Mosaic Evolution of Craniofacial Morphologies in Ghost Electric Fishes (Gymnotiformes: Apteronotidae)

Kassandra L. Ford, Maxwell J. Bernt, Adam P. Summers, James S. Albert

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Ghost electric knifefishes (Gymnotiformes: Apteronotidae) are a dominant component of the species diversity and biomass of large lowland rivers in Greater Amazonia, including 77 species that exhibit diverse craniofacial morphologies associated with trophic and secondary sexual traits. Here we use open-source computed micro-tomography (μCT) scans to generate 3D reconstructions for a majority of apteronotid species and almost all valid genera, and geometric morphometric and phylogenetic analyses to explore patterns of skull evolution. As with most vertebrates, principal component 1 (PC1) summarizes variance from brachycephalic to dolichocephalic morphologies, previously described as heterocephaly, and PC2 summarizes variance from recurved (upturned) to decurved (downturned) snout morphologies, described here as heterorhynchy. Phylomorphospace and traitogram analyses found instances of both convergent and divergent evolution along both of the first two PC axes, as well as a preponderance of clades characterized by morphological stasis or phylogenetic conservatism. Certain phenotypic combinations predominate among species and clades, including elongated-downturned snouts and foreshortened-upturned snouts, while other phenotypic combinations are not observed, including elongated-upturned snouts and foreshortened-downturned snouts. These results highlight the power of 3D geometric morphometrics in the study of craniofacial evolution and indicate developmental or functional constraints in the evolution of craniofacial phenotypes in an ecologically dominant clade of riverine Amazonian fishes.

Original languageEnglish (US)
Pages (from-to)315-326
Number of pages12
JournalIchthyology and Herpetology
Issue number2
StatePublished - May 27 2022
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by National Science Foundation grants (NSF DEB 0614334, 0741450, and 1354511 to J.S.A.) and the Southern Regional Education Board Doctoral Fellowship and the University of Louisiana at Lafayette University Fellowship to K.L.F. We thank Kory Evans for assistance with CT-scanning fishes and discussions. Additional support from Friday Harbor Labs and the Scan All Fishes (National Science Foundation grant DEB-1701665 to A.P.S.) project allowed us to CT scan fishes. Specimens were provided by M. Sabaj-Perez and M. Arce at ANSP.

Publisher Copyright:
© 2022 Ichthyology & Herpetology. All rights reserved.


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