SPECIES LIMITS IN THE GENUS BLEDA-BONAPARTE, 1857 (AVES, PYCNONOTIDAE)

African forest bulbuls of the genus Bleda are usually placed into thre e separate species: B. syndactla and B. eximia distributed both in Upp er and Lower Guinea forest blocks, and B. canicapilla restricted to th e Upper Guinean one. Acoustic data lead to question traditional morpho logically-based species limits m this genus. Colouration patterns and measurements, particularly bill shape and length, wing and tail length s, are reconsidered for all taxa. Multivariate (discriminant functions ) analyses lead to separate nominate B. eximia as an Upper Guinean spe cies distinct from Lower Guinean B. notata. Furthermore B. eximia appe ars closer to B. syndactyla than to the other two species. Acousticall y, by the physical traits of their calls and songs as well as the beha viour associated with their production, B. eximia and B. syndactyla ar e very close and quite different from B. canicapilla and B. notata whi ch constitute another pair of very close species. Obviously, in the fr ame of the biological species concept, the four taxa branched in two g roups from a common ancestor, B. eximia and B. syndactyla represent a species-pair whereas B. notata and B. canicapilla are allospecies of a single superspecies. Allopatric speciation patterns based on alternat e fragmentations and unitings of forests can be drawn from present kno wledge of African forest history in relation to Pleistocene-Holocene e vents. However, a brief review of recent data on interspecific genetic differentiation in birds suggests an important discrepancy between bi ogeographical and molecular time calibrations. The development of mole cular studies appears as a priority for the understanding of the evolu tion of African tropical forests birds.