Meeting Abstract
The ecological opportunities that arise from marine to freshwater transitions are generally regarded as a driving force in the adaptive radiation of a variety of aquatic taxa. Radiations in marine-derived fish are evidenced by rapid diversification of behavioral and morphological adaptations largely pertaining to diet, followed by a slowing of these rates as niches are filled . Here, we study the transition in Needlefishes (Family Belonidae) and their close relatives the viviparous halfbeaks (Family Zenarchopteridae) from marine to freshwater systems and test whether the diversity and tempo of feeding morphological evolution have been substantially altered by these shifts. To compare the morphologies of these lineages, we use micro-computed tomography (µCT) scanning and Horos to obtain morphometrics of relevant characteristics pertaining to feeding. A principal components analysis is then used to visualize putative overlap or clustering of feeding morphologies in this theoretical ‘morphospace’ held by freshwater and marine needlefishes and halfbeaks. 20 species from the needlefish and halfbeak families are used to adequately study this system. Our results support our hypothesis, freshwater fish occupy a larger, more disparate, morphospace than their marine relatives. This is likely due to the variable and complex nature of freshwater habitats in addition to their geographical isolation allowing for a greater range of morphological adaptations in comparison to the more stable open sea environment.
