Patterns of multiple paternity in fruits of Mimulus ringens (Phrymaceae)

Multiply sired fruits provide unambiguous evidence that pollen from two or more donors was deposited on a stigma and successfully fertilized ovules. Such multiple paternity within fruits can have important consequences for both parental and offspring fitness, but little is known about the frequency of multiple paternity or the mechanisms causing it. In this study we quantify the extent of multiple paternity in replicate experimental arrays of Mimulus ringens (square-stem monkeyflower) and use observations of pollinator behavior to infer mechanisms generating multiply sired fruits. In each array, floral displays were trimmed to two, four, eight, or 16 flowers per plant to span the range of display sizes observed in nature. In our sample of 204 fruits, more than 95% had two or more outcross pollen donors. The number of sires per fruit averaged 4.63 ± 0.10 (mean ± 1 SE), including selfs, and did not vary significantly with floral display treatment. Patterns of bumble bee foraging, combined with limited pollen carryover, suggest that observed levels of multiple paternity cannot be fully explained by single probes that deposited mixed pollen loads. Multiple probes to flowers, each delivering pollen from 1-3 different sires, are more likely to have caused the observed patterns. These sequential visits may reduce the potential for pollen competition and female choice based on pollen tube growth rate.     

Multiple paternity in fruits of Ipomopsis aggregata (Polemoniaceae)

Two different mechanisms can result in multiple paternity within fruits: deposition of a mixed pollen load due to carryover of pollen from flower to flower and multiple pollinator visits in close succession. I investigated the extent of multiple paternity within fruits of Ipompsis aggregata containing from 2 to 14 seeds. A paternity analysis based on ten polymorphic isozyme markers revealed multiple paternity in a minimum of 68% (based on simple paternity exclusion) and up to 100% (based on identification of the most likely father) of the multiseeded fruits. The estimated number of fathers increased with the number of seeds in a fruit, with an average of four sires, and up to nine sires, represented in a single fruit. To explore whether this level of multiple paternity could be explained solely by simultaneous deposition of a mixed pollen load, I constructed a computer simulation model based on previous measurements of movement patterns and pollen carryover by the hummingbird pollinators. Model predictions provided a good match to observed values for number of sires per fruit. Thus, the extensive pollen carryover in this species and consequent mixed pollen loads can explain the high levels of multiple paternity in natural populations.     

Pollen load size, reproductive success, and progeny kinship of naturally pollinated flowers of the tropical dry forest tree Pachira quinata (Bombacaceae)

Several studies have demonstrated, using controlled pollinations, that the number and identity of pollen grains deposited onto a flower's stigma affect the reproductive success of plants. However, few studies have shown this relationship under conditions of natural pollination. Using the tropical dry forest tree Pachira quinata, we evaluated the relationship between the number of microgametophytes per pistil and the number of sires with respect to the production of fruits and seeds in a natural population of Pachira quinata. Our study demonstrates that fruit and seed production are directly related to the number of microgametophytes per pistil in natural populations of P. quinata. Only 6% of the marked flowers developed into mature fruits and 10% of the marked flowers initiated fruits but later aborted them. A mean of 23 pollen grains were required to produce a seed. Flowers with >400 pollen grains on the stigma always developed into mature fruits, whereas flowers that received <200 grains never matured fruits. Half of the pollen grains transferred to a flower stigma germinated and developed pollen tubes to the base of the style. The number of pollen grains on a stigma explained 34% of the variation in seed number per fruit, and the number of seeds produced per fruit is positively correlated with the size of the seeds. The population of P. quinata studied is predominantly outcrossing, and seeds within fruits are sired by one or a few donors. The total seed crop within trees was sired by three to five donors. Our study examined the implications of the variation in size of microgametophyte loads per pistil with respect to the breeding system and the paternity of progeny under natural conditions. The competitive ability of pollen and pollen tube attrition are important factors regulating fruit production in P. quinata.     

Pollinator visitation patterns strongly influence among-flower variation in selfing rate

Background and Aims

Adjacent flowers on Mimulus ringens floral displays often vary markedly in selfing rate. We hypothesized that this fine-scale variation in mating system reflects the tendency of bumble-bee pollinators to probe several flowers consecutively on multiflower displays. When a pollinator approaches a display, the first flower probed is likely to receive substantial outcross pollen. However, since pollen carryover in this species is limited, receipt of self pollen should increase rapidly for later flowers. Here the first direct experimental test of this hypothesis is described.

Methods

In order to link floral visitation sequences with selfing rates of individual flowers, replicate linear arrays were established, each composed of plants with unique genetic markers. This facilitated unambiguous assignment of paternity to all sampled progeny. A single wild bumble-bee was permitted to forage on each linear array, recording the order of floral visits on each display. Once fruits had matured, 120 fruits were harvested (four flowers from each of five floral displays in each of six arrays). Twenty-five seedlings from each fruit were genotyped and paternity was unambiguously assigned to all 3000 genotyped progeny.

Key Results

The order of pollinator probes on Mimulus floral displays strongly and significantly influenced selfing rates of individual fruits. Mean selfing rates increased from 21 % for initial probes to 78 % for the fourth flower probed on each display.

Conclusions

Striking among-flower differences in selfing rate result from increased deposition of geitonogamous (among-flower, within-display) self pollen as bumble-bees probe consecutive flowers on each floral display. The resulting heterogeneity in the genetic composition of sibships may influence seedling competition and the expression of inbreeding depression.Key words: Autogamy, bee, Bombus fervidus, floral display, geitonogamy, mating system, monkeyflower, Mimulus ringens, paternity analysis, pollen carryover, pollinator visitation sequence, self-fertilization     

Does multiple paternity affect seed mass in angiosperms? An experimental test in Dalechampia scandens

Flowers fertilized by multiple fathers may be expected to produce heavier seeds than those fertilized by a single father. However, the adaptive mechanisms leading to such differences remain unclear, and the evidence inconsistent. Here, we first review the different hypotheses predicting an increase in seed mass when multiple paternity occurs. We show that distinguishing between these hypotheses requires information about average seed mass, but also about within‐fruit variance in seed mass, bias in siring success among pollen donors, and whether siring success and seed mass are correlated. We then report the results of an experiment on Dalechampia scandens (Euphorbiaceae), assessing these critical variables in conjunction with a comparison of seed mass resulting from crosses with single vs. multiple pollen donors. Siring success differed among males when competing for fertilization, but average seed mass was not affected by the number of fathers. Furthermore, paternal identity explained only 3.8% of the variance in seed mass, and siring success was not correlated with the mass of the seeds produced. Finally, within‐infructescence variance in seed mass was not affected by the number of fathers. These results suggest that neither differential allocation nor sibling rivalry has any effect on the average mass of seeds in multiply sired fruits in D. scandens. Overall, the limited paternal effects observed in most studies and the possibility of diversification bet hedging among flowers (but not within flowers), suggest that multiple paternity within fruits or infructescence is unlikely to affect seed mass in a large number of angiosperm species.     

Effects of floral display size on male and female reproductive success in Mimulus ringens

Background and Aims

The number of flowers blooming simultaneously on a plant may have profound consequences for reproductive success. Large floral displays often attract more pollinator visits, increasing outcross pollen receipt. However, pollinators frequently probe more flowers in sequence on large displays, potentially increasing self-pollination and reducing pollen export per flower. To better understand how floral display size influences male and female fitness, we manipulated display phenotypes and then used paternity analysis to quantify siring success and selfing rates.

Methods

To facilitate unambiguous assignment of paternity, we established four replicate (cloned) arrays of Mimulus ringens, each consisting of genets with unique combinations of homozygous marker genotypes. In each array, we trimmed displays to two, four, eight or 16 flowers. When fruits ripened, we counted the number of seeds per fruit and assigned paternity to 1935 progeny.

Key Results

Siring success per flower declined sharply with increasing display size, while female success per flower did not vary with display. The rate of self-fertilization increased for large floral displays, but siring losses due to geitonogamous pollen discounting were much greater than siring gains through increased self-fertilization. As display size increased, each additional seed sired through geitonogamous self-pollination was associated with a loss of 9·7 seeds sired through outcrossing.

Conclusions

Although total fitness increased with floral display size, the marginal return on each additional flower declined steadily as display size increased. Therefore, a plant could maximize fitness by producing small displays over a long flowering period, rather than large displays over a brief flowering period.     

Plant size,geitonogamy and seed set in Ipomopsis aggregata

Summary We used powdered fluorescent dyes to estimate receipt of self vs. outcross pollen in the self-incompatible species Ipomopsis aggregata (Polemoniaceae). Flowers on small and large plants received equal amounts of outcross pollen, whereas flowers on large plants received more self pollen, so the proportion of self pollen delivered through geitonogamy increased with plant size. In natural populations emasculation of all flowers on a plant raised average seed set per flower from 5.19 to 6.99 and also raised fruit set, though not significantly. From these results one expects a negative correlation between plant size and seeds per flower. The opposite trend was observed in a sample of plants in the field, suggesting that deleterious effects of geitonogamy on female fecundity in large plants can be overruled by other factors such as size-related fruit or seed abortion. Results are discussed in relation to the evolution of gynodioecy.     

The messenger matters: Pollinator functional group influences mating system dynamics

The incredible diversity of plant mating systems has fuelled research in evolutionary biology for over a century. Currently, there is broad concern about the impact of rapidly changing pollinator communities on plant populations. Very few studies, however, examine patterns and mechanisms associated with multiple paternity from cross‐pollen loads. Often, foraging pollinators collect a mixed pollen load that may result in the deposition of pollen from different sires to receptive stigmas. Coincident deposition of self‐ and cross‐pollen leads to interesting mating system dynamics and has been investigated in numerous species. But, mixed pollen loads often consist of a diversity of cross‐pollen and result in multiple sires of seeds within a fruit. In this issue of Molecular Ecology, Rhodes, Fant, and Skogen ( 2017 ) examine how pollinator identity and spatial isolation influence multiple paternity within fruits of a self‐incompatible evening primrose. The authors demonstrate that pollen pool diversity varies between two pollinator types, hawkmoths and diurnal solitary bees. Further, progeny from more isolated plants were less likely to have multiple sires regardless of the pollinator type. Moving forward, studies of mating system dynamics should consider the implications of multiple paternity and move beyond the self‐ and cross‐pollination paradigm. Rhodes et al. ( 2017 ) demonstrate the importance of understanding the roles that functionally diverse pollinators play in mating system dynamics.     

RELATIVE SUCCESS OF SELF AND OUTCROSS POLLEN COMPARING MIXED- AND SINGLE-DONOR POLLINATIONS IN AQUILEGIA CAERULEA

Flowers frequently receive both self (S) and outcross (OC) pollen, but S pollen often sires proportionally fewer seeds. Failure of S pollen can reflect evolved mechanisms that promote outcrossing and/or inbreeding depression expressed during seed development. The relative importance of these two processes was investigated in Aquilegia caerulea, a self-compatible perennial herb. In the field I performed single-donor (S or OC) and mixed-donor (S plus OC) pollinations to compare the relative success of both pollen types at various stages from pollen germination to seed maturity. Single-donor S pollinations produced significantly fewer and lighter seeds (x decrease = 12% and 3%, respectively) than OC pollinations. Abortion rates differed by an average of 38% whereas fertilization rates differed by only 5%, indicating that most differences in seed number arose postzygotically. This suggests that inbreeding depression was responsible for most failure of S pollen. One prezygotic effect measured was that 10% fewer S than OC pollen tubes reached ovaries after 42 hr, suggesting S pollen might fertilize proportionately fewer ovules after mixed pollination. Using allozyme markers, I found mixed-donor pollinations produced significantly more and heavier outcrossed than selfed seeds. However, the proportion of selfed seed, fertilized ovules, and aborted seeds for mixed-donor fruits were each predictable from pollen performance in single-donor fruits, suggesting that differential paternity is best explained by inbreeding depression during seed development. Even given these similarities between mixed- and single-donor fruits in the relative performance of S and OC pollen, both individual seed weight and seed set were significantly higher in multiply-sired fruits.     

Effects of pollen load size on seed paternity in wild radish: the roles of pollen competition and mate choice

For sexual selection to be important in plants, it must occur at pollen load sizes typical of field populations. However, studies of the impact of pollen load size on pollen competition have given mixed results, perhaps because so few of these studies directly examined the outcome of mating when pollen load size was varied. We asked whether seed paternity after mixed pollination of wild radish was affected by pollen load sizes ranging from 22 to 220 pollen grains per stigma. We examined the seed siring abilities of 12 pollen donors across 11 maternal plants. Seed paternity was statistically indistinguishable across the pollen load sizes even though, overall, the pollen donors sired different numbers of seeds. This lack of effect of pollen load size on seed paternity may have occurred because fruit abortion and early abortion or failure of fertilization of seeds increased as load size decreased. Thus, failures of fruits and seeds sired by poorer pollen donors may keep seed paternity constant across pollen load sizes.     

The incidence and selection of multiple mating in plants

Mating with more than one pollen donor, or polyandry, is common in land plants. In flowering plants, polyandry occurs when the pollen from different potential sires is distributed among the fruits of a single individual, or when pollen from more than one donor is deposited on the same stigma. Because polyandry typically leads to multiple paternity among or within fruits, it can be indirectly inferred on the basis of paternity analysis using molecular markers. A review of the literature indicates that polyandry is probably ubiquitous in plants except those that habitually self-fertilize, or that disperse their pollen in pollen packages, such as polyads or pollinia. Multiple mating may increase plants'' female component by alleviating pollen limitation or by promoting competition among pollen grains from different potential sires. Accordingly, a number of traits have evolved that should promote polyandry at the flower level from the female''s point of view, e.g. the prolongation of stigma receptivity or increases in stigma size. However, many floral traits, such as attractiveness, the physical manipulation of pollinators and pollen-dispensing mechanisms that lead to polyandrous pollination, have probably evolved in response to selection to promote male siring success in general, so that polyandry might often best be seen as a by-product of selection to enhance outcross siring success. In this sense, polyandry in plants is similar to geitonogamy (selfing caused by pollen transfer among flowers of the same plant), because both polyandry and geitonogamy probably result from selection to promote outcross siring success, although geitonogamy is almost always deleterious while polyandry in plants will seldom be so.     

Effects of pollination timing on seed paternity and seed mass in Silene latifolia (Caryophyllaceae)

Background and Aims

Competition among genetically different pollen donors within one recipient flower may play an important role in plant populations, increasing offspring genetic diversity and vigour. However, under field conditions stochastic pollen arrival times may result in disproportionate fertilization success of the first-arriving pollen, even to the detriment of the recipient plant''s and offspring fitness. It is therefore critical to evaluate the relative importance of arrival times of pollen from different donors in determining siring success.

Methods

Hand pollinations and genetic markers were used to investigate experimentally the effect of pollination timing on seed paternity, seed mass and stigmatic wilting in the the dioecious plant Silene latifolia. In this species, high prevalence of multiply-sired fruits in natural populations suggests that competition among different donors may often take place (at fertilization or during seed development); however, the role of variation due to pollen arrival times is not known.

Key Results

First-arriving pollen sired significantly more seeds than later-arriving pollen. This advantage was expressed already before the first pollen tubes could reach the ovary. Simultaneously with pollen tube growth, the stigmatic papillae wilted visibly. Individual seeds were heavier in fruits where one donor sired most seeds than in fruits where both donors had more even paternity shares.

Conclusions

In field populations of S. latifolia, fruits are often multiply-sired. Because later-arriving pollen had decreased chances of fertilizing the ovules, this implies that open-pollinated flowers often benefit from pollen carry-over or pollinator visits within short time intervals, which may contribute to increase offspring genetic diversity and fitness.Key words: Reproduction, reproductive success, pollen, siring success, microsatellite DNA, paternity, pollen tube growth, seed mass, Silene alba, stigma wilting     

POLLINATOR EFFECTIVENESS AND SEED SET IN POPULATIONS OF AGALINIS STRICTIFOLIA (SCROPHULARIACEAE)

Examining variation in pollinator effectiveness and seed production resulting from single pollinator visits can provide a deeper understanding of how pollinators may influence reproduction in plant populations. When comparing populations, differences in the number of seeds produced from single pollinator visits to flowers may not always be attributable to differences in pollen deposition, but rather to differences in plant fecundity or resource availability. Pollinator effectiveness and seed production were studied for two populations over a 4-year period and were measured using single bee visit manipulations of flowers. No significant difference in pollinator effectiveness (pollen deposited on stigmas) was observed between the two populations. However, a significant difference between the two populations was observed in the number of seeds produced per flower. The Wellhouse population produced approximately three times as many seeds/flower from a single pollinator visit as did the Firefly Meadow population. Within each population, pollinators (Bombus pennsylvanicus and Apis mellifera) did not differ in the number of pollen grains deposited on stigmas or seeds produced per flower from single visit experiments. Differences in plant density, pollen viability, and ovules per flower also could not account for a significant amount of the variation. A resource augmentation experiment (water and fertilizer application) resulted in a decrease in seeds per flower per bee visit for the water treatment at the Wellhouse population only. For both populations, pollen deposition, pollen viability, and ovules per flower were unaffected by the resource augmentation. Alternative possibilities for the observed differences in seeds per flower per bee visit are discussed.     

Pollen dispersal in Yucca filamentosa (Agavaceae): the paradox of self-pollination behavior by Tegeticula yuccasella (Prodoxidae)

We investigated pollen dispersal in an obligate pollination mutualism between Yucca filamentosa and Tegeticula yuccasella. Yucca moths are the only documented pollinator of yuccas, and moth larvae feed solely on developing yucca seeds. The quality of pollination by a female moth affects larval survival because flowers receiving small amounts of pollen or self-pollen have a high abscission probability, and larvae die in abscised flowers. We tested the prediction that yucca moths primarily perform outcross pollinations by using fluorescent dye to track pollen dispersal in five populations of Y. filamentosa. Dye transfers within plants were common in all populations (mean ± 1 SE, 55 ± 3.0%), indicating that moths frequently deposit self-pollen. Distance of dye transfers ranged from 0 to 50 m, and the mean number of flowering plants between the pollen donor and recipient was 5 (median = 0), suggesting that most pollen was transferred among near neighbors. A multilocus genetic estimate of outcrossing based on seedlings matured from open-pollinated fruits at one site was 94 ± 6% (mean ± 1 SD). We discuss why moths frequently deposit self-pollen to the detriment of their offspring and compare the yucca-yucca moth interaction with other obligate pollinator mutualisms in which neither pollinator nor plant benefit from self-pollination.     

Hierarchical patterns of paternity within crowns of Albizia julibrissin (Fabaceae)

The floral architecture and phenology of the tree species Albizia julibrissin (Fabaceae) offer the potential for flowers within inflorescences to share common pollen donors. Patterns of paternity within individual tree crowns may differ among isolated individuals and those in populations due to differences in pollinator foraging behavior. To determine how genetic diversity is partitioned within individual seed pools and whether these patterns differ among isolated and population trees, we obtained all fruits from three inflorescences from four clusters from three isolated trees and from three population trees in Athens, Georgia. We assayed 14 polymorphic allozymes to genotype all progeny within singly sired fruits to determine the multilocus genotype of each fruit's pollen donor. Inflorescences had multiple pollen donors, but simulation analyses revealed that redundancy of pollen donors tended to be more likely within inflorescences than randomly across the crown. Analysis of genetic and genotypic diversity indicated that individual maternal trees received pollen from many donors in uneven frequencies. Results suggest that isolated trees receive pollen from slightly fewer pollen donors and experience more within-plant pollinator movement than trees in populations. However, isolated trees receive qualitatively similar pollen from many sources, suggesting that these trees are not effectively isolated and that pollen moves long distances in this species.     

Pollination ecology of Christmas Bells (Blandfordia nobilis): Effects of pollen quantity and source on seed set

The effect of a number of experimental handpollination regimens on the numbers of seeds set by Blandfordia nobilis flowers was assessed. Individuals were found to be self-incompatible and to require pollinator visits to set fruit. Pollen limited the female component of reproduction in the two populations studied while pollen source did not have a significant effect on the numbers of seeds set. Experiments using a stuffed honeyeater indicated that maximal seed set could be achieved after just one probe by the pollinator. Appreciable heterogeneity in flowering phenology, the number of seeds naturally setting and the number of seeds setting as a result of hand-pollinations existed within a small area across a single flowering season.     

The reproductive biology of a distylous tree, Sarcotheca celebica (Oxalidaceae) in Sulawesi, Indonesia

Sarcotheca celebica is a tree endemic lo Sulawesi (and Kabaena Island). Kike many species in the Oxalidaceae it is heterostylous (here distylous). The small red flowers, which last less than one day, are produced in loose inflorescences which bloom over a long flowering season (several months). There are two whorls of stamens in each plant, which overlap in length, perhaps indicating a tristylous origin. Long–styled and short–styled plants differed in the measurements of stamens, styles and pollen grains. Only a small amount of pollen was produced by long–styled plants. Effective insect pollinators were mainly large Hymenoptcra, especially Xylocopa species, which visited many flowers and different trees in rapid succession. A wide diversity of insects visited flowers of both morphs, and numbers visiting each morph were approximately equal. The only successful experimental pollinations were from pollen of short–styled plants onto stigmas of long–styled plants. Automatic self–pollination did not occur. In nature not all flowers produced fruit, some fruits were set with no seeds and a low number of seeds was set in all fruits. The differences in seed set per fruit between short–styled, long–styled and experimental crosses indicate that pollinator visits were insufficient for maximum seed set in some fruits, but selective abortion of seeds must also be occurring. We suggest that S. celebica may represent an intermediate stage in the evolution of dioecy from distyly, with the short–styled flowers making their major genetic contribution through pollen and long–styled flowers through ovules.     

A non‐pollinating moth inflicts higher seed predation than two co‐pollinators in an obligate pollination mutualism

1. Mutualisms are relationships of mutual exploitation, in which interacting species receive a net benefit from their association. In obligate pollination mutualisms (OPMs), female pollinators move pollen between the flowers of a single plant species and oviposit eggs within the female flowers that they visit. 2. Competition between co‐occurring pollinator species is predicted to increase pollinator virulence, i.e. laying more eggs or consuming more seeds per fruit. Plants involved in OPMs frequently host various non‐pollinating seed parasites and parasitoids that may influence the outcome of the mutualism. Quantifying the prevalence of parasites and parasitoids and competition between pollinators is important for understanding the factors that influence OPM evolutionary stability. 3. This study investigated the pollination mutualism occurring between the leaf flower plant, Breynia oblongifolia, and its co‐pollinating Epicephala moths. A third moth, Herpystis, also occurs in B. oblongifolia fruits as a non‐pollinating seed parasite. 4. Breynia oblongifolia fruits were collected to quantify seed predation and compare seed predation costs between the three moth species. Results showed that the larvae of the two pollinator species consume similar numbers of seeds, and that adults deposit similar numbers of eggs per flower. As such, no evidence of increases in virulent behaviours was detected as a result of competition between co‐pollinators. 5. By contrast, the seed parasite Herpystis consumed more seeds than either pollinator species, and fruit crops with a high proportion of Herpystis had significantly lower net seed production. 6. This work adds to the growing understanding of the ecology and dynamics of plant–pollinator mutualisms.     

Evaluation of pollinator effectiveness based on pollen deposition and seed production in a gynodieocious alpine plant,Cyananthus delavayi

Examining variations in pollinator effectiveness can enhance our understanding of how pollinators and plants interact. Pollen deposition and seed production after a single visit by a pollinator are often used to estimate pollinator effectiveness. However, seed production is not always directly related to pollen deposition because not all pollen grains that are deposited on a stigma are compatible or conspecific. In the field, we tested pollinator effectiveness based on pollen deposition and the resulting seed production after single visits by different pollinator groups in a gynodieocious alpine plant Cyananthus delavayi (Campanulaceae). Our results showed that mean pollen deposition was generally inconsistent with mean seed production when comparisons were performed among different pollinator groups and sexes. In general, the correlations were not significant between pollen deposition and seed production in both perfect and female flowers after single visits by halictid bees, bumble bees, and hoverflies. We suggest seed set of virgin flowers after single visits is a more reliable indicator of pollinator effectiveness than pollen deposition and would be a better indicator of pollinator effectiveness for future studies.     

Movement herkogamy in Kosteletzkya virginica: Effect on reproductive success and contribution to pollen receipt and reproductive assurance

Herkogamy may act as a mechanism to reduce interference between the reproductive functions of female and male organs, but too great a distance between stigmas and anthers may also decrease the outcross pollen transfer and male and female fitness. Our goal was to quantify the effect of movement herkogamy in Kosteletzkya virginica on reproductive success and its contribution to pollen receipt and reproductive assurance. Field investigations and hand-pollination experiments were performed to test: (1) the relationship between herkogamy before curvature of un-pollinated lobes and reproductive success under pollinator exclusion; (2) the contribution of movement herkogamy to pollen receipt; and (3) the relationship between pollen load and seed set. We noted that variation in herkogamy before curvature of un-pollinated lobes did not affect the outcome of autogamous self-pollination measured by fruit set and mean number of seeds per fruit. Under natural conditions, 39% of pollen grains deposited per flower were from autogamous self-pollination via movement herkogamy resulting in contact between anthers and stigmas. The relationship between the amount of pollen grains and the number of seeds per capsule was highly significant. Flowers producing four or five seeds received more pollen grains than those producing only one seed. Our data provides experimental evidence that movement herkogamy, which decreases the separation between anthers and stigmas and results in delayed self-pollination, contributes to pollen receipt and further enhances seed set when pollinators are scarce or absent.