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The consequences of craniofacial integration for the adaptive radiations of Darwin’s finches and Hawaiian honeycreepers

Navalón, Guillermo; Marugán-Lobón, Jesús; Bright, Jen A.; Cooney, Christopher; Rayfield, Emily

Authors

Guillermo Navalón

Jesús Marugán-Lobón

Christopher Cooney

Emily Rayfield



Abstract

© 2020, The Author(s), under exclusive licence to Springer Nature Limited. The diversifications of Darwin’s finches and Hawaiian honeycreepers are two text-book examples of adaptive radiation in birds. Why these two bird groups radiated while the remaining endemic birds in these two archipelagos exhibit relatively low diversity and disparity remains unexplained. Ecological factors have failed to provide a convincing answer to this phenomenon, and some intrinsic causes connected to craniofacial evolution have been hypothesized. The tight coevolution of the beak and the remainder of the skull in diurnal raptors and parrots suggests that integration may be the prevalent condition in landbirds (Inopinaves). This is in contrast with the archetypal relationship between beak shape and ecology in Darwin’s finches and Hawaiian honeycreepers, which suggests that the beak can adapt as a distinct module in these birds. Modularity has therefore been proposed to underpin the adaptive radiation of these groups, allowing the beak to evolve more rapidly and freely in response to ecological opportunity. Here, using geometric morphometrics and phylogenetic comparative methods in a broad sample of landbird skulls, we show that craniofacial evolution in Darwin’s finches and Hawaiian honeycreepers seems to be characterized by a tighter coevolution of the beak and the rest of the skull (cranial integration) than in most landbird lineages, with rapid and extreme morphological evolution of both skull regions along constrained directions of phenotypic space. These patterns are unique among landbirds, including other sympatric island radiations, and therefore counter previous hypotheses by showing that tighter cranial integration, not only modularity, can facilitate evolution along adaptive directions.

Citation

Navalón, G., Marugán-Lobón, J., Bright, J. A., Cooney, C., & Rayfield, E. (2020). The consequences of craniofacial integration for the adaptive radiations of Darwin’s finches and Hawaiian honeycreepers. Nature Ecology and Evolution, 4(2), 270-278. https://doi.org/10.1038/s41559-019-1092-y

Journal Article Type Article
Acceptance Date Dec 17, 2019
Online Publication Date Feb 3, 2020
Publication Date 2020-02
Deposit Date Feb 18, 2020
Publicly Available Date Aug 4, 2020
Journal Nature Ecology and Evolution
Print ISSN 2397-334X
Electronic ISSN 2397-334X
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 4
Issue 2
Pages 270-278
DOI https://doi.org/10.1038/s41559-019-1092-y
Keywords Coevolution; Evolutionary theory; Macroecology
Public URL https://hull-repository.worktribe.com/output/3404998
Publisher URL https://www.nature.com/articles/s41559-019-1092-y

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