Abstract
A predictive understanding of ecological processes requires identifying
the factors that explain variation in the organismal traits that drive
these processes. Integrating evolutionary history and ecology has been
shown to be essential to understand variation in traits that determine
species interactions in community ecology. However, the extent to which
these factors determine traits relevant for ecosystem dynamics (and thus
ecosystem ecology) is poorly understood. Nutrient cycling is essential
for reef ecosystem dynamics, and consumers are critical drivers of this
process. We use a dataset of nine consumer “chemical traits” (e.g.,
body nutrient content and nutrient excretion rates) associated with
nutrient cycling, collected from 1,572 individual coral reef fish (178
species spanning 41 families) in two biogeographic regions, the
Caribbean and Polynesia, to quantify the relative importance of
phylogenetic history and ecological context as a driver of chemical
trait variation on coral reefs. We find: (1) phylogenetic history is a
better predictor of variation in all chemical traits, overwhelming the
influence of ecological factors, (2) phylogenetic conservatism in
chemical traits is greater in the Caribbean than Polynesia, where our
data suggests that ecological forces may have a greater influence on
chemical trait variation, and (3) differences in chemical traits between
regions can be explained by differences in nutrient limitation
associated with our study locations. Our study provides multiple lines
of evidence that phylogenetic conservatism is a critical determinant of
contemporary nutrient dynamics on coral reefs. More broadly our findings
highlight the utility of evolutionary history to improve prediction in
ecosystem ecology.