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Schwarzbach, Donovan, and Rieseberg extend the body of work being developed in the Helianthus study system. Using the homoploid hybrid species Helianthus anomalus, they compared 53 morphological and ecophysiological traits in the hybrid vs. parental species. Surprisingly, only one trait was identified as intermediate. The authors believe the new combination of parental and extreme (transgressive) characters allowed the hybrid to occupy a new habitat. (see p. 270)

Competent parenting

Marshall and Diggle explore mechanisms of nonrandom mating in Raphanus sativus (Brassicaceae). Their approach is comprehensive, ranging from examination of pollen viability to siring success, and provides a detailed analysis of the time course of mating for multiple male-female combinations. Further, reproductive performance and offspring production are compared under control and stressed conditions. The time course of mating differed significantly among stressed and control maternal plants, and seed paternity was less variable in stressed plants. Thus, more competent maternal tissue may result in more discrimination among potential mates. (see p. 242)

Clarifying a polyploid complex

John Mooring's career-long investigation of the Eriophyllum lanatum (Asteraceae) polyploid complex has resulted in a classic, traditional biosystematic study. His data on the chromosome numbers and chromosome pairing behaviors of members of the complex, as well as on fertility of the taxa and their hybrids as judged by cotton blue-lactophenol staining gathered from 886 intraspecific and interspecific artificial hybrids, elucidate the intricate polyploid structure of this synonymy-ridden, western North American group. (see p. 285)

Model system for evolutionary studies: Ipomopsis

Wolf et al. report on studies of barriers to hybridization between two hummingbird-pollinated and co-occurring species of Ipomopsis, for which hybrids can be made using artificial crosses, but for which natural hybrids are unknown. They performed (1) pollen transfer experiments within and between species using captive, trained broad-tailed hummingbirds, and (2) hand crossing experiments, which included competition experiments between hetero- and homospecific pollen to look at postpollination crossing barriers. Continued work with Ipomopsis is creating another model system (similar to that in Iris, Mimulus, and Helianthus) for understanding the effects of reproductive isolation and hybridization on evolutionary process and pattern. Results suggest that reproductive barriers are asymmetric in these species; effects from pollinators and of pollen performance depended on the direction of the cross (see p. 213)

This Article Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content