Larval characteristics can greatly influence the dynamics of organismal diversification
[1–3]. For instance, pelagic larval duration (PLD), or the time an
aquatic larva spends in the water column, might have influenced the likelihood
of extinction in many fossil marine organisms [4–6]. However,
evolutionary divergence in PLD and its potential relationship with extinction
risk have rarely been examined in extant, freshwater organisms partly because
freshwater organisms often lack a pelagic stage [1]. Furthermore, extant
organisms are by definition the clades that have not gone extinct. Therefore,
assessing the relationship between PLD and the likelihood of extinction in
living groups has been difficult. However, human activity is precipitating a
global wave of extinction, and we used the freshwater fish group known as
darters (Percidae: Etheostomatinae) to take advantage of this anthropogenic
‘experiment’ to comparatively examine the causes and consequences of
evolutionary divergence in PLD.