First molecular scombrid timetree (Percomorpha: Scombridae) shows recent radiation of tunas following invasion of pelagic habitat

Scombrid fishes represent one of the major radiations of marine vertebrates in the pelagic realm, and have historically been a commercially important group. Their rich fossil record dates to the late Paleocene, and it has recently been suggested that the current scombrid diversity is due to a post-Cretaceous radiation that saw the survivors of the KPg extinction replacing a number of non-acanthomorph fish lineages that did not survive the Mesozoic era. In this paper we present the result of the first quantitative macroevolutionary study of scombrid evolution. We assembled a supermatrix consisting of seven nuclear and mitochondrial loci, including 47 of the 52 extant scombrid species. We then used seven fossils to time-calibrate this new molecular phylogeny, the first ever assembled for scombrids that included more than 50% of the diversity of this family, and investigated macroevolutionary patterns within this clade. Our results support a late Cretaceous origin of the scombrids, and show that many lineages originated in the Eocene and Oligocene. Our findings, however, fail to support the hypothesis of a rapid scombrid radiation in the post-KPg ecosystems. We show how the most significant radiation within scombrids has taken place since the Late Miocene in tunas, possibly triggered by a transition from pelagic-neritic to pelagic-oceanic habitats, and matched by a dramatic increase in body size.