PARENT SESSION
Contributed Oral Session 85: Mutualism: Pollination
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal
A comparative study of the effects of fire on an obligate plant-pollinator mutualism: Year 1.
Udovic, Daniel*,1, Bronstein, Judith2, Barnes, Melanie1, 3, 1 University of Oregon, Eugene, OR, United States2 University of Arizona, Tucson, AZ, United States3 University of New Mexico, Albuquerque, NM, United States
ABSTRACT- Little is known about how mutualisms are disrupted by, and reassembled following disturbance. Here, we report on the early effects of fire on the obligate mutualism between the monocarpic yucca Hesperoyucca whipplei and its pollinator, the yucca moth Tegeticula maculata. We have been monitoring the flowering ecology of Hesperoyucca at two sites for several years. One of these sites, the Elliot Chaparral Reserve (ECR) near San Diego, was burned in the Cedar Fire in October 2003. The unburned site, on the Santa Margarita Ecological Reserve (SMER), is approximately 50km N and is physiographically similar. We use pre- and post-fire census data at these two sites to address the following questions: (1) To what extent did H. whipplei plants survive the fire? (2) Did the fire affect the timing and intensity of flowering? (3) Did the fire affect the abundance of yucca moth pollinators? And finally, (4) how did yucca and yucca moth reproductive success compare to previous years and to the same year at the unburned site? Given the intensity of the fire at the ECR site, survivorship of established yuccas was surprisingly high (>90%). Furthermore, the effects on the number of plants flowering and the phenology of flowering in Spring 2004 were minor. In contrast, pollinator abundance at the burned site in 2004 was severely reduced, resulting in very low fruit set and low seed viability. Consequently, how the influence of the fire on the dynamics of the mutualism propagates through time will likely depend on the rate of recovery of the pollinator population. Slow recovery of pollinators could lead to a delayed decline in the yucca population, despite high initial survivorship.
Key words: mutualism, disturbance ecology, fire ecology, pollination ecology