Palatal morphology predicts the paleobiology of early salamanders
Abstract
Ecological preferences and life history strategies have enormous impacts on the evolution and phenotypic diversity of salamanders, but the yet established reliable ecological indicators hinder investigations on the paleobiology of early salamanders. Here we statistically demonstrate using geometric morphometric analysis that both the shape of the palate and many non-shape variables particularly associated with vomerine teeth are ecologically informative in early stem- and basal crown-group salamanders. The morphology of the palate is heavily impacted by convergence constrained by feeding mechanisms and also exhibits clear stepwise evolutionary patterns with alternative phenotypic designs to cope with similar functional demand. Paleoecological disparities in early salamanders had took place before the Middle Jurassic and have achieved all ecological preferences in the Early Cretaceous. Metamorphosis is significant in the expansion of ecomorphospace of the palate in early salamanders. The common ancestor of salamanders is metamorphosed and terrestrial, and share unified lifestyles with other modern amphibians.
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Evaluation Summary:
This paper is of interest to vertebrate paleontologists and other evolutionary biologists interested in the early evolution of amphibians. Using geometric morphometric analysis, the authors demonstrate that both the shape of the palate and several non-shape variables (particularly associated with vomerine teeth) are ecologically informative in early stem- and basal crown-group salamanders. The phylomorphospace analysis reveals that metamorphosis is significant in the expansion of ecomorphospace of the palate in early salamanders. In overall, the main claims of the manuscript are well supported by the data.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1, Reviewer #2 and …
Evaluation Summary:
This paper is of interest to vertebrate paleontologists and other evolutionary biologists interested in the early evolution of amphibians. Using geometric morphometric analysis, the authors demonstrate that both the shape of the palate and several non-shape variables (particularly associated with vomerine teeth) are ecologically informative in early stem- and basal crown-group salamanders. The phylomorphospace analysis reveals that metamorphosis is significant in the expansion of ecomorphospace of the palate in early salamanders. In overall, the main claims of the manuscript are well supported by the data.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1, Reviewer #2 and Reviewer #3 agreed to share their name with the authors.)
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Reviewer #1 (Public Review):
Ecological preferences and life history strategies impact the evolution and phenotypic diversity of salamanders. Using geometric morphometric analysis, the authors demonstrate that both the shape of the palate and several non-shape variables (particularly associated with vomerine teeth) are ecologically informative in early stem- and basal crown-group salamanders. The morphology of the palate is subject to convergence constrained by feeding mechanisms, and metamorphosis is significant in the expansion of ecomorphospace of the palate in early salamanders. The work will add to the knowledge on the early evolutionary pattern of salamanders.
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Reviewer #2 (Public Review):
In this manuscript, Jia and colleagues statistically demonstrate, using geometric morphometric analysis, that the palate is a reliable proxy in ecological reconstructions for early salamanders, and the morphospace of the palate is predominantly shaped by ecological constraints and also displays stepwise evolutionary pattern. The authors also provide evidence that the common ancestor of salamanders was metamorphosed and terrestrial, and shared unified lifestyles with other modern amphibians. The results of the study are of interest to a wide range of zoologists.
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Reviewer #3 (Public Review):
The manuscript investigates, using a large dataset and a broad array of methods that account for phylogenetic nonindependence of the data, whether the shape of the palate correlates with habitat (water, land, or both) in a clade of extant salamanders. After demonstrating that this is the case, it infers the lifestyles of Cretaceous and Jurassic supposed members of that clade as well as a few other early salamanders. If the used phylogenetic tree is indeed accurate, the conclusions are very robust. The methods will be widely imitated to research similar questions all across the tree of life.
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