7. Blending Ecology and Genetics: Progress toward a Unified Population Biology

Travis, Joseph; Mueller, Laurence D.

doi:10.1515/9781400860180.101

Cited by 22 publications

(17 citation statements)

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“…A substantial theoretical literature has focused on whether the stability of population dynamics could be a by-product of Darwinian evolution (reviewed by Travis & Mueller 1989;Travis 1990). In these models, phenotypes (or genotypes in models with explicit genetics) vary in a trait, such as reproductive effort or competitive ability, that responds to density variation and that affects survival or reproductive output.…”

Section: Introductionmentioning

confidence: 99%

Frequency–dependent numerical dynamics in mosquitofish

Horth

Travis

2002

Proc. R. Soc. Lond. B

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Altering the genetic composition of a population can alter several aspects of its numerical dynamics. Whether natural populations routinely contain the genetic variation capable of affecting the stability of those dynamics is less clear. Here we report a study of experimental populations of mosquitofish (Gambusia holbrooki ), designed to examine this issue. The experiment examined the numerical effects of varying the initial relative frequency of a rare male genotype. A higher relative frequency of the rare, melanic genotype produced higher mortality rates in melanic males, higher mortality rates in females, higher juvenile abundance, and fewer fluctuations in the numbers of females across time. This work demonstrates that a natural population can harbour genetic variants in a single gender that are capable of inducing qualitative differences in the numerical dynamics of the opposite gender, through the effects of negative frequencydependent selection.

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Section: Introductionmentioning

confidence: 99%

Frequency–dependent numerical dynamics in mosquitofish

Horth

Travis

2002

Proc. R. Soc. Lond. B

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“…However, this and other theories of density-dependent natural selection have been notoriously difficult to test ex-2 Present address: Department of Animal Ecology, Ecology Building, University of Lund, S-223 62 Lund, Sweden; E-mail: erik.svensson@zooekol.lu.se. perimentally in the wild (Stearns 1977;Travis and Mueller 1989;Mueller 1997).…”

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Experimental Excursions on Adaptive Landscapes: Density-Dependent Selection on Egg Size

2000

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Theories of density-dependent natural selection suggest that intraspecific competition will favor juveniles of high competitive ability. Empirical evidence has been provided from laboratory selection experiments, but field studies are lacking due to the logistical difficulties of experimentally manipulating population densities in natural settings. Here, we present data from a decade-long experimental field study of side-blotched lizards, Uta stansburiana that overcomes these difficulties. We tested the hypothesis that density-dependent natural selection causes egg size to increase from early to late clutches in this and many other species. Using a novel combination of environmental manipulations of hatchling density and phenotypic manipulations of egg size, we demonstrate that the nature of selection on egg size changes dramatically in the absence of older competitors. The strength of selection on egg size among later-clutch hatchlings released in areas without competitors from early clutches became almost doubled in magnitude, compared to that among hatchlings released in the presence of older competitors. These experimental findings demonstrate density-dependent natural selection on egg size; however, they contradict the classical idea that egg size increases during the reproductive season because of competition between early and late hatchlings. The results indicate that competitive age or size asymmetries between early and late hatchlings can override within-cohort asymmetries due to egg size. We suggest that competition could be an important mediator of oscillating selection pressures in this and other systems. Finally, we discuss the utility of "double-level," simultaneous experimental manipulation of both phenotypic traits that are targets of selection (e.g., egg size) as well the environmental agents of selection (e.g., population density).

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“…Offspring performance can also be used to determine the outcome of natural selection if it is related to viability or fertility ofadults in terrestrial habitats (reviewed by Endler, 1986;Travis and Mueller, 1989). In amphibians, recent studies have shown that characteristics related to successful mating such as male body size are positively associated with larval growth rates and size at metamorphosis (Woodward, 1986;Woodward et al, 1988;Mitchell, 1990).…”

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PERFORMANCE OF TADPOLES FROM THE HYBRIDOGENETIC RANA ESCULENTA COMPLEX: INTERACTIONS WITH POND DRYING AND INTERSPECIFIC COMPETITION

Semlitsch

Reyer

1992

Evolution

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Abstract.»-The performance of three genotypes (LL, LR, RR) oftadpoles resulting from the hybrid mating system of Rana lessonae (phenotype L, genotype LL) and Rana esculenta (phenotype E, genotype LR) was determined in artificial ponds. The effects of interspecific competition and pond drying on growth, development, and survival of tadpoles were used to measure the performance of genotypes and the relative fitness of offspring. Among the three genotypes, tadpoles from the homogametic mating RR had the lowest survival, growth, and development under all environmental conditions. Body size of the LL and LR genotype tadpoles at metamorphosis was reduced by competition and pond drying. Days to metamorphosis were also higher for the LL and LR genotype tadpoles in competition ponds. The proportion of individuals metamorphosing of each genotype was differentially lowered by competition and pond drying. The LL genotype produced more metamorphs than the LR genotype in the constant water level ponds, but the LR genotype produced more in drying ponds. In competition ponds, the LR genotype produced more metamorphs than the LL genotype, but the LL genotype produced more metamorphs in ponds without competition. The RR genotype produced no metamorphs in any ofthe experimental environments. Increased performance of LR offspring from the heterogametic mating, in harsh conditions, and reduced performance of RR offspring from the homogametic mating, even under favorable conditions, relative to the parental genotype (LL) suggests that the population dynamics of this hybridogenetic system is strongly dependent on mate choice in mixed populations and the subsequent pond environment females select for oviposition and larval development.

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7. Blending Ecology and Genetics: Progress toward a Unified Population Biology

Cited by 22 publications

References 0 publications

Frequency–dependent numerical dynamics in mosquitofish

Frequency–dependent numerical dynamics in mosquitofish

Experimental Excursions on Adaptive Landscapes: Density-Dependent Selection on Egg Size

PERFORMANCE OF TADPOLES FROM THE HYBRIDOGENETIC RANA ESCULENTA COMPLEX: INTERACTIONS WITH POND DRYING AND INTERSPECIFIC COMPETITION

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