MULTIPLE OCCURRENCES OF MUTUALISM IN THE YUCCA MOTH LINEAGE

The complex mutualism between yuccas and the moths that pollinate thei r flowers is regarded as one of the most obvious cases of coevolution. Studies of related genera show that at least two of the critical beha vioral and life history traits suggested to have resulted from coevolv ed mutualism in yucca moths are plesiomorphic to the family. Another t rait, oviposition into flowers, has evolved repeatedly within the fami ly. One species with these traits, Greya politella, feeds on and polli nates plants of a different family, but pollination occurs through a d ifferent component of the oviposition behavior than in the yucca moths . Major differences compared with yucca moths and their hosts are that G. politella only passively pollinates its host and that copollinator s often contribute to pollination. This analysis suggests that evoluti on of mutualism between yuccas and yucca moths may have required few b ehavioral and life history changes in the moths. The truly coevolved f eatures of this interaction appear to be the evolution of active polli nation by the moths, the associated morphological structures in the mo ths for carrying pollen, and the exclusion of copollinators by yuccas.