Selective nectar robbing in a gynodioecious plant (Glechoma longituba) enhances female advantage

Nectar robbing not only affects the reproductive fitness of the plant but it may also potentially affect the pollination dynamics of the associated coflowering individuals. In this study, we established that the nectar robber Xylocopa sinensis robs nectar only from the hermaphrodite ramets of the gynodioecious plant Glechoma longituba but not from the female ramets. In populations with high rates of nectar robbing, this results in hermaphrodite ramets having reduced seed set whereas the female ramets have a slightly increased seed set. We hypothesize that selective nectar robbing confers an advantage to female individuals and thus ensures their maintenance in gynodioecious populations. Results of controlled experiments indicated that the reduction in the amounts of nectar available occasioned by nectar robbing resulted in some legitimate pollinators switching to visiting flowers on female rather than hermaphrodite ramets. This resulted in lower pollination rates and seed set for hermaphrodites and higher pollination rates and seed set for females. This study presents a previously unreported mechanism causing female advantage in gynodioecious plants.     

Sex expression,female frequency,and reproductive output in a gynodioecious clonal herb, <Emphasis Type="Italic">Glechoma longituba</Emphasis> (Lamiaceae)

We investigated the sex morphs and frequency of females in 24 natural populations of the clonal, gynodioecious species Glechoma longituba. In addition to the presence of hermaphrodites and females, there were some individuals with intermediate sex expression that could not be categorized as either morph. The majority of populations contained a predominance of hermaphrodites, although female frequency varied from 0 to 100%. The sexual expression of individual ramets did not change over three consecutive years or when ramets were transplanted to different populations, but it did change over the course of a flowering season. Seeds from females weighed more than those from hermaphrodites. The seed set of hermaphrodites was relatively constant across populations; the seed set of females was higher than that of hermaphrodites in most populations, but lower in populations in which females occurred at a very high frequency because of pollen limitation. This led to a negative correlation being detected between the seed set of females and the frequency of females in a population. We postulated that the adjustment of sex expression within seasons could be an adaptive mechanism of reproductive assurance in this system.     

Floral micromorphology and microsporogenesis of the gynodioecious herb Glechoma longituba (Lamiaceae)

Gynodioecy, the phenomenon of having both hermaphrodite and female (i.e. male‐sterile) individuals within the same population, is an important intermediate step in the evolution of separate sexes in flowering plants. In this study, we investigated the floral micromorphology and microsporogenesis of the gynodioecious herb Glechoma longituba from four natural populations in Korea. The floral micromorphological characters of the different sex morphs were examined and compared using scanning electron microscopy (SEM), and the ultrastructure of microspores during microsporogenesis was studied. We also examined the development of anthers and pollen grains in the three sexual morphs (i.e. hermaphrodites, females, and gynomonoecious, i.e. individuals with a mixture of female and hermaphroditic flowers) by embryological investigation. The major difference in anther development between the three phenotypes was the early disintegration of the tapetal cells in the anthers of female flowers. While mature fertile pollen grains were found in both hermaphrodite and gynomonoecious phenotypes, females did not produce any pollen grains. In addition, both fertile and sterile pollen grains in gynomonoecious phenotypes were frequently observed. The results of the present study indicate that floral micromorphological characters were not distinct between sexual morphs of G. longituba, except for the structure of the inner cell surfaces of the anther. The observed tapetum abnormalities and degeneration of pollen grains in both gynomonoecious phenotypes and females may be the consequence of inbreeding depression in hermaphrodites.     

The roles of female and hermaphroditic flowers in the gynodioecious–gynomonoecious Silene littorea: insights into the phenology of sex expression

Some gynodioecious species have intermediate individuals that bear both female and hermaphroditic flowers. This phenomenon is known as a gynodioecious–gynomonoecious sexual system. Gender expression in such species has received little attention in the past, and the phenologies of male and female functions have also yet to be explored. In this study, we examined variations in gender patterns, their effects on female reproductive success and sex expression in depth throughout the flowering period in two populations. The studied populations of Silene littorea contained mostly gynomonoecious plants and the number of pure females was very low. The gynomonoecious plants showed high variability in the total proportion of female flowers. In addition, the proportion of female flowers in each plant varied widely across the flowering season. Although there was a trend towards maleness, our measures of functional gender suggested that most plants transmit their genes via both pollen and ovules. Fruit set and seed set were not significantly different among populations; in contrast, flower production significantly varied between the two populations – and among plants – with consequent variation in total seed production. Conversely, gender and sex expression were similar in both populations. Plants with higher phenotypic femaleness did not have higher fruit set, seed set or total female fecundity. The mating environment fluctuated little across the flowering period, but fluctuations were higher in the population with low flower production. We therefore conclude that the high proportion of gynomonoecious individuals in our studied populations of S. littorea may be advantageous for the species, providing the benefits of both hermaphroditic and female flowers.     

Sexual differences in reproductive characters and pollinator attractiveness in gynodioecious Glechoma longituba (Lamiaceae)

We quantified the differences in floral characters and attractiveness to flower visitors under natural conditions between the sexual types in the gynodioecious plant Glechoma longituba. We also manipulated flowers by altering corolla size or nectar volume, or by removing anthers, to examine the effect of these primary and secondary attractants (i.e. rewards and advertisements) on attractiveness. A change in corolla size and shape reduced visiting frequency and pollen load. Removal of anthers did not affect visiting rates, but significantly reduced pollination rates and stigmatic pollen load. A decrease in the nectar volume of a flower was associated with a reduction in handling time and pollen loads on stigmas. These results show that corolla size is an important advertisement to pollinators (particularly at greater distance), which associate hermaphrodite flowers with a larger corolla and a larger volume of nectar than female flowers. We found that artificial changes in population structure affected the behavior of pollinators as well as the pollination rates of flowers. We suggest that the pattern of distribution of hermaphrodite and female clones in a population may serve to avoid pollen limitation in a female clone or patch. This effect may ensure female reproductive success and allow for the maintenance of female individuals in natural populations of this gynodioecious plant.     

Population Size,Pollination and Breeding System of Silene stockenii Chater (Caryophyllaceae), an Annual Gynodioecious Species of Southern Spain

The distribution area, phenology, sex polymorphism, floral characteristics and breeding system of Silene stockenii (Caryophyllaceae), a narrowly endemic annual species of southern Spain, were studied. Only five populations were found in a total area of 2 ha. Silene stockenii is a gynodioecious species with fully female, fully hermaphrodite and intermediate plants bearing hermaphrodite, male-sterile, and partially male-sterile flowers. Male-sterile flowers are typically smaller than hermaphrodites. Nectar production was significantly higher in hermaphrodite plants and during the female phase of hermaphrodite flowers. The red flowers appear during the spring (March-May) and are pollinated by long-tongued Bombyliidae. Hand pollinations revealed that the species is self-compatible; however, natural self-pollination is rare due to marked protandry. Hand pollination significantly increased the number of seeds per fruit and seed set, indicating limited pollination in the field. In controlled pollinations female plants of S. stockenii produced higher seed set than hermaphrodite plants, but in freely pollinated plants fruit set and seed production was similar in both morphs, indicating that pollinators do not discriminate in favour of hermaphrodite plants.     

Males are cheaper,or the extreme consequence of size/age‐dependent sex allocation: sexist gender diphasy in Fritillaria montana (Liliaceae)

The bulbous geophyte Fritillaria montana is partially self‐compatible and capable of switching gender. Small flowering plants produce only single male flowers, but larger plants produce hermaphrodite or, rarely, male and hermaphrodite flowers. Eight populations in peninsular Italy were sampled to determine the frequency and size distributions of male and hermaphrodite plants, and to determine the relationship of plant size to male and hermaphrodite flower production. Male plants were significantly smaller than hermaphrodites and made up 14.5–47.8% (100% in one small population) of flowering plants within populations. There were no significant differences in male fitness among female‐sterile and hermaphrodite flowers, as they both possessed full and comparable fertilizing power. Therefore, the gender variation observed in F. montana is likely to depend on resource‐dependent sex allocation. From an evolutionary perspective, we highlight the occurrence of similar mechanisms of gender variation in other representatives of the order Liliales. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 323–333.     

Pre-dispersal seed predation in gynodioecious Geranium sylvaticum is not affected by plant gender or flowering phenology

Sex-specific interactions with antagonists may explain female maintenance in gynodioecious populations if seeds produced by hermaphroditic plants are preferred over seeds produced by female plants. Among antagonistic interactions, pre-dispersal seed predators have received relatively little attention even though they may exert sex-specific selective pressures on the evolution of floral and flowering traits. In this work, I investigate temporal variation in seed predation in gynodioecious Geranium sylvaticum, where in addition to female and hermaphrodite individuals, plants with an intermediate sexual expression are also present in most populations. Specifically, I examined whether seed predation is linked to flowering phenology, plant gender, and sexual dimorphism in floral and seed traits over the flowering season using an experimental field population. Within the population, I selected female, intermediate, and hermaphrodite plants with different timing of flowering onset (early, mid, or late), and collected seeds across the fruiting period. Seeds were weighed and examined for seed predator damage. The results show that the three genders experienced similar levels of seed predation attack regardless of their flowering phenology, and that overall seed predation was not related to changes in seed production or seed mass. These results suggest that sexual dimorphism in seed predation cannot be responsible for female maintenance in this species.     

Nectar robbing of a carpenter bee and its effects on the reproductive fitness of Glechoma longituba (Lamiaceae)

The floral biology and pollination process of Glechoma longituba (Nakai) Kuprian, a clonal gynodioecious, perennial herb that is widely distributed in China was investigated in natural populations. During visits to the flowers of G. longituba, the carpenter bee—Xylocopa sinensis mainly displayed nectar-robbing behavior with minimal pollination. Nectar robbing behavior began at the onset of flowering and continued for about 3 weeks ending at about the middle of the flowering period. A total of 18.6% floral visits in this period were by nectar robbers, with about 90% of the flowers in the study populations being subjected to two or two nectar-robbing episodes. During controlled experiments, lower pollination efficiency was recorded for X. sinensis compared to legitimate pollinators. Pollination by the robber-like pollinator X. sinensis during the early-mid phase of the flowering season yielded seeds of 16.16%. Although nectar robbing by the carpenter bee seemed to have a slight enhancing effect on seed set in G. longituba, this effect was effectively masked by the more pronounced detrimental effect of nectar robbing. Experiments indicated that nectar robbing by the carpenter bee reduced seed production by more than 26%, largely owing to the consequent shortening of the life span of robbed flowers. Furthermore, 10.43% of the ovules and 13.04% of the nectaries in the robbed flowers were damaged, thus causing a decrease or entire loss of reproductive opportunity in the robbed flowers. In addition, a higher number of pollen grains remained on the androecia of robbed flowers indicating that nectar robbing may have a lowering effect on male fitness in G. longituba.     

Variation in sex ratio, morph-specific reproductive ecology and an experimental test of frequency-dependence in the gynodioecious Kallstroemia grandiflora (Zygophyllaceae)

An enduring puzzle in gynodioecious species is the great variation in female frequency seen among populations. We quantified sex ratio in 44 populations of gynodioecious Kallstroemia grandiflora. Then, we measured pollinator visitation, pollen deposition, autonomous selfing rate and pollen limitation of females. Finally, using experimental populations, we tested whether female fitness responds to the frequency of female plants. We found broad variability in sex ratio among populations (0-44% female). Hermaphrodite flowers received more pollinator visits and pollen grains than females, and bagged hermaphrodite flowers produced fruits. However, we found no evidence of pollen limitation in females. In experimental populations, female plants showed no evidence of frequency-dependent pollinator visitation, fruit set, seed set or total seed mass. These results do not support frequency-dependent variation in fitness as a major mechanism affecting female frequencies in K. grandiflora. Within the context of this study, pollinators are abundant and pollinator movement appears to operate at a large enough scale to overcome the potential reproductive disadvantages of producing solely female flowers.     

The effects of floral display on pollinator visitation vary among populations ofPhacelia linearis (Hydrophyllaceae)

Summary Individual plants in gynodioecious populations ofPhacelia linearis (Hydrophyllaceae) vary in flower gender, flower size, and flower number. This paper reports the effects of variation in floral display on the visitation behaviour of this species' pollinators (mainly pollen-collecting solitary bees) in several natural and three experimental plant populations, and discusses the results in terms of the consequences for plant fitness. The working hypotheses were: (1) that because female plants do not produce pollen, pollen-collecting insects would visit hermaphrodite plants at a higher rate than female plants and would visit more flowers per hermaphrodite than per female; and (2) that pollinator arrival rate would increase with flower size and flower number, the two main components of visual display. These hypotheses were generally supported, but the effects of floral display on pollinator visitation varied substantially among plant populations. Hermaphrodites received significantly higher rates of pollinator arrivals and significantly higher rates of visits to flowers than did females in all experimental populations. Flower size affected arrival rate and flower visit rate positively in natural populations and in two of the three experimental populations. The flower size effect was significant only among female plants in one experimental population, and only among hermaphrodites in another. The effect of flower number on arrival rate was positive and highly significant in natural populations and in all experimental populations. In two out of three experimental populations, insects visited significantly more flowers per hermaphrodite than per female and visited more flowers on many-flowered plants than on few-flowered plants, but neither effect was detected in the third experimental population. Because seed production is not pollen-limited in this species, variation in pollinator visitation behaviour should mainly affect the male reproductive success of hermaphrodite plants. These findings suggest that pollinator-mediated natural selection for floral display inP. linearis varies in space and time.     

Wise flies: a pre‐dispersal seed predator prefers hermaphrodites over females in the gynodioecious Polemonium foliosissimum

1. Oviposition choices can profoundly affect offspring performance. Oviposition decisions of the dipteran pre‐dispersal seed predator, Hylemya sp. (Diptera: Anthomyiidae), when choosing among sex morphs of their host‐plant—Polemonium foliosissimum Hook—were evaluated. Polemonium foliosissimum is gynodioecious, with female and hermaphrodite sex morphs that differ in flower size. 2. It was asked: Do female flies preferentially oviposit on hermaphrodite plants and, if so, are oviposition choices correlated with flower size? Is larval survivorship higher on hermaphrodite plants and, if so, is larval success correlated with flower size? Can the differences in oviposition and/or larval success be explained by slight differences in flowering phenology between the sexes? 3. Hermaphrodite flowers received 45% more Hylemya eggs than females. Although hermaphrodites had larger petals and sepals than females, egg loads were not correlated with petal or sepal size. Larval survival was 30% greater on hermaphrodites than females and higher on plants with larger sepals. However, the difference in sepal area between genders did not fully explain larval survival differences. Egg numbers declined over weeks, but differences in egg loads between the sex morphs were not attributable to a slight phenological delay of females. Larval survival declined over the season; however, larval survival differences between sex morphs were consistent. 4. Hylemya preferentially oviposited on hermaphrodites where their larvae had a significantly greater survival rate compared with females. The present results add to the knowledge that intra‐specific choices have consequences for phytophagous insects and that the relationship between antagonists and their gynodioecious host plants is complex.     

Sex‐biased seed predation in gynodioecious Dianthus superbus var. longicalycinus (Capryophyllaceae) and differential influence of two seed predator species on the floral traits

Gynodioecy, the co‐occurrence of hermaphrodite and female individuals within a species, is maintained by differential reproductive success between sexes. Recently, researchers recognized that not only pollinators but also herbivores are important agents in the evolution and maintenance of gynodioecy, when herbivory is hermaphrodite biased. In this study, we investigated whether there is hermaphrodite‐biased herbivory in a gynodioecious plant, Dianthus superbus var. longicalycinus, and if so, what floral traits influenced hermaphrodite‐biased herbivory. We measured flower morphology (flower diameter, calyx tube length, corolla height and petal width) and phenology of flowers of female individuals, hermaphrodites and gynomonoecious individuals in a natural population. We also investigated seed predation and predator species. At the study site, Sibinia weevils (Curculionidae; Coleoptera) and Coleophora moths (Coleophoridae; Lepidoptera) were common pre‐dispersal seed predators in this species. The weevil appeared early in the flowering season, and weevil predation correlated with flower phenology. Because female individuals did not flower early in the season, weevil predation was less frequent in female individuals. Moth predation correlated with calyx length. The calyx length of flowers of female individuals was smaller than those of hermaphrodites, but a direct comparison of moth predation rates failed to find a significant difference among sex morphs. We found that the two seed predators had different effects on floral traits in D. superbus var. longicalycinus. We suggest that weevil predation contributes to the maintenance of gynodioecy because female individuals successfully escaped weevil predation by flowering late. It remains unclear why flower phenology is different among sex morphs.     

Male‐biased hermaphrodites in a gynodioecious shrub,Daphne jezoensis

Gynodioecy, a state where female and hermaphrodite plants coexist in populations, has been widely proposed an intermediate stage in the evolutionary pathway from hermaphroditism to dioecy. In the gynodioecy–dioecy pathway, hermaphrodites may gain most of their fitness through male function once females invade populations. To test this prediction, comprehensive studies on sex ratio variation across populations and reproductive characteristics of hermaphrodite and female phenotypes are necessary. This study examined the variation in sex ratio, sex expression, flower and fruit production and sexual dimorphism of morphological traits in a gynodioecious shrub, Daphne jezoensis, over multiple populations and years. Population sex ratio (hermaphrodite:female) was close to 1:1 or slightly hermaphrodite‐biased. Sex type of individual plants was largely fixed, but 15% of plants changed their sex during a 6‐year census. Hermaphrodite plants produced larger flowers and invested 2.5 times more resources in flower production than female plants, but they exhibited remarkably low fruit set (proportion of flowers setting fruits). Female plants produced six times more fruits than hermaphrodite plants. Low fruiting ability of hermaphrodite plants was retained even when hand‐pollination was performed. Fruit production of female plants was restricted by pollen limitation under natural conditions, irrespective of high potential fecundity, and this minimised the difference in resources allocated to reproduction between the sexes. Negative effects of previous flower and fruit production on current reproduction were not apparent in both sexes. This study suggests that gynodioecy in this species is functionally close to a dioecious mating system: smaller flower production with larger fruiting ability in female plants, and larger flower production with little fruiting ability in hermaphrodite plants.     

Nectar Sugar Production across Floral Phases in the Gynodioecious Protandrous Plant Geranium sylvaticum

Many zoophilous plants attract their pollinators by offering nectar as a reward. In gynodioecious plants (i.e. populations are composed of female and hermaphrodite individuals) nectar production has been repeatedly reported to be larger in hermaphrodite compared to female flowers even though nectar production across the different floral phases in dichogamous plants (i.e. plants with time separation of pollen dispersal and stigma receptivity) has rarely been examined. In this study, sugar production in nectar standing crop and secretion rate were investigated in Geranium sylvaticum, a gynodioecious plant species with protandry (i.e. with hermaphrodite flowers releasing their pollen before the stigma is receptive). We found that flowers from hermaphrodites produced more nectar than female flowers in terms of total nectar sugar content. In addition, differences in nectar production among floral phases were found in hermaphrodite flowers but not in female flowers. In hermaphrodite flowers, maximum sugar content coincided with pollen presentation and declined slightly towards the female phase, indicating nectar reabsorption, whereas in female flowers sugar content did not differ between the floral phases. These differences in floral reward are discussed in relation to visitation patterns by pollinators and seed production in this species.     

POPULATION SEX STRUCTURE AND REPRODUCTIVE FITNESS IN GYNODIOECIOUS SIDALCEA MALVIFLORA MALVIFLORA (MALVACEAE)

The spatial distribution of females and hermaphrodites within gynodioecious populations is expected to exert considerable selective pressure on gender fitness through pollen limitation of seed set. If pollen flow is predominantly local, seed set in individual plants may be sensitive to the proximity of pollen donors; pollen limitation of seed set may occur if hermaphrodites are locally rare. Under such circumstances, female fitness will be negatively frequency dependent and hermaphrodite fitness will be positively frequency dependent. Given local seed dispersal, a nonrandom clumped distribution of the genders is expected in gynodioecious populations due to the heritability of gender in gynodioecious species. If gender fitness is frequency dependent, such structure should favor hermaphrodites and select against females. To test this hypothesis, I quantified the distribution of the genders in terms of nearest neighbors and neighborhood sex ratio in two populations of gynodioecious Sidalcea malviflora malviflora. I then measured the effect of neighborhood sex ratio on open-pollinated seed set and pollen limitation in both manipulated and unmanipulated neighborhoods. Results indicate that the genders have a patchy distribution and that both genders are pollen limited and show an increase in seed set with an increase in neighborhood hermaphrodite frequency. The observed population sex structure favors hermaphrodites and disadvantages females. These results highlight the importance that population-level traits can have in determining individual fitness and the evolution of sex ratios in gynodioecious species.     

GENDER VARIATION AND SEXUAL DIFFERENCES IN REPRODUCTIVE CHARACTERS AND SEED PRODUCTION IN GYNODIOECIOUS GERANIUM MACULATUM

Variation in sex expression, flowering pattern, and seed production was studied in the self-compatible perennial herb Geranium maculatum in Illinois and Indiana. In a survey of eight populations, female (male-sterile) plants were found in seven (frequencies ranging from 0.5% to 24.3% [median 4.2%]), and intermediate plants (with partly reduced male function) were found in all populations. Gender variation and sexual differences in reproductive characters were studied in detail in two populations. One population consisted of 5% female, 27% intermediate, and 68% hermaphrodite plants; the other consisted of 1% female, 20% intermediate, and 79% hermaphrodite plants. Females produced smaller flowers and began flowering earlier than hermaphrodites. Intermediates produced flowers of an intermediate size and began flowering as early as females. Females and hermaphrodites did not differ in flower number, vegetative size, flowering frequency, survival, or seed size. However, females produced 1.6 times more seeds than hermaphrodites. Intermediates produced 1.3–1.6 times more seeds than hermaphrodites. Some between-year variation in sex expression was observed. Hand-pollination with outcross pollen produced two to four times as many seeds as hand-pollination with self-pollen. A lower outcrossing rate in hermaphrodites than in females may at least partly explain the lower seed set in hermaphrodites. The higher seed production of females, and possibly the high fecundity of the intermediates, should contribute to the maintenance of this sexual polymorphism.     

Small but attractive: female‐biased nectar production and floral visitors in a dimorphic shrub

• In sexually dimorphic species, hermaphrodite flowers in gynodioecious species or male flowers in dioecious species are often larger and produce more nectar than their conspecific female flowers. As a consequence, hermaphrodite or male flowers frequently receive more pollinator visits.
• Sex ratio, flower size, floral display, nectar production and floral visits were evaluated in two natural populations of Fuchsia thymifolia, a morphologically gynodioecious but functionally subdioecious insect‐pollinated shrub.
• Sex ratio did not differ from the expected 1:1 in the two studied populations. As expected, hermaphrodite flowers were larger than female flowers, but in contrast to the general pattern, hermaphrodite flowers did not produce nectar or produced much less than female flowers. Flower visitors were flies (68%) and bumblebees (24%), both of which showed a preference for female flowers. No sex difference was detected in either flower longevity or floral display across the flowering season.
• Higher nectar production by females may attract more pollinators, and may be a strategy to enhance female reproductive success in this species. Finally, floral dimorphism and insect preferences did not seem to hamper the maintenance of sub‐dioecy or prevent the evolution of dioecy in F. thymifolia.

     

Gender variation and the evolution of dioecy in Wurmbea dioica (Liliaceae)

A major obstacle for empirical tests of hypotheses concerning the evolution of dioecy in flowering plants is the limited number of species that possess both cosexual and dioecious populations. Wurmbea dioica (Liliaceae) is a diminutive, fly-pollinated geophyte native to temperate Australia. Marked geographical variation of floral traits is evident, particularly with respect to sex expression. A survey of phenotypic gender in 45 populations from Western Australia (WA), South Australia (SA), Victoria (Vic) and the Australian Capital Territory (ACT) revealed two contrasting patterns. Populations in SA, Vic, and ACT were uniformly dimorphic for gender, containing female and male plants, whereas populations in WA were either monomorphic or dimorphic. In most dimorphic populations varying numbers of male plants produced hermaphrodite flowers (male inconstancy). There was a significant negative relationship between female frequency and the proportion of inconstant male plants. Depending on region and population, male plants produced more flowers of larger size than females. In WA monomorphic populations often occurred on rich, moist soils at high density, whereas dimorphic populations were more commonly found at lower density on shallow soils in drier areas. In an area of sympatry, plants with contrasting sexual systems flowered at different times and were ecologically differentiated. The patterns of gender variation in W. dioica indicate that dioecy has evolved via the gynodioecious pathway. The spread of females in monomorphic populations may be favoured where ecological conditions result in increased selfing and inbreeding depression in hermaphrodites.     

Pollen limitation and variation in floral longevity in gynodioecious Potentilla tanacetifolia

Pollination limitation is common in flowering plants and is thought to be a factor driving the evolution of floral traits.The plasticity of floral longevity to pollination may be an adaptation of plants to pollen limitation.However,this adaptation is less critical in short-lived flowers.To evaluate pollen limitation and the plasticity of floral longevity to pollination in Potentilla tanacetifolia,a gynodioecious herb with short-lived flowers,we analyzed its breeding system,tested sex-differential pollen limitation,and compared variations in floral display size in natural populations in Duolun County,Inner Mongolia,China.Hand pollination experiments and pollinator exclusion treatments revealed that P tanacetifolia is self-compatible and non-autonomously apomictic and shows sex-differential pollen limitation.The plasticity of floral longevity to pollination was observed; the floral duration of female plants was prolonged by approximately 3-4 hours with pollination exclusion treatment.Moreover,the percentage of flowers displayed on female plants during pollination exclusion treatment was significantly higher than that during natural pollination.Under natural pollination conditions,the percentage of flowers displayed on female plants was significantly higher than on hermaphrodite plants.Furthermore,approximately 50％ of the pollen grains spread out of the anthers of hermaphrodite flowers within 2 h of anthesis; the number of pollen grains adhering to the stigmas of hermaphrodite flowers was significantly higher than that adhering to female flowers when flowers shed their petals.These results indicate that variation in floral longevity may be an adaptive strategy to pollination conditions for gynodioecious P tanacetifolia.