Around 40 million years ago, Antarctica’s geographic isolation led to a dramatic cooling of its marine shelf, causing many lineages to go extinct while others adapted and diversified. Among the successful ones is the amphipod family Iphimediidae. Here, we apply advanced phylogenetic comparative methods to explore the evolutionary processes underlying their exceptional diversity. To this end, we combined three datasets: (1) a novel molecular phylogeny, (2) 3D shape data from micro-CT-based geometric morphometrics, and (3) stable isotope ratios (δ13C and δ15N) as proxies for trophic ecology. We tested for evolutionary correlations between mouthpart shape and isotope values, and investigated changes in diversification rates in relation to morphological evolution. Late bursts of lineage diversification (ca. 7–3 Mya), along with late partitioning of mouthpart shape diversity, may reflect the invasion of novel ecological niches. Plio-Pleistocene glacial cycles may also have acted as a diversity pump promoting this late diversification.
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RBINS Staff Publications 2025
