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1 April 2013 Reproductive Ecology of Opuntia macrocentra (Cactaceae) in the Northern Chihuahuan Desert
Maria C. Mandujano
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We studied the floral biology, floral visitors, levels of florivory, and mating system of Opuntia macrocentra in a population of ca. 300 individuals in order to describe what factors affect flower/fruit ratios. Blooming for the species occurred once a year during spring. Flowers were hermaphroditic, produced nectar, and remained open 6 to 9 h during a single day. Anther dehiscence starts at flower aperture and stigma receptivity starts approximately 1 h later. The most important floral visitors were solitary bees from the Anthophoridae family (genus Diadasia). Open- pollinated control and cross pollination treatments had the highest fruit set (96.8 ± 3.2% and 83.9 ± 6.7%, respectively), but fruit set for forced self-pollination treatment (77.4 ± 7.6%) did not differ from the cross-pollination treatment. Seed production was also highest in the open-pollinated treatment; the average number of seeds per fruit in the open-pollinated treatment was 40% higher than the cross-pollinated treatment and 64% higher than the self-pollinated treatment. The flowers were self-compatible and did not require a visitor to set fruit. Flower/fruit ratio was slightly above one over all pollination treatments (fruit ratios between 1.0–1.3), suggesting that almost all flowers turned into fruits. Outcrossing rates suggest a mixed mating system, but inbreeding depression was found for both fruit and seed set. Developing fruits were consumed by the caterpillar (Lepidoptera: Olycella subumbrella) and decreased fruit set from 20% to 100%. Florivory and inbreeding depression were the major factors that decrease fruit set for this species.

2013, American Midland Naturalist
Maria C. Mandujano "Reproductive Ecology of Opuntia macrocentra (Cactaceae) in the Northern Chihuahuan Desert," The American Midland Naturalist 169(2), 274-285, (1 April 2013).
Received: 22 September 2011; Accepted: 1 July 2012; Published: 1 April 2013

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