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PubMed2004

Ecological conditions during winter affect sexual selection and breeding in a migratory bird.

Populations of migratory birds have undergone marked declines, although the causes and mechanisms remain unknown. Because environmental effects on population dynamics are mediated by the effects of ecological factors on individuals, understanding changes in individual phenotypes in response to ecological conditions is key to understanding population trends. We show that breeding individuals of a declining population of trans-Saharan migratory barn swallows, Hirundo rustica, were affected by environmental conditions, as estimated from the normalized difference vegetation index (NDVI), reflecting primary production, in their winter quarters. The breeding dates of the same individuals in consecutive breeding seasons were advanced and clutch sizes were larger after winters with high NDVI in the winter quarters. Feather moult was also affected by winter conditions, with consequences for male sexual attractiveness. Length of tail ornament was positively correlated with NDVI during the previous winter, and males with large tail ornaments reproduced earlier and had larger clutches. The mean annual breeding date of the population was earlier and breeding success was increased after favourable winters, but this result was mainly determined by a single winter with very low NDVI. Thus, ecological conditions in Africa influence individual performance and productivity in a barn swallow population.

Africa South of the Sahara↗
PubMed2005

Trilobite spines and beetle horns: sexual selection in the Palaeozoic?

Raphiophorid trilobites commonly bore median cephalic protuberances such as spines or bulbs, showing a remarkable variety of form. It is unlikely that their primary function was for protection or in hydrodynamics. A case is made that they were secondary sexual features, by comparison with similar morphological structures developed on rhinoceros beetles and other arthropods. This interpretation is supported by four lines of evidence: their ontogeny, their diversity, the existence of plausible examples of sexual dimorphs in some cases and the fact that they show positive allometry.

Animals↗
PubMed2001

Sexual selection: conflict, kindness and chicanery.

Multiple mating by females can result in fitness costs for both sexes, and to reduce these costs each sex may attempt to manipulate the other. Substantial insights into the nature of this sexual antagonism have recently come from studies of two different fly species.

Animals↗
PubMedDate not supplied

Insights into population ecology and sexual selection in snakes through the application of DNA-based genetic markers.

Hypervariable genetic markers have revolutionized studies of kinship, behavioral ecology, and population biology in vertebrate groups such as birds, but their use in snakes remains limited. To illustrate the value of such markers in snakes, we review studies that have used microsatellite DNA loci to analyze local population differentiation and parentage in snakes. Four ecologically distinct species of snakes all show evidence for differentiation at small spatial scales (2-15 km), but with substantial differences among species. This result highlights how genetic analysis can reveal hidden aspects of the natural history of difficult-to-observe taxa, and it raises important questions about the ecological factors that may contribute to restricted gene flow. A 3-year study of genetic parentage in marked populations of the northern water snake showed that (1) participation in mating aggregations was a poor predictor of genetic-based measures of reproductive success; (2) multiple paternity was high, yet there was no detectable fitness advantage to multiple mating by females; and (3) the opportunity for selection was far higher in males than in females due to a larger variance in male reproductive success, and yet this resulted in no detectable selection on morphological variation in males. Thus genetic markers have provided accurate measures of individual reproductive success in this species, an important step toward resolving the adaptive significance of key features including multiple paternity and reversed sexual size dimorphism. Overall these studies illustrate how genetic analyses of snakes provide previously unobtainable information of long-standing interest to behavioral ecologists.

Animals↗