Data from: Convergent evolution of niche structure in Northeast Pacific kelp forests

Much of the morphological and ecological diversity present on earth is
believed to have arisen through the process of adaptive radiation. Yet,
this is seemingly at odds with substantial evidence that niches tend to be
similar among closely related species (i.e., niche conservatism).
Identifying the relative importance of these opposing processes in driving
niche evolution under different circumstances is therefore essential to
our understanding of the interaction between ecological and evolutionary
phenomena. In this study, we make use of recent advances in our
understanding of the phylogeny of kelps (Laminariales) to investigate
niche evolution in one of the most ecologically significant groups of
benthic habitat-forming organisms on the planet. We quantify functional
traits and use community sampling data from a kelp diversity hotspot to
determine which traits are responsible for the habitat (β) niche of kelps
and whether they are labile or conserved across the kelp
phylogeny.  We find that combinations of functional traits have
evolved convergently across kelp subclades and that these functional
traits are significant predictors of community structure. Specifically,
traits associated with whole-kelp structural reinforcement and material
properties were found to be significantly correlated with species
distributions along a gradient of wave disturbance and thus predict the
outcome of environmental filtering. However, kelp assemblages were made up
of species that are more phylogenetically distinct than expected (i.e.,
phylogenetic overdispersion), suggesting that niche partitioning along
this gradient of wave disturbance has been an important driver of
divergence between close relatives. These results are consistent with the
hypothesis that environmental filtering associated with wave disturbance
plays an essential role in determining the habitat niche of kelps across
local communities and further suggest that this process can drive
phenotypic divergence and niche partitioning between close relatives. We
propose that parallel adaptive radiation of kelp subclades has shaped the
diversity and species composition of kelp forests in the Northeast Pacific
and we discuss how evidence from the literature on incipient or ongoing
speciation events support this hypothesis.