Morphological diversification of the endemic Antarctic fishes Trematominae (Notothenioidei, Teleostei)

Adaptive radiation involves the early, rapid ecological and morphological diversification of multiple lineages from a common ancestor into new, diverging adaptive zones. Regarding this definition with emphasis on the tempo of diversification, Antarctic notothenioids represent one of the very few examples of adaptive radiation in marine fishes. Time-calibrated phylogenies suggest that the diversification of most speciose notothenioid lineages occured between 20 and 15 Ma. The subfamily Trematominae is one of those diverse subclades showing a large range of ecological niches. In the present study, we aim to describe the evolutionary history of Trematomus species. By combining a consensus time-tree and a geometric morphometric dataset, we first illustrate their pattern of cephalic shape diversification in a phylomorphospace and we infer the morphology of their common ancestor. We also explore whether the cephalic shape data shows a phylogenetic signal, which is defined as the statistical dependence among species trait values due to their phylogenetic relatedness. The combination of phylogenetic signal test and exploration of the phylomorphospace allows us to assess whether Trematomus rapidly diverged in various adaptive zones as expected under a classic scenario of adaptive radiation.