Testing the hypothesis that a clade has adaptively radiated: iguanid lizard clades as a case study

Area of Science:

• Evolutionary biology
• Ecology
• Herpetology

Background:

• Adaptive radiations are key to understanding evolutionary mechanisms.
• Current definitions lack objective criteria for identifying adaptive diversification.
• Most clades diversify to some extent, necessitating a distinction for exceptional cases.

Purpose of the Study:

• To establish objective criteria for defining adaptive radiation.
• To develop a comparative method for assessing adaptive disparity.
• To test this method on monophyletic groups within the lizard family Iguanidae.

Main Methods:

• Comparative analysis of adaptive disparity across multiple clades.
• Focus on ecological morphology within monophyletic lizard groups.
• Statistical assessment to distinguish exceptional diversity from normal adaptive variation.

Main Results:

• Identified Polychrotinae and Phrynosomatinae (Iguanidae) as exceptionally diverse clades.
• Identified Crotaphytinae and Oplurinae (Iguanidae) as exceptionally nondiverse clades.
• Demonstrated significant variation in adaptive radiation extent within Iguanidae.

Conclusions:

• Proposed a testable, comparative framework for defining adaptive radiation.
• Highlighted the importance of ecological morphology in assessing adaptive disparity.
• Suggests further research into the drivers of varying adaptive diversification.