Abstract
The opercle is a prominent craniofacial bone supporting the gill cover in all bony fish and has been the subject of morphological, developmental, and genetic investigation. We surveyed the shapes of this bone among 110 families spanning the teleost tree and examined its pattern of occupancy in a principal component-based morphospace. Contrasting with expectations from the literature that suggest the local morphospace would be only sparsely occupied, we find primarily dense, broad filling of the morphological landscape, indicating rich diversity. Phylomorphospace plots suggest that dynamic evolution underlies the observed spatial patterning. Evolutionary transits through the morphospaces are sometimes long, and occur in a variety of directions. The trajectories seem to represent both evolutionary divergences and convergences, the latter supported by convevol analysis. We suggest that that this pattern of occupancy reflects the various adaptations of different groups of fishes, seemingly paralleling their diverse marine and freshwater ecologies and life histories. Opercle shape evolution within the acanthomorphs, spiny ray-finned fishes, appears to have been especially dynamic.
Highlights
Understanding the patterns of morphological diversifications among organisms constitutes a central goal of evolutionary biology
We found the local morphospace representing the oceanic-freshwater divergence of a number separate populations across the world, to be rather densely occupied (S1 Fig; [21])
Our survey is based on species from 110 families, representing about a fifth of the approximately 500 families of Actinopterygians, ray-finned bony fishes
Summary
Understanding the patterns of morphological diversifications among organisms constitutes a central goal of evolutionary biology. These patterns can be quantified using multivariate approaches such as geometric morphometrics [1,2] and visualized as plots on spaces of reduced dimensionality. Such spaces are known as morphospaces, and the occupancy within the space may be termed the morphospace landscape (i.e., denoted by the collective of datapoints of the scatterplot). What kind of evolutionary process(es) could result in such a broadly shared evolutionary pattern?
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