Data from: Rates of niche and phenotype evolution lag behind diversification in a temperate radiation

Environmental change can create opportunities for increased rates of
lineage diversification, but continued species accumulation has been
hypothesized to lead to slowdowns via competitive exclusion and niche
partitioning. Such density-dependent models imply tight linkages between
diversification and trait evolution, but there are plausible alternative
models. Little is known about the association between diversification and
key ecological and phenotypic traits at broad phylogenetic and spatial
scales. Do trait evolutionary rates coincide with rates of
diversification, are there lags among these rates, or is diversification
niche-neutral? To address these questions, we combine a deeply sampled
phylogeny for a major flowering plant clade-Saxifragales-with phenotype
and niche data to examine temporal patterns of evolutionary rates. The
considerable phenotypic and habitat diversity of Saxifragales is greatest
in temperate biomes. Global expansion of these habitats since the
mid-Miocene provided ecological opportunities that, with density-dependent
adaptive radiation, should result in simultaneous rate increases for
diversification, niche, and phenotype, followed by decreases with habitat
saturation. Instead, these rates have significantly different timings,
with increases in diversification occurring at the mid-Miocene Climatic
Optimum (~15 mya), followed by increases in niche and phenotypic
evolutionary rates by ~5 mya; all rates increase exponentially to the
present. We attribute this surprising lack of temporal coincidence to
initial niche-neutral diversification followed by ecological and
phenotypic divergence coincident with more extreme cold and dry habitats
that proliferated into the Pleistocene. A lack of density-dependence
contrasts with investigations of other cosmopolitan lineages, suggesting
alternative patterns may be common in the diversification of temperate
lineages.