Meeting Abstract
Reef fishes are one of the most diverse vertebrate assemblages on earth, exhibiting a remarkable variety of shapes, from elongate to deep-bodied and almost spherical to laterally compressed. What drives this diversity? Many ecologies and behaviours such as feeding, courtship and predator evasion are potentially linked to the geometry of fish body shape through its affects on the structural properties of the body and external fluid dynamics. We investigate how lateral shape as well as shape disparity are related to ecology and phylogeny across reef fishes. We used 17 previously published landmarks related to the shape of the head and body for 791 reef acanthomorphs and analyzed them using phylogenetic comparative methods that explicitly incorporate the high-dimensional multivariate nature of geometric morphometric data. Across acanthomorphs shape shows a significant phylogenetic signal (K=0.44 p-value=0.001) but it is weaker than expected under Brownian motion (K=1) and it is highly variable between families. There is also no consistent relationship between shape, shape disparity and feeding ecology across acanthomorphs. Within wrasses and parrotfishes herbivory/detrivory is associated with significantly faster rates and greater disparity but across Acanthomorpha there is no significant difference in the rate of evolution in carnivorous and herbivorous fishes. Similarly, the expectation that pelagic plankton feeders should be elongate is supported in some families (e.g. surgeonfishes) and not in others (e.g. damselfishes). Our results reveal that the relationship between shape and ecology is complex. Therefore, the primary axis of shape variation across fishes, which is one of elongation, is unlikely to have a single, simple ecological explanation.
