Biomedical subjects

Felix Breden

Publications and source records attributed to Felix Breden.

6 recordsLinked to original sources

PubMed2007

Opsin gene duplication and diversification in the guppy, a model for sexual selection.

Identification of genes that control variation in adaptive characters is a prerequisite for understanding the processes that drive sexual and natural selection. Male coloration and female colour perception play important roles in mate choice in the guppy (Poecilia reticulata), a model organism for studies of natural and sexual selection. We examined a potential source for the known variation in colour perception, by analysing genomic and complementary DNA sequences of genes that code for visual pigment proteins. We find high sequence variability, both within and between populations, and expanded copy number for long-wave sensitive (LWS) opsin genes. Alleles with non-synonymous changes that suggest dissimilar spectral tuning properties occur in the same population and even in the same individual, and the high frequency of non-synonymous substitutions argues for diversifying selection acting on these proteins. Therefore, variability in tuning amino acids is partitioned within individuals and populations of the guppy, in contrast to variability for LWS at higher taxonomic levels in cichlids, a second model system for differentiation owing to sexual selection. Since opsin variability parallels the extreme male colour polymorphism within guppy populations, we suggest that mate choice has been a major factor driving the coevolution of opsins and male ornaments in this species.

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PubMed2006

Guppies.

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Animals↗

PubMed2006

An analytical model assessing the potential threat to natural habitats from insect resistance transgenes: continuous transgene input.

The potential effects of 'escape' of genetically modified material (transgenes) into natural communities is a major concern in their use. These effects may be limited in the first instance by limiting the proportion of transgene-carrying plants in the natural community. We previously presented an analytical model of the ecological processes governing the relative abundance and persistence of insect resistance (IR) transgenes in a natural community. In that paper, we illustrated the case in which the transgene is input into the community in a single season using data from oilseed rape (OSR) and its known herbivore, Plutella macropennis. We found that the transgene is unlikely to have a great impact on the natural community. Here, we extend the model for repeated input of crop pollen carrying the transgene. We show the model output, again using OSR, for continuous input of the transgene over 10 years, the projected commercial lifetime of a transgene without associated undesirable agronomic effects. Our results do not change our original conclusion that the IR transgene need not have a large impact on the natural community and our suggestions for assessing and mitigating any threat still stand.

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PubMed2005

An analytical model assessing the potential threat to natural habitats from insect resistance transgenes.

We examine the role of ecological interactions on effective gene flow from genetically manipulated plants to their wild relatives. We do so by constructing and applying to oilseed rape (OSR) an analytical model for interaction between plants with and without an insect resistance (IR) allele in natural communities, incorporating documented levels of herbivore variability. We find that with reasonable values of advantage to the IR allele, little concomitant disadvantage (physiological costs of the allele) restricts it to low proportions of the natural population for large numbers of generations. We conclude that OSR IR transgenes are unlikely to pose an immediate threat to natural communities. Our model identifies those factors best able to regulate particular transgenes at the population level, the most effective being impaired viability of seeds in the period between production and the following growing season, although other possibilities exist. Because solutions rely on ratios, limiting values of regulating factors are testable under controlled conditions, minimizing risk of release into the environment and offering significant advancement on existing testing programmes. Our model addresses folivory but is easily modified for herbivory damaging the seed or directly affecting seed production by infested plants, or for pathogens altering seed survival in the seedbank.

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PubMed2005

Invasion success and genetic diversity of introduced populations of guppies Poecilia reticulata in Australia.

High genetic diversity is thought to characterize successful invasive species, as the potential to adapt to new environments is enhanced and inbreeding is reduced. In the last century, guppies, Poecilia reticulata, repeatedly invaded streams in Australia and elsewhere. Quantitative genetic studies of one Australian guppy population have demonstrated high additive genetic variation for autosomal and Y-linked morphological traits. The combination of colonization success, high heritability of morphological traits, and the possibility of multiple introductions to Australia raised the prediction that neutral genetic diversity is high in introduced populations of guppies. In this study we examine genetic diversity at nine microsatellite and one mitochondrial locus for seven Australian populations. We used mtDNA haplotypes from the natural range of guppies and from domesticated varieties to identify source populations. There were a minimum of two introductions, but there was no haplotype diversity within Australian populations, suggesting a founder effect. This was supported by microsatellite markers, as allelic diversity and heterozygosity were severely reduced compared to one wild source population, and evidence of recent bottlenecks was found. Between Australian populations little differentiation of microsatellite allele frequencies was detected, suggesting that population admixture has occurred historically, perhaps due to male-biased gene flow followed by bottlenecks. Thus success of invasion of Australia and high additive genetic variance in Australian guppies are not associated with high levels of diversity at molecular loci. This finding is consistent with the release of additive genetic variation by dominance and epistasis following inbreeding, and with disruptive and negative frequency-dependent selection on fitness traits.

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PubMed2003

Females prefer carotenoid colored males as mates in the pentamorphic livebearing fish, Poecilia parae.

The first results of female preference and chosen male mating success in a new model organism, the pentamorphic livebearing fish, Poecilia parae, are presented. Poecilia parae is a relative of the guppy, P. reticulata, and is assumed to have similar reproductive behavior. We tested the hypothesis that P. parae females, like female guppies, prefer carotenoid colored males as mates. Here we show that the time a female spent with males was significantly greater for carotenoid coloration in red and yellow melanzona, but time with these two morphs did not differ. The preferred red and yellow males mated significantly more often with their choosing females than did the non-preferred blue and parae males. The few blue melanzona and parae males that mated did so without performing courtship displays. Some females mated with all phenotypes including immaculata males during open group trials. Female P. parae clearly preferred males with carotenoid coloration, thereby corroborating the hypothesis. Alternative male mating tactics by blue melanzona, parae, and immaculata morphs and promiscuous mating by females also resembled features of reproductive behaviors exhibited by guppies.

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