Leaf shape variation and herbivore consumption and performance: a case study with Ipomoea hederacea and three generalists

The effect of leaf shape variation on plant-herbivore interactions has primarily been studied from the perspective of host seeking behavior. Yet for leaf shape to affect plant-herbivore coevolution, there must be reciprocal effects of leaf shape variation on herbivore consumption and performance. We investigated whether alternative leaf morphs affected the performance of three generalist insect herbivores by taking advantage of a genetic polymorphism and developmental plasticity in leaf shape in the Ivyleaf morning glory, Ipomoea hederacea. Across four experiments, we found variable support for an effect of leaf shape genotype on insects. For cabbage loopers (Trichoplusia ni) and corn earworms (Helicoverpa zea) we found opposing, non-significant trends: T. ni gained more biomass on lobed genotypes, while H. zea gained more biomass on heart-shaped genotypes. For army beetworms (Spodoptera exigua), the effects of leaf shape genotype differed depending on the age of the plants and photoperiod of growing conditions. Caterpillars feeding on tissue from older plants (95 days) grown under long day photoperiods had significantly greater consumption, dry biomass, and digestive efficiency on lobed genotypes. In contrast, there were no significant differences between heart-shaped and lobed genotypes for caterpillars feeding on tissue from younger plants (50 days) grown under short day photoperiods. For plants grown under short days, we found that S. exigua consumed significantly less leaf area when feeding on mature leaves than juvenile leaves, regardless of leaf shape genotype. Taken together, our results suggest that the effects of leaf shape variation on insect performance are likely to vary between insect species, growth conditions of the plant, and the developmental stage and age of leaves sampled. Handling editor: May Berenbaum.     

Comparative Analysis of the Photosynthetic Characteristics and Active Compounds of <i>Semiliquidambar cathayensis</i> Chang Heteromorphic Leaves

In the present study, the variation patterns of leaf shape in different populations of individual Semiliquidambar cathayensis plants were analyzed to investigate the relationship among leaf shape variation, photosynthetic properties, and active compounds to understand the genetic characteristics of S. cathayensis and screen elite germplasms. The leaf shape of 18 offspring from three naturalS. cathayensis populations was analyzed to investigate the level of diversity and variation patterns of leaf shape. Furthermore, photosynthetic pigment content, physiological parameters of photosynthesis, and the active compounds in leaves of different shapes were determined. Statistical analysis showed that the leaf shape variation in  S. cathayensis indicated a high level of genetic diversity among and within the populations. Cluster analysis showed that the three natural populations formed two clusters, one whose offspring was dominated by entire leaves and another characterized by palmately trifoliate leaves. The differences in photosynthetic characteristics and active compounds of leaves of three different shapes were comprehensively evaluated using principal component analysis. Two principal components with a cumulative contribution rate of 92.768% were extracted, of which the highest comprehensive score was for asymmetrically lobed leaves. The leaf shape in different S. cathayensis germplasms exhibited distinct patterns, and there were some correlations between the photosynthetic properties and active compounds in leaves of different shapes. Thus, the leaf shape can be used to predict active compound content, and in turn, select varieties based on that purpose; it also provides a simple and effective method to classify S. cathayensis germplasms.     

Phenotypic plasticity inCrepis tectorum (Asteraceae)

Two experiments were carried out using two different approaches to compare populations ofCrepis tectorum (Asteraceae). One was based on a comparison of means of various vegetative and reproductive characters and another was based on a comparison of response patterns of the same characters in a series of environments. Population divergence within two earlier recognized form series, one from weed habitats and one from alvar habitats on Baltic islands, resulted in a partially overlapping pattern in cluster analyses based on character means. However, the pattern revealed by a comparison of the direction and amount of plastic response suggested that populations within the two form series had more similar response patterns than other combinations of populations. It was concluded that patterns of plasticity may provide useful additional information on the overall similarity among taxa. An hypothesis that plants in weed populations should exhibit a greater phenotypic response to the environments than plants in alvar populations was rejected.     

Leaf shape evolution has a similar genetic architecture in three edaphic specialists within the Mimulus guttatus species complex

Background and Aims The genetic basis of leaf shape has long interested botanists because leaf shape varies extensively across the plant kingdom and this variation is probably adaptive. However, knowledge of the genetic architecture of leaf shape variation in natural populations remains limited. This study examined the genetic architecture of leaf shape diversification among three edaphic specialists in the Mimulus guttatus species complex. Lobed and narrow leaves have evolved from the entire, round leaves of M. guttatus in M. laciniatus, M. nudatus and a polymorphic serpentine M. guttatus population (M2L).Methods Bulk segregant analysis and next-generation sequencing were used to map quantitative trait loci (QTLs) that underlie leaf shape in an M. laciniatus × M. guttatus F₂ population. To determine whether the same QTLs contribute to leaf shape variation in M. nudatus and M2L, F₂s from M. guttatus × M. nudatus and lobed M2L × unlobed M. guttatus crosses were genotyped at QTLs from the bulk segregant analysis.Key Results Narrow and lobed leaf shapes in M. laciniatus, M. nudatus and M. guttatus are controlled by overlapping genetic regions. Several promising leaf shape candidate genes were found under each QTL.Conclusions The evolution of divergent leaf shape has taken place multiple times in the M. guttatus species complex and is associated with the occupation of dry, rocky environments. The genetic architecture of elongated and lobed leaves is similar across three species in this group. This may indicate that parallel genetic evolution from standing variation or new mutations is responsible for the putatively adaptive leaf shape variation in Mimulus.     

Leaf variation in a tree of Pourouma tomentosa (Cecropiaceae) in French Guiana

In the flora of French Guiana we find considerable within-plant variation in leaf form. We observed entire, two-lobed, and three-lobed leaves within five separate levels (tiers) of the canopy of a single individual ofPourouma tomentosa subsp.maroniensis. Five branches from each of the five tiers of the tree were collected around the axis of the trunk. From these branches five secondary branchlets were selected and all leaves excised with information recorded as to nodal position, number of leaf nodes, and fertility status of the main branch. This design produced 1015 leaves representing about 20 m² of foliar area and about 2.4 kg of blade dry weight. Our objectives were to determine if statistically significant patterns exist for leaf variation and to suggest improvements for future, general collections. The four lower tiers had 62% entire, 10% 2-lobed, and 28% 3-lobed leaves, in contrast to the top tier with 38% entire, 11% 2-lobed, and 51% 3-lobed leaves. The top tier had no fertile branches. in the lower tiers, fertile branches produced 68% entire leaves whereas nonfertile branches produced only 46% entire leaves. In the top tier, lobed leaves made up 73% of surface area, while in the lower tiers, lobed leaves made up only 48% of total surface area. We selected a random subset of 75 leaves from the 1015, for morphometric analysis using two-way ANOVA (tier×leaf type). The boundaries of leaf images were digitized and rendered into Fourier coefficients, yielding leaf surface area and two variables that quantify aspects of shape: dissection index and leaf complexity. The Fourier coefficients were averaged by tier and by leaf type to reconstruct synthetic, average leaf images. Logistic regression was used to predict the position of leaves on the tree and to provide visualization of the relationships between leaf position on the tree and leaf morphological variables. Within the tree crown, leaf surface area and leaf specific mass (LSM) increases with height, although leaf shape does not change with height. LSM does not vary with leaf form; and sun leaves are larger than shade leaves on this tree. We conducted computer sampling experiments based on exact randomization to simulate the process of obtaining all leaf shapes present in an individual tree when making field collections of varying numbers of duplicates. This also points out the importance of noting the presence of within-tree variation in leaf form on herbarium labeds. Failure to recognize leaf variation can lead to incorrect delimitation of species as well as cause overestimates of the number of species in diversity studies.     

Food preference and performance of the larvae of a specialist herbivore: variation among and within host-plant populations

Specialist herbivores are suggested to be unaffected by or attracted to the defense compounds of their host-plants, and can even prefer higher levels of certain chemicals. Abrostola asclepiadis is a specialist herbivore whose larvae feed on the leaves of Vincetoxicum hirundinaria, which contains toxic alkaloids and is unpalatable to most generalist herbivores. The food choice, leaf consumption and growth of A. asclepiadis larvae were studied to determine whether there is variation among and within host-plant populations in their suitability for this specialist herbivore. There was significant variation in food preference and leaf consumption among host-plant populations, but no differences were found in larval growth and feeding on different host-plant populations. A. asclepiadis larvae preferred host-plant populations with higher alkaloid concentrations, but did not consume more leaf material from plants originating from such populations in a no-choice experiment. There was also some variation in food preference of larvae among host-plant individuals belonging to the same population, suggesting that there was variability in leaf chemistry also within populations. Such variation in larval preference among host-plant genotypes and populations may create potential for coevolutionary dynamics in a spatial mosaic.     

小叶锦鸡儿天然居群叶形态性状变异研究

为揭示小叶锦鸡儿(Caragana microphylla)天然居群叶形态性状的变异规律及其生态适应性特征,该研究以10个小叶锦鸡儿天然居群为对象,通过多重比较、巢式方差分析、相关性分析、聚类分析和主成分分析等方法,对7个叶形态性状进行分析。结果表明：(1)小叶锦鸡儿叶形态性状在居群内和居群间均存在极显著差异(P < 0.01),平均变异系数为10.13%,不同性状的变异幅度为6.23%~12.78%;平均叶形态性状的表型分化系数为43.62%,居群内变异(30.09%)大于居群间变异(24.91%),说明居群内是其叶形态性状变异的主要来源。(2)相关性分析表明,环境因子对小叶锦鸡儿的叶形态性状变异有很大的影响,在地理空间上主要呈现出沿海拔梯度的变异模式;主成分分析的结果显示,小叶宽、叶柄宽和叶柄长对小叶锦鸡儿叶形态变异起主导作用;利用欧式距离对小叶锦鸡儿居群进行UPGMA聚类分析结果显示,基于叶形态性状和环境因子可分别将小叶锦鸡儿10个居群分为3类和2类,Mantel检验结果表明,小叶锦鸡儿的叶形态性状变异不存在地理连续性。研究结果为小叶锦鸡儿的适应性进化和开发利用提供了理论依据。     

濒危植物永瓣藤叶片功能性状对环境因子的响应

植物叶片功能性状能够响应环境条件的变化,反应了植物对环境的适应策略。当前,针对藤本植物叶片功能性状地理格局及其环境驱动力的研究较少。以国家重点保护植物永瓣藤（Monimopetalum chinense）为研究对象,对其分布区内11个种群的15个叶片功能性状进行测量,并结合气候、土壤因子来解释叶性状变异。比较叶片性状在局域和区域尺度上的种内变异程度,利用多元逐步回归分析环境因子对叶性状的影响。结果表明,在局域尺度上,永瓣藤叶功能性状变异系数介于3.0%-22.5%,其中,叶面积变异程度最大,叶片碳含量变异最小。永瓣藤叶片形状随纬度上升而变得宽且圆。叶片磷含量相对较低,永瓣藤的生长可能受到了磷限制。土壤与气候因子是叶片性状的重要驱动因素,解释了25%-97%的叶片性状变异。在温度和水分充足的情况下,永瓣藤叶片趋向于的慢速生长的保守策略。总体来说,永瓣藤叶片功能性状通过一定的种内变异和性状组合,并与气候、土壤因子相互作用,适应当前的环境条件。     

Morphological variation in leaf shape in <Emphasis Type="Italic">Ainsliaea apiculata</Emphasis> with special reference to the endemic characters of populations on Yakushima Island,Japan

We analyzed leaf shape variations in Ainsliaea apiculata Sch. Bip. to evaluate the uniqueness of morphological characters in populations on Yakushima Island, Kagoshima Prefecture, Japan. Leaf size and shape from populations on Yakushima Island (n = 300) were compared with those from populations in other areas of Japan (n = 300). A considerable amount of variation occurred in leaf size in A. apiculata populations both on Yakushima Island and elsewhere, but clear discontinuities in leaf size were not detected. Some variants previously thought to be endemic to Yakushima Island, i.e., A. apiculata var. acerifolia and A. apiculata var. rotundifolia, were also found in other locations in Japan. Moreover, these leaf types were found to be continuous with the typical leaf shape of A. apiculata var. apiculata via various intermediate types, suggesting the need for future revision of these taxa. Based on these results, we reevaluated the uniqueness of the Yakushima populations of A. apiculata in terms of leaf variation. The uniqueness of the Yakushima populations was defined by a more diverse leaf shape than found in populations from other areas.     

Morphometric differentiation,patterns of interfertility,and the genetic basis of character evolution inCrepis tectorum (Asteraceae)

Morphometric analyses of populations ofCrepis tectorum raised under uniform conditions support the earlier finding based on herbarium studies that extensive divergence has taken place in western Europe with a centre of diversity in the Baltic lowland area. A crossing experiment showed that subsp.pumila on the island of Öland has acquired a wide range of derived characters without the establishment of strong reproductive barriers, the only exception being a weak tendency for crosses with other populations on Öland to yield more fertile F₁ offspring than crosses with weedy and non-weedy populations in adjacent regions. Canadian weed populations showed a more uniform response in crosses with subsp.pumila than did morphologically similar weed populations scattered throughout Central Europe. While F₂ data suggest a monogenic basis of differences in the extent of leaf dissection, other distinctive traits appear to be governed by multiple genetic factors with individually slight effects.     

Comparative morphology of populations of Monstera Adans. (Araceae) from natural forest fragments in Northeast Brazil using elliptic Fourier Analysis of leaf outlines

Summary  A comparative study of the leaf outline morphometrics of Monstera adansonii var. klotzschiana, M. adansonii var. laniata and M. praetermissa was carried out. The study focused on populations in isolated montane humid (brejo) forests of Ceará state in Northeast Brazil and compared them with populations from Amazonia and the Brazilian Atlantic Forest. Digitised outlines were prepared from a total of 1,695 field-collected leaf images from 20 populations, and elliptic Fourier analysis was used to generate matrices of coefficients, from which six shape variables (principal components) were extracted using Principal Components Analysis. Intra-population variability and inter-population differences were analysed with multivariate distance methods. Separate analyses were carried out for each of three leaf size classes (juvenile, submature, mature) because of the strong heteroblasty typical of this genus. Juvenile leaves were the least variable size class within populations of M. adansonii var. klotzschiana. The shape variables expressed very similar types of variation in all three size classes. The Ceará brejo populations of M. adansonii var. klotzschiana showed significant differences between mature leaf outlines in all pairwise comparisons; the Pacatuba population was the most distinct. The Ceará populations did not cluster together exclusively. In all three size classes, populations clustered together into their taxonomic groups, most clearly so in mature leaves. No correlation between morphological and geographic distance matrices was found, nor between morphological and molecular distance. The study showed that leaf outline shape is a practicable and useful quantitative trait for studying morphological variability at species, varietal and population levels. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

中国特有属藤山柳属(猕猴桃科)植物的叶表皮形态及其分类学意义

由于形态特征变异和地理分布区域存在重叠,中国特有属藤山柳属(猕猴桃科)的物种划分问题长期以来存在争议,曾被分为20种或修订为含1种4个亚种的单型属。该研究选取了在形态和地理分布上有代表性的29个居群的184份标本,利用光学显微镜和扫描电镜观察了叶表皮形态和微形态特征,以探讨它们的分类学意义。结果表明:(1)藤山柳属植物叶表皮毛被的形态和微形态特征有3类,即光滑-短柱状毛、刚毛-长柱状毛/长刺毛、绒毛-单列多细胞毛,且这些特征在居群间差异明显,并各具明显的地理分布格局,支持把藤山柳属分为3类,即光滑类、刚毛类和绒毛类。(2)3类藤山柳植物在个别居群表现出部分同域分布现象,在峨眉山不同海拔高度的3个居群存在垂直地带性分布特点。(3)藤山柳属植物叶表皮的其他形态特征,如不规则型表皮细胞、6类气孔器、叶表皮初级蜡质纹饰以网状隆起为主,伴随着2～4类次级纹饰,在居群间变化多样等均没有明显的分类学意义。(4)由于具有相同的叶表皮形态特征和地理分布,建议把繁花藤山柳合并到绒毛藤山柳,故支持藤山柳属是1个正处于分化进程中的单型属,包括1个种3个亚种。     

Developmental anatomy of cotyledons and leaves in has mutant of Arabidopsis thaliana

Summary. In this work, we analyzed the developmental anatomy of cotyledons and leaves in the has mutant of Arabidopsis thaliana. It is a recessive T-DNA insertion mutation that causes changes in the size, shape, and tissue organization of the cotyledons and leaves of has plants. Analysis of has cotyledons revealed a prominent decrease in the cell number and an increase in the area of cotyledon cells and intercellular spaces of has plants. At early stages of development, has leaves are fingerlike structures, but later they develop small, lobed blades with rare trichomes. An important characteristic of the mutant leaf anatomy is the absence of mesophyll tissue differentiation. In addition, both cotyledons and leaves display a disrupted pattern of vascular bundles. Furthermore, mutant plants are defective in root and shoot morphology, indicating that the has mutation affects a number of aspects in plant development. Correspondence and reprints: Institute of Botany and “Jevremovac” Botanical Garden, Faculty of Biology, Belgrade University, Takovska 43, 11 000 Belgrade, Serbia.     

The population of the hypogeous fungus<Emphasis Type="Italic"> Tuber aestivum</Emphasis> syn.<Emphasis Type="Italic"> T. uncinatum</Emphasis> on the island of Gotland

The aim of our study was to examine the genetic variation within Tuber aestivum on the Baltic island of Gotland, Sweden. Variation in such a limited geographical area should help illuminate the dispersal abilities of T. aestivum. Knowledge of the genetic variation in this northern outpost could also be useful in the selection of inoculum for the establishment of truffle orchards. Genetic structure and homogeneity of the population were studied using principal component and parsimony analyses of randomly amplified polymorphic DNA data. Our inventories showed that T. aestivum is abundantly distributed in suitable habitats on Gotland. The genetic variation observed suggests sexual reproduction and slow dispersal on the island. It is possible that the present population was established from one introduction, which may be due to ability to survive in this habitat rather than to rare colonising events. The T. aestivum population on Gotland may be an ecotype adapted to the climate and soil conditions on the island.     

Haplotype Frequency Distribution in Northeastern European Saduria entomon (Crustacea: Isopoda) Populations. A Phylogeographic Approach

The distribution pattern of mtDNA haplotypes in distinct populations of the glacial relict crustacean Saduria entomon was examined to assess phylogeographic relationships among them. Populations from the Baltic, the White Sea and the Barents Sea were screened for mtDNA variation using PCR‐based RFLP analysis of a 1150 bp fragment containing part of the CO I and CO II genes. Five mtDNA haplotypes were recorded. An analysis of geographical heterogeneity in haplotype frequency distributions revealed significant differences among populations. The isolated populations of S. entomon have diverged since the retreat of the last glaciation. The geographical pattern of variation is most likely the result of stochastic (founder effect, genetic drift) mechanisms and suggests that the haplotype differentiation observed is probably older than the isolation of the Baltic and Arctic seas.     

Sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system

Summary Studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. Here we report the results of a study which examined causes of this variation. We bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch Betula pubescens ssp. tortuosa by measuring the growth of two instars of Epirrita autumnata larvae. We used only short shoot leaves from trees of a natural stand, uniform in size and age. Damage was caused by larvae and artificial tearing of leaf lamina, varying the scale and time. We separated seasonal changes in plants from instar-dependent effects of the animals by testing experimental larvae in two subsequent growth trials. We found that only larval-made damage induced responses in leaves that made the leaves significantly poorer quality for the test larvae. Artificial damage induced only weak responses, and artificial canopy-wide damage even caused slight improvement of leaf quality. Cumulative leaf damage did not strengthen birch responses. Leaves that were in the expansion phase responded to damage while fully-expanded, mature leaves showed no response. The pattern of responses indicated that there might be physiological constraints: small-scale damage induced resistance against the larvae but largescale damage did not. Prevalent weather conditions might have modified these responses. Larvae of two instars and sexes, of low- and high-density populations responded to leaf damage similarly. However, prior experience of larvae with the host plant may have affected subsequent larval performance. Variation in rapidly inducible responses in birches was caused by plant characters rather than by test animals.     

Constitutive knox1 gene expression in dandelion (Taraxacum officinale, Web.) changes leaf morphology from simple to compound

Seed plants with compound leaves constitute a polyphyletic group, but studies of diverse taxa show that genes of the class 1 KNOTTED-LIKE HOMEOBOX (KNOX1) family are often involved in compound leaf development. This suggests that knox1 genes have been recruited on multiple occasions during angiosperm evolution (Bharathan et al. in Science 296:1858–1860, 2002). In agreement with this, we demonstrate that the simple leaf of dandelion (Taraxacum officinale Web.) can be converted into a compound leaf by the constitutive expression of heterologous knox1 genes. Dandelion is a rosette plant of the family Asteraceae, characterised by simple leaves with deeply lobed margins and endogenous knox1 gene expression. Transgenic dandelion plants constitutively expressing the barley (Hordeum vulgare L.) hooded gene (bkn3, barley knox3) or the related bkn1 gene, developed compound leaves featuring epiphyllous rosettes. We discuss these results in the context of two current models of compound leaf formation.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Influence of Hairiness ofGerbera jamesoniiLeaves on the Searching Efficiency of the ParasitoidEncarsia formosa

To characterize the relationship between the leaf surface ofGerbera jamesoniiHooker cultivars and the searching behavior of the parasitoidEncarsia formosaGahan on a leaf, the trichome density and shape were described, and the walking behavior was quantified. Leaf hair density varied from 80 to more than 1000 trichomes/cm²and the hair shape varied from single erect trichomes to tapestries of entangled trichomes above the leaf surface. The walking activity, speed, and pattern of the parasitoid were tested on leaves with different hair density and shape. In spite of the large differences in leaf surface structure, the walking activity was similar and around 75% on most cultivars. The walking speed was between 0.2 and 0.3 mm/s on all cultivars and was not significantly different from the speed on tomato. On hairless sweet pepper leaves the walking speed is much higher (0.73 mm/s), so the hairs onGerberaleaves do hamper parasitoid females and result in a strong reduction of the walking speed, but the variation in hair density and shape onGerberadoes not lead to differences in walking activity, pattern, and speed. It appears that the hairs ofGerberaare less of an obstacle forE. formosathan the stiff, large hairs occurring in a high density on cucumber, where the walking speed of the parasitoid is less than 0.2 mm/s. A rise of temperature of 5°C gave a significantly higher walking speed (0.39 mm/s) ofE. formosafemales on all cultivars tested. The relative straightness of the walking track was high and the same on all cultivars. Consequences of the results of the searching behavior ofE. formosaonG. jamesoniicultivars are discussed with respect to other host plants. As parasitoid walking speeds are the same onGerberaand tomato, and whitefly reproduction is also similar on these two host plants, we conclude that biological control of whiteflies onGerberais a realistic option. This conclusion is confirmed by the strong increase of commercial biological control onGerberawhich occurred during the past 5 years.     

Speciation inVirgilia (Fabaceae): Allopatric divergence followed by introgression?

Levels of variation revealed by starch gel-electrophoresis were compared with morphological and chemical variation within and among the species and subspecies ofVirgilia:V. oroboides subsp.oroboides, V. oroboides subsp.ferruginea andV. divaricata. The data sets exhibited concordance in that all point to a very close relationship between the taxa. Differences are mostly quantitative and an overlapping east-west gradient of character variation is indicated. Analysis of morphological and chemical characters showed thatV. oroboides subsp.ferruginea andV. divaricata are relatively distinct, whereas allozyme analysis indicated a high degree of genetic similarity among populations of these two taxa. The observed pattern of variation suggests relatively recent speciation with subsequent introgressive hybridisation resulting in a geographical and ecological gradient.