Seed Predation by Yucca Moths on Semelparous, Iteroparous and Vegetatively Reproducing Subspecies of Yucca Whipplei (Agavaceae)

Abstract

Yucca whipplei subspecies are distinguished by differences in reproduction: spp. whipplei and ssp. parishii are semelparous, flowering once and dying; ssp. caespitosa is iteroparous, producing multiple rosettes which may flower in different years; ssp. percursa has clonal reproduction from rhizomes, and ssp. intermedia is intermediate to the latter two. Seed loss due to the symbiotic yucca moth Tegeticula maculata was not evenly distributed among subspecies, nor was such predation correlated with the mode of reproduction. Rather the number of moth larvae per capsule was significantly negatively correlated with distance from the coast and average annual temperature. The number of larvae per capsule varied from 0-14. All subspecies had a percentage of fruits lacking larvae; this percentage was largest in the two semelparous subspecies where nearly half of their fruits were without larvae. There is some evidence that this is the result of egg or larval mortality early in development. Within an inflorescence, larvae in individuals of some subspecies showed a highly clumped dispersion and others a highly uniform dispersion.