The cost of ignoring cryptic diversity in macroecological studies: Comment on Martínez et al. (2017)

Despite ample evidence indicating that Excirolana braziliensis corresponds to a species complex, Martinez et al. (2017; Mar Ecol Prog Ser 583:137-148) considered this isopod as a single species with a wide distribution along the Atlantic and Pacific coasts of the Americas, to evaluate the abundant-centre hypothesis (ACH). Multiple studies, however, have documented the presence of highly divergent lineages within this isopod, some of which may have separated millions of years ago, and with morphological differences reported among some of the lineages. The assumption of a single widespread species has led to misleading inferences regarding the underlying causes of ecological variation in this isopod, as indicated in recent phylogeographic studies. Therefore, it is surprising that a new macroecological study is considering E. braziliensis as a single widespread species again. The cost of ignoring its cryptic diversity is that the Martinez et al. (2017) study does not really contribute to our understanding of the ACH.