Meeting Abstract
Antarctic notothenioid fishes offer a rare example of an extensive adaptive morphological radiation in an extreme environment. During a series of cooling events over the past 40 million years, the dramatic drop in water temperature of the Southern Ocean has led to the local extinction of most near-shore fish lineages. However, the evolution of anti-freeze glycoproteins in notothenioids enabled these ancestrally benthic fishes to survive and adapt in the sub-zero temperatures. The evolution of “secondary pelagicism”, the reinvasion of the pelagic foraging niche, has fostered their morphological evolution, as they diversified to fill the newly available pelagic habitats. In this study, we used a 3D-morphometrics approach to investigate patterns of morphological variation in the craniofacial skeleton, and show that variation in head shape aligns well with niche partitioning among notothenioid fishes, highlighting a key role for divergent selection with respect to foraging niche in this group. We document further the evolution of morphological integration among notothenioids, and show that the evolution of exceptionally high levels of integration coincides with an accelerated rate of morphological evolution in the icefish family Channichthyidae. Taken together, we propose that shifts in integration can be considered as a key innovation in this group, and may have facilitated their radiation into the pelagic feeding habitats.
