Breeding System and Interaccessional Hybridization of Purshia tridentata Plants Grown in a Common Garden

• Published in: Western North American naturalist 2012-08, Vol.72 (2), p.241-249
• Main Authors: Pendleton, Rosemary L., McArthur, E. Durant, Sanderson, Stewart C.
• Format: Article
• Language: English
• Subjects: bags; Botanical gardens; branches; Canyons; Crop science; developmental stages; Distribution; Environmental aspects; flowering; Flowers; Flowers & plants; Forest service; fruit set; Fruits; Growth; Hybridization; hybrids; Identification and classification; insect pollination; insects; landscapes; paternal effect; Phenology; pistil; Plant reproduction; Plants; Pollen; Pollination; progeny; Purshia tridentata; Rosaceae; Seeds; Shrubs; small mammals; stigma; ungulates; wildlife habitats; wind; wind pollination
• ISSN: 1527-0904; 1944-8341
• DOI: 10.3398/064.072.0213

Purshia spp. (Rosaceae) comprise a widespread western North American species complex that is important as landscape dominants, wildlife habitat, browse for wild and domestic ungulates, and seed reserves for small mammals. This study examined aspects of the phenology, compatibility, pollination biology, and progeny fruit characteristics of multiple accessions of bitterbrush (Purshia tridentata), as well as a putative hybrid between bitterbrush and Purshia stansburiana. Except for open- and wind-pollination treatments, mass pollination was accomplished at anthesis within white paper sacks, which were used to isolate treatment branches. Bitterbrush appears to be largely self-incompatible and requires some agent, either wind or animal, to effect pollination. While the majority of pollination of bitterbrush flowers is undoubtedly accomplished by insects, some pollination by wind is possible (ambophily) when shrubs are closely spaced, as flowering is fairly synchronous. Flower duration varied among shrubs, but generally lasted from 12 to 24 hours, depending on weather conditions. Flower development stage had little effect on fruit set, indicating prolonged stigma receptivity. Populations of bitterbrush exhibit considerable interfertility, as well as substantial hybridization with congeners. Intrapopulation crosses were only slightly more successful than interpopulation crosses. One of the populations analyzed exhibits characteristics consistent with its putative hybrid nature, having more than one pistil per receptacle, smaller but longer fruits, and a greater reliance on insects for pollination. Both maternal and paternal effects are important in fruit development. Taxonomic relationships within the complex are discussed.