PARENT SESSION
Poster Session #2: Plant-Animal Interactions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Regulation of fruit production by Yucca whipplei compensates for florivory by sap beetles, Anthoneus agavensis.

Udovic, Daniel¹, ¹

ABSTRACT- Female sap beetles, Anthoneus agavensis, oviposit in flower buds of Yucca whipplei. The larvae destroy pollen and ovaries, causing premature abortion of buds and flowers. Damage to yucca inflorescences resulting from florivory by Anthoneus is quite variable both within and between populations, occasionally exceeding 50% of the flowers on an inflorescence. Infested flowers are too severely damaged to serve as pollen donors or to produce mature fruits. Here I investigate the influence of florivory by sap beetles on fruit and seed production. Previous studies of the flowering biology of Yucca whipplei indicate that plants regulate fruit production by aborting fruit. Consequently, fruit production is largely independent of pollinator abundance. Hence, we might hypothesize that yuccas infested with Anthoneus compensate for floral damage by aborting fewer fruits. I tested this hypothesis by determining the fate of each flower on 35 inflorescences at a study site near Escondido, CA. I constructed floral life tables for each inflorescence, using key factor analysis to determine the relative contribution of different sources of flower and fruit mortality. Regressions of the k-factors for early fruit mortality (abortion) against bud mortality indicate a strong negative relationship (p=0.025), suggesting that plants do compensate for florivory. Infested plants, however, may still suffer a significant fitness disadvantage, since florivory probably reduces both pollen donation and the ability to choose which fruits to mature.

KEY WORDS: Yucca whipplei, florivory, key-factor analysis, flowering biology