Data from: Contrasting trajectories of morphological diversification on continents and islands in the Afrotropical white-eye radiation

Aim Morphological and lineage evolution are predicted to follow different
patterns in island and mainland radiations. However, the extent to which
these geographical contexts influence evolutionary trajectories remains
poorly understood, in part because few studies have focused on
species-rich clades colonising continents and archipelagos over comparable
timeframes. Focusing on a diverse songbird clade radiating on the African
continent and adjacent islands, we tested whether morphological evolution
is best explained by adaptive or non-adaptive processes, and whether
mainland and island lineages evolved to occupy different regions or
volumes of morphological space (morphospace). Location Palaeotropics, with
a particular focus on the Afrotropical region. Taxon White-eyes, Zosterops
(Aves: Zosteropidae) Methods We generated principal component axes from
novel trait data for 120 species and combined this information with a
comprehensive dated phylogeny. We then analysed the dynamics of trait and
lineage diversification using comparative evolutionary methods. Results An
early burst and slowdown pattern of lineage accumulation is not mirrored
by phenotypic evolution, which instead shows an apparent convergence on
particular phenotypes. However, the overall signature of phenotypic
convergence is strongly driven by mainland taxa, in which phenotypes
appear to be highly constrained within elevational zones, while speciation
events are often associated with phenotypic divergence from one body plan
to the other after colonisation of highland from lowland habitats, or vice
versa. By contrast, island lineages have repeatedly explored novel areas
of morphospace with patterns of phenotypic divergence generally not
distinguishable from a random-walk model. Main conclusions Diversification
of Zosterops highlights contrasting evolutionary trends and dynamics for
continental versus island species. We suggest the different trajectory of
evolution in insular lineages arises from reduced species competition
leading to an increase in ecological opportunity, thereby providing a
release to phenotypic constraints experienced by continental taxa.