Abstract
Aim The goatfish genus M ulloidichthys is abundant on reefs throughout the tropics. Characteristic of this genus is a long larval and pelagic juvenile phase, which could potentially confer large dispersal capacity. We sampled its mitochondrial DNA to answer the following questions: What speciation events have led to the formation of the extant species? How do they correlate with geological and oceanographic events? Are M . dentatus and M . martinicus geminate species formed by the rise of the I sthmus of P anama? Is there genetic structure between conspecific populations? Location All tropical oceans. Methods We constructed a phylogeny of M ulloidichthys , based on the ATP ase‐8 and ATP ase‐6 genes and the control region. We estimated degree of genetic structuring in four species. Results The phylogeny revealed that the I ndo‐ P acific M . pflugeri diverged first, followed by M . flavolineatus , also from the Indo‐Pacific, followed by the central P acific M . mimicus . The most recent splitting event resulted in a tritomy composed of the A tlantic M . martinicus , the eastern P acific M . dentatus and the I ndo‐ P acific M . vanicolensis . The differentiation between M . martinicus and M . dentatus was substantially smaller than divergence in the same DNA fragments in eight other fish genera likely to have been split by the rise of the I sthmus of P anama. Low genetic structuring was found between conspecific populations of M ulloidichthys , even across the entire I ndo‐ P acific. Only populations at C lipperton A toll and at A scension Island in the A tlantic were genetically isolated from other conspecific populations. Main conclusions The oldest extant species of M ulloidichthys are found in the I ndo‐ P acific. Younger species probably maintained genetic contact between the Atlantic and the Indo‐Pacific until the late P leistocene. The low degree of genetic structuring and the unusual recent connections around the globe are likely to be the result of the large, highly mobile, and long‐lived juvenile phase in this genus.