Flower Visitation, Pollen Deposition, and Pollen‐tube Competition in Hibiscus Moscheutos (Malvaceae)

Spira, Timothy P.; Snow, Allison A.; Whigham, Dennis F.; Leak, Jen

doi:10.1002/j.1537-2197.1992.tb14570.x

Cited by 60 publications

(59 citation statements)

References 17 publications

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“…However, on a single visit to a virgin S. siamensis flower pollen‐laden Trigona bees always deposited more than five pollen grains ( n = 20), and as plants generally require more than one pollen grain to initiate seed set (e.g. Spira et al . 1992) a stigma load of five pollen grains was chosen to indicate successful pollination.…”

Section: Resultsmentioning

confidence: 99%

Disturbance‐induced density‐dependent seed set in Shorea siamensis (Dipterocarpaceae), a tropical forest tree

1998

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Summary 0The reproductive output of Shorea siamensis\ a widespread dipterocarp tree\ was assessed in relation to disturbance and tree density at three sites in western Thailand during the 0885 and 0886~owering seasons[ The locations were similar except in disturbance history\ which was re~ected in decreasing tree density from undisturbed via moderately disturbed to disturbed sites[ 1 Hand pollination experiments showed S[ siamensis to be partially self!incompatible due to di}erential pollen tube growth and abortion of inbred fruit[ Although more than 89) of~owers from trees at all sites were pollinated\ pollen tubes developed in only a small proportion of these~owers[ Both pollen tube development and initial fruit production were highest at the undisturbed site[ Many fruit\ presumably selfed\ were aborted during development at all sites\ but signi_cantly more fruit were aborted at the disturbed site\ resulting in lowered production of mature fruit[ 2 Shorea siamensis was pollinated by small Tri`ona bees\ which exhibited signi_cant declines in intertree movements with increasing distance between~owering trees[ As resource availability did not di}er between sites\ di}erences in mature fruit set were considered to be mediated by changes in pollinator foraging behaviour at di}ering tree densities[ Variation in seed set was found to be negatively correlated with distance to nearest conspeci_c both within and between sites[ 3 At the two least disturbed sites observed seed set values corresponded with those expected by calculation[ However\ seed set at the disturbed site was signi_cantly lower than expected[ 4 Our results suggest that high reproductive success of S[ siamensis is dependent upon cross!pollination which\ through pollinator behaviour\ is a function of tree isolation[ This species may thus be subject to the Allee e}ect\ where population viability is reduced disproportionately with a decline in population size or\ as in this study\ population density[ The implications of these results for population recovery and genetic structure following disturbance are discussed[ Keywords] Allee e}ect\ disturbance\ forest regeneration\ gene~ow\ outcrossing\ pol! lination\ population viability Journal of Ecology "0887# 75\ 351Ð362

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Section: Resultsmentioning

confidence: 99%

Disturbance‐induced density‐dependent seed set in Shorea siamensis (Dipterocarpaceae), a tropical forest tree

1998

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“…Hibiscus moscheutos, commonly known as wild rose mallow, is a well-studied species in which pollen competition may affect male fitness (Snow and Spira, 1996). At our study sites in Edgewater, Maryland, USA, bumble bees (Bombus spp.)…”

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Effects of sequential pollination on the success of “fast” and “slow” pollen donors in Hibiscus moscheutos (Malvaceae)

Snow

2000

American J of Botany

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Competition among pollen grains for the chance to fertilize ovules typically involves two stages: arrival times on stigmas and/or the growth of pollen tubes through styles. In a previous study of Hibiscus moscheutos, we found that individual pollen donors often differed in pollen tube competitive ability. Here we determined whether short delays in pollen arrival time altered the average success of "fast" and "slow" pollen donors when both types of pollen experienced the same delays. Hand-pollination experiments were carried out using four pairs of pollen donors that differed in competitive ability. We allowed delays of 15 or 30 min between the first and second pollen donor and then determined seed paternity using allozyme markers. The second donor typically sired fewer seeds than pollen that arrived earlier, but, contrary to expectation, "faster" pollen did not always sire significantly more seeds than "slower" pollen when each was applied after delays of the same duration. In two of the four pairs of donors, differences that were seen following simultaneous pollinations disappeared when each type of pollen was applied following identical delays of 15 or 30 min. This unexpected response suggests that the dynamics of pollen tube competition are more complex than anticipated.

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“…Details of the reproductive ecology of H. moscheutos are given in Spira (1989), Snow and Spira (1991a, b), and Spira et al (1992). Briefly, the large, one-day flowers are pollinated by solitary anthophorid bees (Ptilothrix bombiformisi and by bumblebees (Bombus spp.).…”

Section: Methodsmentioning

confidence: 99%

“…Self-compatibility was demonstrated in two previous experiments, which showed no differences in the number of seeds per fruit from self vs. outcross pollen (Spira, 1989;Snow and Spira, 1991a). Self-compatibility was demonstrated in two previous experiments, which showed no differences in the number of seeds per fruit from self vs. outcross pollen (Spira, 1989;Snow and Spira, 1991a).…”

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confidence: 86%

Individual Variation in the Vigor of Self Pollen and Selfed Progeny in Hibiscus moscheutos (Malvaceae)

Snow¹

1993

American Journal of Botany

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In some self‐compatible species, self pollen tubes grow more slowly than outcross pollen, presumably leading to low selfing rates when mixtures of self and outcross pollen reach the stigma simultaneously. Here we show that the competitive ability of self pollen differed among individuals of Hibiscus moscheutos. Self pollen tubes grew slower than outcross pollen in three plants, faster than outcross pollen in four plants, and showed no difference in five other plants (based on rates of callose plug formation). Levels of inbreeding depression were examined by comparing progeny from self and outcross pollinations in seven maternal families. Self pollination led to reduced seed number in only one maternal family, and a slight decrease in seed size was seen in two maternal families. Considerable inbreeding depression occurred later in the life cycle, and the degree of inbreeding depression varied among maternal families of 6‐week‐old plants. Our results demonstrate the potential for unpredictable effects of pollen competition on individual selfing rates, which in turn may affect progeny vigor. This complex situation contrasts with previous reports of species in which outcross pollen consistently outcompetes self pollen (cryptic self‐incompatibility).

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Flower Visitation, Pollen Deposition, and Pollen‐tube Competition in Hibiscus Moscheutos (Malvaceae)

Cited by 60 publications

References 17 publications

Disturbance‐induced density‐dependent seed set in Shorea siamensis (Dipterocarpaceae), a tropical forest tree

Disturbance‐induced density‐dependent seed set in Shorea siamensis (Dipterocarpaceae), a tropical forest tree

Effects of sequential pollination on the success of “fast” and “slow” pollen donors in Hibiscus moscheutos (Malvaceae)

Individual Variation in the Vigor of Self Pollen and Selfed Progeny in Hibiscus moscheutos (Malvaceae)

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