| dc.description.abstract | The only family of birds endemic to the Oriental zoogeographical region is the Irenidae (genera *Irena*, *Chloropsis*, and *Aegithina*). The ranges of the 57 races (in 14 species) are described, and some taxonomic and distributional questions are raised. The southern Malay peninsula and Sumatra contain the largest number of species and sub-species, with numbers decreasing outward to their lowest values at the peripheries of the family's range. Several lines of evidence indicate that Malaya-Sumatra has served as the center of evolution of the Irenidae. Water gaps are important barriers to dispersal of birds as this family in which 28.6% of the species and 43.9% of the races are confined to a single island or island group. Mountains also impede dispersal, but ecological factors associated with altitude, latitude, and precipitation are probably more important than elevation *per se*. Much of the diversity of the Irenidae fauna in the Malaysian subregion may be attributable to Pleistocene sea-level oscillations. Some races and even species probably have evolved since the end of the last glaciation 11,000 years ago, making insular southeast Asia a natural laboratory for the study of bird evolution. Suggestions are made for ecological, ethological, zoogeographical, and taxonomic research to explain the restriction of this family. | |
