AOBPreview originally published online on January 4, 2006
Annals of Botany 2006 97(3):423-427; doi:10.1093/aob/mcj045
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Diurnal and Nocturnal Pollination of Marginatocereus marginatus (Pachycereeae: Cactaceae) in Central Mexico
1 Departamento de Ecología de la Biodiversidad, Instituto de Ecología UNAM, A.P. 70-275 México D.F., CP 04510, Mexico, 2 FES Iztacala UNAM, Laboratorio de Ecología UBIPRO, Av. De los Barrios 1, Los Reyes Iztacala, Tlanepantla, Edo. México, CP 54090, Mexico, 3 Canadian Wildlife Service, Environment Canada, Pacific and Yukon Region, 5421 Robertson Road, RR1, Delta, British Columbia, Canada V4K 3N2 and 4 Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
* For correspondence. E-mail avali{at}servidor.unam.mx
Received: 20 May 2005 Returned for revision: 26 July 2005 Accepted: 11 November 2005 Published electronically: 4 January 2006
• Background and Aims Chiropterophillous and ornithophillous characteristics can form part of a single reproductive strategy in plants that have flowers with diurnal and nocturnal anthesis. This broader pollination strategy can ensure seed set when pollinators are scarce or unpredictable. This appears to be true of hummingbirds, which presumably pollinate Marginatocereus marginatus, a columnar cactus with red nocturnal and diurnal flowers growing as part of dense bat-pollinated columnar cacti forests in arid regions of central Mexico. The aim of this study was to study the floral biology of M. marginatus, and evaluate the effectiveness of nocturnal vs. diurnal pollinators and the contribution of each pollinator group to overall plant fitness.
• Methods Individual flower buds were marked and followed to evaluate flower phenology and anthesis time. Flowers and nectar production were measured. An exclusion experiment was conducted to measure the relative contribution of nocturnal and diurnal pollinators to seed set.
• Key Results Marginatocereus marginatus has red hermaphroditic flowers with nocturnal and diurnal anthesis. The plant cannot produce seeds by selfing and was pollinated during the day by hummingbirds and during the night by bats, demonstrating that both pollinator groups were important for plant reproduction. Strong pollen limitation was found in the absence of one of the pollinator guilds.
• Conclusions Marginatocereus marginatus has an open pollination system in which both diurnal and nocturnal pollinators are needed to set seeds. This represents a fail-safe pollination system that can ensure both pollination, in a situation of low abundance of one of the pollinator groups (hummingbirds), and high competition for nocturnal pollinators with other columnar cacti that bloom synchronously with M. marginatus in the Tehuacan Valley, Mexico.
Key words: Bats, columnar cacti, fail safe pollination, hummingbirds, pollination
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