Pollination to Population Structure - How Understanding Reproductive Biology Can Inform Conservation of Rare Plants
Weekley, Carl W. , Menges, E.S. , Nicklen, E. Fleur , Zaya, David N. .
Breeding system, seed predation, and germination ecology of Prunus geniculata, an andromonoecious Florida shrub.
Conservation of an imperiled plant species may require an understanding of several aspects of its reproductive biology, including its breeding system and seed ecology. Prunus geniculata is a federally endangered shrub endemic to xeric upland habitats on Florida’s Lake Wales Ridge. Although plants are long-lived and individuals may flower profusely, fruit yield is sparse and seedlings are rare. To determine the causes of low rates of fruit set and seedling recruitment, we have been investigating the reproductive biology of P. geniculata since 1996. We have shown that P. geniculata is andromonoecious (male and bisexual flowers on the same plant) and that bisexual flowers include two floral morphs defined by style length. Results from experimental hand-pollinations conducted in two study populations in 2007 suggest that P. geniculata has partial gametophytic self-incompatibility, and that inbreeding depression is high in self-compatible individuals. In one population, no fruits were initiated from 50 selfed and 80 outcrossed flowers. In the second population, percent fruit initiation did not differ between 103 selfed and 84 outcrossed flowers; however, no selfed flowers produced mature fruits while 55% of outcrossed flowers did so. In monitoring 1354 bagged and unbagged fruits, we found that most fruits abscised before maturation. Fruit loss was significantly higher in unbagged fruits due to pre-dispersal seed predation by the plum curculio (Conotrachelus nenuphar) and an unidentified orthoptoran. In a field germination experiment using intact caged and uncaged seeds placed into microsites with or without litter, we found that germination was <5% for unprotected seeds. These results suggest that seedling recruitment in P. geniculata may be limited by multiple factors, including sexual reproductive failure, high rates of pre-dispersal seed predation, and low rates of seed germination. Despite annual adult mortality rates <1%, these factors may result in population declines if mortality outpaces annual recruitment.
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1 - Archbold Biological Station, Plant Ecology Lab, P.O. Box 2057, Lake Placid, Florida, 33862, USA
2 - Big Bend National Park, PO Box 129, Big Bend National Park, TX, 79834, USA
3 - University of Illinois/Chicago, Dept. of Biological Sciences, 845 W. Taylor, Chicago, IL, 60607, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Room 3/Woodward
Date: Monday, July 28th, 2008
Time: 8:15 AM