Thinking in continua: beyond the "adaptive radiation" metaphor

Area of Science:

• Evolutionary Biology
• Ecology
• Phylogenetics

Background:

• The metaphor of adaptive radiation has been a cornerstone in evolutionary biology for over a century.
• It describes explosive evolutionary divergence across diverse organisms and phylogenetic levels.
• However, its broad application has led to vagueness, hindering precise scientific communication.

Purpose of the Study:

• To critically evaluate the utility of the "adaptive radiation" metaphor in light of modern quantitative evolutionary techniques.
• To highlight the limitations of the current metaphor in capturing nuanced evolutionary dynamics.
• To advocate for the adoption of new conceptual frameworks that better represent evolutionary processes.

Main Methods:

• Analysis of the historical application and conceptual evolution of the "adaptive radiation" metaphor.
• Examination of how new phylogeny-based techniques quantify evolutionary variables.
• Critique of the reification of arbitrary thresholds in "adaptive radiation: yes/no" classifications.

Main Results:

• Modern phylogenetic and quantitative methods provide detailed insights into speciation rates, tree shape, and morphological diversity.
• The "adaptive radiation" metaphor fails to adequately encompass the complexity revealed by these new techniques.
• Classifying evolutionary events as "adaptive radiation: yes/no" oversimplifies and misrepresents continuous evolutionary processes.

Conclusions:

• The "adaptive radiation" metaphor is becoming an outdated heuristic due to its inherent vagueness.
• New conceptual frameworks are needed to accurately describe the full spectrum of diversity, disparity, and speciation rates in life.
• Adopting new concepts will improve the precision and explanatory power of evolutionary biology.