Data from: Peripheral morphology is associated with restricted lineage diversification and endemism across a large passerine radiation

Aim: Across a variety of taxonomic scales species diversity is unevenly
distributed among its constituent units, and clades with few species are
more common than expected assuming homogeneous rates of speciation and
extinction among lineages. In order to explain the prevalence of species
poor families among a global and speciose radiation of passerine birds, we
test whether these groups share common eco-morphological, geographic and
phylogenetic attributes. Location: Global Time period: Late Oligocene to
the present day Major taxa studied: The Corvides (ca. 790 species)
Methods: We obtained 10 linear measurements of external morphology for 782
species of corvoid passerines. Using these measurements as a proxy for
species ecology, we assessed the positioning of corvoid families in
eco-morphological trait space, and how these factors are associated with
their species richness and rates of lineage diversification. Subsequently,
we compared these same characteristics (species richness, morphological
positioning and rates of lineage diversification), between families that
are currently endemic to the Australasian ancestral area of the Corvides,
with those that have dispersed and diversified throughout other
continental and insular landmasses. Results: Families with low species
richness and rates of diversification tend to occupy the most peripheral
positions in eco-morphological trait space, with almost all of these
groups being endemic to Australasia. The peripheral eco-morphological
positioning of the Australasian groupings is generally greater than
expected upon accounting for differences in phylogenetic isolation and
heterogeneity in rates of trait evolution, implying that species poor
corvoid families commonly evolved towards marginal areas of morphospace.
Main conclusions: The overrepresentation of species poor clades across
diverse sets of organismal groups is consistent with their evolution
towards, and the maintenance in, marginal areas of ecological niche space.
The evolution of peripheral eco-morphological characters represents a
potentially significant limit to rates of range expansion and lineage
diversification.