of Annals Botany 86: 415420, 2000 doi:10.1006/anbo.2000.1202, available online at http://www.idealibrary.com on
A Measure of the Various Modes of Inbreeding in Kalmia latifolia
MAUREEN A. LEVRI* Seton Hill College, Seton Hill Drive, Greensburg, PA 15601, USA
Received: 24 January 2000 Returned for revision: 8 March 2000 Accepted: 2 May 2000
Inbreeding can occur in several ways. For a given species, analysing overall inbreeding down to its component parts can be useful in explaining how and why inbreeding is maintained in a population. Kalmia latifolia, a long-lived evergreen shrub, was chosen for this study for two reasons: its unique oral morphology suggested that it was specially adapted to assure reproduction in the delayed mode of self-fertilization, and previous studies had suggested that populations that were more limited by pollinators showed higher rates of within-ower self-fertilization when pollinators were excluded. Floral manipulations, controlled pollinations, and paternity analysis were performed to determine the most common form of inbreeding within a ower, among owers of one individual, or among related individuals. Although plants are capable of setting seed within a ower, the overall rate of inbreeding was low. Among the modes of inbreeding within one individual, a negligible selng rate among emasculated owers suggests that selng is more prevalent within a ower than among owers on the same plant. In addition, as the multi-locus estimate of inbreeding was less than the single-locus estimate, inbreeding among related individuals also contributes # 2000 Annals of Botany Company to the natural level of inbreeding. Key words: Kalmia latifolia; mountain laurel; pollination; geitonogamy; autogamy; self-fertilization; inbreeding.
I N T RO D U C T I O N The adaptive signicance of inbreeding gures prominently in theoretical work on plant mating-systems. Inbreeding can result from matings between related individuals, `biparental', or within one individual, `uniparental'. Lloyd and Schoen (1992) discuss the dierent `modes' or strategies for eecting uniparental breeding, including geitonogamy, delayed selng, and competing selng. The dierent categories are dened by such distinctions as the morphology of the ower, the relative timing of the presentation of outcrossed and selfed pollen, whether a pollinator is required, and whether a pollinator presents the stigma of a ower with selfed pollen from the same ower or another ower. For a given species, decomposing inbreeding into relative contributions of each form of inbreeding can be useful in explaining how and why inbreeding is maintained in a population. Lloyd (1992) developed a model predicting the conditions under which each mode of inbreeding would be favoured. The conditions include parameters such as the benet of uniparental reproduction over biparental reproduction (i.e. `the cost of meiosis'), the loss of male and female tness that could have been gained through outcrossing had the plant avoided inbreeding (i.e. `pollen and ovule discounting'), the reduction in tness in inbred progeny compared to outcrossed progeny (i.e. `inbreeding depression'), and the tn...
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