Data from: Pelagic zone is an evolutionary catalyst, but an ecological dead end, for North American minnows

Colonization of a novel geographic area is a classic source of ecological
opportunity. Likewise, complex microhabitats are thought to promote
biodiversity. We sought to reconcile these two predictions when they are
naturally opposing outcomes. We assess the macroevolutionary consequences
of an ancestral shift from benthic to pelagic microhabitat zones on rates
of speciation and phenotypic evolution in North American minnows. Pelagic
species have more similar phenotypes and slower rates of phenotypic
evolution, but faster speciation rates, than benthic species. These are
likely two independent, opposing responses to specialization along the
benthic-pelagic axis, as rates of phenotypic evolution and speciation are
not directly correlated. The pelagic zone is more structurally homogenous
and offers less ecological opportunity, acting as an ecological dead end
for minnows. In contrast, pelagic species may be more mobile and prone to
dispersal and subsequent geographic isolation and, consequently,
experience elevated instances of allopatric speciation. Microhabitat
shifts can have decoupled effects on different dimensions of biodiversity,
highlighting the need for nuance when interpreting the macroevolutionary
consequences of ecological opportunity.