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A survey of restriction site variation in the chloroplast genome of the annual plant genus Amsinckia, together with estimation of outcrossing rates, was conducted to analyze the evolutionary history of the mating system. Species, and in some cases populations within species, differ markedly in their mating system. Five taxa are distylous and predominantly outcrossing, or show mixed mating systems, while the remaining taxa are homostylous and predominantly self-fertilizing. Reconstruction of the molecular phylogeny of the group places different distylous and homostylous taxa at four separate branch tips. When distyly is treated as ancestral in the group, or when the loss of distyly is assumed to be more common than its gain, the results of the phylogenetic analysis support the hypothesis that the self-fertilizing taxa are of recent origin from outcrossing relatives. These findings are discussed with respect to theory for the evolution and breakdown of distyly and the probability of extinction of selfing lineages.

Summary Marsolais, J. V., Pringle, J. S. & White, B. N.: Assessment of random amplified polymorphic DNA (RAPD) as genetic markers for determining the origin of interspecific lilac hybrids. – Taxon 42: 531–537. 1993. – ISSN 0040‐0262. RAPD markers were used to assess the relationship among species, cultivars and hybrids of lilacs. Thirteen random primers were used to examine 87–130 bands per cultivar or hybrid. The percent band sharing among Syringa xchinensis ‘Alba’, S. xchinensis ‘Saugeana’, S. xchinensis ‘Red Rothomagensis’ and S. xpersica, was surprisingly high (98.3 % to 99.6 %), supporting the theory that S. xpersica has the same species parentage as the three S. xchinensis hybrids, but also indicating that all four are of different clonal origin since they do not share 100 % of their bands. The percent band sharing among the hybrids and their putative parental species, S. vulgaris L. (3 selections) and S. protolaciniata P. S. Green & M. C. Chang (2 selections), were also determined. On average the first shared 48.9 % of their bands with the hybrids, and the second shared 50.7 %, thus strongly supporting the postulated parentage. Most bands found in the hybrids were shared with at least one of the selections, but 11 bands were found exclusively in all four hybrids. They might either represent genetic characteristics specific to these hybrids or might indicate that the exact parental selection combination has not yet been studied. The two studied selections of S. protolaciniata shared only 90,7 % of their bands, thus confirming that they are of different provenances. It is felt that RAPD markers will be very useful for assessing the origin of cultivars and hybrids of many plant species.

The first tandemly repeated sequence examined in a passerine bird, a 431-bp PstI fragment named pMAT1, has been cloned from the genome of the brown-headed cowbird (Molothrus ater). The sequence represents about 5-10% of the genome (about 4 x 10(5) copies) and yields prominent ethidium bromide stained bands when genomic DNA cut with a variety of restriction enzymes is electrophoresed in agarose gels. A particularly striking ladder of fragments is apparent when the DNA is cut with HinfI, indicative of a tandem arrangement of the monomer. The cloned PstI monomer has been sequenced, revealing no internal repeated structure. There are sequences that hybridize with pMAT1 found in related nine-primaried oscines but not in more distantly related oscines, suboscines, or nonpasserine species. Little sequence similarity to tandemly repeated PstI cut sequences from the merlin (Falco columbarius), saurus crane (Grus antigone), or Puerto Rican parrot (Amazona vittata) or to HinfI digested sequence from the Toulouse goose (Anser anser) was detected. The isolated sequence was used as a probe to examine DNA samples of eight members of the tribe Icterini. This examination revealed phylogenetically informative characters. The repeat contains cutting sites from a number of restriction enzymes, which, if sufficiently polymorphic, would provide new phylogenetic characters. Sequences like these, conserved within a species, but variable between closely related species, may be very useful for phylogenetic studies of closely related taxa.