Aggressive mimicry in Aspidontus and Plagiotremus (Pisces: Blenniidae): some mimetic phenotypes are not phylogenetically informative

In the absence of sympatry, the delineation of species is essentially hypothesis open to refutation and mimicry can be a confounding factor. Two nominal species of Blenniidae, Aspidontus tractus and Plagiotremus flavus, previously recognized as subspecies but recently elevated to full species status, differ from their presumed allopatric sister species, Aspidontus taeniatus and Plagiotremus laudandus, only in having a different color pattern, which closely matches their mimetic models. We show that both taxa can exhibit differing and inconsistent color patterns over their biogeographic range, corresponding to variation in their local mimetic model. These mimetic phenotypes do not reflect genetic distances between independently evolving sibling species, but are local adaptations to the model, not necessarily linked to reproductive isolating mechanisms and not consistent with typical biogeographical boundaries for sibling species in the Indo-Pacific region. Indeed, both newly elevated taxa share their mitochondrial haplotypes with their original species, indicating that gene flow may not be interrupted. Thus, we consider Aspidontus tractus and Plagiotremus flavus to be junior synonyms of A. taeniatus and P. laudandus, respectively.