Simulation analyses of the evolution of intra-inflorescence flowering patterns assuming selection on anthesis interval among individual flowers.

What conditions select flowering patterns within inflorescences, or variation in the anthesis interval within inflorescences among plants? Under what conditions are gradual blooming and simultaneous blooming, both traits related to floral display size, advantageous? We constructed a simulation model in which the opening times and longevities of individual flowers within inflorescences, the sizes of attractive structures of individual flowers, and the numbers of ovules and pollen grains produced by individual flowers evolve. Individual plants in the population compete for pollinators, and plants are selected by pollinators according to their floral display sizes and amounts of resources allocated to attractive structures. We found that, if the proportion of pollen on a pollinator deposited on a stigma was low, gradual blooming did not evolve even if inbreeding depression was greater than 0.

Effects of floral display size, local open raceme density, patch size, and distance between patches on pollinator behaviour in Salvia nipponica.

Flowers cluster at various spatial scales, so pollinators use information from multiple scales when foraging in natural plant populations. Little is known about the effects of interactions between scales or their relative strength. We examined bumblebee foraging behaviour in a natural population of Salvia nipponica in 10 and 7 patches in 2019 and 2020, respectively.

Pollen morphology for successful pollination dependent on pollinator taxa in a generalist plant: relationship with foraging behavior.

Pollen morphology varies at inter- and intraspecific levels. Its interaction with pollinator behavior and morphology determines the probability of successful pollination. We tested whether pollen morphology promoting successful pollination differs depending on pollinator taxa in a generalist shrub, Weigela hortensis (Caprifoliaceae).

Effect of temporal changes in stamen position on reproductive success in flowers with many stamens: Manipulations of stamen position.

Premise: Male and female reproductive success is enhanced (increased outcrossing and seed production, respectively) by stamen movement in species that have few stamens per flower. Does such enhancement also occur in species that have many stamens per flower?

Methods: We examined the effects of stamen movement on male and female reproductive success in Anemone flaccida, which has many stamens per flower. We measured stamen movement, including temporal changes in anther-stigma and anther-anther distances.

Evolution of mixed mating: Effects of among-parent variation in early-acting inbreeding depression coupled with overproduction of ovules.

Theoretical models were developed to propose a new mechanism enhancing mixed mating (reproduction by both outcrossing and selfing) in hermaphroditic plants; mixed mating can be maintained if there exists among-parent variation in early-acting inbreeding depression in embryos and parents can replace dead embryos by overproduction of ovules. In the two main models developed, the number of embryos produced is allowed to evolve, parents may overproduce embryos, and among-parent variation in early-acting inbreeding depression does not exist or exists. I found that mixed mating does not evolve if among-parent variation in early-acting inbreeding depression does not exist, whereas it evolves if it exists.

Why are deleterious mutations maintained in selfing populations? An analysis of the effects of early- and late-acting mutations by a two-locus two-allele model.

Frequencies of deleterious mutations are higher than expected in many plants. Here, by developing a two-locus two-allele model, I examine the effects of differential timing of the expression of deleterious mutations (two-stage effects) on the maintenance of mutations. I assume early- and late-acting loci to distinguish whether maintenance of mutations in populations with high selfing rates is explained better by two-stage effects of single mutations, or by separate mutations in both early- and late-acting loci.

Optimal pollen stickiness to pollinators for maximizing paternal fitness: Increased number of recipient flowers or increased pollen deposition on recipient flowers?

A plant can sire more seeds by increasing the number of pollen recipient flowers or the amount of pollen deposited on recipient flowers. We theoretically analyzed how pollen stickiness contributes to paternal fitness through changing the pattern of pollen dispersal including both the number of recipient flowers and overall pollen deposition (the overall amount of pollen deposited on recipient flowers) in animal-pollinated plants. We developed a numerical model in which pollen stickiness to pollinators increases with production of expensive materials on pollen surfaces, and a high level of stickiness diminishes the proportions of pollen lost from a pollinator body during a flight and pollen deposited on a stigma during a visit.

Maintenance of high inbreeding depression in selfing populations: Two-stage effect of early- and late-acting mutations.

High estimates of inbreeding depression have been obtained in many plant populations with high selfing rates. However, deleterious mutations might be purged from such populations as a result of selfing. I developed a simulation model assuming the presence of mutations at two sets of loci, namely, early- and late-acting loci, and the selective abortion of embryos coupled with ovule overproduction.

Low mutation rates promote the evolution of advantageous traits by preventing interference from deleterious mutations.

We studied how mutation rates promote the evolution of advantageous traits in an asexual population. First, to examine the effects of mutation rates on the evolution of an advantageous trait (high competitive ability), we carried out simulation analyses with competition between individuals for survival. Second, to examine the mechanism underlying the promotion of advantageous trait evolution, we calculated the probabilities that new favorable effects of mutations on the phenotype were acquired and that existing favorable effects were maintained.

Ovule and seed production patterns in relation to flower size variations in actinomorphic and zygomorphic flower species.

Zygomorphic flower species tend to show lower flower size variation than actinomorphic flower species. Have these differences also brought an association in ovule and seed production that has arisen due to natural selection in these species? Flowers were collected from 29 actinomorphic and 20 zygomorphic flower species, and fruits were collected from 21 actinomorphic and 14 zygomorphic flower species in Miyagi and Aomori prefectures, in Japan. The coefficient of variations (CVs) of flower sizes, mean ovule sizes of flowers, ovule numbers of flowers and mean seed sizes of fruits were calculated.

Inherited dimorphism in cleistogamous flower production in Portulaca oleracea: a comparison of 16 populations growing under different environmental conditions.

Background And Aims: Cleistogamy is considered to be an adaptive strategy resulting in plasticity in chasmogamous (CH) and cleistogamous (CL) flower production depending on environmental conditions and plant size. The aim of this study was to investigate whether CH and CL flower production in Portulaca oleracea is genetically differentiated among populations in association with climatic conditions.

Methods: First, we conducted growth experiments with P.

Evolution towards minimum ovule size? Ovule size variations and the relative sizes of ovules to seeds.

Background And Aims: Is there selection minimizing the costs of ovule production? Such selection should lead to a smaller ovule size in relation to seed size and, at the same time, smaller variation in ovule size within plants, the latter because the minimum structures and resources for functioning of ovules should be the same among ovules. Additionally, within species, ovule size should not depend on the plant's resource status.

Methods: To confirm these predictions, we examined ovule and seed production for a variety of species.

Intraflower variation in nectar secretion: Secretion patterns and pollinator behavior in male- and female-phase flowers.

Premise Of The Study: Plants that secrete abundant nectar attract many pollinator visits, potentially leading to a high frequency of geitonogamous pollination. However, intraflower variation in nectar volume might enhance early departure from the flower or inflorescence, reducing geitonogamy. To examine the adaptive significance of multiple nectar-producing spurs within flowers, we related intraflower variation in nectar characteristics to pollinator foraging behavior and plant reproductive success in protandrous Aquilegia buergeriana var.

How Have Self-Incompatibility Haplotypes Diversified? Generation of New Haplotypes during the Evolution of Self-Incompatibility from Self-Compatibility.

I developed a gametophytic self-incompatibility (SI) model to study the conditions leading to diversification in SI haplotypes. In the model, the SI system is assumed to be incomplete, and the pollen expressing a given specificity is not fully rejected by the pistils expressing the same specificity. I also assumed that mutations can occur that enhance the rejection of pollen by pistils with the same haplotype variant and reduce rejection by pistils with other variants in the same haplotype.

Relation between flower head traits and florivory in Asteraceae: a phylogenetically controlled approach.

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Premise Of The Study: While much research has examined the relation between leaf traits and herbivory, very little is known about the interaction between floral traits, particularly biochemical traits, and florivory. We investigated patterns between floral traits and florivory across multiple species using phylogenetic comparative approaches to enhance our understanding of the evolution of plant-florivore interactions.•

Methods: The relation between the intensity of florivory and five biochemical traits (concentrations of carbon, nitrogen, phosphorus, water, and total phenolics) and two morphological traits (diameter and number of flower heads) were investigated in wild individuals of 18 native species of Asteraceae.

Initial invasion of gametophytic self-incompatibility alleles in the absence of tight linkage between pollen and pistil S alleles.

In homomorphic self-incompatibility (SI) systems of plants, the loci controlling the pollen and pistil types are tightly linked, and this prevents the generation of compatible combinations of alleles expressing pollen and pistil types, which would result in self-fertilization. We modeled the initial invasion of the first pollen and pistil alleles in gametophytic SI to determine whether these alleles can stably coexist in a population without tight linkage. We assume pollen and pistil loci each carry an incompatibility allele S and an allele without an incompatibility function N.

Difference in defense strategy in flower heads and leaves of Asteraceae: multiple-species approach.

Although a vast number of studies have investigated defenses against herbivores in leaves, relatively little is known about defenses in flowers. Using wild individuals of 34 species of Asteraceae, we investigated differences in five traits that are thought to affect the intensity of herbivory (C, N, P, water, and total phenolic contents). Combinations of these traits between flower heads and leaves were studied as well.

Evolutionarily stable size of a megagametophyte: evolution of tiny megagametophytes of angiosperms from large ones of gymnosperms.

To examine the factors favoring large megagametophytes of gymnosperms and tiny ones of angiosperms, a game model for seed production was developed in which megagametophytes growing in the same female parent compete for resources provided by the parent. In the model, megagametophytes may continue to grow until seed completion or may cease to grow at a certain time and regrow at pollination or fertilization. Autonomous abortion of unpollinated or unfertilized megagametophytes may occur either at pollination or fertilization.

With whom is the gene in conflict in offspring production? Synthesis of the theories of intragenomic and parent-offspring conflict.

In offspring production, with whom are the maternally derived (madumnal), paternally derived (padumnal), and maternal genes in conflict? I developed a model, in which those genes independently regulate resource absorption of developing offspring, and offspring with a high realized resource absorption rate may become large, but may suffer abortion due to overgrowth. I analyzed two cases: maternal control is weak (maternal genes cannot completely inhibit the resource demand by the madumnal or the padumnal genes) and is strong (maternal genes can completely inhibit it). I found that, under weak maternal control, the maternal genes inhibit resource absorption, but the madumnal and padumnal genes enhance it if the abortion cost of overgrowth is low.

Optimal defense strategy against herbivory in plants: conditions selecting for induced defense, constitutive defense, and no-defense.

To examine the conditions selecting for induced defense, constitutive defense, and no-defense, we developed a model of plant defense strategy against herbivory. In the model, a plant consists of two modules between which signal inducing defense compounds can be translocated. We assume three strategies: plants produce defense compounds responding to herbivory (induced defense), they have the compounds beforehand (constitutive defense), and they never produce the compounds (no-defense).

Overproduction and selective abortion of ovules based on the order of fertilization revisited.

Given that seeds fertilized by slowly growing pollen are of low quality genetically, we theoretically reanalyzed the hypothesis that plants selectively abort ovules fertilized later to enhance the mean quality of resulting seeds. We assumed that both superior and inferior pollen exist, the superior pollen growing faster to fertilize ovules, resulting in seeds of higher quality than those of ovules fertilized by inferior pollen. We developed two models to determine the conditions under which selective abortion is favored.

A new hypothesis for the evolution of overproduction of ovules: an advantage of selective abortion for females not associated with variation in genetic quality of the resulting seeds.

A new hypothesis for the evolution of overproduction of ovules within flowers is proposed: overproduction is a counter-strategy of female seed production in the conflict with males and/or offspring. It is advantageous for females to produce a uniform size of seeds, whereas it is advantageous for fertilized ovules to absorb more resources than this size. If there is a variance in resource absorption ability among fertilized ovules, nonuniform seeds are produced.

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.

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.

The relative importance of carbohydrate and nitrogen for the resprouting ability of Quercus crispula seedlings.

Background And Aims: Plants need some kind of stored resources to resprout after shoot destruction. The aim of this study was to determine the relative importance of carbohydrate and nitrogen (N) storage levels for their ability to resprout.

Methods: A shoot clipping experiment was conducted on Quercus crispula seedlings, which were grown in a factorial experimental design, with two light levels (40% and 3% of full light) and three nutrient concentrations (low, medium and high).