||Taxonomy and phylogeny of pheretimoid earthworms (Clitellata:Megascolecidae) from Mindanao and associated islands, Philippines
Aspe, Nonillon Mante
This dissertation presents a total of 39 new pheretimoid species of the familyMegascolecidae, from Mindanao and associated islands, in the Philippines. Amongthese, 29 are in the genus Pheretima, characterized by having nephridia on thespermathecal ducts, having prominent dome-shaped copulatory bursae, and having apair of caeca originating in xxvii. Of these, 27 are in the subgenus Pheretima, whiletwo species are the first records of the subgenus Parapheretima in the Philippines.Parapheretima is characterized by having secretory diverticula projecting from thecopulatory bursae, in contrast to members in the subgenus Pheretima, which do notpossess such organ. Also, three species are in Pithemera, characterized by having apair of caeca originating in or near xxii, three are in Polypheretima, characterized byhaving no caeca, and three are in Amynthas, characterized by having no copulatorybursae. The three latter genera also do not possess nephridia on the spermathecal ducts,in contrast to Pheretima. With the new species described, there are now 80 knownPheretima Pheretima,and there are now 14 species of Pithemera, comprisin Pithemera.These figures suggest that the Philippine archipelago may be the center of speciesradiation for these groups. Also, there are now 16 species of Amynthas in theAmynthas and there are now 10species of PolypheretimaPolypheretima. The high diversity of the two latter genera in mainland Asia andiiiIndonesia, respectively, strongly suggests that Indochina may be the center of speciesradiation for these two genera. The known ranges of the Philippine species arerestricted to areas around the type localities. This pattern indicates a remarkabledegree of endemicity, both among local areas, among islands in the Philippines, and inthe Philippines as a whole, and suggesting that many species remain to be detected inthe Philippines.A molecular phylogenetic study was done in attempt to infer phylogeneticrelationships among the pheretimoid species in Mindanao and associated islands. Genemarkers used include the mitochondrial cytochrome c oxidase subunit I (COI) and 16SrRNA, and the nuclear 28S rRNA and protein-coding histone H3 genes. Despitehaving limited taxa and limited genes included in the analyses, the combined data setgenerated a phylogeny more or less consistent with morphology-based expectation.Results show that taxonomic assignment of the genus Amynthas and the subgenusParapheretima do not reflect phylogeny. The species grouping in Pheretima based onthe location of spermathecae is partially reflected in the pheretimoid phylogeny. Also,results show that loss of spermatheca or fusion of two spermathecae into one canoccur in pheretimoid evolution. In general, several of the nodes of the tree based oncombined data set have support values that are very weak and have formed polytomies,which is most likely due to insufficient data. The results could have improved if moredata were available. Further molecular work including more taxa is needed to be ableto establish a more robust system of classification of the pheretimoid species and comeup with a better-resolved phylogeny.
Hokkaido University（北海道大学）. 博士(理学)