Bumble Bee Pollination and Floral Morphology: Factors Influencing Pollen Dispersal in the Alpine Sky Pilot, Polemonium Viscosum (Polemoniaceae)

Abstract

Pollen dispersal success in entomophilous plants is influenced by the amount of pollen produced per flower, the fraction of pollen that is exported to other flowers during a pollinator visit, visitation frequency, and the complementarity between pollen donor and recipients. For bumble bee-pollinated Polemonium viscosum the first three determinants of male function are correlated with morphometric floral traits. Pollen production is positively related to corolla and style length, whereas pollen removal per visit by bumble bee pollinators is a positive function of corolla flare. Larger-flowered plants receive more bumble bee visits than small-flowered individuals. We found no evidence oftradeoffs between pollen export efficiency and per visit accumulation of outcross pollen; each was influenced by unique aspects of flower morphology. Individual queen bumble bees ofthe principal pollinator species, Bombus kirbyellus, were similar in male, female, and absolute measures of pollination effectiveness. An estimated 2.9% of the pollen that bumble bees removed from flowers during a foraging bout was, on average, deposited on stigmas of compatible recipients. Significant plant-to-plant differences in pollen production, pollen export per visit, and outcross pollen receipt were found for co-occurring individuals of P. viscosum indicating that variation in these fitness related traits can be seen by pollinatormediated selection.

Distilia e homostilia em espécies de Palicourea Aubl. (Rubiaceae) do Cerrado do Brasil Central

“…Acredita-se que as estruturas morfológicas maiores no morfo brevistilo é uma maneira de compensar uma possível assimetria no fl uxo de pólen em sua direção, devido a disposição estrutural do morfo longistilo facilitar a polinização (Ganders 1979). Realmente, alguns trabalhos têm demonstrado que o "display" fl oral exerce uma função importante em sistemas reprodutivos intermediado por animais, contudo estudos direcionados para espécies distílicas seriam necessários para constatar até que ponto estruturas morfológicas maiores entre os morfos infl uenciam na atração do polinizador (Galen & Stanton 1989, Mal & Lovett-Doust 1997. Além disso, outros estudos mostram que nem sempre essa diferença existe ou ocorre nesse sentido (Stone 1995, Teixeira & Machado 2004, Coelho & Barbosa 2004, Pereira et al 2006.…”

The genetic control of self-incompatibility in Linanthus parviflorus (Polemoniaceae)

“…Despite a long history of interest in the diverse pollination mechanisms and reproductive biology of the family (e.g. Grant & Grant, 1965;Levin, 1972;Schoen, 1982;Galen & Stanton, 1989;Campbell et al, 1991), and despite the prevalence of SI in the Polemoniaceae [found in at least eight of the 18 genera (Grant & Grant, 1965)1, the genetic basis of SI has been studied in only a single species, Phlox drummondii (Levin, Experimental crosses among full-siblings have been used extensively for elucidating the genetic basis of SI. Expectations for incompatibility relationships among full-siblings (assuming that parents are heterozygotes and share no S-alleles) differ for GSI and SSI in several respects (Richards, 1986).…”

Heterogeneity Among Floral Visitors Leads to Discordance Between Removal and Deposition of Pollen

“…The differences may be manifest in their effect on reproductive success either through female or through male function (Lloyd and Yates 1982, Bell 1985, Campbell 1989, Snow 1989. A number of recent studies have measured pollen removal as a component of male function (Snow and Roubik 1987, Cruzan et al 1988, Galen and Stanton 1989, Harder and Thomson 1989, Wolfe and Barrett 1989, Harder 1990, Murcia 1990, Young and Stanton 1990; however, high pollen removal need not result in high subsequent deposition of the removed pollen or in high success at siring seeds. Here we provide an example in which pollen-collecting bees remove more pollen but deposit less of it than nectar-collecting bees.…”