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Reproductive biology of Darlingtonia californica
Various aspects of the ecology and natural history of Darlingtonia californica Torrey 1853, populations in northern California were studied as they relate to the species' reproductive biology. Experimental investigations of the breeding system to estimate natural levels of selfing and outcrossing rates were performed by measuring seed set in six treatments. Seed set in an open-pollinated control treatment was quite high and almost entirely the product of cross-pollination. Seed set in the treatment involving extra pollen added through hand-pollination was even higher, which suggested that there was competition for limited pollinator services and that seed set was pollinator, not resource, limited. Seed set was lowest in the treatment where pollinator access was denied, indicating that while the species is not autogamous, it is marginally self-compatible. The pollinator-exclusion treatment suggests that the species sets few to no seeds in the absence of pollinators. However, extended field examinations of flowering Darlingtonia populations, totaling over 120 hours, failed to detect any pollinators visiting the species. An as yet un-described, yellow-petaled flower variety was discovered in the course of field studies, and found to be similar to typical purple-petaled flowers in seed set, peduncle height, number of bracts and number of anthers. An extensive search of the literature on Darlingtonia californica was conducted and resulted in an annotated bibliography consisting of 60 articles, books and reports. To my knowledge, it is the most complete conducted to date.