Accurate inference of the dates of common ancestry among species forms a central problem in understanding the evolutionary history of organisms. Molecular estimates of divergence time rely on the molecular evolutionary prediction that neutral mutations and substitutions occur at the same constant rate in genomes of related species. This underlies the notion of a molecular clock. Most implementa...

Caenorhabditis briggsae provides a natural comparison species for the model nematode C. elegans, given their similar morphology, life history, and hermaphroditic mode of reproduction. Despite C. briggsae boasting a published genome sequence and establishing Caenorhabditis as a model genus for genetics and development, little is known about genetic variation across the geographic range of this s...

The evolution of self-fertilization from outcrossing has occurred on numerous occasions in flowering plants. This shift in mating system profoundly influences the morphology, ecology, genetics and evolution of selfing lineages. As a result, there has been sustained interest in understanding the mechanisms driving the evolution of selfing and its environmental context. Recently, patterns of mole...

As a major agent of rapid speciation, interspecific hybridization has played an important role in plant evolution. When hybridization involves species that exhibit self-incompatibility (SI), this prezygotic barrier to self-fertilization must be overcome or lost to allow selfing. How SI, a normally dominant trait, is lost in nascent hybrids is not known, however. Here we demonstrate that hybrid ...

The harsh climatic conditions and paucity of potential pollinators on Southern Ocean Islands (SOIs; latitude 46°S-55°S) lead to the expectation that anemophily or self-fertilization are the dominant modes of plant sexual reproduction. However, at least some species have showy inflorescences suggesting biotic pollination or dimorphic breeding systems necessitating cross-pollination. This study i...

Gene combinations conferring local fitness may be destroyed by mating with individuals that are adapted to a different environment. This form of outbreeding depression provides an evolutionary incentive for self-fertilization. We show that the yeast Saccharomyces paradoxus tends to self-fertilize when it is well adapted to its local environment but tends to outcross when it is poorly adapted. T...

In mammals, only a few spermatozoa arrive at the fertilization site. During the last step in the journey to the egg, apart from their self-propulsion, spermatozoa may be assisted by oviduct movement and/or a guidance mechanism. The proportion of rabbit spermatozoa that arrive at the fertilization site was determined under in vivo conditions, in which either the ovulation products (secreting che...

We present a Bayesian method for characterizing the mating system of populations reproducing through a mixture of self-fertilization and random outcrossing. Our method uses patterns of genetic variation across the genome as a basis for inference about pure hermaphroditism, androdioecy, and gynodioecy. We extend the standard coalescence model to accommodate these mating systems, accounting expli...