Spatial and temporal dispersion patterns of pollinators and their relationship to the flowering strategy of Yucca whipplei (Agavaceae)

Abstract

A field investigation of the mutualistic interaction between a monocarpic perennial plant, Yucca whipplei, and its host-specific pollinator and seed predator, Tegeticula maculata (Lepidoptera: Prodoxidae), was conducted to determine how the resource utilization pattern and population dynamics of the pollinator have influenced the evolution of the flowering and fruiting pattern of the plant. Although the temporal pattern of emergence of pollinators results in a relatively close tracking of flower abundance within a season, the ratio of pollinators to open flowers does vary significantly within a season, as well as between seasons. At any point in time during the flowering season, the population of adult yucca moths is distributed evenly among the available flowers, so that the number of pollinators on an inflorescence is directly proportional to the number of open flowers available. The relative isolation of individual flowering plants appears to have little effect on the distribution of pollinators among inflorescences. The number of fruits initiated on a plant is directly proportional to the number of flowers produced, and is also partially determined by the time of flowering. Yucca whipplei always produces many more flowers than fruits. Most flowers are not fertilized, and the plants also generally abort and abscise immature fruits after flowering. Fruit production of at least some plants, however, appeared limited by pollination. It is also expected that in some years the relative abundance of pollinators will be low enough that most plants will be pollinator-limited. It is suggested that the pattern of flowering and fruiting of this species has evolved in response to the unpredictability of pollinator availability, both within and between seasons. Resource uncertainty and selection acting on the male component of fitness may also be involved.

Pollination ecology of Tabebuia aurea (Manso) Benth. & Hook. and T. ochracea (Cham.) Standl. (Bignoniaceae) in Central Brazil cerrado vegetation

“…Fruit maturation in many plant species has been pointed out as a pollinator limitation which reflects the shortage of pollinators or the lack of successful pollination (Schemske 1981, Bertin 1982, Aker 1982, Waser 1983. It has been also regarded as result of sexual selection in which male genetic success is limited by its ability to reach the ovules, while female fitness is limited by the availability of resources for the egg (Janzen 1977, Willson 1979, Stenphenson & Bertin 1983, the ultimate cause of fruit abortion (Janzen 1977, Stephenson 1981, Stephenson et al 1985, Lee 1984.…”

Geographic and population variation in pollinating seed-consuming interactions between senita cacti ( Lophocereus schottii ) and senita moths ( Upiga virescens )

“…On average, only 37% (range 30-46%) of flowers set fruit. Similarly, on average 8% (range 3-14%) of flowers set fruit in different Yucca populations and species throughout their geographic range (Schaffer and Schaffer 1979;Udovic 1981;Udovic and Aker 1981;Aker 1982aAker ,1982bKingsolver 1984;Fuller 1990;James et al 1993James et al , 1994Pellmyr and Huth 1994;Huth and Pellmyr 1997;Addicott 1998).…”

Multiple origins of the yucca-yucca moth association.

“…Astel., Asteliaceae; Convall., Convallariaceae; Drac., Dracaenaceae; Funk., Funkiaceae; Hyac., Hyacinthaceae; Nol., Nolinaceae. recessed hidden stigmas of all Yucca species except Y whipplei strongly suggest that pollen transfer would be quite difficult in the absence of the moths. Nevertheless, all detailed pollination studies have indicated that T. maculata is Y whipplei's primary, and usually only, pollinator (33)(34)(35)(36)(37)(38). Hesperaloe has a more common nectar-based animal pollination system.…”