FECAL PROGESTERONE METABOLITES IN POSTPARTUM SIBERIAN FLYING SQUIRRELS.

The Siberian flying squirrel ( Pteromys volans) produces up to two litters a year. To deliver second litters in breeding season, P. volans may have a postpartum estrus similarly to that of a variety of small mammals. If this were the case, females would have periods of elevated progesterone levels because of the formation of corpora lutea (CL) after postpartum ovulation. To test this hypothesis, fecal progesterone metabolite dynamics was investigated during lactation in this species using an enzyme immunoassay. In five of the six lactating females, periods of high fecal progesterone metabolite concentration were observed, and, furthermore, progesterone secretion patterns were periodic. Therefore, the source of progesterone during lactation could be arising CL from postpartum ovulation, indicating that ovarian activity was reinitiated after parturition and the CL that formed began secreting progesterone. This study thus showed that P. volans likely has the physiologic potential to mate during lactation.

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.