The association of shorter darter PLD with Red List inferred
extinction risk (figure 1) is consistent with inferences from
marine paleontological studies [1,3,6]. Some caution in accepting
this result is probably warranted as the Red List might
not perfectly reflect ‘natural’ extinction factors, but this measure
of extinction risk did allow us to perform one of the first tests of
this relationship in extant taxa. Furthermore, in many fossil
taxa, it is only feasible to test whether the qualitative presence
or absence of a larval stage influences extinction [1–3], and our
continuous estimates of darter PLD allowed a more fine-scaled
parsing of the putative association between PLD and extinction.
Because both paleontological and neontological inferences provide
incomplete views of evolution [23], increased examination
of traits like PLD in extant taxa will provide a more robust
understanding of mechanisms influencing macroevolutionary
patterns of diversification.