Fruit abortion in <i>Yucca elata</i> and its implications for the mutualistic association with yucca moths

TitleFruit abortion in Yucca elata and its implications for the mutualistic association with yucca moths
Publication TypeJournal Article
Year of Publication1994
AuthorsJames CD, M. Hoffman T, Lightfoot DC, Forbes GS, Whitford WG
Date Published1994
Call Number00630
Keywordsarticle, articles, insect, Tegeticula, insect, yucca moth, journal, journals, Tegeticula, Yucca pollination, yucca moth, SEE <TEGETICULA>, Yucca, fruit abortion, Yucca, mutualism, Yucca, pollination, Yucca, yucca moth

The yucca moth Tegeticula yuccasella is the sole pollinator of Yucca elata, and relies on yucca fruits to complete its life cycle. A high percentage of pollinated flowers abort, killing the T. yuccasella eggs and larvae in them. We examined patterns of fruit production and abortion in Y. elata, and related these patterns to vegetative characteristics, moth abundance, and environmental conditions. We studied 38 inflorescences throughout their flowering period, during one season in southern New Mexico, USA. Each night we recorded the number of flowers opening, the number of fruit formed, the relative abundance of yucca moths, and climatic conditions. We monitored 11,786 flowers, resulting in 699 mature fruit. Large inforescences produced more, but proportionately fewer fruit than small inflorescences. Inflorescences flowering late in the season produced proportionately more fruit than inflorescences flowering early. Only 6.6% (extremes 1.4-15.1%) of flowers produced mature fruits. Hand-pollination of all flowers on inflorescences did not significantly increase the proportion of flowers that developed into mature fruit. Fruit production appeared to be resource-, not pollinator- limited. Ninety per cent of observed moth-pollinated flowers aborted (N=31), resulting in the death of moth eggs and larvae laid in the flowers. Neither yucca moth abundance or climatic conditions correlated with fruit production. Inflorescences usually developed mature fruit from flowers opening during a "window" of consecutive nights, lasting for five nights on average (36% of the flowering period of an inflorescence). The timing of the window of fruit production was highly variable and unpredictable: mature fruits were produced from flowers opening at the beginning, in the middle, or at the end of the flowering period of an inflorescence. The results for Y. elata do not support existing hypotheses that attempt to explain patterns of selective fruit production. High rate of abortion of initiated fruit, and the apparently unpredictable pattern of fruit production by individual inflorescences, may stabilize the mutualistic interaction by preventing yucca moths from hyper-ovipositing flowers that have a high probability of developing into mature fruits. A risk-spreading strategy of oviposition is likely to be more successful for the moth than multiple ovipositions per flower.