TY - JOUR
T1 - Convergence is Only Skin Deep
T2 - Craniofacial Evolution in Electric Fishes from South America and Africa (Apteronotidae and Mormyridae)
AU - Ford, Kassandra L.
AU - Peterson, Rose
AU - Bernt, Maxwell
AU - Albert, James S.
N1 - Publisher Copyright:
©
PY - 2022
Y1 - 2022
N2 - Synopsis Apteronotidae and Mormyridae are species-rich clades of weakly electric fshes from Neotropical and Afrotropical freshwaters, respectively, known for their high morphological disparity and often regarded as a classic example of convergent evolution. Here, we use CT-imaging and 3D geometric morphometrics to quantify disparity in craniofacial morphologies, and to test the hypothesis of convergent skull-shape evolution in a phylogenetic context. For this study, we examined 391 specimens representing 78 species of Apteronotidae and Mormyridae including 30 of 37 (81%) of all valid genera with the goal to sample most of the craniofacial disparity known in these clades. We found no overlap between Apteronotidae and Mormyridae in the skull-shape morphospace using PCA and a common landmark scheme, and therefore no instances of complete phenotypic convergence. Instead, we found multiple potential instances of incomplete convergence, and at least one parallel shift among electric fsh clades. The greatest components of shape variance in both families are the same as observed for most vertebrate clades: heterocephaly (i.e., opposite changes in relative sizes of the snout and braincase regions of the skull), and heterorhynchy (i.e., dorsoventral changes in relative snout flexion and mouth position). Mormyrid species examined here exhibit less craniofacial disparity than do apteronotids, potentially due to constraints associated with a larger brain size, ecological constraints related to food-type availability. Patterns of craniofacial evolution in these two clades depict a complex story of phenotypic divergence and convergence in which certain superfcial similarities of external morphology obscure deeper osteological and presumably developmental differences of skull form and function. Among apteronotid and mormyrid electric fshes, craniofacial convergence is only skin deep.
AB - Synopsis Apteronotidae and Mormyridae are species-rich clades of weakly electric fshes from Neotropical and Afrotropical freshwaters, respectively, known for their high morphological disparity and often regarded as a classic example of convergent evolution. Here, we use CT-imaging and 3D geometric morphometrics to quantify disparity in craniofacial morphologies, and to test the hypothesis of convergent skull-shape evolution in a phylogenetic context. For this study, we examined 391 specimens representing 78 species of Apteronotidae and Mormyridae including 30 of 37 (81%) of all valid genera with the goal to sample most of the craniofacial disparity known in these clades. We found no overlap between Apteronotidae and Mormyridae in the skull-shape morphospace using PCA and a common landmark scheme, and therefore no instances of complete phenotypic convergence. Instead, we found multiple potential instances of incomplete convergence, and at least one parallel shift among electric fsh clades. The greatest components of shape variance in both families are the same as observed for most vertebrate clades: heterocephaly (i.e., opposite changes in relative sizes of the snout and braincase regions of the skull), and heterorhynchy (i.e., dorsoventral changes in relative snout flexion and mouth position). Mormyrid species examined here exhibit less craniofacial disparity than do apteronotids, potentially due to constraints associated with a larger brain size, ecological constraints related to food-type availability. Patterns of craniofacial evolution in these two clades depict a complex story of phenotypic divergence and convergence in which certain superfcial similarities of external morphology obscure deeper osteological and presumably developmental differences of skull form and function. Among apteronotid and mormyrid electric fshes, craniofacial convergence is only skin deep.
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U2 - 10.1093/iob/obac022
DO - 10.1093/iob/obac022
M3 - Article
C2 - 35976714
AN - SCOPUS:85144976751
SN - 2517-4843
VL - 4
JO - Integrative Organismal Biology
JF - Integrative Organismal Biology
IS - 1
M1 - obac022
ER -