Data from: Convergent evolution of locomotor morphology but not performance in gymnotiform swimmers

Convergent evolution of a novel locomotor strategy implies that a fitness
benefit may be associated with the new gait. Opportunities to study this
phenomenon are often constrained by a lack of transitional taxa, but
teleost fishes offer examples of extant species across such evolutionary
shifts in gait. For instance, one species from Osteoglossiformes and the
entire order of Gymnotiformes independently evolved a novel gait,
gymnotiform locomotion, where thrust is produced by the undulation of an
elongate anal fin. Here, we investigate whether this convergence in gait
is also associated with similarities in shape, burst swimming abilities,
and/or steady‐swimming energetics. Specifically, we measured body and fin
morphology of fish within Gymnotiformes and Osteoglossiformes, along with
closely related Siluriformes and Cypriniformes, to examine the link
between gymnotiform locomotion and morphology in a phylogenetic context.
Second, we tested the burst swimming capabilities and oxygen consumption
during endurance swimming of a subset of the same gymnotiform,
osteoglossiform, and cypriniform species, including “transitional”
Osteoglossiformes that exhibit intermediate gaits, to determine if the
evolution of this specialized gait is associated with a change in either
of these performance metrics. Our results suggest that convergence on the
gymnotiform gait is associated with morphological convergence, but does
not constrain a fish's maximum sprinting speeds or their energetic
demands during steady swimming.