Experimentally assessing the relative importance of predation and competition as agents of selection

  title={Experimentally assessing the relative importance of predation and competition as agents of selection},
  author={Ryan G. Calsbeek and Robert M. Cox},
Field experiments that measure natural selection in response to manipulations of the selective regime are extremely rare, even in systems where the ecological basis of adaptation has been studied extensively. The adaptive radiation of Caribbean Anolis lizards has been studied for decades, leading to precise predictions about the influence of alternative agents of selection in the wild. Here we present experimental evidence for the relative importance of two putative agents of selection in… 
Natural selection by pulsed predation: survival of the thickest.
Measurements of density dependence in body composition in a bivalve prey during bouts of intense predation by an avian predator show that Red Knots imposed a strong selection pressure on cockles to grow fast with thick shells and little flesh mass, with selection gradients among the highest reported in the literature.
An experimental test of the role of predators in the maintenance of a genetically based polymorphism
Limited evidence is provided that predation may play a role in maintaining a genetically based polymorphism in dorsal patterning that is expressed by female brown anole lizards, Anolis sagrei, which occur in Bar, Diamond and intermediate Diamond–Bar morphs.
Reversal of response to artificial selection on body size in a wild passerine
The evolvability of phenotypes is demonstrated and that selection may favor an intermediate phenotype in wild populations from an eleven‐year experiment with four years of artificial selection for long and short tarsus length, a proxy for body size.
The contribution of an avian top predator to selection in prey species.
Quantifying the effect of a key predator (Eurasian sparrowhawks) on selection on fledging body mass in two bird species was able to separate individual from brood-level effects of fledging mass on predation probability and recruitment, providing compelling evidence that sparrowhawk predation acts as an important causal agent of selection on fleeging mass in great tits but not in blue tits.
The predictability and magnitude of life-history divergence to ecological agents of selection: a meta-analysis in livebearing fishes.
There was a negative, asymmetric relationship between offspring-number and offspring-size divergence, suggesting greater costs of increasing offspring size than number, and highlights the importance of comparing phenotypic divergence across species and ecological selective agents.
The fitness consequences of genetic variation in wild populations of mice
This work conducts a large-scale manipulative field experiment with wild populations of deer mice in distinct habitats to directly estimate natural selection on pigmentation traits and next test whether this selection drives changes in allele frequency at an underlying pigment locus.
On the utility of meta‐analyses in the study of natural selection
The history of attempting to measure natural selection on quantitative characters goes back nearly 120 years (Bumpus, 1899). On a wintery morning in February, 1898, D.H. Bumpus came upon 136 English
AssessIng the relAtIve ImportAnce of IntrAspecIfIc And InterspecIfIc InterActIons on the ecology of Anolis nebulosus lIzArds from An IslAnd vs . A mAInlAnd populAtIon
—Predation and competition are key ecological interactions that may drive island syndrome characteristics. However, the relative importance of these interactions in island and mainland environments
The ecological causes of evolution.
  • A. MacColl
  • Biology
    Trends in ecology & evolution
  • 2011
No evidence of selection by predators on tadpole boldness
Animals typically exhibit adaptive behaviors that reduce their risk of predation. The term ‘boldness’ describes individual variation in the propensity to exhibit risk-reducing behavior and is the


Experimentally Replicated Disruptive Selection on Performance Traits in a Caribbean Lizard
It is shown that the forms of selection acting within a species support an ecological mechanism for diversification and the results provide evidence for the short-term repeatability of selection and its potency in the diversification of anoles.
Predator-induced behaviour shifts and natural selection in field-experimental lizard populations
It is demonstrated that lizards alter their habitat use in the presence of an introduced predator, but that these behavioural shifts do not prevent patterns of natural selection from changing in experimental populations.
  • R. Calsbeek, D. Irschick
  • Biology, Environmental Science
    Evolution; international journal of organic evolution
  • 2007
The results support the long-standing hypothesis that correlated selection on locomotor performance, morphology, and habitat use drives the evolution of ecomorphological correlations within Caribbean Anolis lizards, potentially providing a microevolutionary mechanism for their remarkable adaptive radiation.
Selection in Nature: Experimental Manipulations of Natural Populations1
A combination of field and laboratory selection experiments has revealed the importance of population size and structure in shaping the genetics of adaptation, and compared the patterns of senescence in guppies from high and low mortality rate environments in the laboratory and in the field.
The Strength of Phenotypic Selection in Natural Populations
Comparisons of estimated linear selection gradients and differentials suggest that indirect components of phenotypic selection were usually modest relative to direct components, and no evidence that stabilizing selection is stronger or more common than disruptive selection in nature.
Rapid Temporal Reversal in Predator-Driven Natural Selection
Experimental studies on 12 islets confirmed predictions that the introduction of a terrestrial predator would first select for longer-legged lizards, but as the lizards shifted onto high twigs to avoid the predator, selection would reverse toward favoring the shorter-legged individuals better able to locomote there.
Experimental Evidence That Competition Promotes Divergence in Adaptive Radiation
Disproportionately severe competition between similar phenotypes indicates frequency-dependent selection, verifying a crucial element of theory of competition and character divergence and resolving outstanding debates on the ecological causes of diversification and the evolutionary consequences of competitive interactions.
Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles
This major work, written by one of the best-known investigators of Anolis, reviews and synthesizes an immense literature and illustrates how different scientific approaches to the questions of adaptation and diversification can be integrated and examines evolutionary and ecological questions of interest to a broad range of biologists.
Sexual dimorphism and adaptive radiation in Anolis lizards
It is shown that sexual differences contribute substantially to the ecomorphological diversity produced by the adaptive radiations of West Indian Anolis lizards: within anole species, males and females occupy mostly non-overlapping parts of morphological space; the overall extent of sexual variation is large relative to interspecific variation; and the degree of variation depends on ecological type.
A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard ( Anolis carolinensis ) populations
Overall, the data reveal substantial ecological, behavioural, morphological, and functional dif-ferences among populations, some of which may be adaptive.