Relationship between floral longevity and sex allocation among flowers within inflorescences in Aquilegia buergeriana var. oxysepala (Ranunculaceae)

Understanding the fitness of plants with inflorescences requires examining variation in sex allocation among flowers within inflorescences. We examined whether differences in the duration of the male and female phases of flowering lead to variation in sex allocation and reproductive success among flowers within inflorescences. In 2002 and 2003, we quantified floral longevity, floral sex allocation, and reproductive success between the first and the second flowers within inflorescences in a protandrous species, Aquilegia buergeriana var. oxysepala. Floral longevity was greater in the first flowers than in the second ones in both years. The male phase lasted longer, and the initial number of pollen grains and the number of pollen grains removed were greater in the first flowers than in the second ones in both years. Within first flowers, the number of pollen grains removed was greater in flowers that had longer male phases, thus duration of the male phase may positively affect male reproductive success in the first flowers. The female phase lasted longer and the number of ovules was greater in the first flowers than in the second only in 2002. However, seed production per flower and female phase duration in both years were not significantly related. The variation in the number of pollen grains among flowers in this species may be caused by the variation in male phase duration.     

Size-dependent sex allocation within flowers of the annual herb Clarkia unguiculata (Onagraceae): ontogenetic and among-plant variation

The relative allocation of resources to male and female functions may vary among flowers within and among individual plants for many reasons. Several theoretical models of sex allocation in plants predict a positive correlation between the resource status of a flower or individual and the proportion of reproductive resources allocated to female function. These models assume that, independent of resource status, a negative correlation exists between male and female investment. Focusing on the allocation of resources within flowers, we tested these theoretical predictions and this assumption using the annual Clarkia unguiculata (Onagraceae). We also sought preliminary evidence for a genetic component to these relationships. From 116 greenhouse-cultivated plants representing 30 field-collected maternal families, multiple flowers and fruits per plant were sampled for gamete production, pollen?:?ovule ratio, seed number, ovule abortion, seed biomass/fruit, mean individual seed mass, and petal area. If sex allocation changes as predicted, then (1) assuming that flowers produced early have access to more resources than those produced later, basal flowers should exhibit a higher absolute and proportional investment in female function than distal flowers and (2) plants of high resource status (large plants) should produce flowers with a higher proportional investment in female function than those of low resource status. Within plants, variation in floral traits conformed to the first prediction. Among plants and families, no significant effects of plant size (dry stem biomass) on intrafloral proportional sex allocation were observed. We detected no evidence for a negative genetic correlation between male and female investment per flower, even when controlling for plant size.     

Temporal variation in floral display size and individual floral sex allocation in racemes of Narthecium asiaticum (Liliaceae)

We analyzed the effects of temporal variation in floral display size (number of flowers open at one time on a plant) on the rate of pollen removed and receipt of individual flowers for the sequential blooming plant Narthecium asiaticum (Liliaceae). Because of the acropetal blooming of this species, the display sizes when upper flowers opened was much greater than the display sizes when lower flowers opened. Our experiments revealed that large displays lead to a high rate of pollen removal from individual flowers, though they do not lead to a high rate of ovule fertilization. Consequently, the rate of pollen grains removed per flower by pollinators was greater in upper flowers than in lower flowers. The pattern of sex allocation in individual flowers within a raceme was consistent with such variation. Namely, both maleness [stamen mass/(stamen mass + pistil mass)] and pollen?:?ovule ratio were larger in upper flowers. We suggest that the temporal variation in display size, in addition to such factors as dichogamy and pollinator directionality, also produces variation in the probability of successful pollen transfer from individual flowers that may cause the variation in the sex allocation of individual flowers.     

Floral display, pollinator visitation and reproductive success in the dioecious perennial herb Wurmbea dioica (Liliaceae)

Floral traits that increase attractiveness to pollinators are predicted to evolve through selection on male function rather than on female function. To determine the importance of male-biased selection in dioecious Wurmbea dioica, we examined sexual dimorphism in flower size and number and the effects of these traits on pollinator visitation and reproductive success of male and female plants. Males produced more and larger flowers than did females. Bees and butterflies responded to this dimorphism and visited males more frequently than females, although flies did not differentiate between the sexes. Within sexes, insect pollinators made more visits to and visited more flowers on plants with many flowers. However, visits per flower did not vary with flower number, indicating that visitation was proportional to the number of flowers per plant. When flower number was experimentally held constant, visitation increased with flower size under sunny but not overcast conditions. Flower size but not number affected pollen removal per flower in males and deposition in females. In males, pollen removal increased with flower size 3 days after flowers opened, but not after 6 days when 98% of pollen was removed. Males with larger flowers therefore, may have higher fitness not because pollen removal is more complete, but because pollen is removed more rapidly providing opportunities to pre-empt ovules. In females, pollen deposition increased with flower size 3 days but not 6 days after flowers opened. At both times, deposition exceeded ovule production by four-fold or more, and for 2 years seed production was not limited by pollen. Flower size had no effect on seed production per plant and was negatively related to percent seed set, implying a tradeoff between allocation to attraction and reproductive success. This indicates that larger flower size in females is unlikely to increase fitness. In both sexes, gamete production was positively correlated with flower size. In males, greater pollen production would increase the advantage of large flowers, but in females more ovules may represent a resource cost. Selection to increase flower size and number in W. dioica has probably occurred through male rather than female function. Received: 15 June 1997 / Accepted: 12 February 1998     

SEX ALLOCATION IN THE MONOECIOUS HERB BEGONIA SEMIOVATA

Sex-allocation models predict that the evolution of self-fertilization should result in a reduced allocation to male function and pollinator attraction in plants. The evolution of sex allocation may be constrained by both functional and genetic factors, however. We studied sex allocation and genetic variation for floral sex ratio and other reproductive traits in a Costa Rica population of the monoecious, highly selfing annual Begonia semiovata. Data on biomass of floral structures, flower sex ratios, and fruit set in the source population were used to calculate the average proportion of reproductive allocation invested in male function. Genetic variation and genetic correlations for floral sex ratio and for floral traits related to male and female function were estimated from the greenhouse-grown progeny of field-collected maternal families. The proportion of reproductive biomass invested in male function was low (0.34 at flowering, and 0.07 for total reproductive allocation). Significant among-family variation was detected in the size (mass) of individual male and female flowers, in the proportion of male flowers produced, and in the proportion of total flower mass invested in male flowers. Significant among-family variation was also found in flower number per inflorescence, petal length of male and female flowers, and petal number of female flowers. Except for female petal length, we found no difference in the mean value of these characters between selfed and outcrossed progeny, indicating that, with the possible exception of female petal length, the among-family variation detected was not the result of variation among families in the level of inbreeding. Significant positive phenotypic and broad-sense genetic correlations were detected between the mass of individual male and female flowers, between male and female petal length, and between number of male and number of female flowers per inflorescence. The ratio of stamen-to-pistil mass (0.33) was low compared to published data for autogamous species with hermaphroditic flowers, suggesting that highly efficient selfing mechanisms may evolve in monoecious species. Our results indicate that the study population harbors substantial genetic variation for reproductive characters. The positive genetic correlation between investment in male and female flowers may reflect selection for maximum pollination efficiency, because in this self-pollinating species, each female flower requires a neighboring male flower to provide pollen.     

慈姑花的开放式样及其花粉流

对一野生慈姑（ＳａｇｉｔａｒｉａｔｒｉｆｏｌｉａＬ．）居群的性表达状态及其花粉流散布规律进行了观测。慈姑雌雄同株,单株雄花数是雌花数的３．６倍。雌雄花单花期均为１ｄ,但二者开放式样不同。尽管雌花的数目较少,但在１ｄ内开放较多的花,其花的开放速率比雄花快。在居群水平上表现出雌雄花比例随时间大幅度波动。在传粉者进行的２６１２次访花活动中,传粉者表现出偏“雌性”访问,对每朵雌花的访问是雄花的１．４倍。用番红染色法标记慈姑的花粉运动表明,花的不同开放式样影响花粉流的散布。当雄花数占高比例时,花粉主要在邻近的个体间散布;而雄花的比例较低、雌花相对较多时,花粉远距离散布的强度加大。     

雌全同株植物三脉紫菀花期偏雄的个体大小依赖的性别分配

经典的虫媒传粉植物个体大小依赖的性别分配模型通常预期:分配给雌性功能的资源比例将随着个体大小的增大而增加;但一些研究表明,花期个体大小依赖的性别分配模式表现出随个体大小增大而偏雄的趋势.我们以植株高度衡量个体大小,从花和花序两个水平上研究了雌花、两性花同株植物三脉紫菀(Aster ageratoides)花期个体大小依赖的性别分配策略.随着植株高度的增大,植株产生的头状花序数量增加,表明三脉紫菀投入到繁殖的资源不是固定不变的,而是随个体大小增大而增加的.在花和花序水平上,繁殖资源在雌雄性别功能之间的分配均表现为随个体大小的增大而更偏雄的模式,即花粉/胚珠比增加,产生花粉的两性花占两性花和雌花总花数的比例升高.这些结果与花期个体越大、性别分配越偏雄的预期一致.花期更偏雄的性别分配可能有助于植物在花期通过输出花粉提高雄性适合度,从而实现个体适合度的最大化.     

Differential self‐fertilization rates in response to variation in floral traits within inflorescences of Aquilegia buergeriana var. oxysepala (Ranunculaceae)

To assess variation in the proportion of self‐fertilized seeds among flowers within inflorescences and the relationship between floral traits and the rate of self‐fertilization, the proportion of self‐fertilized seeds among individual flowers was estimated using ten microsatellite markers in self‐compatible plants of Aquilegia buergeriana var. oxysepala. Within‐inflorescence variation in floral traits, such as the duration of the male and female phases, flower size, herkogamy and the number of pollen grains and ovules in two natural populations, were investigated. The first flower in an inflorescence produced more seeds and a higher proportion of self‐fertilized seeds than the second flower. The higher proportion of self‐fertilized seeds in the first flowers was accompanied by a higher number of pollen grains and ovules in the bud stage and the female phase. These results indicate that the high proportion of self‐fertilized seeds in the first flowers in an inflorescence may be due to the high number of remaining pollen grains in the female phase. This suggests that variation in floral traits within inflorescences affects seed quality and quantity among flowers within inflorescences.     

Pollen and Resource Limitation in Veratrum nigrum L. （Liliaceae）, an Andromonoecious Herb

Pollen limitation and resource limitation were invoked to account for the pattern that flowering plants produce more flowers and ovules than fruits and seeds. This study aimed to determine their relative importance in Veratrum nigrum, a self-compatible, perennial, andromonoecious herb. In order to determine whether female production was limited by pollen grains on stigmas or by available resources, we performed supplemental hand pollination in three populations, male-flower-bud removal in three other populations, and emasculation of hermaphroditic flowers in still another population, resulting in a total of seven populations experimentally manipulated. Across the three populations, supplemental hand pollination did not significantly increase fruit set, seed number per fruit, and total seed production per individual, nor did emasculation of hermaphroditic flowers. Taken together, our results suggest that pollen grains deposited on stigmas were abundant enough to fertilize all the ovules. Male-flower-bud removal significantly increased the mean size of hermaphroditic flowers in all three populations. Female reproductive success was increased in one population, but not in the other two populations possibly due to heavy flower/seed predation. We concluded that the female reproductive success of V. nigrum was not limited by pollen grains but by available resources, which is consistent with Bateman＇s principle. Furthermore, the female reproduction increase of male-flower-bud removal individuals might suggest a trade-off between male and female sexual functions.     

ANDROMONOECY IN ZIGADENUS PANICULATUS (LILIACEAE): SPATIAL AND TEMPORAL PATTERNS OF SEX ALLOCATION

I describe patterns of sex allocation and gamete packaging in the andromonoecious lily Zigadenus paniculatus. In this species, pistil length was continuously, but bimodally, distributed within plants, and smaller pistils contained fewer mature ovules. In hermaphrodite flowers, ovule number per flower increased with blooming rank in small plants but decreased with blooming rank in large plants. Flowers with pistils less than three-fourths stamen length almost never produced fruits and were classified as males. The pedicel, tepals, stamens, and pistil of hermaphrodite flowers were all heavier than those of males. Hermaphrodite flowers were concentrated on the terminal raceme, males on the lower racemes. In combination with acropetal blooming, this spatial separation of flower types resulted in a seasonal decline in the proportion of open flowers that were hermaphrodite. However, individual flowers were protandrous, so that the population sex ratio, initially strongly male-biased, declined as the season progressed. Hand pollinations showed that plants were self-incompatible. Inflorescence size was positively correlated with bulb size, and plants with large inflorescences had a higher proportion of male flowers. Nutrient supplementation had no effect on inflorescence size, but increased the proportion of hermaphrodite flowers. Nutrient-supplemented plants also began blooming earlier than controls. I discuss these patterns in relation to the adaptive significance of andromonoecious breeding systems.     

Gender variation of sequential inflorescences in a monoecious plant Sagittaria trifolia (Alismataceae)

In protogynous plants, female flowers of early blooming plants are at a reproductive disadvantage because they cannot set fruit due to the lack of available pollen. To study this phenomenon, gender expression of the monoecious herb Sagittaria trifolia was investigated over the entire flowering season in two field and two cultivated populations in Hubei and Hunan Provinces, China. In racemes of S. trifolia, flowers open sequentially from bottom to top, with female flowers opening first followed by male flowers. This creates a temporal separation of sexes in the species. Under field conditions small plants are often male, with production of both male and female flowers increasing with plant size. Femaleness increased among sequential inflorescences since female flower production increased whereas male flower production did not. Seed production was greater in large inflorescences because they contain more female flowers, and the number of ovules increased in female flowers at basal positions within the raceme. A consistent pattern of high seed set was observed in flowers from both field and cultivated populations. About 1 % of unfertilized ovules resulted from no pollination and 2 % of the seeds produced were only partly developed due to resource limitation. In the first inflorescence of the six experimental populations, 6.7-40.0 % of individuals produced only male flowers, and female flowers of 1.9-6.5 % individuals were aborted. The occurrence of male flowers in early blooming inflorescences could be an adaptive strategy to conserve resources and enhance pollination of female flowers in protogynous S. trifolia.     

雄全同株植物簇花芹花期性别分配与开花式样

簇花芹(Soranthus meyeri)是古尔班通古特沙漠中常见的、具雄全同株性系统的伞形科多年生早春短命植物。该文对簇花芹花期性比(两性花数/总花数)与植株大小的关系及其开花式样进行了研究, 重点对花期大小依赖的性别资源分配进行了讨论。结果表明: 2006-2008年簇花芹群体水平的性比分别为0.69 ± 0.03、0.62 ± 0.03和0.69 ± 0.02, 彼此间无显著差异( p > 0.05), 表明其性比是相对稳定的, 可能受遗传因素的控制。雄花生物量与花粉量均比两性花的小, 说明产生雄花比产生两性花所需资源少。一级复伞形花序比二级复伞形花序具有较多的两性花, 说明前者易从植株上获得资源用于增加雌性适合度; 而后者产生较多的雄花以避免在雌性功能上资源投入的浪费, 增大花展示以吸引更多传粉者来增加花粉输出总量, 提高其整体适合度。植株水平的性比与地上营养器官的生物量间呈正相关关系, 说明较大个体对雌性功能的投资较大, 雌性繁殖成功受资源限制。复伞形花序内各伞形花序几乎同时向心开放, 且所有两性花及花序均为雄性先熟, 雌雄阶段完全分离, 但一级复伞形花序比二级复伞形花序早开放约5天, 彼此开花重叠期约为1天。这些特征对于一级复伞形花序进行异株异花授粉以及植株内不同级别花序间的同株异花传粉、避免雌雄功能间的干扰具有重要意义。     

Effects of floral sexual investment and dichogamy on floral longevity

Aims Floral longevity, the duration that a flower remains open and functional, varies greatly among species. Variation in floral longevity has been considered to be optimal strategy for resource allocation under different ecological conditions, mainly determined by the rates of pollination and cost of flower maintenance. However, it is unclear whether an intrinsic factor, floral sexual investment, constrains evolution of floral longevity. The theoretical model also predicts that dichogamy favors long-lived flowers, but empirical studies to test this prediction remain unexplored.Methods To examine the effect of floral sexual investment on floral longevity, we measured flower size together with pollen and ovule production in 37 sympatric flowering plants in a natural community. The duration of the female and male phase in 21 protandrous species and floral longevity of the other 16 adichogamous species were documented in the field.Important findings Floral longevity varied from 1 day to 15 days, while pollen number per flower varied from 643 to 710880 and ovule number per flower from 1 to 426 in the 37 species. Flower size was correlated with pollen production as well as ovule production. Floral longevity was positively related to pollen production but not to ovule production. Consistent with the prediction that dichogamy favors long-lived flowers, we found the floral longevity of protandrous species was significantly longer than that of adichogamous species. In the protandrous species, pollen production per flower was observed to be positively related to male duration, while ovule production was not related to female duration. Our analyses of variation in floral longevity and sexual investment among different species suggest that the floral sexual investment could be an intrinsic factor contributing to the selected floral longevity, particularly the male phase, and that high pollen production could potentially increase pollen removal, i.e. male productive success.     

Gender variation in Actinidia deliciosa,the kiwifruit

Summary Flower and fruit characters were measured in ten female, five male and five fruiting male selections of A. deliciosa var deliciosa (A. Chev) Liang and Ferguson. Flowers from female vines had functional pistils, which contained many ovules. Stamens appeared to be fully developed but produced only empty pollen grains. Flowers from male vines had functional stamens that produced high percentages of pollen grains with stainable cytoplasmic contents. Pistils did not contain ovules and were generally small with vestigial styles. Fruiting male vines had both staminate and bisexual flowers. Staminate flowers were similar to those found on strictly male vines. Bisexual flowers produced ovules and stainable pollen. Pistils were smaller than in pistillate flowers. Although the three flower sexes differed in style length, ovary dimensions and ovules per carpel, staminate and bisexual flowers were similar in number of flowers per inflorescence, stamen filament length, pollen stainability, inflorescence rachis length and carpel number, and differed from pistillate flowers in these characters. The three flower sexes had similar sepal and petal numbers. The fruit of fruiting males were considerably smaller than those of females. Low ovule number appears to be the major factor limiting fruit size in the fruiting males studied. Prospects for developing hermaphroditic kiwifruit cultivars through breeding are discussed.     

Determinants of sex allocation in a gynodioecious wild strawberry: implications for the evolution of dioecy and sexual dimorphism

One evolutionary pathway from plants with combined male and female functions (hermaphroditism) to those with separate sexes (dioecy) involves females coexisting with hermaphrodites (gynodioecy). The research presented here explores sex allocation in Fragaria virginiana (a gynodioecious wild strawberry), within the context of theory on the gynodioecy–dioecy transition. By growing clonally replicated plants in the greenhouse and surveying six populations in situ, I evaluated the effects of plant size, genotype, sexual identity, population of origin and female frequency on sex allocation. I found significant positive effects of plant size on most sex allocation traits studied. In addition to strong sex-specific allocation patterns, I found significant broad-sense heritabilities for all traits, suggesting that plants could respond to selection. Moreover, there was a negative genetic correlation between pollen production and fruit set per flower within hermaphrodites, lending support to a basic assumption of sex allocation theory. On the other hand, several sex allocation traits, namely pollen and ovules per flower in hermaphrodites, were positively genetically correlated, suggesting that they may act to constrain the evolution of sexual dimorphism. Populations differed in the frequency of females, and females were more prevalent on sites with lower soil moisture and where hermaphrodites were least likely to produce fruit, suggesting that females’ seed fitness relative to that of hermaphrodites may be strongly environment-dependent in this species.     

How geitonogamous selfing affects sex allocation in hermaphrodite plants

Does the mode of self-pollination affect the evolutionarily stable allocation to male vs. female function? We distinguish the following scenarios. (1) An ‘autogamous’ species, in which selfing occurs within the flower prior to opening. The pollen used in selfing is a constant fraction of all pollen grains produced. (2) A species with ‘abiotic pollination’, in which selfing occurs when pollen dispersed in one flower lands on the stigma of a nearby flower on the same plant (geitonogamy). The selfing rate increases with male allocation but a higher selfing rate does not mean a reduced export of pollen. (3) An ‘animal-pollinated’ species with geitonogamous selfing. Here the selfing rate also increases with male allocation, but pollen export to other plants in the population is a decelerating function of the number of simultaneously open flowers. In all three models selfing selects for increased female allocation. For model 3 this contradicts the general opinion that geitonogamous selfing does not affect evolutionarily stable allocations. In all models, the parent benefits more from a female-biased allocation than any other individual in the population. In addition, in models 2 and 3, greater male allocation results in more local mate competition. In model 3 and in model 2 with low levels of inbreeding depression, hermaphroditism is evolutionarily stable. In model 2 with high inbreeding depression, the population converges to a fitness minimum for the relative allocation to male function. In this case the fitness set is bowed inwards, corresponding with accelerating fitness gain curves. If the selfing rate increases with plant size, this is a sufficient condition for size-dependent sex allocation (more allocation towards seeds in large plants) to evolve. We discuss our results in relation to size-dependent sex allocation in plants and in relation to the evolution of dioecy.     

ALLOCATION TO ATTRACTIVE STRUCTURES IN ANIMAL-POLLINATED FLOWERS

An optimal allocation model was developed for the evolutionarily stable size of attractive structures of flowers (ESA) in animal-pollinated plants. It was assumed that a plant can change the sizes of attractive and sexual structures of a flower and the size and the number of flowers. In the absence of constraints on flower size, the ESA should not depend on the frequency of self-fertilization or the sexuality of plants. However, with constraints on flower size, the ESA decreases with increasing self-fertilization, except in special cases, and it is possible that males have a larger or a smaller ESA than females. Thus, differences in self-fertilization and sexuality alone cannot explain the differences in allocation among nondomesticated plants. In addition, attractive structures can contribute more to male or female function depending on the cost of gamete production, pollination efficiency for pollen and ovules, and pollinator availability.     

RESPONSES OF FLORAL TRAITS TO SELECTION ON PRIMARY SEXUAL INVESTMENT IN SPERGULARIA MARINA: THE BATTLE BETWEEN THE SEXES

Two widespread assumptions underlie theoretical models of the evolution of sex allocation in hermaphroditic species: (1) resource allocations to male and female function are heritable; and (2) there is an intrinsic, genetically based negative correlation between male and female reproductive function. These assumptions have not been adequately tested in wild species, although a few studies have detected either genetic variation in pollen and ovule production per flower or evidence of trade-offs between male and female investment at the whole plant level. It may also be argued, however, that in highly autogamous, perfect-flowered plant taxa that exhibit genetic variation in gamete production, strong stabilizing selection for an efficient pollen:ovule ratio should result in a positive correlation among genotypes with respect to mean ovule and mean pollen production per flower. Here we report the results of a three-generation artificial selection experiment conducted on a greenhouse population of the autogamous annual plant Spergularia marina. Starting with a base population of 1200 individuals, we conducted intense mass selection for two generations, creating four selected lines (high and low ovule production per flower; high and low anther production per flower) and a control line. By examining the direct and correlated responses of several floral traits to selection on gamete production per flower, we evaluated the expectations that primary sexual investment would exhibit heritable variation and that resource-sharing, variation in resource-garnering ability, or developmental constraints mold the genetic correlations expressed among floral organs. The observed direct and correlated responses to selection on male and female gamete production revealed significant heritabilities of both ovule and anther production per flower and a significant negative genetic correlation between them. When plants were selected for increased ovules per flower over two generations, ovule production increased and anther production declined relative to the control line. Among plants selected for decreased anthers per flower, we observed a decline in anther production and an increase in ovule production relative to the control line. In contrast, the lines selected for low ovules per flower and for high anthers per flower exhibited no evidence for significant genetic correlations between male and female primary investment. Correlated responses to selection also indicate a genetically based negative correlation between the production of normal versus developmentally abnormal anthers (staminoid organs); a positive correlation between the production of ovules versus staminoid organs; and a positive correlation between the production of anthers and petals. The negative relationship between male versus female primary investment supports classical sex allocation theory, although the asymmetrical correlated responses to selection indicate that this relationship is not always expressed.     

毛翠雀花花序内的性分配和繁殖成功

两性花植物花序内不同位置的性分配和繁殖成功一般存在差异,通常认为资源竞争、结构效应和交配环境是形成这种差异的主要原因。为了研究雄性和雌性繁殖资源在花序内不同位置间的最优分配问题,该文以青藏高原高寒草甸典型高山植物毛翠雀花为材料,通过比较花序内不同位置的花部特征和种子性状,对其花序内的性分配模式和雌性繁殖成功进行研究,并通过观察传粉者运动特点以及人工去花和补授花粉实验,探讨花序内资源竞争和交配环境对繁殖资源分配的影响。结果表明:(1)不同位置间的雄蕊数、雄蕊鲜重/雌蕊鲜重、花粉数及花粉胚珠比从花序基部到上部显著增加,而雌蕊鲜重和胚珠数逐渐减少,表现出上部花偏雄的性分配;上部花的结籽率显著低于基部花和中部花,不同位置间的发育种子数/果实和发育种子重/果实随着花位置的升高而显著降低,说明基部花具有更佳的雌性繁殖成效。(2)去花处理后,剩余果实的单个种子重/果实显著增加,但发育种子数/果实没有显著增加;而给上部花人工补授异花花粉后,位置间结籽率的差异消失,说明传粉限制而非资源竞争导致了花序内位置依赖的种子生产模式。(3)毛翠雀花雄性先熟的开花特征,以及传粉者苏氏熊蜂从花序基部到上部的定向访花行为,导致了花序内交配环境的变化。综上结果表明,毛翠雀花花序内的性分配和繁殖成功差异是对交配环境适应的结果,对其在高山环境中实现雌雄适合度最优化具有重要意义。