Different cost of reproduction for the males and females of the rare dioecious shrub Corema conradii (Empetraceae)

Males and females of dioecious plant species often differ in their reproductive investment. Such differences frequently result in differential demographic costs represented by lower growth, survival, and/or frequency of reproduction, and/or by more variable reproductive effort through time for females. We present the results of a study on Corema conradii, a rare dioecious shrub of the coastal dune heathlands of northeastern North America. We estimated the reproductive investment of both males and females, determined their age structure, and compared their spatial patterns in a population at ?les-de-la-Madeleine, Quebec. We also determined the sex ratio of the four populations known to occur on the islands. Males invested more in reproduction at flowering, but when fruit production was considered, female reproductive investment was higher in terms of biomass, Mg, and Ca, but not in terms of N, P, and K. The age frequency distribution of males and females did not differ significantly from one another. The population dispersion pattern was contagious, with patches of similar-age individuals. There was no spatial segregation between males and females, although the sex ratio varied somewhat spatially. Females did not start reproducing at a later age than males and did not appear to have a shorter longevity. However, the crown and radial growth rates of females were lower than those of males. When estimated by the crown intercept method, the sex ratio of all four populations was male biased. However, because males had a higher crown growth rate, genet sex ratio was in fact balanced. Higher investment in reproduction was associated with a lower growth rate, which represents a differential cost of reproduction according to sex in this species.     

Sex ratio and sexual dimorphism in the dioecious Borderea pyrenaica (Dioscoreaceae)

Sex ratio and sexual dimorphism of Borderea pyrenaica, a long-lived dioecious geophyte endemic to the Pyrenees (north-east Iberian Peninsula), were examined in three alpine populations. In this species, age can be estimated and the sex of nonreproductive adult plants identified. Male plants attain sexual maturity earlier, flower more frequently and grow faster than female plants, whereas females allocate a higher biomass to reproduction than males. These results support the hypothesis that female plants incur a higher cost of sexual reproduction and that this higher cost is measurable as reduced vegetative growth and lower flowering frequency. Variation of sex ratio among young, intermediate and old adults within populations suggests, however, that this higher female reproductive investment does not result in sexual differences in mortality. The overall male-biased sex ratio in B. pyrenaica is mainly a consequence of the tendency of males to reproduce at an earlier age and more frequently than females.     

Does the silver moss Bryum argenteum exhibit sex-specific patterns in vegetative growth rate,asexual fitness or prezygotic reproductive investment?

Background and Aims

Expected life history trade-offs associated with sex differences in reproductive investment are often undetected in seed plants, with the difficulty arising from logistical issues of conducting controlled experiments. By controlling genotype, age and resource status of individuals, a bryophyte was assessed for sex-specific and location-specific patterns of vegetative, asexual and sexual growth/reproduction across a regional scale.

Methods

Twelve genotypes (six male, six female) of the dioecious bryophyte Bryum argenteum were subcultured to remove environmental effects, regenerated asexually to replicate each genotype 16 times, and grown over a period of 92 d. Plants were assessed for growth rates, asexual and sexual reproductive traits, and allocation to above- and below-ground regenerative biomass.

Key Results

The degree of sexual versus asexual reproductive investment appears to be under genetic control, with three distinct ecotypes found in this study. Protonemal growth rate was positively correlated with asexual reproduction and sexual reproduction, whereas asexual reproduction was negatively correlated (appeared to trade-off) with vegetative growth (shoot production). No sex-specific trade-offs were detected. Female sex-expressing shoots were longer than males, but the sexes did not differ in growth traits, asexual traits, sexual induction times, or above- and below-ground biomass. Males, however, had much higher rates of inflorescence production than females, which translated into a significantly higher (24x) prezygotic investment for males relative to females.

Conclusions

Evidence for three distinct ecotypes is presented for a bryophyte based on regeneration traits. Prior to zygote production, the sexes of this bryophyte did not differ in vegetative growth traits but significantly differed in reproductive investment, with the latter differences potentially implicated in the strongly biased female sex ratio. The disparity between males and females for prezygotic reproductive investment is the highest known for bryophytes.     

Determinants of biased sex ratios and inter-sex costs of reproduction in dioecious tropical forest trees

Estimates of the sex ratio and cost of reproduction in plant populations have implications for resource use by animals, reserve design, and mechanisms of species coexistence, but may be biased unless all potentially reproductive individuals are censused over several flowering seasons. To investigate mechanisms maintaining dioecy in tropical forest trees, we recorded the flowering activity, sexual expression, and reproductive effort of all 2209 potentially reproductive individuals within 16 species of Myristicaceae over 4 years on a large forest plot in Amazonian Ecuador. Female trees invested >10 times more biomass than males in total reproduction. Flowering sex ratios were male-biased in four species in ≥1 year, and cumulative 4-year sex ratios were male-biased in two species and for the whole family, but different mechanisms were responsible for this in different species. Annual growth rates were equivalent for both sexes, implying that females can compensate for their greater reproductive investment. There was no strict spatial segregation of the sexes, but females were more often associated with specific habitats than males. We conclude that male-biased sex ratios are not manifested uniformly even after exhaustive sampling and that the mechanisms balancing the higher cost of female reproduction are extremely variable.     

Response to Midgley: the costs of reproduction cannot differ between the sexes

Many studies have compared the reproductive cost and vegetative growth at a particular time point. In our review (Liu et al. 2021b), we summarized those results but did not compare absolute reproductive costs between the sexes (Hultine et al. 2016; Juvany and Munné-Bosch 2016). Moreover, we did not propose that the observed vegetative and environmental differences between the sexes were the only reasons for differences in sexual functioning, especially in the spreading and receiving of pollen (Midgley 2022). Yet, we need further evidence to support the argument. Previous studies have shown that differences in primary and physiological traits between the sexes strongly depend on the plant species and their environmental conditions, and that they may arise from a number of reasons, such as differences in trait optima of each sex along a series of resource gradients, sexual selection and sex-specific responses to sexual selection (Barrett and Josh 2013; Geber et al. 1999; Juvany and Munné-Bosch 2016; Kohorn et al. 1994; Rabska et al. 2021; Retuerto et al. 2018; Scopece et al. 2021; Wang et al. 2021). In the comment, Midgley (2022) stated that our general argument is that ‘the net reproductive costs are higher for females because they not only flower but must also produce fruits/cones/seeds (Figure 3). Midgley (2022) suggests (Figure 2) that females can ameliorate their higher costs of reproduction by maximizing resource acquisition and resource gain’. However, in our review, we summarized the general opinion and pointed out that this pattern was not universal (see more detail in Liu et al. 2021b). In consistent with previous reviews, our review argues that there is no widespread rule in sex-related differences in the cost of reproduction despite the general opinion that females have higher reproductive costs than males (Darwin 1877; Liu et al. 2021b; Lloyd and Webb 1977). We summarized possible factors causing biased sex ratios in plants, rather than only underpinning the higher net reproductive costs in females than in males (Liu et al. 2021b). Similarly, we proposed possible mechanisms causing sexual differences in responses to biotic stress, rather than underpinning the higher net reproductive costs in females than in males (Liu et al. 2021b), which is also adapted from Núñez-Farfán and Valverde (2020).     

Flower bud abortion influences clonal growth and sexual dimorphism in the understorey dioecious shrub Aucuba japonica (Cornaceae)

Sexual differences were investigated to determine the significance of flower bud abortion in the dioecious shrub Aucuba japonica Thunb. The mean number of flowers per inflorescence and the mean number of flowering inflorescences (as opposed to aborted inflorescences) per individual were greater in males than in females in 1997 and 1998. Reproductive investment by males was 0.4-times (1997) and 1.4-times (1998) that by females. In addition, females aborted 30.9% (1997) and 42.7% (1998) of their total flower buds without blooming, whereas no male flower buds aborted. One of the architectural traits of this shrub is that in the year that a flower bud is produced at the shoot apex, the shoot will branch into two or more shoots. Thus, there was less sexual difference in the number of current shoots per individual than there was in the number of flowering inflorescences. The relationship between annual growth and reproduction, and the probability of reproduction in the following year, suggested that the higher investment in female reproduction was manifested as a cost for reproductive frequency rather than as a cost for annual growth. The spatial distribution of both males and females was clumped, which may be the result of clonal growth. In addition, overall sex ratios were not skewed and the number of sprouts did not differ significantly between sexes. These results suggested that flower bud abortion by females might reduce sexual dimorphism in terms of clonal growth.     

Sex determination and evolution of unisexuality in the Conchostraca

Field collected or laboratory-reared samples of 60 species of conchostracans (representing all extant genera) indicate that males and females are equally common in most species. Deviations from this pattern occur in four lineages.Cyzicus andLeptestheria each include at least one unisexual species; many species of Limnadiinae are either unisexual or characterized by female-biased sex ratios; and Cyclestheriidae are either unisexual or express males in the later generations of their life cycles. Laboratory studies indicate that species with sex ratios near unity are gonochoric (obligately sexual), whereas females in species with female-biased sex ratios are capable of both outcrossing and selfing modes of reproduction. Phylogenetic analysis of patterns of reproduction suggest that sexual reproduction is the primitive condition. Genetic analysis of sexual species indicate that gender is determined by one or a few genetic factors and that the male-determining allele is recessive. The inheritance of gender in androdioecious species (where females are capable of self-fertilization) is similar to that in sexual species. Androdioecy is likely to be the intermediate stage between obligately sexual reproduction and unisexuality in the Limnadiinae. The phylogenetic distribution of sex ratio variation suggests that unisexuality in Cyzicidae, Leptestheriidae, and Cyclestheriidae has arisen independently of that in the Limnadiinae and that these cases have evolved by different evolutionary pathways.     

Sexual and vegetative reproduction in the aboveground part of a dioecious clonal plant, <Emphasis Type="Italic">Dioscorea japonica</Emphasis> (Dioscoreaceae)

In dioecious clonal plants, the reproductive effort required to set seeds will be responsible for the larger investment in sexual reproduction by females. If there will be a trade-off in resource allocation between sexual and clonal reproduction, this differential sexual reproduction will lead to sexual differentiation in the relative amount of clonal reproduction. To test this prediction, we studied differences between the sexes in their phenologies and investments in sexual and vegetative reproduction (clonal reproduction by means of bulbils) with respect to ramet size in a dioecious clonal plant, Dioscorea japonica Thunb. The period of bulbil production overlapped the period during which infructescences developed. Females flowered later, produced heavier inflorescences, and fewer flowers per inflorescence than did males. Regression analysis using the size of the individual plants demonstrated that large females made smaller investments in inflorescences and larger investments in sexual reproduction than did large males. In contrast, females invested fewer resources in vegetative reproduction than did males. However, the total investments in sexual and vegetative reproduction did not differ between the sexes. These results supported our hypothesis on the sexual differentiation in sexual and clonal reproduction.     

Do sexual dimorphisms in reproductive allocation and new shoot biomass increase with an increase of altitude? A case of the shrub willow Salix reinii (Salicaceae)

Based on the general tendency for females of dioecious plants to pay higher reproductive cost than males, it has been predicted that females should have much more reduced reproductive outputs and diminished vegetative production than males in energy-limited habitats. Nevertheless, this prediction has rarely been directly investigated. We investigated altitudinal changes in reproductive biomass and shoot production, normalized by plant size, for females and males of a shrub willow, Salix reinii, on Mt. Hakkoda, northeast Japan. Females maintained higher reproductive biomass than males at all altitudes; however, reproductive allocation for both sexes tended to decrease at a similar rate with an increase in altitude. Moreover, females vegetatively produced at the same rate as males at all altitudes. These findings suggest that females have a mechanism to compensate for the extra investment in reproduction irrespective of a changing environment. Shoot production did not change with altitude, suggesting that S. reinii gave priority to vegetative investment at the cost of reproductive output at higher altitudes. Inconsistent with general predictions, females did not respond more sensitively than males to severe environmental conditions in either reproductive allocation or shoot production, despite much higher resource investment in reproduction.     

Costs of reproduction as related to the timing of phenological phases in the dioecious Shrub Pistacia lentiscus L

Females of woody dioecious species usually devote more resources to reproduction than males. This may lead to a decrease in female survival and growth. The costs of reproduction, however, can be lightened through a number of mechanisms, as for example avoiding the temporal coincidence of reproduction and vegetative growth. The aim of this study was to evaluate whether males and females of P. lentiscus differ in the timing of their vegetative growth, and to assess whether the sequencing of vegetative growth and reproduction reduces reproductive costs. We monitored phenology in males and females. We also compared male and female allocation of nutrients and biomass in the branch, and the developmental stability of the growing shoots. We did this both prior to and at the end of the fruiting period. Males and females showed similar vegetative and flowering phenologies. Males invested more biomass in flowering, but the sexes showed equal vegetative biomass and nutrient content prior to the fruiting period. In female branches, no trade-off was found between fruit load and current-year vegetative growth. In P. lentiscus, avoiding the overlap of flowering, vegetative growth and fruiting probably contributes to reduce the immediate costs of reproductive efforts, both in males and females.     

Sex Ratios and Resource Allocation among Sexually Reproducing Plants of Rubus chamaemorus

Sex ratios and patterns of size variation and resource allocationwere investigated in the dioecious species Rubus chamaemorus.Sex ratios among flowering ramets varied from 6% to 40% of females.Female ramets were slightly, although not significantly, tallerthan males. It appeared that population effects (including bothgenetic population and environmental site effects) on plantsize and allocation patterns at flowering are considerably greaterthan sex effects. If both flowering and fruit production areconsidered, then female allocation to reproduction clearly exceedsmale allocation. In females, no significant relationship wasdetected between the mass of reproductive and vegetative tissues,while males did exhibit such a relationship. Reproductive effortwas less for tall males than for small males. Despite the occurrence of sexual reproduction, the main modeof reproduction in R. chamaemorus is vegetative propagation,which is the best strategy for reproduction in the unpredictableclimate of high latitudes but which leads to skewed sex ratios.As a consequence of vigorous vegetative reproduction, individualclones can grow to be large. The results of electrophoreticstudies show that the numbers of clones per population are low.Copyright1994, 1999 Academic Press Rubus chamaemorus, cloudberry, sex ratios, resource allocation, clonal structure, electrophoresis     

Sex differences in the energetic content of reproductive tissues in the Blackeye Goby,Rhinogobiops nicholsii

Differential energetic investment in reproduction between the sexes has been a driving a force of life history theory and sexual selection. However, reproductive costs between the sexes have often been based on morphology, such as gonad mass and gonadosomatic indices (GSI), and few have directly measured the energy content of gonadal tissues in relation to GSI. Using the blackeye goby, Rhinogobiops nicholsii, we measured the energetic content of whole gonadal tissues, specifically testes, ovaries and associated reproductive tissues using oxygen bomb calorimetry. The energy content per gram unit of gonadal tissues was generally predictive of GSI, indicating that GSI is a reasonable measure of energetic costs. Interestingly, although females had greater gonadal mass, GSI and energy content per gram than males, the sex difference in energy content per mass unit was only 13 %, suggesting that gross indices such as gonadal mass or GSI may overestimate energetic costs where instead the cost difference in a unit gram of gonadal tissues between the sexes is smaller than often predicted. This study also demonstrates that although the cost of ovaries is greater than testes, males’ investment in reproductive tissue can be considerable, which is consistent with the often inflated reproductive success for males in haremic mating systems.     

Sex investment ratios in monogyne and polygyne populations of the fire ant Solenopsis invicta

Both monogyne (single queen per colony) and polygyne (multiple queens per colony) populations of the fire ant Solenopsis invicta are good subjects for tests of kin selection theory because their genetic and reproductive attributes are well-characterized, permitting quantitative predictions about the degree to which sex investment ratios should be female-biased if workers and not queens control reproductive allocation. In the study populations, an investment ratio of 3 females: 1 male is predicted (a proportional investment in females of 0.75) in the monogyne form, whereas a proportional investment in females between 0.637 and 0.740 is expected in the polygyne form. To test these predictions, colonies from a single population of each social form were collected and censused during three different seasons. Consistent with their alternative modes of colony founding, monogyne colonies invested more in reproduction (sexual production) and less in growth/maintenance (worker production) than did the polygyne colonies. Overall, the sex investment ratios were female-biased in both forms, although there was considerable seasonal variation. After adjusting for sex-specific energetic costs, the proportional investment in females was 0.607 in the monogyne population, a value in between those expected under complete control by either the queen or the workers. However, when combined with data from four other previously studied monogyne populations in the U.S.A., the mean investment ratio did not differ significantly from the value predicted if workers have exclusive control. In the polygyne population, the proportional investment in females of 0.616 was consistent with the level of female bias expected under partial to complete worker control, although the potential influence of two confounding factors — possible contact with monogyne colonies and the preponderance of sterile diploid males — weakens this conclusion somewhat. Taken as a whole, the sex investment ratios of monogyne and polygyne populations of S. invicta are consistent with at least partial worker control. Of several ultimate and proximate explanations that have been proposed to explain inter-colonial variation in the sex investment ratio, only the effect of the primary sex ratio (female-determined eggs: male-determined eggs) laid by the queen appears to account for the observed variation among monogyne colonies. In the polygyne population, there is limited support for the hypothesis that greater resource abundance favors investment in females.     

Trade-offs between clonal and sexual reproduction in Sagittaria latifolia (Alismataceae) scale up to affect the fitness of entire clones

? Many plants combine sexual reproduction with vegetative propagation, but how trade-offs between these reproductive modes affect fitness is poorly understood. Although such trade-offs have been demonstrated at the level of individual shoots (ramets), there is little evidence that they scale up to affect genet fitness. For hermaphrodites, reproductive investment is further divided between female and male sexual functions. Female function should generally incur greater carbon costs than male function, which might involve greater nitrogen (N) costs. ? Using a common garden experiment with diclinous, clonal Sagittaria latifolia we manipulated investment in reproduction through female and male sex functions of 412 plants from monoecious and dioecious populations. ? We detected a 1?:?1 trade-off between biomass investment in female function and clonal reproduction. For male function, there was no apparent trade-off between clonal and sexual reproduction in terms of biomass investment. Instead, male function incurred a substantially higher N cost. ? Our results indicate that: trade-offs between investment in clonal propagation and sexual reproduction occur at the genet level in S.?latifolia; and sexual reproduction interferes with clonal expansion, with investment in female function limiting the quantity of clonal propagules produced, and investment in male function limiting the nutrient content of clonal propagules.     

苔藓植物生殖生态学研究

近年来苔藓植物生殖生态学研究主要集中于繁育系统、生殖代价与对策,以及不同生殖方式对种群遗传变异的影响等方面。生殖结构的原始性及其对水分的独特需求,以及雌雄异株比例较高等导致苔藓植物中有性生殖比例偏低;雌配子体很少完成整个有性生殖过程,其“真实的生殖代价”主要指雌性性表达(雌配子发生)的能耗,并且显著低于雄性性表达;基于对资源有效分配的生殖对策而导致雌性偏向及部分孢子体败育。无性生殖有利于不同生境条件下有效种群的发展与维持,其多样化的繁殖方式导致复杂的种群动态。苔藓植物具有较高的种群遗传多样性,生殖方式与种群遗传变异无直接因果关系,孢子与无性繁殖体不同的散布能力对于种群间遗传分化具有一定的影响。     

Assessment of costs of reproduction in a pelagic seabird using multistate mark-recapture models

We used a long‐term population band‐resight survey database, a parallel reproduction database, and multistate mark–recapture analysis to assess the costs of reproduction, a keystone concept of life‐history evolution, in Nazca boobies (Sula granti) from Punta Cevallos, Isla Española, Galápagos, Ecuador. We used eight years of resight and breeding data to compare models that included sex‐ and state‐specific survival probabilities and probabilities of transition between reproductive states using multistate mark–recapture models. Models that included state‐specific effects were compared with models lacking such effects to evaluate costs of reproduction. The top model, optimizing the trade‐off of model simplicity and fit to the data using the Akaike Information Criterion (AIC), showed evidence of a temporally varying survival cost of reproduction: nonbreeders showed higher annual survival than breeders did in some years. Because increasing investment among breeders showed no negative association with survival and subsequent breeding success, this evidence indicates a cost to both males and females of initiating, but not of continuing, a reproductive attempt. In some cases, breeders reaching the highest reproductive state (fledging an offspring) showed higher survival or subsequent breeding success than did failed breeders, consistent with differences in overall quality that promote both survival and reproduction. Although a male‐biased adult sex ratio was observed in this population of Nazca boobies, models of state‐ and sex‐specific survival and transition probabilities were not supported, indicating that males and females do not incur different costs of reproduction, and that the observed sex ratio bias is not due to sex‐specific adult mortality.     

Both sexes suffer increased parasitism and reduced energy storage as costs of reproduction in the brown anole,Anolis sagrei

Sexual selection theory proposes that males suffer reduced immune function and increased parasitism as costs of expressing sexual signals. Life‐history theory proposes that females suffer the same costs because of inherent trade‐offs between reproduction and self‐maintenance. Mechanistically, each theory invokes an energetic trade‐off, although few experiments have directly compared these costs of reproduction between the sexes as a result of fundamental sex differences in the nature of reproductive investment and a tendency for each theory to focus on a single sex. To test whether males and females experience comparable costs of reproduction in terms of energetics, immune function, and parasitism, we used gonadectomy to eliminate most aspects of reproductive investment in wild brown anole lizards (Anolis sagrei) of both sexes. We compared these nonreproductive males and females with intact, reproductive controls with respect to stored energy (fat bodies), immune function (swelling response to phytohemagglutinin), and the prevalence and intensity of infection by four types of parasite (gastric nematodes, intestinal nematodes, faecal coccidia, and ectoparasitic mites). Gonadectomized anoles experienced dramatic increases in fat storage that were accompanied by decreases in the prevalence of intestinal nematodes and in the intensity of coccidia infection. These costs of reproduction were comparable between males and females, although neither sex exhibited the predicted increase in immune function after gonadectomy. Our results suggest that, despite fundamental sex differences in the nature of reproductive investment, both male and female anoles experience similar costs of reproduction with respect to energy storage and some aspects of parasitism.     

Sexual Conflict over the Maintenance of Sex: Effects of Sexually Antagonistic Coevolution for Reproductive Isolation of Parthenogenesis

Sexual reproduction involves many costs. Therefore, females acquiring a capacity for parthenogenetic (or asexual) reproduction will gain a reproductive advantage over obligately sexual females. In contrast, for males, any trait coercing parthenogens into sexual reproduction (male coercion) increases their fitness and should be under positive selection because parthenogenesis deprives them of their genetic contribution to future generations. Surprisingly, although such sexual conflict is a possible outcome whenever reproductive isolation is incomplete between parthenogens and the sexual ancestors, it has not been given much attention in the studies of the maintenance of sex. Using two mathematical models, I show here that the evolution of male coercion substantially favours the maintenance of sex even though a female barrier against the coercion can evolve. First, the model based on adaptive-dynamics theory demonstrates that the resultant antagonistic coevolution between male coercion and a female barrier fundamentally ends in either the prevalence of sex or the co-occurrence of two reproductive modes. This is because the coevolution between the two traits additionally involves sex-ratio selection, that is, an increase in parthenogenetic reproduction leads to a female-biased population sex ratio, which will enhance reproductive success of more coercive males and directly promotes the evolution of the coercion among males. Therefore, as shown by the individual-based model, the establishment of obligate parthenogenesis in the population requires the simultaneous evolution of strong reproductive isolation between males and parthenogens. These findings should shed light on the interspecific diversity of reproductive modes as well as help to explain the prevalence of sexual reproduction.     

Serial monogamy and sex ratio bias in Nazca boobies

Biased operational sex ratios (OSRs) can drive sexual selection on members of the over-represented sex via competition for mates, causing higher variance and skew in reproductive success (RS) among them if an individual's quality is a persistent characteristic. Alternatively, costs of reproduction may degrade breeding performance, creating the opportunity for members of the limiting sex to switch mates adaptively, effectively homogenizing variance and skew in RS among the sex in excess. We tested these two contrasting models in a male-biased population of the Nazca booby (Sula granti) with demonstrated costs of reproduction with data on total RS over a 14-year period. Variances and skews in RS were similar, and males changed from breeder to non-breeder more frequently than females. Under the persistent individual quality model, females should mate only with high quality males, and non-breeding males should seldom enter the breeding pool, yet 45% of non-breeding males (re)entered the breeding pool each year on average. Many Nazca booby females apparently exchange a depleted male for a new mate from the pool of current non-breeder males. Our evidence linking serial monogamy to costs of reproduction is novel and suggests selection on female mating preferences based on an interaction between at least two life-history components (OSR and reproductive effort).     

绞股蓝雌雄种群觅源行为和繁殖对策比较

绞股蓝（Ｇｙｎｏｓｔｅｍｍａ ｐｅｎｔａｐｈｙｌｌｕｍ）雌雄异株,种群性比偏雄。作者利用比较生态学方法,从行为生态学角度探讨相同生境中绞股蓝雌雄种群的觅源行为和繁殖对策,得到如下初步结果和结论：（１）绞股蓝雄性种群的主枝生物量比显著大于雌性种群,这意味着雄性种群的营养繁殖投资显著增加,而两性种群在其它结构中的生物量分配无显著差异;（２）雌性种群的叶面积比和单位叶面积比雄性种群显著增加,这与两性种群