Bioessays 31 (12):1337-1346 (
2009)
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Abstract
‘‘Adaptive radiation’’ is an evocative metaphor for explosive
evolutionary divergence, which for over 100 years
has given a powerful heuristic to countless scientists
working on all types of organisms at all phylogenetic
levels. However, success has come at the price of making
‘‘adaptive radiation’’ so vague that it can no longer reflect
the detailed results yielded by powerful new phylogeny-based
techniques that quantify continuous adaptive
radiation variables such as speciation rate, phylogenetic
tree shape, and morphological diversity. Attempts to
shoehorn the results of these techniques into categorical
‘‘adaptive radiation: yes/no’’ schemes lead to reification,
in which arbitrary quantitative thresholds are regarded
as real. Our account of the life cycle of metaphors in
science suggests that it is time to exchange the spent
metaphor for new concepts that better represent the full
range of diversity, disparity, and speciation rate across
all of life.