Variation in Floral Sex Allocation and Reproductive Success in Sequentially Flowering Inflorescence of Corydalis remota var. lineariloba(Fumariaceae)

In hermaphroditic plants, female reproductive success often varies among different positions within an inflorescence. However, few studies have evaluated the relative importance of underlying causes such as pollen limitation, resource limitation or architectural effect, and few have compared male allocation. During a 2-year investigation, we found that female reproductive success of an acropetally flowering species, Corydalis remota Fisch. ex Maxim. var. lineariloba Maxim. was significantly lower in the upper late developing flowers when compared with the lower early flowers. Supplementation with outcross pollen did not improve female reproductive success of the upper flowers, while removal of the lower developing fruits significantly increased female reproductive success of the upper flowers in both years, evidencing resource limitation of the upper flowers. Female production in upper flowers was greatly improved by simultaneous pollen supplementation of the upper flowers and removal of the lower fruits, suggesting that, when resources are abundant, pollen may limit the female reproductive success of the upper flowers. The less seed mass in the upper flowers didn＇t increase in all treatments due to architecture. In the upper flowers, ovule production was significantly lower and the pollen ： ovule ratio was significantly higher. These results suggest that male-biased sex allocation in the upper flowers may lead to increased male reproductive success, whereas the lower flowers have higher female reproductive success.

Plasticity of floral sex allocation within inflorescences of hermaphrodite Aconitum gymnandrum

Aims sex allocation in plants is often plastic,enabling individuals to adjust to variable environments.However,the predicted male-biased sex allocation in response to low resource conditions has rarely been experimentally tested in hermaphroditic plants.in particular,it is unknown whether distal flowers in linear inflorescences show a larger shift to male allocation relative to basal flowers when resources are reduced.in this study,we measure position-depend-ent plasticity of floral sex allocation within racemes of Aconitum gymnandrum in response to reduced resource availability.Methods using a defoliation treatment in the field applied to potted plants from a nested half-sibling design,we examined the effects of the treatment,flower position,family and their interactions.Important Findingsallocation to male function increased with more distal flower posi-tion,while female allocation either did not change with position or declined at the most distal flowers.Defoliation significantly reduced the mass of both the androecium and gynoecium,but not anther number or carpel number.gynoecial mass declined more strongly with defoliation than did androecial mass,resulting in a significant increase in the androecium/gynoecium ratio as predicted by sex allocation theory.Plastic responses of androecium mass and gynoecium mass were affected by flower position,with less mass lost in basal flowers,but similar plastic magnitude in both sexual traits across flower position lead to consistent variation in the androecium/gynoecium ratio along the inflorescence.a sig-nificant treatment*paternal family interaction for the androecium/gynoecium ratio is evidence for additive genetic variation for plastic floral sex allocation,which means that further evolution of alloca-tion can occur.

Function of male and hermaphroditic flowers and size-dependent gender diphasy of Lloydia oxycarpa (Liliaceae) from Hengduan Mountains

Although hermaphroditism is common in flowering plants, unisexual flowers occur in many plant taxa,forming various sexual systems. However, the sexual system of some plants is difficult to determine morphologically, given that their sex expression may be influenced by both genetic and environmental factors. Specifically, androdioecy(the coexistence of both male and hermaphroditic individuals in the same population) has often been confused with the gender diphasy, a gender strategy in which plants change their sex expression between seasons. We studied the reproductive function of male and hermaphroditic flowers of Lloydia oxycarpa(Liliaceae), in order to investigate its sexual system and determine whether it is a gender-diphasic species. We found that although male flowers occur in a considerable number of plants, relative to hermaphrodites, they did not exhibit any significant reproductive advantage in terms of flower size, pollen quantity, attractiveness to visitors or siring success. In addition, this plant has spontaneous self-pollination and showed no inbreeding depression. These results render the maintenance of male individuals almost impossible. Furthermore, a considerable number of individuals changed their sex in successive years. The sex expression was found to be related to bulb size and dry weight, with larger individuals producing hermaphroditic flowers and smaller individuals producing male flowers. These results suggest that L. oxycarpa is not an androdioecious plant but represents a rare case of size-dependent gender diphasy.

Both small and large plants are likely to produce staminate(male)flowers in a hermaphrodite lily

Resource allocation to female and male function may vary among individual plants in species with variable sex expression.Size-dependent sex allocation has been proposed in hermaphrodites,in which female-biased allocation may increase with plant size.In many hermaphrodites with large floral displays,however,later-produced flowers tend to be functionally male.This paradoxical relationship between female and male function and plant size remains poorly understood.The subalpine lily Lilium lankongense has individuals of three sexual types:males with only staminate flowers,hermaphrodites with only perfect flowers,and andromonoecious plants with both perfect and staminate flowers.Here we tested theoretical predictions of size-dependent sex allocation in L.lankongense by measuring plant height and flower number of individuals of each sex at five field sites in the mountainous region of Shangri-La,southwestern China.To investigate variation in phenotypic gender,we identified sex expression of 457 individuals one year later.Our investigation showed that male plants,which usually produced one flower,were significantly smaller than and ro monoecious and hermaphrodite plants.In addition,the total flower numbers of andromonoecious and hermaphrodite plants increased significantly with plant size.Large individuals were more likely to produce terminal staminate flowers,as there were more flowers in andromonoecious than in hermaphrodite individuals.Non-flowered plants were significantly smaller than flowering ones.Perfect flowers had significantly larger petals and pistils than staminate flowers,but they did not differ in dry weight of stamens.Our findings indicate that when plants are small,the less costly sex is favored,consistent with the‘size-advantage hypothesis’.When plants are large,both female and male investments change isometrically,as later-produced flowers tend to be functionally male.

Sex ratio variation and sex determination in the mallee dragon Ctenophorus fordi

Recent evidence suggests that many Australian agamids show temperature-dependent sex determination(TSD)with variation in sex determining mechanisms among closely related taxa.However,as shown in other vertebrates,sex ratios can also be influenced by genetic or phenotypic differences among females in their propensity to produce sons or daughters,and these influences might confound any thermal effects of incubation per se.To address these issues,we investigated the determinants of sex ratios in the mallee dragon Ctenophorus fordi,together with a detailed analysis of karyotypes.There was no detectable variation in sex ratios arising from variation among females,clutches or incubation temperatures,which might indicate genetic sex determination for this species.However,there was no evidence of cytologically distinct sex chromosomes using standard banding techniques.The sex ratio pattern in C.fordi strongly contrasts with the results for the congener Ctenophorus pictus,where sex ratios show variation among females.Thus,Australian agamids offer promising opportunities to address fundamental issues in sex ratio biology.

Multiple aspects of the maternal reproductive investmentin a polytocous species:What do mothers really control?

One of the factors facilitating the expansion and proliferation of wild boar Sus scrofa is the plasticity of its reproductive biology.Nevertheless,the real influence of maternal and environmental factors on number and sex of the offspring is stll controversial.While the litter size was shown to be related with the maternal condition,the strength of this relation remains to be understood,together with the possible role played by environmental conditions.Analogously,it is unclear whether wild boar females can adjust their offspring sex.We investigated multiple aspects of wild boar maternal investment by means of a 10-year dataset of female reproductive traits and a set of biologically meaningful environmental variables.The maternal condition slightly affected the litter size but not the offspring sex,and environment did not affect the litter size or the offspring sex.Moreover,mothers did not cope with the higher costs entailed by producing sons by placing them in the most advantageous intrauterine position,nor by allocating less resources on daughters.Our set of results showed that the female reproductive investment is quite rigid in comparison with other aspects of wild boar reproductive biology.Wild boar females seem to adopt a typical rstrategy,producing constantly large litters and allocating resources on both sexes regardless of internal and external conditions.Such strategy may be adaptive to cope with environmental unpredictability and an intense human harvest,contributing to explain the extreme success of wild boar within human-dominated landscapes.

Direct and cross-generational effects of reproduction on fitness and behavioral variability in male-biased environments

Population structure determines individuals’interactions and trade-offs with evolutionary consequences.Male-biased populations increase intrasexual competition and intersexual harassment,reducing female resource acquisition,and thus,resources availability for the following generation.We analyzed direct and cross-generational effects of male harassment in two generations of damselflies(Odonata).We exposed adult females to treatments with different sex-ratio and density(balanced and male-biased)to modify the male harassment level.We analyzed female fecundity,fertility,and number of faecal deposits as an indirect measure of resources acquisition.We studied female flight performance after repeated exposures to males.We analyzed survivorship,development,exploration,thigmotaxis,and feeding latency of larvae produced by the experimental females.In both generations,we analyzed four metrics of behavior:mean value,interindividual differences in plasticity,intra-individual unpredictability,and repeatability.Mating duration increased in male-biased treatment,whereas female resources acquisition and fertility decreased.Females that mated longer showed higher fecundity when they were exposed to balanced treatment,but not if they were exposed to male-biased treatment.Females from the male-biased treatment showed interindividual differences in plasticity and no repeatability in flight performance.Offspring showed balanced sex-ratio and similar survivorship,development,and feeding latency independently of the parental treatment;however,females exposed to male-biased treatment produced offspring with higher differences in exploration plasticity and daughters less explorative and with higher unpredictable thigmotaxis.We propose prolonged copulation as courtship at balanced sex-ratio but a cost to females under male-biased sex-ratio.Cross-generational effects in behavioral variability may be a mechanism to cope with predicted future environments.

Increased Maleness at Flowering Stage and Femaleness at Fruiting Stage with Size in an Andromonoecious Perennial, Veratrum nigrum

Theory predicts that cosexual plants should adjust their resource investment in male and female functions according to their size if female and male fitness are differentially affected by size. However, few empirical studies have been carried out at both the flowering and fruiting stages to adequately address size-dependent sex allocation in cosexual plants. In this paper, we investigated resource investment between female and male reproduction, and their size-dependence in a perennial andromonoecious herb, Veratrum nigrum L. We sampled 192 flowering plants, estimated their standardized phenotypic gender, and assessed the resource investment in male and female functions in terms of absolute dry biomass. At the flowering stage, male investment increased with plant size more rapidly than female investment, and the standardized phenotypic femaleness （ranging from 0.267 to 0.776） was negatively correlated with plant size. By contrast, female biased allocation was found at the fruiting stage, although both flower biomass and fruit biomass were positively correlated with plant size. We propose that increased maleness with plant size at the flowering stage may represent an adaptive strategy for andromonoecious plants, because male flowers promote both male and female fertility by increasing pollinator attraction without aggravating pollen discounting.

Pollen-Ovule Ratio and Gamete Investment in Pedicularis （Orobanchaceae）

The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.