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Simon C Griffith

Publications and source records attributed to Simon C Griffith.

7 recordsLinked to original sources
PubMed2007

The evolution of infidelity in socially monogamous passerines: neglected components of direct and indirect selection.

A recent study by Goran Arnqvist and Mark Kirkpatrick in the American Naturalist (165:S26-S37) suggested that female polyandry in birds is not driven by females because quantitative genetic approximations of selection demonstrated that indirect selection for female infidelity is weaker than natural selection against it. Instead, it was argued that extrapair copulations are the result of antagonistic selection on male behavior driving female coercion. While the approach and framework of the study were very good, the conclusions of the study were premature because a number of potential adaptive components of polyandry were unaccounted for, and several critical assumptions are unsupported by the current empirical data. Our understanding of extrapair paternity in birds, and perhaps polyandry in general, will be improved by a better empirical understanding of the direct benefits of fertility assurance and postcopulatory cryptic female choice and the relationship between polyandry and male investment. In addition, we need to develop a greater awareness of the limitations of trying to study behavior by proxy in the molecular laboratory. Together, these challenges and the framework recently presented should improve our understanding of the true function of extrapair paternity in birds.

Agonistic Behavior↗
PubMed2006

Evolutionary genetics: evolution of mate choice in the wild.

Qvarnström et al. test whether the preference of female collared flycatchers (Ficedula albicollis) for males with large forehead patches could have evolved as a by-product of selection acting on male patch size. They find that the crucial genetic correlation between female choice and male patch size is not significant, and conclude that preference for large patches must have been shaped directly by selection. However, their use of the patch size of a female's social partner as a measure of choice is incomplete, and will result in low estimates of the potential for direct selection to shape female preference. Their study is therefore unable to resolve the question of how female preference for large forehead patches has evolved.

Animals↗
PubMed2006

Red dominates black: agonistic signalling among head morphs in the colour polymorphic Gouldian finch.

Recent sexual selection studies on the evolution of bird colouration have mainly focused on signals with a high level of condition-dependent variation, with much less attention given to colour traits whose expression is genetically controlled. Here, we experimentally tested the relative importance of a genetic colour polymorphism in determining male dominance in the Gouldian finch (Erythrura gouldiae), a species displaying three completely discrete but naturally co-occurring genetically inherited phenotypes; yellow-, red- (carotenoid) and black-headed (melanin) morphs. First, in staged dominance contests between unfamiliar birds of different head morphs, red-headed males dominated black-headed males, both of which dominated the yellow-headed birds. Second, within morphs, the intensity and size of the strongly ultraviolet-blue collar determined the outcome of these contests, and among the red-headed males, redder males dominated less chromatic birds. Lastly, when the dominance signal of red-headed birds was experimentally destabilized (i.e. blackened or reddened), naturally red-headed morphs continued to dominate both the black-and yellow-headed morphs. Together, these results suggest that intrinsic dominance-related behavioural differences between the three colour morphs, which are likely to influence the relative fitness of each morph, contribute to the complex selective patterns maintaining these three discrete phenotypes in relatively stable frequencies in wild populations.

Animal Communication↗
PubMed2003

Condition-dependent sex allocation in a lek-breeding wader, the ruff (Philomachus pugnax).

Sex allocation theory predicts that females should bias the production of offspring towards the sex that will maximize maternal fitness. Here we demonstrate evidence for nonrandom sex allocation by female ruffs (Philomachus pugnax), at both the individual and population level in relation to female condition. At the population level, female condition varies significantly across 3 years and is mirrored by population sex ratio, such that in years when females are in poor condition the population offspring sex ratio is female-biased, while in years when females are in better condition there was little or no bias. In the year when females were in overall poor condition, females in better condition produced more daughters. The same relationship is also revealed by comparing the sex ratios of individual females breeding in two consecutive years in different condition. As the condition of an individual female improves (across years) she tends to produce more female offspring. Although we have shown that, as in other birds, female condition is an important determinant of sex allocation, our results also suggest that such nonrandom allocation does not occur in every year, being particularly strong in a year when females, on average, are in poorer condition. We suggest that our results are consistent with the idea that skewing the sex ratio is likely to carry a cost to females and that it is adaptive only when the fitness differential between sons and daughters is sufficient to outweigh probable costs.

Animals↗
PubMed2002

Experimental analysis of sperm competition mechanisms in a wild bird population.

Recent work on wild birds has revealed the importance of sperm competition as a source of sexual selection, but behavioral and paternity studies have previously provided only indirect evidence for mechanisms of sperm competition in wild birds. In a field study of collared flycatchers Ficedula albicollis we used a previously uncharacterized method to determine the frequency and timing of extra-pair inseminations. By counting the number of sperm trapped on the perivitelline layer of eggs, we determined the timing of inseminations and estimated, on a day-to-day basis, the amount of sperm females stored. Our results showed that female collared flycatchers preferentially engaged in extra-pair copulations when mated to an unattractive male with a small white forehead patch. These copulations were timed for the middle part of their fertile period, at least 2 days after the last within-pair insemination. Although the mean number of extra-pair insemination events was only 1.33 per cuckolding female, the ratio between the number of sperm from extra-pair and pair inseminations was at least 5 to 1. Thus a single, well timed extra-pair insemination caused by female behavior could greatly bias fertilization probability in favor of an attractive extra-pair male. Our results suggest a possible behavioral mechanism for female control of sperm competition.

Animals↗
PubMed2002

Extra pair paternity in birds: a review of interspecific variation and adaptive function.

The application of molecular genetic techniques has revolutionized our view of avian mating systems. Contrary to prior expectations, birds are only very rarely sexually monogamous, with 'extra-pair offspring' found in approximately 90% of species. Even among socially monogamous species, over 11% of offspring are, on average, the result of extra-pair paternity (EPP). Based on over 150 molecular genetic studies of EPP in birds, we review two topical areas: (i) ecological explanations for interspecific variation in the rate of EPP; and (ii) evidence bearing on the adaptive function of EPP. We highlight the remaining challenges of understanding the relative roles of genes and ecology in determining variation between taxa in the rate of extra paternity, and testing for differences between extra-pair offspring and those sired within-pair.

Adaptation, Physiological↗