogenetic relationships within each subfamily show different traits. Scolopendrinae and its genera are monophyletic in both Maximum likelihood and Bayesian inference analyses. Species of the genus Scolopendra indicated compatibility between genetic composition and geographical distribution. Moreover, phylogenetic results also suggest evidence of transfer of regional biodiversity with neighboring faunas. Three Scolopendra species groups were found congruently with morphological and molecular identification. In the case of Otostigminae, relationships between genera are still ambiguous and the group depicts high morphological and genetic diversity. At least four putative morphological and molecularly distinct groupings within Otostigminae that likely represent new/cryptic species were found in this study. The genetic composition of some genera, such as the Indian-Burmese Digitipes, suggests that diversification within regional faunas may be shared with adjacent regions. Systematic revision of the genera Rhysida and Alluropus established the significance of male secondary characters as diagnostic characters for taxonomic identification. This morphological feature has also been recorded in other Scolopendromorpha during field surveys throughout Thailand and neighboring countries. Some information gaps in Southeast Asian centipedes such as feeding and brooding behaviours were recorded in several genera such as Otostigmus, Rhysida, Alluropus, Cormocephalus and Scolopendra. The integrative results from this study may improve the biological knowledge of these predatory animals in this region and may also suggest further utilization and applications in the future.