Density-dependent adaptive topography in a small passerine bird, the collared flycatcher

TY - JOUR

T1 - Density-dependent adaptive topography in a small passerine bird, the collared flycatcher

AU - Sæther, Bernt Erik

AU - Engen, Steinar

AU - Gustafsson, Lars

AU - Grøtan, Vidar

AU - Vriend, Stefan J.G.

N1 - Publisher Copyright: © 2020 by The University of Chicago.

PY - 2021/1

Y1 - 2021/1

N2 - Adaptive topography is a central concept in evolutionary biology, describing how the mean fitness of a population changes with gene frequencies or mean phenotypes.We use expected population size as a quantity to be maximized by natural selection to show that selection on pairwise combinations of reproductive traits of collared flycatchers caused by fluctuations in population size generated an adaptive topography with distinct peaks often located at intermediate phenotypes. This occurred because r- and K-selection made phenotypes favored at small densities different from those with higher fitness at population sizes close to the carrying capacity K. Fitness decreased rapidly with a delay in the timing of egg laying, with a densitydependent effect especially occurring among early-laying females. The number of fledglings maximizing fitness was larger at small population sizes than when close to K. Finally, there was directional selection for large fledglings independent of population size. We suggest that these patterns can be explained by increased competition for some limiting resources or access to favorable nest sites at high population densities. Thus, r- and K-selection based on expected population size as an evolutionary maximization criterion may influence life-history evolution and constrain the selective responses to changes in the environment.

AB - Adaptive topography is a central concept in evolutionary biology, describing how the mean fitness of a population changes with gene frequencies or mean phenotypes.We use expected population size as a quantity to be maximized by natural selection to show that selection on pairwise combinations of reproductive traits of collared flycatchers caused by fluctuations in population size generated an adaptive topography with distinct peaks often located at intermediate phenotypes. This occurred because r- and K-selection made phenotypes favored at small densities different from those with higher fitness at population sizes close to the carrying capacity K. Fitness decreased rapidly with a delay in the timing of egg laying, with a densitydependent effect especially occurring among early-laying females. The number of fledglings maximizing fitness was larger at small population sizes than when close to K. Finally, there was directional selection for large fledglings independent of population size. We suggest that these patterns can be explained by increased competition for some limiting resources or access to favorable nest sites at high population densities. Thus, r- and K-selection based on expected population size as an evolutionary maximization criterion may influence life-history evolution and constrain the selective responses to changes in the environment.

KW - Collared flycatcher

KW - Density dependence

KW - Eco-evolutionary dynamics

KW - Fitness variation

KW - Life-history evolution

KW - R- and K-selection

U2 - 10.1086/711752

DO - 10.1086/711752

M3 - Article

C2 - 33417521

AN - SCOPUS:85097224047

SN - 0003-0147

VL - 197

SP - 93

EP - 110

JO - American Naturalist

JF - American Naturalist

IS - 1

ER -