How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism

The origins of obligate pollination mutualisms, such as the classic yucca yucca moth association, appear to require extensive trait evolution and specialization. To understand the extent to which traits truly evolved as part of establishing the mutualistic relationship, rather than being pre-adaptations, we used an expanded phylogenetic estimate with improved sampling of deeply-diverged groups to perform the first formal reconstruction of trait evolution in pollinating yucca moths and their nonpollinating relatives. Our analysis demonstrates that key life-history traits of yucca moths, including larval feeding in the floral ovary and the associated specialized cutting ovipositor, as well as colonization of woody monocots in xeric habitats, may have been established before the obligate mutualism with yuccas. Given these pre-existing traits, novel traits in the mutualist moths are limited to the active pollination behaviours and the tentacular appendages that facilitate pollen collection and deposition. These results suggest that a highly specialized obligate mutualism was built on the foundation of pre-existing interactions between early Prodoxidae and their host plants, and arose with minimal trait evolution. (C) 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 847-855.