Bateman’s principle states that male fitness is usually limited by the number of matings achieved, while female fitness is usually limited by the resources available for reproduction. When applied to flowering plants this principle leads to the expectation that pollen limitation of fruit and seed set will be uncommon. However, if male searching for mates (including pollen dissemination via external agents) is not sufficiently successful, then the reproductive success of both sexes (or both sex functions in hermaphroditic plants) will be limited by number of matings rather than by resources, and Bateman’s principle cannot be expected to apply. Limitation of female success due to inadequate pollen receipt appears to be a common phenomenon in plants. Using published data on 258 species in which fecundity was reported for natural pollination and hand pollination with outcross pollen, I found significant pollen limitation at some times or in some sites in 159 of the 258 species (62%). When experiments were performed multiple times within a growing season, or in multiple sites or years, the statistical significance of pollen limitation commonly varied among times, sites or years, indicating that the pollination environment is not constant. There is some indication that, across species, supplemental pollen leads to increased fruit set more often than increased seed set within fruits, pointing to the importance of gamete packaging strategies in plant reproduction. Species that are highly self-incompatible obtain a greater benefit relative to natural pollination from artificial application of excess outcross pollen than do self-compatible species. This suggests that inadequate pollen receipt is a primary cause of low fecundity rates in perennial plants, which are often self-incompatible. Because flowering plants often allocate considerable resources to pollinator attraction, both export and receipt of pollen could be limited primarily by resource investment in floral advertisement and rewards. But whatever investment is made is attraction, pollinator behavioral stochasticity usually produces wide variation among flowers in reproductive success through both male and female functions. In such circumstances the optimal deployment of resources among megaspores, microspores, and pollinator attraction may often require more flowers or more ovules per flower than will usually be fertilized, in order to benefit from chance fluctuations that bring in large number of pollen grains. Maximizing seed set for the entire plant in a stochastic pollination environment might thus entail a packaging strategy for flower number or ovule number per flower that makes pollen limitation of fruit or seed set likely. Pollen availability may limit female success in individual flowers, entire plants (in a season or over a lifetime), or populations. The appropriate level must be distinguished depending on the nature of the question being addressed.

Bateman's principle and plant reproduction: The role of pollen limitation in fruit and seed set

CHAPTER 12 – Competition and Facilitation among Plants for Pollination

Summary 1 In flowering plants the balance between sexual and clonal, asexual reproduction can vary widely. We quantified variation in sexual reproduction in a tristylous, clonal, aquatic plant, Decodon verticillatus , and investigated the role of ecological and genetic factors in causing this variation. 2 We surveyed components of sexual fertility and vegetative growth in 28 populations distributed along a 500-km latitudinal transect in New England, USA. Northerly populations tend to be monomorphic (M) for style length, and probably therefore have reduced sexual reproduction compared with southerly, trimorphic (T) populations. 3 Compared with T populations ( n = 10), M populations ( n = 18) exhibited large reductions for all components of sexual reproduction, including flower production, pollen deposition, pollen tube growth, fertilization, fruit set and seeds per fruit. Seven M populations produced no seed at all, and the other 11 very little (mean = 24 vs. 1139 seeds per plant in trimorphic populations). Clonal propagation was also greatly reduced in M populations. 4 A survey of three polymorphic allozyme loci detected only single, usually heterozygous, genotypes in 15 M populations, whereas all T populations were genotypically diverse. The other three M populations contained three or fewer genotypes and one always predominated. Sexual recruitment is therefore extremely rare. 5 Comparison of the sexual fertility of M and T populations in a concurrent common glasshouse experiment with our field data revealed that reduced sexual performance in northern M populations is principally due to genetic factors, but is also caused by ecological factors that covary with latitude. 6 This abrupt shift away from sexual reproduction in populations at the northern periphery of the geographical range in D . verticillatus may greatly limit their evolutionary potential and restrict further northward expansion.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2745.2001.00558.x

Severely reduced sexual reproduction in northern populations of a clonal plant, Decodonverticillatus (Lythraceae)

Environmental challenge vis a vis opportunity: the case of water hyacinth.

On the average, nectar-collecting bumble bees deposited 0.6% of the pollen removed from the flowers of Erythronium grandiflorum (Liliaceae) onto the stigmas of subsequently visited flowers. Because the proportion deposited declined as the amount removed increased, an individual plant would maximize its total pollen dispersal by relying on many pollen-removing visits while limiting the pollen removed by each pollinator. This restriction of pollen removal could be achieved by a plant presenting only a small portion of its pollen at one time (packaging) and/or by limiting the amount of presented pollen that a pollinator removes during a single visit (dispensing). The restriction of pollen removal required to maximize the expected total deposition on stigmas depends on the number of pollinator visits a plant receives, variation in the frequency of visits, and the pattern of pollen removal during a series of visits. Many aspects of floral biology contribute to a plant's ability to restrict pollen removal, incl...

Evolutionary options for maximizing pollen dispersal of animal-pollinated plants

In this paper, an incubation test with soil columns was carried out for 35 days to study the dynamics of DOC leaching from the organic layers (2 approximately 13 cm) of two meadow marsh soils, and the correlation of DOC release with soil respiration, NH4+ formation, and leachate pH. The results showed that in the first week, DOC release presented a fast decrease, and then held on a steady level, which could be well described by one order exponential equation (R2 > 0.96, P < 0.05). During 35 days incubation, the cumulative release of DOC from two test soils was 210.9 microg C x g(-1) and 506.58 microg C x g(-1), and the cumulative emission of CO2 was 679.64 microg C x g(-1) and 455.54 microg C x g(-1), respectively. It was suggested that in the course of incubation, the lower DOC release might be related to the microbial carbon limitation because of the greater CO2 production rate. A significantly positive correlation was found between DOC release and NH4+ formation (rXI = 0.886, P<0.05; rXII = 0.972, P<0.01), while no significant correlation was observed between DOC release and leachate pH. Multiple regression analysis showed that the nitrogen mineralization potential of meadow marsh soil was the main factor affecting DOC production.

Dynamics of dissolved organic carbon (DOC) leaching in meadow marsh soil and related affecting factors

Calamagrostis angustifolia is the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain. The study on its biomass structure and the N and P contents in its different organs showed that the biomass of different C. angustifolia organs in the two types of wetland communities was distinctly different, which could be described by Y = A + B1t + B2t2 + B3t3. The biomass of aboveground part and each organ presented single peak changing, with the maximum value of the latter occurred 15 d after. The F/C values were all less than 1, which was bigger in typical meadow than in marsh meadow. The total N and P contents in different organs of aboveground part all descended linearly in growth season, with the order of leaf > vagina> stem. The total N content in the roots of two C. angustifolia types was consistent, while that of total P was quite different. The contents of total N, NH4+ -N and NO3- -N, especially of NH4+ -N and NO3- -N, varied widely in different organs, with NH4+ -N/NO3- -N >1. Root was the important storage of N and P, but the storage of N and P in stem, leaf and vagina fluctuated greatly. The N/P ratios of two C. angustifolia types were all less than 14, which implied that N might be the limiting nutrient of C. angustifolia, and the limitation degree was higher in typical meadow than in marsh meadow.

Biomass structure and nitrogen and phosphorus contents of Calamagrostis angustifolia populations in different communities of Sanjiang Plain

Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes. Water table and nutritious availability are significant impact factors to influence responses of CO2 emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen status have been incubated to measure rates of CO2 emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3 nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO2 emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m2·h) and 307.89mg/(m2·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however, highest CO2 emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might be important to influence the effect of water table on the CO2 emission from the wetland soil. Nitrogen addition led to enhancing CO2 emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious treatments, low CO2 emissions at high water tables and high CO2 emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table changes and nutritious imports would effect the CO2 emission from wetland.

Effects of water table and nitrogen addition on CO 2 emission from wetland soil

From May 2005 to September 2006, the potential effects of wetland water change on the decomposition and nitrogen (N) dynamics of the typical meadow Calamagrostis angustifolia (TMC) and marsh meadow C. angustifolia (MMC) litters were studied by litterbag technique in the typical depressional wetland in the Sanjiang Plain. In this study, the natural water gradient in the depressional wetland was applied to simulate the changes of wetland water conditions, and six decomposition sub-zones were laid in turn in the six communities, Carex pseudocuraica (PF), Carex lasiocarpa (MG), Carex meyeriana (WL), Marsh meadow C. angustifolia (XII), Typical meadow C. angustfolia (XI), and Island forest (DZL), along the water gradient. The results show that water condition has significant effects on the decomposition of litters. If the hydrous environment is formed in C. angustfolia wetland due to the change of precipitation pattern in the future, the litter weightless rates of TMC and MMC will increase 4.33%-16.76% and 24.84%-53.97%, the decomposition rates will increase 10.51%-32.73% and 77.85%-93.92%, and the 95% decomposition time will decrease 0.72-1.85 a and 3.67-4.05 a, respectively. The changes of N contents and N accumulation indices of TMC and MMC litters are relatively consistent, but the change patterns indifferent sub-zones are different. In general, the N in litters in DZL, XI, WL, MG and PF sub-zones show the alternant change characteristics of release and accumulation, but the release process is predominated. In contrast with that, the N in litters in XII sub-zone show release at all times. The C/N ratios have important regulation functions to the changes of N in litters in decomposition process. The estimation results show that the N standing crops of TMC and MMC litters are 12.75 g x m(-2) and 8.29 g x m(-2), and the N annual returning amounts are larger than 1.95 g x (m2 x a)(-1) and 2.25 g x (m2 x a)(-1), respectively. The studies of affecting factors indicate that temperature has promotion effects on the relative decomposition rates of litters, while water condition has restraint effects on them. Further analysis shows that the relative decomposition rates, to some extent, depend on the substrate quality of litters if the nutrient status of decomposition environment does not change greatly. In reverse, if the nutrient status of decomposition environment changes greatly, the relative decomposition rates, to some extent, depend on the supply status of nutrient in decomposition environment.

Sheng-jin Qin

Papers

Dynamics of dissolved organic carbon (DOC) leaching in meadow marsh soil and related affecting factors

Biomass structure and nitrogen and phosphorus contents of Calamagrostis angustifolia populations in different communities of Sanjiang Plain

Effects of water table and nitrogen addition on CO 2 emission from wetland soil

Effects of simulated wetland water change on the decomposition and nitrogen dynamics of Calamagrostis angustifolia litter