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Published on: December 14, 2006
A phylogenetic test for adaptive convergence in rock-dwelling lizards
Liam J Revell1, Michele A Johnson, James A Schulte
1Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Evolution; International Journal of Organic Evolution
|September 27, 2007
Summary
Phenotypic similarity in similar habitats doesn't always mean adaptation. Similar traits may arise from exaptation, where features evolved for other reasons allow species to occupy new environments, not direct selection pressures.
Area of Science:
- Evolutionary biology
- Comparative morphology
- Herpetology
Background:
- Phenotypic similarity is often interpreted as adaptation to similar environments.
- This interpretation assumes similarities are evolutionarily derived through shared selection pressures.
- However, similarities may arise from exaptation, where pre-existing traits facilitate niche occupation.
Purpose of the Study:
- To investigate whether phenotypic similarities in rock-dwelling lizards result from convergent adaptation or exaptation.
- To analyze evolutionary changes in morphology associated with occupying vertical rock surfaces across different lizard clades.
- To determine if similar evolutionary trajectories lead to convergence.
Main Methods:
- Phylogenetic analysis of four lizard clades.
- Comparative morphological analysis of rock-dwelling and non-rock-dwelling species.
- Examination of evolutionary changes in limb length and body/head shape.
Main Results:
- Evolutionary transitions to rock-dwelling were linked to longer hindlimbs and flatter bodies.
- Similarities in head depth resulted from both adaptation and exaptation.
- Clade-specific differences in limb elongation meant overall limb length did not differ significantly between rock- and non-rock-dwellers.
Conclusions:
- Evolutionary change in the same direction across independent lineages does not guarantee convergence.
- Similar advantageous structures in species occupying similar habitats may not always indicate direct adaptation.
- Exaptation can play a significant role in shaping phenotypes for new ecological niches.
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