CaraDonna, Paul , Ackerman, James D. .
Reproductive assurance for a rewardless epiphytic orchid in Puerto Rico (Pleurothallis ruscifolia).
Most flowering plants sustain pollinator visitation by offering rewards such as nectar or pollen. Although this is an effective system to attract and maintain pollinator interest, there are nevertheless plants that do not offer rewards and instead rely on deception for successful pollen transfer. Unless rewardless plants have an extremely efficient means of deceit or are autogamous, they tend to experience less fruit set than plants that offer pollinator rewards. In Puerto Rico, we studied the reproductive biology of a rewardless epiphytic orchid, Pleurothallis ruscifolia, a species with a widespread neotropical distribution. Previous literature has reported P. ruscifolia as autogamous; however, more recent studies have shown that Pleurothallis species in Brazil are primarily non-autogamous and reliant upon animals for pollination. Because P. ruscifolia populations in Puerto Rico exhibit an unusually high fruit set (~70%) for a rewardless orchid, we predicted that our population is autogamous and its reproductive effort and success limited by plant size. During the 2009 flowering season, we monitored 168 plants in a single population to determine the breeding system of P. ruscifolia and looked for evidence of reproductive constraints. Plants produced both chasmogamous and cleistogamous flowers, the majority of fruits produced by the latter. Furthermore, both reproductive effort (flower production) and fruiting success increased with plant size, which may be explained by larger plants (those with more shoots) being more efficient at obtaining available resources and/or translocation of these resources throughout the plant. We expect that autogamy is prevalent in Pleurothallis ruscifolia of the West Indies, while in contrast outcrossing should be dominant in continental populations. Selection for reproductive assurance in the absence or rarity of an effective pollinator in this island population is the likely process leading to an autogamous system.
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1 - Humboldt State University, Department of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA
2 - UPR Rio Piedras, Departamento de Biologia, FB246, San Juan, PR, 00931, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 552B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 2:30 PM