Fitness in Naturally Occurring and Restored Populations of a Grassland Plant Lychnis flos‐cuculi in a Swiss Agricultural Landscape

Wildflower seed mixtures are widely used for restoration of grasslands. However, the genetic and fitness consequences of using seed mixes have not been fully evaluated. Here, we studied the role of genetic diversity, origin (commercial regional seed mixtures, natural populations), and environmental conditions for the fitness of a grassland species Lychnis flos‐cuculi. First, we examined the relationship between genetic diversity, environmental parameters, and fitness in sown and natural populations of this species in a Swiss agricultural landscape. Second, we established an experiment in the study area and in an experimental garden to study the implications of local adaptation for plant fitness. Third, to examine the response of plants to different soil properties, we conducted an experiment in climate chambers, where we grew plants from sown and natural populations of L. flos‐cuculi as well as from seed suppliers on soils with different nutrient and moisture content. We detected no significant effect of genetic diversity on the fitness of sown and natural populations. There was no clear indication that plants from natural populations were better adapted to local environment than plants from sown populations or seed suppliers. However, plants of natural origin invested more into generative reproduction than plants from sown populations or seed suppliers. Furthermore, in the climate chamber, plants originating from natural populations tended to flower earlier. Our results indicate that using nonlocal seeds for habitat recreation may influence restoration success even if the seeds originate from the same seed zone as the restored site.     

The effects of floral display on pollinator visitation vary among populations ofPhacelia linearis (Hydrophyllaceae)

Summary Individual plants in gynodioecious populations ofPhacelia linearis (Hydrophyllaceae) vary in flower gender, flower size, and flower number. This paper reports the effects of variation in floral display on the visitation behaviour of this species' pollinators (mainly pollen-collecting solitary bees) in several natural and three experimental plant populations, and discusses the results in terms of the consequences for plant fitness. The working hypotheses were: (1) that because female plants do not produce pollen, pollen-collecting insects would visit hermaphrodite plants at a higher rate than female plants and would visit more flowers per hermaphrodite than per female; and (2) that pollinator arrival rate would increase with flower size and flower number, the two main components of visual display. These hypotheses were generally supported, but the effects of floral display on pollinator visitation varied substantially among plant populations. Hermaphrodites received significantly higher rates of pollinator arrivals and significantly higher rates of visits to flowers than did females in all experimental populations. Flower size affected arrival rate and flower visit rate positively in natural populations and in two of the three experimental populations. The flower size effect was significant only among female plants in one experimental population, and only among hermaphrodites in another. The effect of flower number on arrival rate was positive and highly significant in natural populations and in all experimental populations. In two out of three experimental populations, insects visited significantly more flowers per hermaphrodite than per female and visited more flowers on many-flowered plants than on few-flowered plants, but neither effect was detected in the third experimental population. Because seed production is not pollen-limited in this species, variation in pollinator visitation behaviour should mainly affect the male reproductive success of hermaphrodite plants. These findings suggest that pollinator-mediated natural selection for floral display inP. linearis varies in space and time.     

Population size and the nature of genetic load in Gentianella germanica

Abstract Theory predicts a significant relationship between the size of a population and the magnitude and composition of its genetic load, but few natural populations have been investigated. We examined the magnitude of genetic load due to recessive deleterious alleles (GL) both segregating and fixed within Gentianella germanica populations of varying size by selfing and reciprocally crossing plants within and between natural populations according to a partial diallel design and by comparing the performance of the experimental progeny in a common-garden experiment. The results show that GL for total fitness in small populations (fewer than 200 plants) was mainly due to fixed recessive deleterious alleles, whereas GL for total fitness in larger populations (more than 200 plants) appeared to be mainly due to segregating deleterious recessive alleles. The total fitness of selfed plants increased with decreasing population size, indicating some purging of deleterious alleles associated with declining population sizes. The magnitudes of GL due to fixed deleterious alleles in small populations and segregating deleterious alleles in large populations, however, were overall similar, suggesting that purging selection was an insignificant force when compared to genetic drift in determining the magnitude of GL in small natural populations in this species. The results of this study highlight the importance of population size in determining the dynamics of genetic loads of natural populations and are overall in line with a large body of theoretical work indicating that small populations may face higher extinction risks due to the fixation and accumulation of deleterious alleles of small effect.     

Individual variation in pathogen attack and differential reproductive success in the annual legume,Amphicarpaea bracteata

Summary Demographic analyses in two natural populations of the annual legume Amphicarpaea bracteate examined whether variation in attack by the host-specific fungal pathogen Synchytrium decipiens was associated with variation in the reproductive success of individual plants. In both populations, fungal infection early in life was significantly associated with reduced seedling growth rates. Laboratory inoculation experiments confirmed that S. decipiens infection had a negative impact on plant growth. The laboratory experiments further indicated that there was significant variation among the progenies of different plant genotypes in the degree of growth reduction caused by pathogen attack. Prereproductive mortality rates in natural environments were significantly higher for plants with infection intensities above the median; for the two populations studied, heavily infected plants had 3.8 and 12 gimes higher death rates compared with low infection plants. Among surviving plants, fungal infection intensity was significantly negatively correlated with total seed biomass in both populations. As a result of these associations between plant survivorship, fecundity, and fungal infection, lifetime relative fitness within both plant populations was strongly negatively correlated with the intensity of S. decipiens infection. These results demonstrate the existence of consistent natural selection for increased resistance to pathogen attack in this plant species.     

Effects of herbivory and its timing across populations of Trillium grandiflorum (Liliaceae)

The goal of this study was to identify the degree to which the frequency and timing of herbivory by white-tailed deer (Odocoileus virginianus) and subsequent plant response varied across 12 populations of the perennial herb Trillium grandiflorum. Effects of natural and experimental herbivory on the stage and size of reproductive plants were measured. Both the frequency and timing of herbivory varied across T. grandiflorum populations. Reproductive plants were more likely to regress to nonreproductive stages in the next growing season when (1) reproductive plants were consumed by deer (vs. intact reproductive plants); (2) reproductive plants were consumed early in the growing season (vs. reproductive plants consumed late in the growing season); (3) reproductive plants were smaller in size. Clipped plants that remained reproductive were smaller in the following season than unclipped controls. Plant size was positively correlated with the number of ovules, suggesting that reductions in the growth rate of reproductive plants diminish their future reproductive success. Populations with high levels of natural herbivory had a greater proportion of reproductive plants that regressed to nonreproductive stages, probably because reproductive plants in these populations were smaller in size. However, the plant response to herbivory was similar across populations.     

Distyly and variation in heteromorphic incompatibility in Gaertnera vaginata (Rubiaceae) endemic to La Reunion Island

Documenting the floral biology of species throughout the Rubiaceae family is of particular interest since heterostyly and dioecy may have evolved more than once in this large family. Unfortunately many species in several tropical regions remain unstudied. The purpose of this paper is to describe the floral biology, the nature of self-incompatibility, morph ratios, and fecundity in natural populations of Gaertnera vaginata, a small tree endemic to the island of La Reunion in the Indian Ocean. Measurements of floral characters in populations across the entire distribution of this species showed that G. vaginata exhibits a reciprocal stigma height and anther height dimorphism characteristic of a distylous species. Pollen grain size and corolla tube length are consistently greater in short-styled plants and long-styled plants produce more pollen per flower. Controlled pollinations in a natural population showed that 25% of the short-styled plants gave at least one fruit on intramorph (illegitimate) pollination, whereas no long-styled plants set fruit on illegitimate pollination. In total, 19.4% of illegitimate pollinations produced fruit on short-styled plants. No self-pollination gave fruit on either morph and between-morph pollinations produced 92.2 and 92.8% for short and long-styled plants, respectively. Overall, short-styled plants were significantly more abundant than long-styled plants. Short-styled plants outnumbered long-styled plants in 16 of the 19 populations. In three of these populations the morph ratio was significantly different from 1:1. In two natural populations, fruit set was significantly higher on long-styled plants, although the number of seeds per fruit was not significantly different between the two morphs. The possible effect of variation in the strength of heteromorphic incompatibility on observed variation in morph abundance and the possible causes for the variation in fruit set are discussed.     

Restricted seed contribution and clonal dominance in a free-floating aquatic plant <Emphasis Type="Italic">Utricularia australis</Emphasis> R. Br. in southwestern Japan

Utricularia australis R. Br. is an aquatic angiosperm species common in natural and irrigation ponds in temperate regions. This species reproduces both sexually and vegetatively, but in southwestern Japan the occurrence of male-sterile populations, in which plants produce no pollen and propagate only vegetatively, has been recorded. We studied the reproductive contribution of seeds in normal pollen-producing populations using isozyme analyses, a pollination experiment under culture and field observations. Although seedlings obtained from controlled mating indicated segregation of isozyme, polymorphism of the isozyme genotype was detected mainly among populations, but rarely within each pond population. This suggested clonal dominance and rarity of seed or seedling survival in natural populations. In the pollination experiment, the mean seed set ratio in cross-pollination between plants of the same isozyme genotype (7.6%) did not differ significantly from self-pollination (7.6%), but was lower than cross-pollination between plants of different genotypes (45.7%). The low ratio in crossing between the same genotype plants was ascribed to the clonality of the parents. In general, these results corresponded with the low ratios in seed setting observed in natural populations (7.9–13.7%). All the male-sterile populations we surveyed showed the same genotype, thus male sterility in the study area was considered to have the same origin.     

害虫天敌的植物支持系统

保护天敌,使天敌长期有效地控制害虫是保护性生物防治的核心内容。其中,植物在维持和促进天敌控制害虫中的重要性和作用越来越受到关注。本文概述了各种支持天敌发挥效能的植物类群,论述了蜜源植物、储蓄植物、栖境植物、诱集植物、指示植物、护卫植物等在支持天敌生存和繁殖方面的生物功能,评述了研究和应用这些植物时需注意的问题,提出了科学利用这些植物以维持和增强农业生态系统中天敌发挥控害作用的植物支持系统,并指出了由于对这些植物类别的界定和定义模糊所带来的不便,给出了相应的建议。     

The role of spatial scale and intraspecific variation in secondary chemistry in host-plant location by Ceutorhynchus assimilis (Coleoptera: Curculionidae)

To understand the ecological role of secondary plant compounds in host location by phytophagous insects it is important to consider attraction at different scales in natural populations. The cabbage seed weevil, Ceutorhynchus assimilis, which lays eggs in pods of crucifers where the larvae feed on seed, is attracted to purified extracts of specific glucosinolate-derived volatiles. We considered the possibility that C. assimilis adults are attracted to and preferentially attack patches of plants and/or individual plants producing these volatiles. Using discrete natural populations of Brassica oleracea and Brassica nigra, we found that oviposition was highest in populations of B. oleracea producing high amounts of 3-butenylglucosinolate. No links were found between the other glucosinolates, 2-propenylglucosinolate, 2-hydroxy-3-butenylglucosinolate, 1-indolylmethylglucosinolate or 1-methoxy-3-indolylmethylglucosinolate, and oviposition in B. oleracea. B. nigra, which contains only 2-propenylglucosinolate, was not attacked by C. assimilis. Within populations of B. oleracea, neither oviposition nor the number of seeds eaten was related to the glucosinolate profiles of individual plants. We suggest that C. assimilis adults use 3-butenylglucosinolate-derived volatiles to locate host populations, whereas other cues determine oviposition on individual plants. The consequences of these results for natural selection of glucosinolate phenotypes are discussed.     

Effects of human disturbance on reproductive success and population viability of Serapias cordigera (Orchidaceae)

Fragmentation of habitats by roads, railroads, fields, buildings and other human activities can affect population size, pollination success and fruit production, especially in plants showing pollinator limitation, such as Mediterranean orchids. In this study, we investigated the effect of human activity on the population dynamics and reproductive success of the orchid Serapias cordigera. Three anthropic and three natural populations were monitored over 14 years (1999–2012), classifying individuals into five stage classes and evaluating reproductive success. Population growth rates differed between anthropic and natural populations. Our results demonstrated that small anthropic populations have lower population viability compared with large natural populations. The proportion of flowering plants, the number of reproductive plants and the percentage of fruits were significantly lower in anthropic than in natural populations. This strong decline in fruit production in populations in urban areas may reflect lower pollination attraction and higher inbreeding in small than in natural populations. Calculation of extinction probabilities showed that the anthropic populations will drop below the survival threshold of 15–20 years. This study highlights that continued monitoring is needed to improve information on population viability and for appropriate conservation management. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 408–420.     

The prevalence and spatial distribution of viruses in natural populations of Brassica oleracea

We report a survey of four viruses (beet western yellows luteovirus (BWYV), cauliflower mosaic caulimovirus (CaMV), turnip mosaic potyvirus (TuMV), turnip yellow mosaic tymovirus (TYMV)) in five natural populations of Brassica oleracea in Dorset (UK). All four viruses were common; 43% of plants were infected with BWYV, 60% with CaMV, 43% with TuMV and 18% with TYMV. For each virus there were significant differences in the proportion of infected plants among populations, which were not completely explained by differences in the age of plants. Multiple virus infections were prevalent, with 54% of plants having two or more virus types. There were statistically significant associations between pairs of viruses. The CaMV was positively associated with the other three viruses, and BWYV was also positively associated with TuMV. There was no detectable association between BWYV and TYMV, whereas TuMV and TYMV were negatively associated. We suggest these associations result from BWYV, CaMV and TuMV having aphid vectors in common, as aphids are attracted to plants that already have a virus infection. Infected plants were distributed randomly or were very weakly aggregated within populations. The implications of widespread multiple virus infections in natural plant populations are discussed with respect to the release of transgenic plants expressing virus-derived genes.     

长江流域野生拟南芥种群QTL作图平台的建立

对模式植物的研究不仅能揭示众多具有普遍规律的生物现象,而且能为其它植物物种,特别是与人类生活紧密相关的经济植物提供具有借鉴与参考意义的研究方法。QTL遗传作图是寻找那些影响不同地域植物自然变异等位基因的传统且有效的工作方法。对不同分化时长和不同遗传背景的植物种群,有针对性地开发特异的分子标记,一直是QTL遗传作图工作的重要内容。该研究利用二代测序技术得到的全基因组重测序结果,根据其中鉴定到的结构变异(SV)多态性设计引物,开发了针对分化时间短、多态性位点少的中国长江流域野生拟南芥(Arabidopsis thaliana)种群的QTL作图分子标记平台,得到了有效适用的结果,该方法不仅在模式植物拟南芥中适用,而且也适用于其它植物。     

Morph-specific patterns of variation in stigma height in natural populations of distylous Jasminum fruticans

The purpose of this study was to describe morph-specific patterns of stigma–anther separation and style curling in the distylous Jasminum fruticans . We also examined whether variation in floral traits is correlated with variation in seed production. Stigma–anther separation is more variable in short-styled plants than in long-styled plants. In all populations studied, some plants bear flowers that lack any stigma–anther separation. These plants have the pollen characteristics (size and number) and compatibility relations of short-styled plants. Comparison with other distylous species illustrates that the variability of stigma–anther separation in short-styled plants is a novel finding for a distylous species. Long-styled plants have greater stigma–anther separation than short-styled plants, styles are often curled and protrude from the corolla, and anthers are placed well within the corolla tube. The frequency of long-styled plants with curled styles and the mean degree of style curling were significantly correlated with style length. Short-styled plants have larger corollas than long-styled plants and never have curled styles. Morph ratios are always 50:50 in natural populations. Mean values of each floral trait in the two morphs were significantly correlated among populations. There were no consistent differences in fecundity of the two morphs nor any correlation between floral traits and seed set for each morph in natural populations. We discuss the potential causes and significance of the two morph-specific patterns we describe; reduced stigma–anther separation in short-styled plants and the presence of curled styles in long-styled plants.     

Outcrossing rates and male sterility in natural populations of Plantago coronopus

Summary Outcrossing rates were estimated in three populations of the gynodioecious species Plantago coronopus by means of electrophoresis of adult plants and their natural progenies. A multilocus estimation procedure was used. Heterogeneity among the pollen-pool allele frequencies did not exist either in space of in time. Differences between populations in mean outcrossing rates were large (range: 0.34–0.93), probably caused by differences in densities of flowering plants. In addition, there was considerable variability between individuals, which was at least partly caused by the presence of male sterility. Population density may, via its influence on outcrossing rates, be a factor influencing the maintenance of male sterile plants in the population. The level of outcrossing in hermaphrodites was not low enough to explain the maintenance of male steriles. Outcrossing rates in two populations, established via progeny analysis, were much lower than calculated with the fixation index, possibly indicating heterozygote advantage in these natural populations.Grassland Species Research Group Publication no. 134     

利用SSR荧光标记对野慈姑异交率的估测

对自交亲和植物交配系统进行估测,有利于了解植物的繁殖状态、自异交进化的轨迹和特定种群的自然历史或选择压力。自交亲和的野慈姑有性繁殖和克隆繁殖并存,且其花序内和无性系分株间存在雌雄花同时开放的现象即给自交带来了机会。本研究利用SSR标记估测野慈姑自然种群的异交水平,并比较分析异交率估测中荧光定量法的准确性和优势,探讨野慈姑不同自然种群微卫星位点的多态性。结果表明,从28对SSR引物中筛选出3对多态性较高的引物,其多种群水平的位点数分别是5、6、6;对1个自然种群的6棵植株共计31个果实的异交率进行估测,其整体异交率为92.87%±2.5%,揭示了野慈姑自然种群的交配系统以异交为主,且无性繁殖对后代的贡献有限;单引物水平下,荧光定量技术检测出的多态性位点数和杂合率均高于NativePAGE成像电泳,且其对异交率估测的结果也更准确;另外,从检测效率实验耗时和实验成本等方面综合分析,本研究推荐使用荧光定量技术。     

Effect of insecticides and Plutella xylostella (Lepidoptera: Plutellidae) genotype on a predator and parasitoid and implications for the evolution of insecticide resistance

In the laboratory and in cages in the greenhouse, we evaluated the toxicity of two insecticides (lambda-cyhalothrin and spinosad) on the parasitoid, Diadegma insulare (Cresson), and the predator, Coleomegilla maculate (DeGeer), both natural enemies of the diamondback moth, Plutella xylostella (L.). Lambda-cyhalothrin was very toxic to both natural enemies. Spinosad was less toxic to C. maculata adults and larvae, and slightly toxic to D. insulare. Both natural enemies suppressed P. xylostella populations in cages with 80% spinosad-treated and 20% nontreated plants; such suppression was not seen when lambda-cyhalothrin was used. Using broccoli, Brassica oleracea L. variety italica, a common host for P. xylostella, we also studied direct and indirect effects of both natural enemies in the presence and absence of the two insecticides and to different P. xylostella genotypes: resistant to the insecticide, susceptible, or heterozygous. Neither natural enemy could distinguish host genotype if P. xylostella were feeding on nontreated plants. They could also not distinguish between larvae feeding on spinosad-treated plants and nontreated plants, but D. insulare could distinguish between larvae feeding on lambda-cyhalothrin treated and nontreated plants. Our studies suggest that lambda-cyhalothrin has direct toxicity to these two natural enemies, can affect their host foraging and acceptance of P. xylostella and consequently would not be compatible in conserving these natural enemies in a program for suppression of P. xylostella. In contrast, our studies suggest that treatment with spinosad has much less effect on these natural enemies and would allow them to help suppress populations of P. xylostella. These findings are discussed in relation to the evolution of insecticide resistance and suppression of the pest populations.     

Principal component analysis of intraspecific responses of tartary buckwheat to UV-B radiation under field conditions

Fifteen populations of tartary buckwheat (Fagopyrum tataricum Gaertn.) occurring in habitats with different natural UV-B levels were sampled, and the plants were exposed to enhanced UV-B radiation under field conditions simulating 25% depletion of the stratospheric ozone layer. The experimental design was a 2 × 15 factorial, with two levels of UV-B radiation (ambient and enhanced UV-B radiation) and plants from 15 populations. The responses of plants in growth, morphology, productivity and in the composition of photosynthetic pigments were measured. The results demonstrated that there were significant differences among populations in responses to UV-B radiation: some populations exhibited a positive effect while others were negatively affected. The UV-B effects on plant traits were correlated with the constitutive values. A principal component analysis (PCA) was used to evaluate the overall sensitivity of responses to UV-B radiation. Our results suggest that the sensitivity of plants to UV-B radiation is not only associated with the ambient UV-B level in natural habitats but also with the relative growth rate and other factors.     

A heritable glucosinolate polymorphism within natural populations of Barbarea vulgaris

In natural populations of Barbarea vulgaris we found two distinctly different glucosinolate profiles. The most common glucosinolate profile is dominated (94%) by the hydroxylated form, (S)-2-hydroxy-2-phenylethyl-glucosinolate (glucobarbarin, BAR-type), whereas in the other type 2-phenylethyl-glucosinolate (gluconasturtiin, NAS-type) was most prominent (82%). NAS-type plants have a 108-fold increase of gluconasturtiin concentration in rosette leaves compared to BAR-type plants. The glucosinolate composition of both chemotypes is consistent throughout all plant organs and after induction with jasmonic acid. Although the glucosinolate profile of the roots has a more diverse composition than other plant organs, it still matches the chemotype. In 12 natural populations that we sampled in Germany, Belgium, France and Switzerland solely BAR-type plants were found. However, eight out of the 15 Dutch populations that were sampled contained 2-22% NAS-type plants. Controlled crosses showed that the chemotype was heritable and determined by a single gene with two alleles. The allele coding for the BAR-type was dominant and the allele for the NAS-type was recessive. The different glucosinolate profiles will yield different hydrolysis products upon damage, and therefore we expect them to differentially affect the multitrophic interactions associated with B. vulgaris in their natural environment.     

The transmission of rye B chromosomes in natural pollination

Summary This paper examines the transmission of B chromosomes in natural (but controlled) pollination, in order to obtain results which can be applied to natural populations of rye. The frequencies of the female gametes in both 2n= 14+1 and 2n=14+2 rye plants have been estimated with reference to their chromatid constitution. From the results obtained on the offspring, it seems that preferential distribution takes place during female meiosis of 2n= 14+2 plants. It has been demonstrated that pollen carrying B chromosomes formed in plants of 2n=14+2 was more competitive than normal pollen. On the contrary, when it was formed from plants 2n=14+1, B chromosome elimination by pollen was total. This process may be considered as sporophytic determination. The genetic significance of the presence of B chromosomes in natural populations is discussed. It is proposed that B chromosomes may be the cytological expression of a complex evolutionary system which results in conservation of population genetic variability.     

Differences in growth and herbivory damage of native and invasive kudzu (Peuraria montana var. lobata) populations grown in the native range

The invasion success of exotic plants is often attributed to escape from natural enemies in their introduced ranges and subsequent evolutionary change in resource allocation from defense to growth and reproduction. We tested this idea by comparing resistance, tolerance, and growth between native (China) and invasive (US) populations of kudzu (Peuraria montana var. lobata) exposed to natural herbivores in the native range. The percentage of foliar damage was much higher in invasive populations than in native populations, indicating that plants from invasive populations had lower resistance to herbivory. Regression of total mass on percentage of foliar damage showed no significant differences in tolerance to herbivory between native and invasive populations. However, stem diameter and mass were significantly greater in invasive populations than in native populations. Our results may suggest geographic variation in herbivory damage and plant growth among kudzu native and invasive populations, but the role of herbivores influencing kudzu invasion requires further investigation.