Testing for adaptive radiation: A new approach applied to Madagascar frogs

Area of Science:

• Ecology and evolutionary biology
• Speciation research

Background:

• Adaptive radiation is a central concept in evolutionary biology, but its definition and identification remain challenging.
• Existing definitions of adaptive radiation have limitations, necessitating new approaches for robust identification.

Purpose of the Study:

• To introduce and apply a novel approach for identifying adaptive radiation by integrating key aspects of two widely used definitions.
• To test the hypothesis of adaptive radiation in a specific frog clade from Madagascar (Mantellidae).

Main Methods:

• Comparing evolutionary rates (morphology, performance, diversification) between a candidate clade and other related clades.
• Utilizing new data on mantellid frog morphology and performance.
• Employing multivariate analyses to assess rates of evolution in size, shape, and performance.

Main Results:

• Mantellidae frogs exhibited accelerated evolutionary rates in shape, but not in size, performance, or diversification.
• The findings support the concept of "adaptive non-radiation," where accelerated phenotypic evolution occurs without rapid diversification.
• Challenges in testing for adaptive radiation, such as taxon sampling and comparator clade selection, were highlighted.

Conclusions:

• The study proposes a new framework for identifying adaptive radiation by comparing evolutionary rates.
• Mantellidae frogs represent a case of potential adaptive non-radiation, demonstrating accelerated phenotypic evolution without increased diversification.
• Further research on other Malagasy radiations and comparisons with extra-Madagascan clades are recommended to understand evolutionary patterns in island systems.