Data from: Global variation in the relationship between avian phylogenetic diversity and functional distance is driven by environmental context and constraints

Aim: If evolutionary distance is akin to evolutionary chance,
then it follows that species assemblages that are distantly related will
also be more disparate in terms of their traits, features and the niches
they occupy. Yet, studies have found that the total phylogenetic distance
of an assemblages, known as phylogenetic diversity, is an unreliable
surrogate for functional diversity. We investigate global variation in the
relationship between Faith’s Phylogenetic Diversity (PD) and Mean Pairwise
Functional Distance (MPFD) across latitude and the influence of migratory
species on both these aspects of diversity. Location: Global.
Time period: Present day. Major taxa studied: Birds.
Methods: We measure PD and MPFD for over 9,000 species of bird
across more than 17,000 globally distributed assemblages. We obtain
standardised effect sizes for both indices by simulating assemblage
composition under an ecologically informed null model. We employ path
analysis to characterise variation in the relationship between PD’s and
MPFD across latitude, elevation and with proportion of migratory species.
Results: Globally, assemblages that were phylogenetically diverse
tended to be less functionally dispersed than expected; however this
relationship showed considerable variation across latitude decreasing with
distance from the equator. The proportion of migratory species in an
assemblage was found to be an important predictor of functional diversity,
with migrant rich assemblages generally showing less functional diversity
than expected. We identify the Andes and Hengduan Mountains as regions of
exceptional bird functional diversity. Main conclusions: The
relationship between phylogenetic diversity and function diversity is
context specific, varying across environmental gradients such as latitude,
and influenced by ecological phenomena such a migration. Thus, care should
be taken using phylogenetic diversity as a proxy for functional diversity,
particularly in clades with sparse functional data. Instead we recommend
that studies consider how phylogenetic diversity’s surrogacy for
functional diversity may be impacted by environmental context and evaluate
empirical observations against biogeographically constrained and
ecological informed null models.