Tatsuo Oshida

Phylogeography of the Russian flying squirrel (Pteromys volans): implication of refugia theory in arboreal small mammal of Eurasia.

A phylogeographical study of the Russian (Siberian) flying squirrel (Pteromys volans) was carried out using the complete mitochondrial (mt) cytochrome b gene sequences with special reference to the refugia theory for the arboreal traits of this species. We examined 31 specimens from 24 localities, resulting in 28 haplotypes. One breeding specimen with a unique haplotype from Hokkaido, Japan was included in the phylogenetic analysis. There were three mtDNA lineages: Hokkaido, Far Eastern, and northern Eurasia. Divergence data among lineages demonstrated that the Hokkaido group separated from the other groups during the Holsteinian interglacial. The phylogeographical pattern of P. volans is different from that previously reported for terrestrial rodents associated with treeless habitats. Unlike grasslands, forests decreased during glaciation and moved southward because of the cold and arid environmental conditions. The glacial refugia of P. volans would have been associated with forest dynamics in the Pleistocene.

Phylogeography of the Japanese Giant Flying Squirrel, Petaurista leucogenys, Based on Mitochondrial DNA Control Region Sequences

Abstract To investigate genetic diversity among populations of the Japanese giant flying squirrel Petaurista leucogenys, the mitochondrial DNA control region sequences (1,052–1,054 bases) were determined in 37 specimens from 17 localities on the Honshu, Shikoku, and Kyushu Islands of Japan. Of the 37 animals examined, 24 haplotypes were identified. All haplotypes from Kyushu consisted of 1,052 bases, whereas those from Honshu and Shikoku consisted of 1,054 bases including two insertions, except for three haplotypes (which had 1,052 or 1,053 bases). Phylogenetic relationships reconstructed using neighbor-joining and maximum parsimony methods indicated that P. leucogenys is essentially separated into three major lineages: Group A consisting of a single haplotype from Kyushu, Group B consisting of some haplotypes from Kyushu and one haplotype from Honshu, and Group C consisting mostly of haplotypes from Honshu and Shikoku. Animals with the Kyushu haplotypes were split into two lineages (Groups A and B), suggesting that Group A diverged at an earlier point from the other groups. Genetic distances in Group C were not related to geographic distances between sampling localities, indicating that ancestral populations of this group recently expanded their distribution in a short time, possibly after the last glacial stage.

Phylogeography of Pallas's Squirrel in Taiwan: Geographical Isolation in an Arboreal Small Mammal

Abstract To. test for isolation by mountain ranges in small arboreal mammals, phylogeography of Pallass squirrel .Callosciurus erythraeus) was investigated using complete mitochondrial control region sequences (1,079–1,081 bases). This common species is distributed in the low and middle elevations of Taiwan, Republic of China. We examined 71 specimens from 6 sites in 3 study regions divided by mountain ranges in Taiwan. The 43 haplotypes found in the Taiwan populations revealed association with geography. There were 4 main mitochondrial DNA phylogroups (northern, western, southern, and eastern), but 4 haplotypes were not included in any phylogroup. Distribution range of each phylogroup was similar to defined geological categories, suggesting mountain range isolation influenced populations of C. erythraeus. The 4 phylogroups may be the result of glacial refugia during the Pleistocene.

Phylogeography of the mole-shrew (Anourosorex yamashinai) in Taiwan: implications of interglacial refugia in a high-elevation small mammal

To test the Pleistocene interglacial refugia hypothesis with a high‐elevation mammal, we studied the phylogeography of the mole‐shrew (Anourosorex yamashinai) using partial mitochondrial cytochrome b gene sequences (737 bases). This shrew is endemic to Taiwan. It is mainly distributed in the highlands from 1000 to 2500 m in elevation. We examined 103 specimens from 24 localities in three mountain ranges of Taiwan and found 36 haplotypes. These haplotypes separated into two major phylogroups (Northern and Southern) plus a minor phylogroup (Houhuan) of only one haplotype. This demonstrated strong association with geography. The formation of these three phylogroups may be the result of interglacial refugia during the middle Pleistocene. Distinct sublineages were not found within each major phylogroup, suggesting that the populations (phylogroups) explosively expanded from the interglacial refugia of ancestral founder haplotypes. The present distribution pattern of haplotypes suggests that Mount Houhuan is an effective refugium in central Taiwan. It was not possible to specify the refugia for the Northern and Southern phylogroups.

Comparison of banded karyotypes between two subspecies of the red and white giant flying squirrelS Petaurista albomfus (Mammalia, Rodentia)

Abstract Banded karyotypes of two related subspecies of Petaurista alborufus castaneus from southern China and Petaurista alborufus lena from Taiwan are presented and compared. Both subspecies had 2n=38 with a fundamental number of FN=72, and shared the gross chromosomal similarity and G-band homology.However, the size of their X chromosomes, C-band patterns and the number and sites of Ag-NORs revealed gross differences. These cytogenetic information suggest that each subspecies developed independently from the common ancestral form. Robertsonian mechanism was absent for their karyotype evolution. With regard to the number of NORs, the P. alborufus lena karyotype seemed to be primitive. The present findings suggest that P. alborufus lena could be categorized as a distinct species.

A Mitochondrial Phylogeny and Biogeographical Scenario for Asiatic Water Shrews of the Genus Chimarrogale: Implications for Taxonomy and Low-Latitude Migration Routes

The six species and three subspecies in the genus Chimarrogale (Soricomorpha: Soricidae) are commonly referred to as Asiatic water shrews. The Chimarrogale are the most widely distributed group of Nectogaline shrews, extending throughout the Oriental region and Japan. Because of the limited numbers of specimens available for study, the phylogenetic relationships and biogeographical history of this genus have not been comprehensively discussed. We used mitochondrial cytochrome b gene sequences to estimate phylogenetic relationships and divergence times among four Chimarrogale species, including all three subspecies of Chimarrogale himalayica. We also conducted a species delimitation analysis and tested two alternative migration scenarios in Asia through species distribution modeling and a reconstruction of the ancestral distribution. Here, we present the first proposed hypothesis regarding the Asiatic water shrew phylogeny and reveal ten putative species within the four recognized species. Distinct phylogenetic statuses of Chimarrogale phaeura, Chimarrogale platycephala, and Chimarrogale styani were confirmed. Chimarrogale himalayica was strongly supported as paraphyletic. We suggest that three subspecies of Chimarrogale himalayica should be reconsidered as distinct species. However, these suggestions must be considered with caution because only a single locus of a mtDNA gene was used. Four additional putative species, possibly distributed in central southwestern China and Taiwan, are currently undescribed; therefore, comprehensive morphological analyses are warranted to test their taxonomic statuses. The estimated molecular divergence times indicated that rapid speciation occurred during the early Pliocene, and current distribution patterns may have been affected by global cooling during the Pliocene/Pleistocene boundary. Reconstruction of the ancestral distribution and species distribution modeling for Asiatic water shrews revealed a low-latitude migration route over which ancestral Chimarrogale migrated from Europe via Central Asia to their current distribution. Our results demonstrated that Asiatic water shrews could have evolved throughout the low-latitude migration route from Europe to East and Southeast Asia.

Comparisons of the banded karyotypes between the smallJapanese flying squirrel,Pteromys momonga and the Russian flying squirrel, P. volans(Rodentia, Sciuridae)

Abstract Two flying squirrel species, Pteromys momonga and Pteromys volans contain 2nequals;38 with the same fundamental number of 68, but differ in their karyotypes. Almost all the autosomes and the sex chromosomes have either complete or partial G-band correspondence, and thus provide definitive evidence for the taxonomic relationship of these Pteromys species. The karyotypic differences occurred as results of pericentric inversion, tandem fusion, and deletion of autosomes and the Y chromosome. No Robertsonian event occurred. Both species possess one pair ofAg-NORs in identical G-banded chromosomes but different morphology resulting from pericentric inversion. Despite the conservatism of G-band patterns, a striking accumulation of C- heterochromatin has occurred in the P. momonga karyotype. Flow-cytometric DNA determination demonstrated that P. volans genome contains approximately 15 %% less DNA. These differences seem to be prima rily reflected by chromosomal deletions in the P. volans karyotype rather than ac cumulation of the Cheterochromatin in the P. momonga karyotype. The present findings are crucial for explaining the direction of karyotype evolution of these species, and suggest that the karyotype of P. momonga is ancestral and that P. volans is derived from it.

Banded karyotypes of the hairy-footed flying squirrel Belomys (Trogopterus) pearsonii (Mammalia, Rodentia) from Taiwan

Abstract The chromosomes of the hairy-footed flying squirrel Belomys pearsonii from Taiwan were analyzed with conventional and Ag-NOR staining and G- and C-banding technique. The diploid chromosome number (2n) and fundamental autosomal arm number (FN) were 38 and 72, respectively. The karyotype consisted of six pairs of metacentrics (nos. 1–6), twelve pairs of submetacentrics or subtelocentrics (nos. 7–18), an unusually large-sized metacentric X chromosome, and an acrocentric Y chromosome. The satellite structure, which corresponded to the NOR detected by silver-staining, was observed on the long arm of no. 1 chromosomes. All autosomes and the X chromosome had centromeric constitutive heterochromatin (C-heterochromatin), and the long arms of nos. 17 and 18 chromosomes were entirely heterochromaic. By the C-banding technique, the Y chromosome was entirely stained somewhat darkly than euchromatic region, but did not seem to be genuinely heterochromatic. On the basis of the cytogenetical characteristics of sex chromosomes, the phylogenetic position of Belomys in the group of flying squirrels was briefly referred.

Chromosomal characterization of the Formosan striped squirrel Tamiops maritimus formosanus (Mammalia, Rodentia)

Abstract Chromosomes of the Formosan striped squirrel Tamiops maritimus formosanus were analyzed with conventional and silver staining and G- and Cbanding technique. The diploid chromosome number (2n) and fundamental autosomal arm number (FN) were 38 and 68, respectively. Karyotype consisted of seven pairs of metacentrics (nos. 1–7), nine pairs of submetacentrics or subtelocentrics (nos. 8–16), two pairs of acrocentrics (nos. 17 and 18), a medium-sized submetacentric X chromosome, and a small acrocentric Y chromosome. All autosomes and the X chromosome carried centromeric constitutive heterochromatin, but the Y chromosome was entirely euchromatic. In the short arm of no. 17 chromosomes, the prominent satellite structure with its long stalk, which corresponded to the nucleolus organizer region (NOR), was observed, suggesting that it could have been shared with other squirrel species through the evolutionary process.

A preliminary note on banded karyotypes of the Perny's long-nosed squirrel Dremomys pernyi (Mammalia, Rodentia) from Taiwan

Abstract The chromosomes of the Pernys long-nosed squirrel Dremomys pernyi owstoni that is endemic subspecies to Taiwan were examined with conventional and Ag-NOR staining and G- and C-banding technique. The diploid chromosome number (2.) and fundamental autosomal arm number (FN) of this squirrel were 38 and 68, respectively. The karyotype consisted of 7 pairs of metacentrics (nos. 1–7), 9 pairs of submetacentrics or subtelocentrics (nos. 8–16), 2 pairs of acrocentrics (nos. 17 and 18), a medium-sized submetacentric X chromosome, and an acrocentric Y chromosome. On the terminal region of short arm of no. 17 chromosomes, the prominent satellite the stalk potion of which essentially corresponded to Ag-NOR was recognized. The no. 18 chromosome was markedly minute acrocentric. In the C-banded karyotype, the all autosomes and X chromosome carried centromeric constitutive heterochromatin (C-heterochromatin), and the Y chromosome appeared to be entirely heterochromatic. Based on the cytogenetical characteristics, it was critically suggested that the present classification of Dremomys squirrels might be unsuitable.