Large morphological transitions underlie exceptional shape diversification in an adaptive radiation.

Area of Science:

• Evolutionary biology
• Comparative anatomy
• Morphological diversification

Background:

• Adaptive radiations increase species and phenotypic diversity as organisms fill ecological niches.
• Anolis lizards are a model for adaptive radiation studies, but skull shape diversification remains under-investigated.
• Previous research focused on post-cranium morphology, neglecting skull shape evolution.

Purpose of the Study:

• To investigate whether the tempo or mode of skull shape diversification changed during anole evolution.
• To compare skull shape evolution in anoles with related lizard clades.
• To understand the evolutionary mechanisms behind anole skull diversity.

Main Methods:

• Geometric morphometric analysis of skull shape.
• Comparative analysis across 12 Iguanian families, including anoles (110 species).

Main Results:

• Anolis lizards occupy a unique and wider morphological space for skull shape compared to other Iguanian families.
• No significant difference in the evolutionary rate of skull shape diversification was found between anoles and their relatives.
• Anole skull diversity arose through a distinct mode involving larger morphological transitions into novel regions of morphospace.

Conclusions:

• Anole skull diversity is driven by a unique mode of evolution characterized by significant morphological jumps, not accelerated rates.
• Traits not directly linked to ecological niche specialization can undergo exceptional diversification patterns.
• This study reveals novel insights into the evolutionary processes shaping phenotypic diversity during adaptive radiations.