BACKGROUND AND AIMS Variation in mating patterns may be particularly evident in colonizing species because they commonly experience wide variation in plant density. Here, the role of density for the mating system of Ambrosia artemisiifolia (common ragweed), a wind-pollinated annual colonizing species previously reported as self-compatible, is explored. METHODS The effect of population density...

Recent advances in molecular biology have allowed the development of techniques to contrast spatial differentiation in nuclear and cytoplasmic genes and thus provide important data on relative levels of gene flow by pollen and seed in higher plants. In this paper, we compare the spatial structure of nuclear (allozymes) and cytoplasmic (cpDNA) genes among populations of the gynodioecious Thymus ...

The genetic basis of spontaneous melanoma formation in spotted dorsal (Sd) Xiphophorus platyfish-swordtail hybrids has been studied for decades, and is adequately explained by a two-gene inheritance model involving a sex-linked oncogene, Xmrk, and an autosomal tumor suppressor, DIFF. The Xmrk oncogene encodes a receptor tyrosine kinase related to EGFR; the nature of the DIFF tumor suppressor ge...

Two large experiments designed to detect allozyme-associated heterosis for growth rate in Drosophila melanogaster were performed. Heterosis associated with allozyme genotypes may be explained either by functional overdominance at the allozyme loci, or closely linked loci; or by genotypic correlations between allozyme loci and loci at which deleterious recessive alleles segregate. Such genotypic...

Spatial genetic structure in populations of mosquitofish (Gambusia) sampled throughout the south-eastern United States was characterized using mitochondrial (mt) DNA and allozyme markers. Both sets of data revealed a pronounced genetic discontinuity (along a broad path extending from south-eastern Mississippi to north-eastem Georgia) that corresponds to a recently recognized distinction between...

Estimates of genetic diversity within, and of variation among, semi-isolated populations of the common toad (Bufo bufo) were derived and compared across four classes of nuclear genetic markers, including allozymes, microsatellites, and single and multilocus minisatellites. Estimates of multilocus heterozygosity and the number of alleles per locus derived from allozymes were lower than for each ...

We present a statistical method for identifying species hybrids using data on multiple, unlinked markers. The method does not require that allele frequencies be known in the parental species nor that separate, pure samples of the parental species be available. The method is suitable for both markers with fixed allelic differences between the species and markers without fixed differences. The pr...