Size-dependent ESS sex allocation in wind-pollinated cosexual plants: fecundity vs. stature effects

To theoretically investigate the single and compound effects of relative fecundity and relative stature of plants on size-dependent sex allocation (SDS) in wind-pollinated cosexual species, we developed a game model and analysed ESS sex allocation of large and small plants having totally or partially different reproductive resources and different pollen and seed dispersal areas in a population. We found that e.g. when both sized plants have large pollen dispersal areas relative to their seed dispersal areas, which plants are male-biased is largely determined by relative fecundity (t) and relative size of seed dispersal area (k) of the large plants to the small plants: If t >k, large plants tend to be more male-biased even if relative size of pollen dispersal area of large to small plants (l) is smaller than k. If t相似文献   

Sex and size in cosexual plants

There are conceptual and practical difficulties in measuring the exact shape of fitness-gain curves and sex allocation, and these hamper empirical testing of some of the basic predictions of sex allocation theory for plants. Nevertheless, our knowledge of the processes that shape fitness-gain curves allows us to formulate hypotheses to test predictions of sex allocation theory. One such hypothesis is that plants adjust their gender according to size. The connection between plant size and gender was generally thought to be weak. Recent data, however, suggest that size-dependent sex allocation (SDS) is a common phenomenon in hermaphrodites and other cosexual plants.     

On sex allocation and selfing in higher plants

Summary Sex allocation (male allocation/female allocation) as a function of selfing rate is studied in the wild riceOryza perennis. Using dry weight measures, the male/female ratio is linearly related to the selfing rate. This linear relationship may have a fairly radical interpretation in terms of current sex allocation theory. It suggests that the intermediate selfing rates are themselves maintained by a form of frequency dependence. In particular, the linearity suggests: (i) the relative fitness of a selfed versus outcrossed offspring decreases with increased selfing; (ii) in equilibrium, a selfed offspring is approximately half as fit as an outcrossed offspring; (iii) the frequency dependence, being the opposite of that proposed in most selfing models, may result from the same forces thought to be involved in the maintenance of sex itself, and (iv) the position of the fitted line contains information about the plant's use of wind pollination for male reproduction. It suggests that wind shows much less mixing of pollen than previously assumed, and/or that there are severe morphological constraints on pollen presentation. The above interpretations are clearly speculative and tentative. Possible problems in the analysis, and some alternatives for data interpretation are discussed.     

Size and sex allocation in monoecious woody plants

The female size advantage hypothesis predicts that the allocation ratio of female: male reproductive effort should increase with plant size (total reproductive effort). A male height advantage hypothesis has also been proposed, based on the supposed greater advantage of height to male reproductive success in wind-pollinated plants. These ideas were tested with data for wind-pollinated, monoecious trees and shrubs which exhibit a suitably large range of sizes. Number of male inflorescences increased faster with size than did number of female inflorescences in 2 of 9 species; in the remaining 7 species there was no significant difference. The male:female ratio of inflorescence numbers increased with height in 4 of 7 species and did not change significantly in the remaining 3 species, as shown by regression. Height and size are highly correlated and so their effects could not be distinguished. The fact that many conifers place the female cones uppermost in the crown suggests that size and not height favors increased allocation to male function, as does well-established theory connecting the existence of male versus female size advantage to pollen and seed dispersal chacteristics. Regression analysis of the relation between male and female reproductive effort should be done by reduced major axis regression; ordinary least squares regression underestimates slopes; in this study opposite conclusions could be drawn from ordinary least squares and reduced major axis regressions.     

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.     

Size‐dependent resource allocation and sex allocation in herbaceous perennial plants

Individuals within a population often differ considerably in size or resource status as a result of environmental variation. In these circumstances natural selection would favour organisms not with a single, genetically determined allocation, but with a genetically determined allocation rule specifying allocation in relation to size or environment. Based on a graphical analysis of a simple evolutionarily stable strategy (ESS) model for herbaceous perennial plants, we aim to determine how cosexual plants within a population should simultaneously adjust their reproductive allocation and sex allocation to their size. We find that if female fitness gain is a linear function of resource investment, then a fixed amount of resources should be allocated to male function, and to post‐breeding survival as well, for individuals above a certain size threshold. The ESS resource allocation to male function, female function, and post‐breeding survival positively correlate if both male and female fitness gains are a saturating function of resource investment. Plants smaller than the size threshold are expected to be either nonreproductive or functionally male only.     

Skewed paternity and sex allocation in hermaphroditic plants and animals

Models predict a reduced allocation to sperm when females preferentially use one of two males' sperm and the males do not know who is favoured. An analogous discounting occurs in plants when their paternity success is skewed by random, non-heritable factors such as location in the population and pollinator behaviour. We present a model that shows that skewed paternity can affect the sex allocation of hermaphrodites, that is it leads to a female-biased investment. The model highlights the close links between local mate competition and sperm competition. We use paternity data from Ficus in order to illustrate that skews in paternity success can lead to a high degree of sibling gamete competition in an apparently open breeding system. Since skews in paternity are ubiquitous in hermaphroditic plants and animals these findings should apply broadly.     

Context-dependent sex allocation: constraints on the expression and evolution of maternal effects

Despite decades of research, whether vertebrates can and do adaptively adjust the sex ratio of their offspring is still highly debated. However, this may have resulted from the failure of empirical tests to identify large and predictable fitness returns to females from strategic adjustment. Here, we test the effect of diet quality and maternal condition on facultative sex ratio adjustment in the color polymorphic Gouldian finch (Erythrura gouldiae), a species that exhibits extreme maternal allocation in response to severe and predictable (genetically-determined) fitness costs. On high-quality diets, females produced a relatively equal sex ratio, but over-produced sons in poor dietary conditions. Despite the lack of sexual size dimorphism, nutritionally stressed foster sons were healthier, grew faster, and were more likely to survive than daughters. Although these findings are in line with predictions from sex allocation theory, the extent of adjustment is considerably lower than previously reported for this species. Females therefore have strong facultative control over sex allocation, but the extent of adjustment is likely determined by the relative magnitude of fitness gains and the ability to reliably predict sex-specific benefits from environmental (vs. genetic) variables. These findings may help explain the often inconsistent, weak, or inconclusive empirical evidence for adaptive sex ratio adjustment in vertebrates.     

Sex allocation of a cosexual wind-pollinated tree, Quercus dentata, in terms of four currencies

Sex allocation of a cosexual wind-pollinated species, Quercus dentata (Fagaceae), was analyzed using biomass, carbon, nitrogen and phosphorus as currencies based on data accumulated for 61 individuals from 1997–2004. Strongly female-biased sex allocation was indicated when measured in terms of biomass and carbon, but no significant bias was detected when measured in terms of nitrogen or phosphorus. From an adaptive viewpoint, there is little support for strong female-biased sex allocation, suggesting that sex allocation in terms of nitrogen or phosphorus is closer to the real picture. The relative sex allocation considerably varied from year to year, but the relative femaleness of individuals in the population was rather constant across years. No significant correlation was observed between relative sex allocation and fecundity or tree height, but individuals that showed very low fecundity tended to produce only acorns.     

Effects of brood manipulation costs on optimal sex allocation in social hymenoptera

In eusocial Hymenoptera, queens and workers are in conflict over optimal sex allocation. Sex ratio theory, while generating predictions on the extent of this conflict under a wide range of conditions, has largely neglected the fact that worker control of investment almost certainly requires the manipulation of brood sex ratio. This manipulation is likely to incur costs, for example, if workers eliminate male larvae or rear more females as sexuals rather than workers. In this article, we present a model of sex ratio evolution under worker control that incorporates costs of brood manipulation. We assume cost to be a continuous, increasing function of the magnitude of sex ratio manipulation. We demonstrate that costs counterselect sex ratio biasing, which leads to less female-biased population sex ratios than expected on the basis of relatedness asymmetry. Furthermore, differently shaped cost functions lead to different equilibria of manipulation at the colony level. While linear and accelerating cost functions generate monomorphic equilibria, decelerating costs lead to a process of evolutionary branching and hence split sex ratios.     

Regulation of assimilation and senescence by the fruit in monocarpic plants

Intercellular acidic isoperoxidases (EC 1.11.1.7) isolated from exponentially growing lupin ( Lupinus albus . L. cv. multolupa) hypocotyls are under the control of exogenously applied auxins. Application of auxins leads to a short-term reduction in the level of free intercellular peroxidases, and this effect is associated with a binding of these free peroxidases to the cell walls, probably mediated by an acidification of the cell wall. The ratio of free intercellular peroxidases to the total intercellular peroxidase activity, varies along the axis of exponentially growing hypocotyls. It has a V-shaped distribution with the minimum value in the elongation III-zone, where high levels of auxins have previously been implied in differentiation. This minimum value coincides spatially with the first signs of cell wall thickening in the hypocotyl cells and, paradoxically, it is out of phase with respect to the maximal cell elongation. On the other hand, the ratio of free intercellular peroxidases reaches its maximal values in both the most undiffercntiated phloem cells and the differentiated xylem cells. High levels of free intercellular peroxidase activity in phloem cells are hard to explain, since phloem cell walls remain unlignified during almost all stages of differentiation. However, association of free intercellular peroxidase activity with xylem cells is clearly associated with the lignification of the xylem cell walls. The physiological significance of the binding vs release of intercellular peroxidase is discussed in relation to the catalytic properties and stability at acidic pH of both the bound and free forms of this enzyme.     

Size-dependent sex allocation in hermaphroditic plants: the effects of resource pool and self-incompatibility

The effects of the resource pool and resource obtained during a season for seed maturation and self-incompatibility on the size-dependency of evolutionarily stable sex allocation were analysed theoretically. In hermaphroditic plants, reproductive resources allocated between male and female function may not be paid from a single resource pool, because plants can mature seeds using not only reserved resources but also newly gained resources after flowering. But the resource investment to male function is limited to the flowering stage. Under the assumption of constant reserve efficiency and diminishing resource return per investment to leaves, large plants should use both reserved and newly gained resources for seed maturation, while small plants should use only new resources. When both reserved and new resources are used, the optimal allocation for self-compatible species is to invest a constant amount of resources into male function irrespective of resource size, because the female fitness curve increases linearly and the male curve decelerates due to local mate competition. In self-incompatible species, on the other hand, fitness gain per investment through male function and the optimal amount of resources invested in male function decrease with size. Thus a decrease in maleness with size should be emphasized more in self-incompatible species than in self-compatible one. When only new resources are used for seed growth, the female fitness curve as well as male one decelerates with investment. Consequently, the investment in both male and female functions should increase with size, in both self-compatible and self-incompatible species. The magnitude of reserve efficiency relative to efficiency of resource gain after flowering affects size-dependent pattern of sex allocation, while the cost of seed maturation relative to ovule production has little effect on it. The plant size variation in a population emphasizes size-dependency of sex allocation. When size variation is large enough, it is possible that large plants become complete female in self-incompatible species, but it is not in self-compatible species.     

白刺不同物候期的生物量分配规律

植物生物量的分配模式是植物对环境适应的结果, 并伴随着植物生活史的每一个阶段, 与植物的生长和发育息息相关。目前关于植物生物量分配的大小依赖性已有相关报道, 但关于其对物候期的响应尚鲜有报道。该研究以乌兰布和沙漠地区白刺(Nitraria tangutorum)为研究对象, 通过对其2016与2017年连续2个生长季里盛花期、盛果期与营养生长期3个物候期的根、压条、新枝、老枝、叶、繁殖器官等部分的生物量测定, 采用标准化主轴回归方程的斜率和截距的显著性比较, 分别探讨了白刺在不同物候期的异速生长的大小依赖程度和相对生物量分配比例, 特别是地上与地下部分之间、支持与同化器官之间, 在不同物候期的生物量分配规律。结果表明: 白刺的繁殖生长对生物量分配模式造成的影响主要体现在相对生物量分配比例(36.00%)而不是个体大小的依赖性程度上(16.67%), 且对新枝的影响较大, 使其不同物候期的大小依赖性程度发生了改变, 但是变化趋势不一致, 同时繁殖生长增加对叶片的相对生物量分配比例, 减少对老枝的相对生物量分配比例, 但并没有改变他们的大小依赖性程度。白刺生长过程中的地下部分生物量分配率随个体生物量的累积均增大, 而繁殖分配会在一定程度内减弱这种速率。白刺随着个体生物量的增大其生物量向支持器官分配率也越大, 但随着生长时间推移, 更倾向于将生物量分配给同化吸收器官。     

Variation in biomass allocation of Nitraria tangutorum during different phenological phases

植物生物量的分配模式是植物对环境适应的结果, 并伴随着植物生活史的每一个阶段, 与植物的生长和发育息息相关。目前关于植物生物量分配的大小依赖性已有相关报道, 但关于其对物候期的响应尚鲜有报道。该研究以乌兰布和沙漠地区白刺(Nitraria tangutorum)为研究对象, 通过对其2016与2017年连续2个生长季里盛花期、盛果期与营养生长期3个物候期的根、压条、新枝、老枝、叶、繁殖器官等部分的生物量测定, 采用标准化主轴回归方程的斜率和截距的显著性比较, 分别探讨了白刺在不同物候期的异速生长的大小依赖程度和相对生物量分配比例, 特别是地上与地下部分之间、支持与同化器官之间, 在不同物候期的生物量分配规律。结果表明: 白刺的繁殖生长对生物量分配模式造成的影响主要体现在相对生物量分配比例(36.00%)而不是个体大小的依赖性程度上(16.67%), 且对新枝的影响较大, 使其不同物候期的大小依赖性程度发生了改变, 但是变化趋势不一致, 同时繁殖生长增加对叶片的相对生物量分配比例, 减少对老枝的相对生物量分配比例, 但并没有改变他们的大小依赖性程度。白刺生长过程中的地下部分生物量分配率随个体生物量的累积均增大, 而繁殖分配会在一定程度内减弱这种速率。白刺随着个体生物量的增大其生物量向支持器官分配率也越大, 但随着生长时间推移, 更倾向于将生物量分配给同化吸收器官。     

植物与传粉者物候错配效应研究进展

开花植物与传粉者之间稳定互惠模式的建立是维持互作双方种群适合度的关键。在全球变化的背景下,植物与传粉者对温度、融雪、人类活动等外界扰动的响应差异,易于引起两者关键物候期的不同步发生,由此可能减少传粉互作的重叠时间,改变相互作用的成本和收益,进而对两者的种群动态产生潜在的深远影响（即物候错配效应）。近年来国内外对植物花期与传粉者活动物候的错配研究主要集中在两方面：一是物候错配现象发生的原因及机制;二是这种物候错配带来的生态后果,尤其是对互惠双方种群动态的影响。但由于研究方法及数据获取等方面的局限性,物候错配研究仍存在一些薄弱环节,如物候匹配模式对环境变化的响应机制、传粉效率对错配效应的调节影响、物候数据获取的独立性等。本文综述了植物-传粉者物候错配效应的最新研究进展,并对未来的研究展望进行初步探讨,以期为物种多样性、动植物种群动态的合理预测等方面的研究提供有益的参考。     

Starting dates and basic temperatures in phenological observations of plants

 Several methods have been used in plant phenology to find the best starting date in spring and the best threshold or basic temperature for growth and development of perennial plants. In the present paper the date giving the highest correlation coefficient for development to various phenophases, in relation to 24-hourly mean air temperatures was chosen as the best starting value in further analyses. For many woody plants this date was very often found to be 1 April based on phenological and climatological observations at about 60 sites in western Norway (at about 61°N). The early flowering species Corylus avellana and Salix caprea and the early leaf-bud breaking Prunus padus seemed to start development earlier in Spring, while the late sprouting Fraxinus excelsior showed the highest correlation coefficient using 15 April. If daytime temperatures were used in the calculations, the ”best” starting date was generally found to be later than for the 24-hour mean temperatures. This variation must be seen as resulting from the different basic temperatures for the development of various species. Estimates of basic temperatures in various species and periods may be given, for example by finding the value having the least variance in heat sums or by various regression analyses. A technique has been developed to minimise the influence of significance of correlation, using the intercept with the temperature axis by merging the two least squares rectilinear regression lines that can be found between plant development and mean air temperature (from the estimated best starting date) at r=+1 or –1. The basic temperature seemed to vary from –5.9°C for leaf-bud break of P. padus to 5.5°C for leaf-bud break of F. excelsior, with basic temperatures of several other woody plants having intermediate values. These values are compared with those found by other methods. Received: 26 May 1998 / Accepted: 7 September 1998     

Sex allocation in heterostylous plants

This paper examines the heterostylous breeding system in plants from the perspective of sex allocation theory. Models are used to predict the frequencies of the different floral morphs in populations of heterostylous species and the relative amounts of resources allocated to pollen and seeds in each morph. We note that in natural populations morph ratios may deviate from equality and that the morphs may specialize in the production of either pollen or seeds. Our sex allocation models are an attempt to explain why such patterns exist.     

雌雄同花植物的性分配

性分配理论假定雌雄功能之间存在着trade-off,对一种性别的投入增多必然会减少对另一性别的投入。雌雄功能投入的适合度曲线的形状决定了哪种繁育系统是进化稳定的。因此,性分配理论可以解释植物繁育系统的进化,尤其被认为是雌雄异株进化的选择机制之一。目前的实验研究分别在物种间、种群间、个体间及花间四个层次上进行:自交率的程度对物种和种群的性分配都有影响;虫媒和风媒植物的性分配是个体大小依赖的;而且花序内花的性分配模式受昆虫访花行为的影响。相对于理论,性分配的实验研究明显滞后,随着分子标记技术的普及,性分配理论将会获得更大的发展。繁殖分配需要进一步与性分配理论结合,尤其在空间尺度上资源分配与繁育系统变化的研究是很有意义的。     

Sex allocation in hermaphroditic plants

Hermaphroditic plants allocate their reproductive resources to different functions: male, female and pollinator attraction. While earlier sex-allocation models considered only male and female functions, more recent ones can divide reproductive resources into multiple functions. The basic predictions derived from these models are similar. While most models predict sex allocation at the fruit stage (pollen and seeds), some have examined allocation at the flower stage (pollen and ovules). Selfing rate, mode of pollination and competition among offspring of the same parent are some of the factors that can influence sex allocation among populations. Although the empirical evidence lags behind the theoretical development, sex-allocation theory has been quite successful at predicting trends among populations.