Yucca aloifolia (Asparagaceae) opts out of an obligate pollination mutualism1. Issue 12 (1st December 2014)

• Record Type: Journal Article
• Authors: Rentsch, Jeremy D.; Leebens‐Mack, Jim
• Is Part Of: American journal of botany. Volume 101:Issue 12(2014)
• Page Start: 2062
• Page End: 2067
• Publication Date: 2014-12-01
• Subjects: European honey bee -- obligate mutualism -- Yucca -- yucca moth; Botany -- Periodicals; Botany; Electronic journals; Periodicals; 580
• DOI: 10.3732/ajb.1400351
• Languages: English
• ISSNs: 0002-9122

Abstract

Abstract : Premise of the study: According to Cope's 'law of the unspecialized' highly dependent species interactions are 'evolutionary dead ends, ' prone to extinction because reversion to more generalist interactions is thought to be unlikely. Cases of extreme specialization, such as those seen between obligate mutualists, are cast as evolutionarily inescapable, inevitably leading to extinction rather than diversification of participating species. The pollination mutualism between Yucca plants and yucca moths ( Tegeticula and Parategeticula ) would seem to be locked into such an obligate mutualism. Yucca aloifolia populations, however, can produce large numbers of fruit lacking moth oviposition scars. Here, we investigate the pollination ecology of Y. aloifolia, in search of the non‐moth pollination of a Yucca species. Methods: We perform pollinator exclusion studies on Yucca aloifolia and a sympatric yucca species, Y. filamentosa . We then perform postvisit exclusion treatments, an analysis of dissected fruits, and a fluorescent dye transfer experiment. Key results: As expected, Yucca filamentosa plants set fruit only when inflorescences were exposed to crepuscular and nocturnal pollinating yucca moths. In contrast, good fruit set was observed when pollinators were excluded from Y. aloifolia inflorescences from dusk to dawn, and no fruit set was observed when pollinators were excluded during the day. Follow up experiments indicated that European honeybees ( Apis mellifera ) were passively yet effectively pollinating Y. aloifolia flowers. Conclusions: These results indicate that even highly specialized mutualisms may not be entirely obligate interactions or evolutionary dead ends.