Significance of flower exploding pollination on the reproduction of the Scotch broom, Cytisus scoparius (Leguminosae)

Abstract

The significance of single flower visits by pollinators on the reproductive success of the Scotch broom, Cytisus scoparius, with explosive flowers was investigated. Unexploded flowers (intact flowers) produced no fruit, implying that autonomous selfing and apomixis do not occur and that the explosion of flowers by insects is necessary for the fertilization of flowers. The fruit set in the natural condition was intermediate between that in artificial selfing or exploding and that in artificial outcrossing. Seed set and the ratio of seeds to ovules did not differ significantly between the natural condition and artificial outcrossing. The fruit set by a single flower visit from Apis mellifera was similar to natural conditions. Apis mellifera was the most frequent visitor and the number of flowers tripped open per hour was the highest among all the flower visitors. Approximately 75% of pollen on a flower disappeared in a single flower visit by A. mellifera. The small amount of pollen remaining on already‐exploded flowers appears to be the reason why A. mellifera do not frequently visit already‐exploded flowers. The higher seed set by outcrossing was believed to contribute to the seed set in both natural conditions and single flower visits by A. mellifera, and did not differ between them. Therefore, at least in Japan, A. mellifera appears to be the most important pollinator for C. scoparius, resulting in a high outcrossing rate with each single flower visit.

Visitor diversity and pollinator specialization in Mediterranean legumes

“…The pollination system of C. scoparius is relatively specialized, as previously reported by other authors (Parker, 1997;Stout, 2000;Suzuki, 2003): in the studied population flowers were visited by very few pollinator taxa among which only Bombus spp. were able to trigger the floral explosive mechanism.…”

Reproductive biology of Protium spruceanum (Burseraceae), a dominant dioecious tree in vegetation corridors in Southeastern Brazil

“…Two of the most observed visitors of dense inflorescences of P. spruceanum are Apis mellifera and Trigona sp., and the opportunistic behavior of such family (Apidae) has been reported in many habitats and associated with plant density and clusters (Ramalho 1990). Thought exotic honeybees can be important competitors of native pollinators (Carmo et al 2004), sometimes they have neutral or even beneficial effects on the pollination of native plants (Gross 2001, Dick et al 2003, Suzuki 2003, because of their high density, social organization and propensity for agricultural landscapes (Dick et al 2003). High temperatures around midday could result in high insect activity, as observed in this study, and this could lead to high visiting rates (Arroyo et al 1985).…”

Effect of Density and Flower Size on the Reproductive Success of Nothoscordum Graminum (Alliaceae)

“…It is well known that increases in pollinator's visitation produce increases in seed output (Aizen & Feinsinger 1994, Suzuki 2003). Thus, it should be expected that individuals with greater flower sizes have greater seed output than their co-specific with smaller flower sizes in patches with low density of flowers, however this difference should decrease as population density increases.…”