Punctuational ecological changes rather than global factors drive species diversification and the evolution of wing phenotypes in Morpho butterflies

Assessing the relative importance of geographical and ecological drivers
of evolution is paramount to understand the diversification of species and
traits at the macroevolutionary scale. Here, we use an integrative
approach, combining phylogenetics, biogeography, ecology, and quantified
phenotypes to investigate the drivers of both species and phenotypic
diversification of the iconic Neotropical butterfly genus Morpho. We
generated a time-calibrated phylogeny for all known species and inferred
historical biogeography. We fitted models of time-dependent (accounting
for rate heterogeneity across the phylogeny) and
paleoenvironment-dependent diversification (accounting for global effect
on the phylogeny). We used geometric morphometrics to assess variation of
wing size and shape across the tree, and investigated their dynamics of
evolution. We found that the diversification of Morpho is best explained
when considering variable diversification rates across the tree, possibly
associated with lineages occupying different microhabitat conditions.
First, a shift from understory to canopy was characterized by an increased
speciation rate partially coupled with an increasing rate of wing shape
evolution. Second, the occupation of dense bamboo thickets accompanying a
major host-plant shift from dicotyledons towards monocotyledons was
associated with a simultaneous diversification rate shift and an
evolutionary “jump” of wing size. Our study points to a diversification
pattern driven by punctuational ecological changes instead of a global
driver or biogeographic history.