Enemy at the gates: Rapid defensive trait diversification in an adaptive radiation of lizards.
Adaptive radiation (AR), the product of rapid diversification of an ancestral species into novel adaptive zones, has become pivotal in our understanding of biodiversity. Although it has widely been accepted that predators may drive the process of AR by creating ecological opportunity (e.g., enemy-free space), the role of predators as selective agents in defensive trait diversification remains controversial. Using phylogenetic comparative methods, we provide evidence for an "early burst" in the diversification of antipredator phenotypes in Cordylinae, a relatively small AR of morphologically diverse southern African lizards. The evolution of body armor appears to have been initially rapid, but slowed down over time, consistent with the ecological niche-filling model. We suggest that the observed "early burst" pattern could be attributed to shifts in vulnerability to different types of predators (i.e., aerial versus terrestrial) associated with thermal habitat partitioning. These results provide empirical evidence supporting the hypothesis that predators or the interaction therewith might be key components of ecological opportunity, although the way in which predators influence morphological diversification requires further study.
Department of Botany & Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa. cbroeck@sun.ac.za.|Theoretical Ecology Group, Department of Mathematical Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa. cbroeck@sun.ac.za.
Chris
C
Broeckhoven
Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.
Genevieve
G
Diedericks
Theoretical Ecology Group, Department of Mathematical Sciences, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.|Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.|Theoretical and Physical Biosciences, African Institute for Mathematical Sciences, Cape Town, 7945, South Africa.
Cang
C
Hui
National Museum, Bloemfontein, P.O. Box 266, Bloemfontein, 9300, South Africa.
Buyisile G
BG
Makhubo
Department of Botany & Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, Stellenbosch, South Africa.
P le Fras N
PL
Mouton
D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D017753:Ecosystem; D049810:Genetic Speciation; D014644:Genetic Variation; D008116:Lizards / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics*; D010641:Phenotype; D010802:Phylogeny; D011235:Predatory Behavior; D012641:Selection, Genetic
Body armor; comparative methods; diversification rate; early burst; ecological opportunity; model fitting; predation