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EARLY BURSTS OF BODY SIZE AND SHAPE EVOLUTION ARE RARE IN COMPARATIVE DATA
Author(s) -
Harmon Luke J,
Losos Jonathan B,
Jonathan Davies T,
Gillespie Rosemary G,
Gittleman John L,
Bryan Jennings W,
Kozak Kenneth H,
McPeek Mark A,
MorenoRoark Franck,
Near Thomas J,
Purvis Andy,
Ricklefs Robert E,
Schluter Dolph,
Schulte II James A,
Seehausen Ole,
Sidlauskas Brian L,
TorresCarvajal Omar,
Weir Jason T,
Mooers Arne Ø
Publication year - 2010
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2010.01025.x
Subject(s) - adaptive radiation , biology , clade , divergence (linguistics) , evolutionary biology , rate of evolution , phylogenetic comparative methods , phylogenetic tree , biochemistry , linguistics , philosophy , gene
George Gaylord Simpson famously postulated that much of life's diversity originated as adaptive radiations—more or less simultaneous divergences of numerous lines from a single ancestral adaptive type. However, identifying adaptive radiations has proven difficult due to a lack of broad‐scale comparative datasets. Here, we use phylogenetic comparative data on body size and shape in a diversity of animal clades to test a key model of adaptive radiation, in which initially rapid morphological evolution is followed by relative stasis. We compared the fit of this model to both single selective peak and random walk models. We found little support for the early‐burst model of adaptive radiation, whereas both other models, particularly that of selective peaks, were commonly supported. In addition, we found that the net rate of morphological evolution varied inversely with clade age. The youngest clades appear to evolve most rapidly because long‐term change typically does not attain the amount of divergence predicted from rates measured over short time scales. Across our entire analysis, the dominant pattern was one of constraints shaping evolution continually through time rather than rapid evolution followed by stasis. We suggest that the classical model of adaptive radiation, where morphological evolution is initially rapid and slows through time, may be rare in comparative data.