Archipelago-endemic bird radiations are familiar to evolutionary
biologists as key illustrations of evolutionary patterns. However, such
radiations are in fact rare events. White-eyes (Zosteropidae) are birds
with an exceptionally high colonization and speciation potential; they
have colonized more islands globally than any other passerine group and
include the most species-rich bird genus. The multiplication of white-eye
island-endemics has been consistently attributed to independent
colonisations from the mainland; the white-eyes of the Gulf of Guinea
archipelago had been seen as a classic case, spanning as great a breadth
of phenotypic diversity as the family worldwide. Contrary to this
hypothesis, our molecular phylogenetic analysis places the Gulf of Guinea
white-eyes in just two radiations, one grouping all five oceanic island
taxa and the other grouping continental island and land bridge taxa.
Numerous ‘aberrant’ phenotypes (traditionally grouped in the genus
Speirops) have evolved independently over a short space of time from
non-aberrant (Zosterops) phenotypes; the most phenotypically divergent
species have separated as recently as 0.22 Ma. These radiations rival
those of Darwin’s finches and the Hawaiian honeycreepers in terms of the
extent of adaptive radiation per unit time, both in terms of species
numbers and phenotypic diversity. Tempo and patterns of morphological
divergence are strongly supportive of an adaptive radiation in the oceanic
islands driven by ecological interactions between sympatric white-eyes.
Here, very rapid phenotypic evolution mainly affected taxa derived from
the youngest wave of colonization, in accordance with the model of
asymmetric divergence due to resource competition in sympatry. Microsatellite
genotyping of the Gulf of Guinea white-eyes and the Cape white-eye
(Zosteropidae)Zosteropidae-Gulf of
Guinea-microsatellites.txt