FITNESS CONSEQUENCES OF OUTCROSSING IN IMPATIENS CAPENSIS: TESTS OF THE FREQUENCY-DEPENDENT AND SIB-COMPETITION MODELS.
Using field and greenhouse experiments, we tested two hypotheses that could account for the maintenance of outcrossing in Impatiens capensis. Seedlings derived from cleistogamous (CL) and chasmogamous (CH) flowers were grown under competitive conditions while flanked by neighbors that were either related or unrelated. In both experiments, CH progeny sometimes expressed more phenotypic variability than CL progeny. In the greenhouse experiment, CH progeny attained the same weight as CL progeny, and the relatedness of neighboring plants did not affect the growth of either type. In the field experiment, CL and CH progeny performed similarly when grown with related competitors. However, CH progeny were somewhat larger when planted with nonsibs, while CL progeny were somewhat smaller under those conditions. Thus, there is no evidence that either frequency-dependent selection or the avoidance of competition among siblings favors the maintenance of outcrossing in this species. We also modeled the relative variability of selfed and outcrossed progeny under several reproductive systems. When females mate with one male (progeny are full sibs), selfed progeny are often more variable than outcrossed progeny. When females engage in both selfing and outcrossing, variation among progeny is frequently maximized at an intermediate selfing rate. The sib-competition mechanism, under a range of genetic models, is not apt to promote outcrossing, since selfed progeny are commonly more variable than outcrossed progeny.
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Related Subject Headings
- Evolutionary Biology
- 3104 Evolutionary biology
- 3103 Ecology
- 0603 Evolutionary Biology
- 0602 Ecology
Citation
Published In
DOI
EISSN
ISSN
Publication Date
Volume
Issue
Start / End Page
Related Subject Headings
- Evolutionary Biology
- 3104 Evolutionary biology
- 3103 Ecology
- 0603 Evolutionary Biology
- 0602 Ecology