Macroevolution in axial morphospace: innovations accompanying the transition to marine environments in elapid snakes
Date
2022
Authors
Sherratt, E.
Nash-Hahn, T.
Nankivell, J.
Rasmussen, A.R.
Hampton, P.M.
Sanders, K.
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Journal article
Citation
Royal Society Open Science, 2022; 9(12):1-12
Statement of Responsibility
Emma Sherratt, Tamika Nash-Hahn, James H. Nankivell, Arne R. Rasmussen, Paul M. Hampton, and Kate L. Sanders
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Abstract
Sea snakes in the Hydrophis-Microcephalophis clade (Elapidae) show exceptional body shape variation along a continuum from similar forebody and hindbody girths, to dramatically reduced girths of the forebody relative to hindbody. The latter is associated with specializations on burrowing prey. This variation underpins high sympatric diversity and species richness and is not shared by other marine (or terrestrial) snakes. Here, we examined a hypothesis that macroevolutionary changes in axial development contribute to the propensity, at clade level, for body shape change. We quantified variation in the number and size of vertebrae in two body regions (pre- and post-apex of the heart) for approximately 94 terrestrial and marine elapids. We found Hydrophis-Microcephalophis exhibit increased rates of vertebral evolution in the pre- versus postapex regions compared to all other Australasian elapids. Unlike other marine and terrestrial elapids, axial elongation in Hydrophis-Microcephalophis occurs via the preferential addition of vertebrae pre-heart apex, which is the region that undergoes concomitant shifts in vertebral number and size during transitions along the relative fore- to hindbody girth axis. We suggest that this macroevolutionary developmental change has potentially acted as a key innovation in Hydrophis-Microcephalophis by facilitating novel (especially burrowing) prey specializations that are not shared with other marine snakes.
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© 2022 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.