Hideaki Watabe

Phylogeny of the African and Asian Phortica (Drosophilidae) deduced from nuclear and mitochondrial DNA sequences

Phylogenetic relationships of 26 Phortica species were investigated based on DNA sequence data of two mitochondrial (ND2, COI) and one nuclear (28S rRNA) genes. Five monophyletic groups were recovered in the genus Phortica, of which three were established as new subgenera, Alloparadisa, Ashima, and Shangrila. The subgenus Allophortica was suggested as the most basal lineage in Phortica, followed by the lineage of P. helva + P. sobodo + P. varipes. The remaining Phortica species, most of Oriental distribution, formed a monophyletic group, and were subdivided into three lineages (i.e., the subgenera Ashima, Phortica, and Shangrila). The subgenera Shangrila and Phortica were suggested as sister taxa, and four clades were recovered in the subgenus Ashima. The result of reconstruction of ancestral distribution and estimation of divergence times indicates that, the ancestor of the genus Phortica restricted to Africa, its initial diversification was dated back to ca. 23 Mya (coinciding with the Oligocene/Miocene boundary); sympatric speciation and an Africa-to-Asia dispersal was proposed to account for the current distribution of Allophortica and the rest Phortica; most of the rest diversification of Phortica occurred in southern China, and the divergence between the African clade and its Oriental counterpart was suggested as a result of vicariance following a dispersal of their ancestral species from southern China to Africa.

A Revision of the Drosophilidae (Diptera) in East Siberia and Russian Far East : Taxonomy and Biogeography

Abstract Compiling all the previous and new records, the most recent list of drosophilid species from East Siberia (56 spp.) and Russian Far East (120 spp.) is provided along with descriptions of five new species, supplementary descriptions of two known species, some nomenclatural changes (five new synonymies, a new homonymy, and a change in status of a taxon from the specific to the subspecific rank), and a key to all the species. Drosophilid faunas of these two regions are compared with those of surrounding six regions in the Northern Hemisphere. Russian Far East constitutes the northeastern Asiatic realm in drosophilid biogeography together with northeastern China and Hokkaido, northern Japan. On the other hand, East Siberia belongs to the northern Palearctic realm extending to northern Europe. The border between these two biogeographic realms lies on the Stanovoy Mts.

Variation in morphological and behavioral traits among isofemale strains of Drosophila prolongata (Diptera: Drosophilidae)

Drosophila prolongata, a member of the rhopaloa subgroup of the melanogaster species group, occurs in Southeast Asia. Drosophila prolongata is known to have unique and prominent sexual dimorphism, with extraordinarily thick and elongated forelegs only in males. Mating behavior of D. prolongata is also characteristic: males perform “leg vibration” in their courtship toward females, in which the elongated forelegs play an important role. Comparisons with closely related species suggest that these morphological and behavioral traits have evolved rapidly after the divergence of D. prolongata. In the present study, variation in morphological and behavioral traits was examined among D. prolongata strains derived from single females collected in their natural habitats. Significant variations were detected in the size of various body parts, aggressiveness of interactions between males, and mating behavior. However, no obvious relationship was observed between morphological and behavioral traits. These results suggested that genetic factors contribute to the variation in morphological and behavioral traits in D. prolongata. The strains characterized in this study are useful for studies on the genetic mechanisms underlying the evolution of characteristic traits in D. prolongata.

The Drosophila obscura Species-group (Diptera, Drosophilidae) from Yunnan Province, Southern China

Abstract Three new and two known species of the Drosophila (Sophophora) obscura species-group are reported from Yunnan Province, southern China. The sinobscura species-subgroup is newly established by D. sinobscura, D. hubeiensis and D. luguensis sp. nov. Geographic distribution of the obscura group in and around China is discussed, and a key to 10 Chinese species of the obscura group is provided.

Taxonomic Problems in the Drosophila melanica Species Group (Diptera: Drosophilidae) from Southern China, with Special Reference to Karyotypes and Reproductive Isolation

Abstract Karyotypes and reproductive isolation were studied in two allopatric populations of Drosophila tsigana, one from Guizhou Province in southern China and the other from Hokkaido in northern Japan, and in one population of a closely related species, D. longiserrata, from Guizhou. In metaphase plates of larval brain cells, both geographic strains of Drosophila tsigana showed 2n=10 chromosomes, with 2 pairs of metacentric (V-shape), 2 pairs of acrocentric (R-shape), and 1 pair of dot-liked (D-shape) chromosomes. Drosophila longiserrata showed the same number, 10 chromosomes, comprising 2V, 1J (sub-metacentric chromosome), 1R, and 1D. X chromosomes of both species were acrocentric, the presumed ancestral form. Premating isolation was complete between D. tsigana and D. longiserrata, and successful mating was also limited in crosses between the two geographic populations of D. tsigana, especially in crosses between Japanese (JP) females and Guizhou (GZ) males. F1 hybrids were obtained only from crosses between GZ females and JP males, and fertilities of both F1 females and males were quite incomplete. The results of morphological observations, karyotypic analyses, and crossing experiments clearly showed that the GZ and JP populations of “D. tsigana” were highly divergent from each other and that each population should be recognized as a biologically valid species. The present morphological observations and chromosomal analyses, together with the original descriptions, strongly suggest that “Guizhou D. tsigana” might be conspecific with D. bisetata Toda, 1988 from Myanmar, and that D. longiserrata might be conspecific with D. afer Tan, Hsu, and Sheng, 1949 from Meitan, Guizhou.

Discovery of the Drosophila (Drosophila) robusta species group (Diptera, Drosophilidae) from Southeast Asian tropics, with the descriptions of six new species

Six new species of the Drosophila robusta species group are described from Southeast Asian Islands. Kalimantan and Sunda Islands lie east of Bali, from which Drosophila barobusta sp.nov and D. uncinata sp.nov belong to the lacertosa subgroup, and D. sungaicola sp.nov, D. baliensis sp.nov, D. hitam sp.nov and D. subaquatica sp.nov to the okadai subgroup. The robusta group from Southeast Asian tropics exclusively inhabits streamsides in mountainous highlands with an elevation of more than 600 m from the sea level.

A new subgenus Parastegana (Allstegana) (Diptera, Drosophilidae), with descriptions of two new species from South China

A new subgenus Allstegana is established within the genus Parastegana, including two known and two new species from southern China: P. (A.) maculipennis (Okada, 1971), P. (A.) drosophiloides (Toda and Peng, 1992), P. (A.) brevivena Chen and Zhang, sp. nov., and P. (A.) punctalata Chen and Watabe, sp. nov. A key to all known species of Parastegana is provided.

Revision of Asian species of the Drosophila melanica species group (Diptera: Drosophilidae), with a description of a new species from Vietnam

A new species of the Drosophila (Drosophila) melanica species group (Diptera: Drosophilidae), Drosophila denruoi Suwito & Watabe, sp. nov., is described from northern Vietnam. It is proved by crossing experiments that reproductive isolation is complete between this species and other morphologically similar species. Larval ganglion cells of D. denruoi possess 2n = 12 chromosomes, comprised of four pairs of acrocentric, one pair of metacentric and one pair of micro‐chromosomes. This is the largest number of acrocentric chromosomes in the group and implies that the species has the most primitive chromosomal configuration in the melanica group. Based on the results of crossing experiments and close morphological examination, Drosophila pengi Okada & Kurokawa, 1957 from central Japan, once regarded as a synonym of Drosophila tsigana Burla & Gloor, 1952, is shown to be distinct from D. tsigana. Drosophila pengi is thus resurrected as a member of the melanica group. We synonymize Drosophila bisetata Toda, 1988, described from central Myanmar, with D. pengi. In addition, a population from Guizhou, southwestern China, once regarded as D. tsigana, is also identified as D. pengi. These populations from central Myanmar and southwestern China share the diagnostic characters of D. pengi. At the same time, it is reconfirmed that the Hokkaido population is conspecific with European D. tsigana. Furthermore, another species, Drosophila longiserrata Toda, 1988 described from central Myanmar, is synonymized with Drosophila afer Tan, Hsu & Sheng, 1949 from China, based on their having identical karyotypes and external morphology.

Review of the Drosophila (Drosophila) quadrisetata species group (Diptera: Drosophilidae), with descriptions of three new species from the Oriental Region.

A review of the Drosophila (Drosophila) quadrisetata species group is provided on the basis of samples collected from tropical to warm–temperate areas of the Oriental Region and the collection records so far accumulated for all known species. Three new species, D. (D.) aotsukai Suwito & Watabe sp. nov., D. (D.) rinjaniensis Suwito & Watabe sp. nov. and D. (D.) sundaensis Suwito & Watabe sp. nov., are described, and new distribution records and supplementary, revised descriptions are given for known species. A multiple‐entry key, based on a character database, to all species of this species group is constructed and uploaded to the Internet.