Abstract
The study of species environmental niches underpins numerous questions
in ecology and evolutionary and has increasing relevance in a rapidly
changing world. Environmental niches, characterized from observations of
organisms, inform about a species’ specialization in multivariate
environment space and help assess their exposure and sensitivity to a
changing climate. Environmental niches are also the central concept
behind the species distribution models (SDMs) which assess and predict
the geographic variation in environmental suitability. Despite the clear
role of past evolutionary processes in driving contemporary biodiversity
distribution, the assessment of multivariate or n-dimensional (where n
is the number of environmental axes) niches in a phylogenetic framework
has remained limited and constrained by restrictive assumptions. This
hampers important existing and emerging applications, such as
assessments of niche conservatism, estimates of species’ adaptive
potential under changing climates, and prediction of niches in
less-studied parts of the tree of life. Here we introduce a framework
that extends SDMs to estimate n-dimensional environmental niches jointly
with underlying evolutionary processes. Specifically, we fit the
relationship between niche distance and phylogenetic distance as a
latent Gaussian Process across all species in a clade. We demonstrate
mathematically how the parameters of the Gaussian Process can be linked
to existing traditional evolutionary models. Simulations indicate that
the approach successfully recovers evolutionary parameters. Applied to
two clades of hummingbirds, the presented joint framework uncovers the
relationships among species’ niches in phylogenetic space and supports
the quantification and hypothesis testing of niche evolution. A key
advantage of the presented framework is its joint estimation of the
evolutionary process alongside niches directly from species observations
with uncertainty propagated to evolutionary model parameters. The
proposed approach has the potential to increase the robustness of
inference about niche evolution and improve understanding of how the
processes of niche formation and evolution interact.