Herbivore-mediated ecological costs of reproduction shape the life history of an iteroparous plant

Plant reproduction yields immediate fitness benefits but can be costly in terms of survival, growth, and future fecundity. Life-history theory posits that reproductive strategies are shaped by trade-offs between current and future fitness that result from these direct costs of reproduction. Plant reproduction may also incur indirect ecological costs if it increases susceptibility to herbivores. Yet ecological costs of reproduction have received little empirical attention and remain poorly integrated into life-history theory. Here, we provide evidence for herbivore-mediated ecological costs of reproduction, and we develop theory to examine how these costs influence plant life-history strategies. Field experiments with an iteroparous cactus (Opuntia imbricata) indicated that greater reproductive effort (proportion of meristems allocated to reproduction) led to greater attack by a cactus-feeding insect (Narnia pallidicornis) and that damage by this herbivore reduced reproductive success. A dynamic programming model predicted strongly divergent optimal reproductive strategies when ecological costs were included, compared with when these costs were ignored. Meristem allocation by cacti in the field matched the optimal strategy expected under ecological costs of reproduction. The results indicate that plant reproductive allocation can strongly influence the intensity of interactions with herbivores and that associated ecological costs can play an important selective role in the evolution of plant life histories.     

Molecular evolution of flower development

Flowers, as reproductive structures of the most successful group of land plants, have been a central focus of study for both evolutionists and ecologists. Recent advances in unravelling the genetics of flower development have provided insight into the evolution of floral structures among angiosperms. The study of the evolution of genes that control floral morphogenesis permits us to draw inferences on the diversification of developmental systems, the origin of floral organs and the selective forces that drive evolutionary change among these plant reproductive structures.     

繁殖保障和延迟自交的研究进展

尽管植物在进化过程中面临不利自花授粉的选择,但许多植物仍维持混合的授粉机制。繁殖保障假说是解释自交进化的最重要因子之一,一直是植物生殖生态学和进化生物学关注的焦点之一。概述了近年来的主要研究热点及其进展,包括自交进化的遗传和生态机制及理论模型探讨、繁殖保障假说的提出、验证自交能否提供繁殖保障的例证、延迟自交的类型及延迟自交能否提供繁殖保障的例证等方面。介绍了我国在繁殖保障和延迟自交方面研究的现状和不足之处,结合国际上研究繁殖保障假说的发展趋势已由单季节、单种群、单因子的研究阶段过渡到多季节、多种群、多因子（自交方式及其所占比例、花粉折损、种子折损、自交率和近交衰退）的综合研究阶段,及由传统的、经典的研究方法过渡到应用现代实验手段（如SSR、SNP等分子标记）和先进仪器设备的研究阶段,提出今后研究中应注意的问题。有必要借用多学科（植物学、生态学和分子生物学）的方法及手段进行不同物种的对比和综合细致的研究。     

Plant population dynamics, pollinator foraging, and the selection of self-fertilization

Many flowering plants rely on pollinators, self-fertilization, or both for reproduction. We model the consequences of these features for plant population dynamics and mating system evolution. Our mating systems-based population dynamics model includes an Allee effect. This often leads to an extinction threshold, defined as a density below which population densities decrease. Reliance on generalist pollinators who primarily visit higher density plant species increases the extinction threshold, whereas autonomous modes of selfing decrease and can eliminate the threshold. Generalist pollinators visiting higher density plant species coupled with autonomous selfing may introduce an effect where populations decreasing in density below the extinction threshold may nonetheless persist through selfing. The extinction threshold and selfing at low density result in populations where individuals adopting a single reproductive strategy exhibit mating systems that depend on population density. The ecological and evolutionary analyses provide a mechanism where prior selfing evolves even though inbreeding depression is greater than one-half. Simultaneous consideration of ecological and evolutionary dynamics confirms unusual features (e.g., evolution into extinction or abrupt increases in population density) implicit in our separate consideration of ecological and evolutionary scenarios. Our analysis has consequences for understanding pollen limitation, reproductive assurance, and the evolution of mating systems.     

The evolution of partial reproductive isolation as an adaptive optimum

Decades of theoretical work on the evolution of adaptive prezygotic isolation have led to an interesting finding—namely that stable partial reproductive isolation is a relatively common outcome. This conclusion is generally lost, however, in the desire to pinpoint when exactly speciation occurs. Here, we argue that the evolution of partial reproductive isolation is of great interest in its own right and matches empirical findings that ongoing hybridization is taxonomically widespread. We present the mechanisms by which partial reproductive isolation can be a stable evolutionary endpoint, concentrating on insights from theoretical studies. We focus not on cases in which hybridization results from constraints imposed by ongoing migration or mutation, but on the intriguing idea that partial reproductive isolation may instead be an adaptive optimum. We identify three general categories of selective mechanisms that can lead to partial reproductive isolation: context-dependent hybrid advantage, indirect selection due to the varying actions of sexual selection in different geographic contexts, and a balance of costs of choosiness with indirect selection for stronger mating preferences. By any of these mechanisms, stable partial reproductive isolation can potentially provide a robust evolutionary alternative to either complete speciation or population fusion.     

花寿命的进化生态学意义

花寿命 (Floral longevity) 是指一朵花保持开放并具有功能的持续时间, 它作为一种重要的繁殖策略影响着植物的繁殖, 在植物繁殖策略的进化生态学研究中具有非常重要的意义。近年来, 进化生态学家开始重视花寿命的研究, 在传粉与非传粉因素对花寿命的影响、花展示和繁殖成功与花寿命的关系等方面取得了长足的进展。生活史进化模型表明, 最优花寿命取决于开花成本和两性适合度实现速率之间的权衡。大量的实验研究支持此模型。实验研究表明:授粉可导致某些植物的花寿命显著缩短, 但是, 花粉移除对花寿命一般没有显著影响;部分植物的花具有最短花寿命, 这可能是一种保证植物雄性适合度的机制;温度和水分等非传粉因素的变化, 因改变开花成本而影响到花寿命;在花的群体水平上, 植物根据传粉状况和资源状况, 会调节花序上不同花的开放时间, 进而改变花展示的结构和功能;长的花寿命是保障植物繁殖成功的重要机制之一, 但可能要付出一定的适合度代价。该文概述了花寿命进化生态学的理论和实验研究进展, 最后指出:在理论研究上, 雌雄利益冲突为理解花寿命的进化提供了新的视角。在实验研究中, 需要重视植物通过优化花寿命而增强雄性适合度的研究思路。对花寿命的成本-收益分析, 需要考虑单花与花展示的功能关系。     

Consequences of reproductive mode on genome evolution in fungi

An organism's reproductive mode is believed to be a major factor driving its genome evolution. In theory, sexual inbreeding and asexuality are associated with lower effective recombination levels and smaller effective population sizes than sexual outbreeding, giving rise to reduced selection efficiency and genetic hitchhiking. This, in turn, is predicted to result in the accumulation of deleterious mutations and other genomic changes, for example the accumulation of repetitive elements. Empirical data from plants and animals supporting/refuting these theories are sparse and have yielded few conclusive results. A growing body of data from the fungal kingdom, wherein reproductive behavior varies extensively within and among taxonomic groups, has provided new insights into the role of mating systems (e.g., homothallism, heterothallism, pseudohomothallism) and asexuality, on genome evolution. Herein, we briefly review the theoretical relationships between reproductive mode and genome evolution and give examples of empirical data on the topic derived to date from plants and animals. We subsequently focus on the available data from fungi, which suggest that reproductive mode alters the rates and patterns of genome evolution in these organisms, e.g., protein evolution, mutation rate, codon usage, frequency of genome rearrangements and repetitive elements, and variation in chromosome size.     

'Haldane's Sieve' in a metapopulation: sifting through plant reproductive polymorphisms

An important result of population genetics is that advantageous mutations will be fixed by selection in a population with a greater probability if they are dominant rather than recessive. This selective filter on new variants entering a population, termed 'Haldane's Sieve', has hitherto been invoked to account for the greater role of dominant than completely recessive mutations in adaptive evolution. Here, we suggest that a process similar to Haldane's Sieve will act on migrants into subpopulations of a metapopulation, and that the repeated action of Haldane's Sieve on alleles maintained by frequency-dependent selection, such as those responsible for many plant reproductive polymorphisms, is expected to bias their frequency distribution in favour of dominant alleles. The genetic and phenotypic signatures left by these processes might provide additional indirect support for the contentious idea that metapopulation dynamics have had an important role in shaping the ecology and evolution of some plant species.     

The Evolution of Hermaphroditism from Dioecy in Crustaceans: Selfing Hermaphroditism Described in a Fourth Spinicaudatan Genus

The evolution of reproductive systems has intrigued evolutionary biologists for well over a century. Recent empirical and theoretical work has elucidated the evolution of dioecy (separate males and females) from hermaphroditism in many plant species. The reverse transition, evolving hermaphroditism from dioecy, has occurred many times in animals, and yet is poorly studied relative to its reverse analog in plants. Crustaceans in the sub-order Spinicaudata have evolved hermaphroditism from dioecy three separate times, in some cases forming all-hermaphroditic species and in others forming androdioecious (males + hermaphrodites) species. Herein we report evidence of hermaphroditism in a fourth spinicaudatan genus: the newly described Calalimnadia. We present sex ratio and anatomical evidence that Calalimnadia mahei comprises selfing hermaphrodites, with no males being found in over 10,000 offspring reared. We combine these reproductive results with those of other Spinicaudata to estimate the evolution of hermaphroditism in this crustacean sub-order. We use these genetic data combined with anatomical evidence to suggest that C. mahei represents a fourth, independent derivation of hermaphroditism from dioecy in these reproductively labile crustaceans.     

QUANTITATIVE GENETICS OF SIZE AND PHENOLOGY OF LIFE-HISTORY TRAITS IN CHAMAECRISTA FASCICULATA

Despite numerous adaptive scenarios concerning the evolution of plant life-history phenologies few studies have examined the heritable basis for and genetic correlations among these phenologies. Documentation of genetic variation for and covariation among reproductive phenologies is important because it is this variation/covariation that will determine the potential for response to evolutionary forces. To address this problem, I conducted a breeding experiment to determine narrow-sense heritabilities for and genetic correlations among the phenologies of life-history events and plant size in Chamaecristafasciculata, a temperate summer annual plant species. Paternal families showed no evidence of heritable variation for two estimates of plant size, six measures of reproductive phenology or two fitness components. Similarly, paternal estimates of genetic correlations among these traits were low or zero. In contrast, maternal estimates of heritability suggested the influence of maternal parent on one estimate of plant size and four phenological traits. Likewise, maternal effects influenced maternal estimates of genetic correlations. These maternal effects can arise from three sources: endosperm nuclear, cytoplasmic genetic and/or maternal phenotypic. The degree to which the phenology of one life-history trait acts as a constraint on the evolution of other phenological traits depends on the source of the maternal influence in this species.     

Speciation via habitat specialization: the evolution of reproductive isolation as a correlated character

Summary A diverse group of theoretical and empirical studies are integrated into a composite model of sympatric speciation via habitat specialization. It is shown that disruptive selection on a continuous distribution of habitat preference can lead to the evolution of prezygotic reproductive isolation as a correlated character. The form of selection eliminates the major theoretical objections to the process of sympatric speciation. The principal difference between this model and the allopatric model of speciation is that the initial barrier to gene flow between subpopulations is produced by the evolution of gaps in the phenotypic distribution of spatial/temporal habitat use, rather than an extrinsic geographical barrier.     

The evolution of reproductive structures in seed plants: a re-examination based on insights from developmental genetics

The study of developmental genetics is providing insights into how plant morphology can and does evolve, and into the fundamental nature of specific organs. This new understanding has the potential to revise significantly the way we think about seed plant evolution, especially with regard to reproductive structures. Here, we have sought to take a step in bridging the divide between genetic data and critical fields such as paleobotany and systematics. We discuss the evidence for several evolutionarily important interpretations, including the possibility that ovules represent meristematic axes with their own type of lateral determinate organs (integuments) and a model that considers carpels as analogs of complex leaves. In addition, we highlight the aspects of reproductive development that are likely to be highly labile and homoplastic, factors that have major implications for the understanding of seed plant relationships. Although these hypotheses may suggest that some long-standing interpretations are misleading, they also open up whole new avenues for comparative study and suggest concrete best practices for evolutionary analyses of development.     

A short history of MADS-box genes in plants

Evolutionary developmental genetics (evodevotics) is a novel scientific endeavor which assumes that changes in developmental control genes are a major aspect of evolutionary changes in morphology. Understanding the phylogeny of developmental control genes may thus help us to understand the evolution of plant and animal form. The principles of evodevotics are exemplified by outlining the role of MADS-box genes in the evolution of plant reproductive structures. In extant eudicotyledonous flowering plants, MADS-box genes act as homeotic selector genes determining floral organ identity and as floral meristem identity genes. By reviewing current knowledge about MADS-box genes in ferns, gymnosperms and different types of angiosperms, we demonstrate that the phylogeny of MADS-box genes was strongly correlated with the origin and evolution of plant reproductive structures such as ovules and flowers. It seems likely, therefore, that changes in MADS-box gene structure, expression and function have been a major cause for innovations in reproductive development during land plant evolution, such as seed, flower and fruit formation.     

From over to undercompensation: Variable responses to herbivory during ontogeny of a Neotropical monocarpic plant

Empirical and theoretical work has suggested that plants can change their compensatory responses to herbivory as they develop. However, such a relationship is likely to be more complex than previously thought since the amount and type of damage a plant receives can also change as the plant develops. Here, we determined the survival, growth, and reproductive output of plants (Actinocephalus polyanthus) from different ontogenetic stages that received variable levels of natural or simulated herbivore damage. Juvenile plants and non‐reproductive adults in which leaves were damaged showed full vegetative compensation, whereas pre‐reproductive plants were not able to replace the lost leaves. However, these same pre‐reproductive plants produced more inflorescences and thus more seeds and seedlings than control plants. In contrast, damage to vegetative and/or reproductive structures during the reproductive phase resulted in a negative effect on seed and seedling production. Herbivory effects on plant survival, growth, and reproduction during the vegetative and pre‐reproductive phases were independent of the amount of damage. However, during reproduction, the magnitude of these effects was strongly influenced by the amount of damage and the reproductive stage of the plant at the time of the damage. In short, our results demonstrate that the survival, growth, and reproductive responses to herbivory of A. polyanthus can be dependent on the timing and/or intensity of damage. The reproductive response of A. polyanthus to our simulated herbivory treatments during the pre‐reproductive phase represents an example of overcompensation. Furthermore, it indicates that vegetative regrowth is not necessarily a driving factor for tolerance.     

3D打印技术在植物繁殖生态学中的应用进展与评述

3D打印(3D printing)是以数字化模型为基础,运用粉末状金属或塑料等可粘合材料,通过逐层打印的方式构造物体的一项技术。由于3D打印具有灵活和精密的特点,这一技术已经在军工、航天等制造行业中发挥了重要作用。鉴于3D打印的独特优势,该技术也可以在植物繁殖生态学研究中发挥作用而且具有广阔的应用前景,但目前还处于探索阶段。该文概述了3D打印技术以及植物繁殖生态学的花特征进化研究,同时总结了3D打印技术在植物繁殖生态学领域的最新研究进展,并探讨将来可能的发展方向。     

Correlated evolution of self-incompatibility and clonal reproduction in Solanum (Solanaceae)

It has been suggested that clonality provides reproductive assurance in cross-fertilizing species subject to pollen limitation, relieving one of the main selective pressures favoring the evolution of self-fertilization. According to this hypothesis, cross-fertilizing species subject to pollen limitation should often be clonal. Here, we investigated the association between clonality and a genetic mechanism enforcing outcrossing, self-incompatibility, in Solanum (Solanaceae). We collected self-incompatibility and clonality information on 87 species, and looked for an association between these two traits. To account for the contribution of shared evolutionary history to this association, we incorporated phylogenetic information from chloroplast (NADH dehydrogenase subunit F) sequence data. We found that self-incompatibility is strongly associated with clonal reproduction: all self-incompatible species reproduce clonally, while the absence of clonality is widespread among self-compatible taxa. The observed correlation persists after taking into account shared phylogenetic history, assumptions about the evolutionary history of self-incompatibility, uncertainty associated with phylogeny estimation, and associations with life history (annual/perennial). Our results are consistent with the hypothesis that clonality provides reproductive assurance, and suggest that the consequences of clonal growth in the evolution of plant reproductive strategies may be more significant than previously thought.     

Lack of evidence for reproductive isolation among ecologically specialised lycaenid butterflies

Abstract 1. The evolution of reproductive isolation between recently diverged or incipient species is a critical component of speciation and a major focus of speciation models. In phytophagous insects, host plant fidelity (the habit of mating and ovipositing on a single host species) can contribute to assortative mating and reproductive isolation between populations adapting to alternative hosts. The potential role of host plant fidelity in the evolution of reproductive isolation was examined in a pair of North American blue butterfly species, Lycaeides idas and L. melissa .
2. These species are morphologically distinct and populations of each species utilise different host plants; however they share 410 bp haplotypes of the mitochondrial cytochrome oxidase subunit I (COI) gene, indicating recent divergence.
3. Some populations using native hosts exhibited strong fidelity for their natal host plant over the hosts used by nearby populations. Because these butterflies mate on or near the host plant, the development of strong host fidelity may create reproductive isolation among populations on different hosts and restrict gene flow.
4. Tests of population differentiation using allozyme allele frequency data did not provide convincing evidence of restricted gene flow among populations. Based on morphological differences, observed ecological specialisation, and the sharing of genetic markers, these butterflies appear to be undergoing adaptive radiation driven at least partially by host shifts. Neutral genetic markers may fail to detect the effects of very recent host shifts in these populations due to gene flow and/or the recency of divergence and shared ancestral polymorphism.     

Offspring size-number trade-off in a lizard with small clutch sizes: tests of invariants and potential implications

Models of small clutch sizes predict a number of invariant relationships between means and variances of measures of reproductive investment. However, empirical tests of the models have been lagging behind theoretical work. We tested the predictions using data on the mallee dragon, Ctenophorus fordi, a species where the basic assumptions of the models are likely to be fulfilled. Some, but not all, qualitative predictions of the models were shown to hold true, but the data fitted poorly to quantitative predictions. The patterns of deviation from theory may suggest the presence of a lower, and potentially an upper, limit on egg mass. We also argue that multiple and non-independent allocation decisions between total reproductive effort, growth and maintenance, and offspring size-number allocation could be important factors in the evolution of size-number strategies in lizards and thus need to be taken into account in theoretical models. The present study shows the potential to use small clutch size models to gain further insights into reproductive investment and allocation decisions in squamates.     

拟南芥花药绒毡层细胞中具有基因簇特征的基因进化和功能分析

在植物基因组中, 除了同源基因成簇现象外, 近年来还发现一些具有共表达特性的异源基因也能够以基因簇形式存在, 但这些异源基因簇的进化和生物学功能尚不清楚。花药发育和花粉形成是植物进化出的特有的生殖生物学过程, 同时产生了一些在花药绒毡层中特异表达和特定功能的基因簇基因。该研究通过筛选和分析花药绒毡层中基因簇基因的分子特性、表达调控、基因年龄和基因重复进化等信息, 探讨花药基因簇基因与植物开花功能进化之间的关系。结果表明, 在拟南芥(Arabidopsis thaliana)中共筛选到84个(13个基因簇)花药绒毡层特异高表达的基因簇基因, 它们主要产生于串联重复事件, 76%的基因出现在开花植物分化后的阶段, 主要参与生殖发育、花粉鞘组成和脂代谢等生物学过程。研究初步解析了拟南芥花药绒毡层中基因簇基因的基本特征、生物学功能和基因进化机制, 为深入揭示植物基因簇基因的遗传学功能奠定了基础。