S3-1.3 Jan. 4 Pelagic Amphipods: Hyperiids, Hypertrophies, and Homoplasies on the High Seas BROWNE, W.E.; Kewalo Marine Lab, University of Hawaii email@example.com
Homoplasies, the reappearance of similarities between related lineages, are one of the most fascinating and perplexing phenomena in evolution. The amphipods rank as one of the most ecologically successful and speciose extant orders of the Crustacea. Surprisingly, the phylogenetic relationships among amphipods have remained a mystery despite their abundance. Lineage analyses based on morphology have been plagued by homoplasy combined with a lack of stable synapomorphies. Amphipods as a group have very successfully invaded a multitude of ecosystems, including the open ocean environment that collectively constitutes 99.9% of the habitable space on our planet. In comparison to more familiar nearshore intertidal benthic amphipods, the hyperiids have highly divergent morphologies due to their pelagic life history. Some of the more readily apparent adaptations include hypertrophied olfactory and visual systems, eye duplications, and appendage modifications. Employing a three-pronged approach that combines molecular phylogenetics, morphological analyses, and developmental analyses offer an opportunity to identify and assess character homoplasy in detail. I will present the first molecular phylogeny sampling a wide range of taxa in the group, revealing some of the critical homoplasies between lineages. I will also highlight recent studies on the organization and formation of the head and anterior nervous system in the experimentally tractable amphipod model system, Parhyale hawaiensis, which impinge on the evolution and development of these important traits. I will show that detailed comparative studies of aspects of these results in a phylogenetic context allow for exploration of developmental mechanisms associated with some of the character traits that appear to be important for successful existence in Earth's dominant environment.