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Biomedical subjects

E H Bryant

Publications and source records attributed to E H Bryant.

10 recordsLinked to original sources
PubMed2004

Phenotypic correlations among fitness and its components in a population of the housefly.

An individual's or a population's fitness is the result of a large number of interacting life history traits and the environment. Little information is available on the phenotypic correlations among fitness components and fitness itself, especially outside of Drosophila melanogaster. We also lack detailed information on trade-offs among life history traits. Here we present the relationship between adult progeny production and eight components of fitness, as well as some observed trade-offs between life history traits in the housefly (Musca domestica). We briefly discuss some of the ramifications of these relationships.

Age Factors↗
PubMed2003

A direct experimental test of founder-flush effects on the evolutionary potential for assortative mating.

Founder-flush speciation models propose that population bottlenecks can enhance evolutionary potential for reproductive isolation. To test this prediction, we subjected bottlenecked (three-pair founder-flush) and nonbottlenecked populations of the housefly to 18 generations of selection for assortative mating. After the selection regime, we analysed videotaped courtship bouts in these lines to identify correlated responses to the selection protocol. The realized heritabilities for assortative mating for both the bottlenecked and nonbottlenecked treatments were very low, but still significant. The founder-flush populations had thus responded to selection as well as the nonbottlenecked populations, although not significantly greater (i.e. total increases in assortative mating were 9.6 and 8.6%, respectively). Multivariate analyses on the courtship repertoires found that, although both bottlenecked and nonbottlenecked treatments attained similar levels of assortative mating, the treatments exhibited different evolutionary solutions in their correlated responses. Specifically, the bottlenecked lines demonstrated a significantly more diverse set of evolutionary trajectories (i.e. significant shifts along the second principal component for courtship). This suggests that the bottlenecked lines had greater potential for the evolution of novel phenotypes as predicted by founder-induced speciation models. Our results, however, cannot distinguish whether the more variable evolutionary responses resulted from increased heritabilities in courtship components, reduced potential to follow the convergent evolutionary trajectories noted for the nonbottlenecked lines, or some combination of both general processes in determining the resultant multivariate phenotype.

Animals↗
PubMed2000

The evolution of senescence under curtailed life span in laboratory populations of Musca domestica (the housefly).

The evolution of senescence may be explained by two different, but not mutually exclusive, genetic mechanisms. The antagonistic pleiotropy hypothesis predicts that senescence is a consequence of the fixation of alleles with pleiotropic effects favouring early life fitness, but bearing a cost in later life. The mutation-accumulation hypothesis attributes senescence to the accumulation of deleterious mutations with late-acting effects on fitness in mutation-selection balance. Experiments were carried out on the housefly, Musca domestica, in which large and small populations were maintained so that reproduction was limited to four or five days after reaching sexual maturity. Longevity declined significantly under the husbandry protocol and was largely the same in large and small populations; this is consistent with the random accumulation of deleterious alleles affecting longevity under curtailed life span, although laboratory adaptation cannot be ruled out entirely as a causal mechanism. An analysis of life-history data did not provide evidence for a trade-off between longevity and age at sexual maturity, developmental time, or dry body weight, but there was an apparent trade-off between longevity and early progeny production, in support of antagonistic pleiotropy.

Aging↗
PubMed1990

Loss of electrophoretic variation in serially bottlenecked populations.

Experimental bottleneck lines were generated from a single outbred population of the housefly using one, four, or 16 pairs of flies. These lines were followed through one, three, or five successive founder-flush cycles. After each flush 30 individuals from each line were assayed for electrophoretic variation at four initially polymorphic loci. Electrophoretic variation largely followed neutral expectation, the major exception being that the differentiation among 16-pair lines was greater than expected. All bottleneck sizes showed significant losses in genetic variation compared to the control, particularly for losses in numbers of alleles. These findings contrast theoretical predictions in that few lines and loci would be required to detect historical bottlenecks.

Alleles↗
PubMed1985

Fecundity and longevity of houseflies after space flight.

After 7 days of space flight house flies, Musca domestica, exhibited similar longevity, but a reduction in reproductive output as compared to earthbound controls. This reduction was not observed in later generations. These data suggest that space flight directly alters the rate of ovarian development, but that this effect is not genetically transmitted.

Animals↗
PubMed1980

A rare-male advantage in the housefly induced by wing clipping and some general considerations for Drosophila.

Multiple-choice crosses among five geographic strains of the housefly, Musca domestica L., were carried out in equal (10:10) and low-frequency (4:16) ratios. Initially, a low-frequency-male mating advantage was apparent, but further analyses related this minority advantage to a reduction of male mating success during marking by wing clipping. When there are fluctuating differences in the level of sexual vigor between competing male types over replicate trials of a cross, a mating advantage will accrue to the minority type. Even if males from the two competing strains are equally vigorous, such fluctuating differences will occur during sampling of flies. Harming the flies during marking will serve to enhance this effect and make significant departures toward greater mating success of rare males highly likely. This statistical bias in favor of minority males was substantiated in simulations of the KENCE-BRYANT model of mating success and compared with our results of a minority advantage in the housefly and with published results of a minority advantage in Drosophila. Our evidence, though circumstantial, that an advantage to minority males could have been induced by such an experimental bias suggests that a re-examination of existing data, as well as new experimentation, is necessary to discern whether or not a real rare-male advantage exists.

Animals↗
PubMed1979

Inbreeding and heterogamic mating: an alternative to Averhoff and Richardson.

An alternative explanation to the pheromonal control of mating through chemoreceptor saturation proposed by Averhoff and Richardson (1974) is offered for the apparent rise in heterogamic mating in their experiments, after several generations of full-sib mating. In a multiple-choice mating between two genotypic strains differing in their level of sexual vigor, there is a sequence from heterogamic to homogamic mating. It is proposed that, by reducing mating speed, inbreeding changes the rate of this sequence but not its pattern, so the apparent level of heterogamic mating will increase during inbreeding, for a fixed observation period. This hypothesis was tested using the Kence-Bryant model of mating success.

Animals↗