【作者】 刘志国；

【导师】 蔡永立； 李恺；

【作者基本信息】 华东师范大学 ， 生态学， 2011， 博士

【摘要】 植物与昆虫是森林生态系统的重要组成成分,它们通过长期的协同进化形成了密切的相互关系。两者在森林生态系统中发挥着承上启下的作用,连接初级生产和高级消费,是森林生态系统中重要的动态中心。由于营养丰富且较为脆弱,幼叶受到了食叶昆虫的广泛取食,面临巨大的取食压力,是植物叶片受损的主要时期。因此,幼叶期虽然短暂,却是了解植物与食叶昆虫相互关系的关键时期。植物的幼叶如何应对食叶昆虫的取食压力,一直是进化生物学和生态学研究关注的热点问题。要解决这一关键问题,则主要取决于下几个方面问题的回答：1)植物的幼叶面临怎样的虫食压力?2)面对虫食压力,植物幼叶又是如何进行防御,形成了怎样的防御对策?3)幼叶对虫食的防御对策受到哪些因素的影响?4)幼叶质量对食叶昆虫产生了怎样的影响,食叶昆虫如何与之适应?常绿阔叶林是我国亚热带地区的地带性植被,具有与热带森林和温带森林明显不同的种类组成和群落结构。论文选择位于我国亚热带南部的福建梅花山(116°45’25"--116°57’24",25°15’24"-25°35’44")和中北部的浙江天童(29°48’N,121°47’E)两地常绿阔叶林中代表植物作为研究对象,通过野外跟踪观测、室内属性分析、人工控制模拟、食叶昆虫调查和饲养等多种手段,研究了幼叶的物候特征、营养物质含量、物理特性、防御物质含量、叶片虫食强度以及食叶昆虫的多样性、生长发育和防御特征,以探讨亚热带常绿阔叶林中植物叶片的虫食特征、幼叶的综合防御对策、幼叶防御对策的影响因素以及幼叶质量对食叶昆虫的影响。主要研究结果如下：1.常绿阔叶林植物表现出介于热带雨林与温带落叶阔叶林之间的过渡性的叶片虫食特征,幼叶期是虫食发生的主要时期为了解亚热带常绿阔叶林植物面临怎样的虫食压力,本文对福建梅花山和浙江天童两地76种常绿阔叶林植物的叶片的虫食进行了调查,结果显示：76种植物平均虫食率为7.21%,虫食频度为32.95%,多数植物的叶片虫食率低于10%,叶片虫食频度主要分布在10-60%之间。乔木种与灌木种、优势植物与伴生植物之间的叶片虫食率和虫食频度均不存在显著差异(p>0.05)。超过60%的叶片虫食率和虫食频度发生在展叶期。福建梅花山常绿阔叶林植物的叶片虫食率(p=0.012)和虫食频度(p=0.74)均高于浙江天童。植物幼叶的虫食率随着海拔的升高而下降。以上结果表明,常绿阔叶林植物的叶片虫食强度介于热带雨林和温带森林之间,展叶期是叶片虫食发生的主要阶段,表现出过渡性特征；叶片的虫食在不同生活型和优势程度的植物间存在差异；叶片虫食率随纬度的升高和海拔的上升而降低。2.幼叶的不同属性之间存在相互关系,具有防御功能的属性共同作用,形成了三种综合防御对策为明确亚热带常绿阔叶林植物如何应对昆虫的取食压力,本文以浙江天童地区38种常绿阔叶林植物幼叶属性和虫食数据为基础,开展了幼叶对食叶昆虫的防御对策研究。结果显示,幼叶的物候、营养和次生代谢物含量等具有防御功能的属性之间存在相互关联,不同的属性常常共同发生变化,形成固定的防御属性组合。亚热带常绿阔叶林植物幼叶的综合防御对策可以分为以下三种：小叶片出叶时间早,植物叶片含氮量和含水量均很低,符合“低营养质量”对策；大叶片的植物出叶时间晚,但展叶速度快,叶片营养质量高,防御能力不强,采取“逃避”对策；较大叶面积的植物叶片营养质量虽然也很高但物理和化学防御能力明显较高,采用“高营养且防御”的对策。以上结果表明,亚热带常绿阔叶林植物幼叶中多种具有防御功能的属性之间存在相互关联,这些防御属性共同变化,形成集中的综合防御对策。不同的植物在面对类似的昆虫取食压力时形成了“低营养质量”、“逃避”和“高营养且防御”三种综合防御对策。3.幼叶的防御对策受到发育阶段、展叶阶段和早期虫食诱导的影响幼叶对食叶昆虫的防御能力受到多种因素的影响,本文以亚热带常绿阔叶林中的典型代表植物木荷(Schima superba)和栲树(Castanopsis fargesii)为研究对象,通过对不同发育阶段植株、不同展叶阶段和不同早期昆虫取食状况的幼叶的叶片属性和虫食的比较分析,探讨幼叶防御对策的影响因素。(1)植物的发育阶段会影响叶片的质量,从而造成植物在不同的发育阶段受到不同的虫食压力。为了解植物发育阶段对叶片质量的影响,本项研究对木荷幼树和成树叶片的营养和防御属性进行了测定。研究结果显示,幼树的食叶昆虫密度为成树的1.52倍,幼树的叶片虫食率(F1,29=6.7,p<0.01)和虫食频度(F1,29=8.2,p<0.01)均明显高于成树叶片。造成不同发育阶段叶片虫食不同的主要原因是由于叶片属性之间的差异,虽然两个发育阶段植株的叶片硬度、含水量和含氮量不存在显著差异,但是成熟植株叶片的出叶同步性(p=0.005)和总酚含量明显高于幼树(44%-4月；29.7%-8月)。研究结果表明,植物的发育阶段对植物的防御能力产生了影响：随着树龄的增加,木荷叶片的防御能力逐渐增强,从而导致成树受到的虫食率和虫食频度均明显低于幼树(p<0.01)。(2)栲树叶片展叶期虫食频度50.72%,叶片虫食率8.25%,展叶过程可分为折叠期和打开期两个阶段,不同展叶阶段的栲树叶片属性和虫食格局存在较大的差异：打开阶段的日虫食频度和日虫食率显著高于折叠阶段(F1,32=8.97p=0.0054；F1,32=12.38,p=0.0014)。折叠期叶片主要受到低强度的虫食,打开期叶片虫食则以较大强度的虫食为主。展叶期,昆虫对叶片的取食主要发生在夜间,夜间虫食率显著高于日间虫食率(t=2.51,p=0.017),变化趋势与每日平均虫食率一致。研究结果表明,栲树的展叶阶段可能影响植物的防御对策,栲树叶片在展叶的两个阶段分别采用“防御”和“逃避”两种不同的防御对策以应对植食性昆虫的取食。(3)诱导防御是植物用来降低昆虫取食偏好性和取食行为的普遍对策。昆虫的取食可以改变植物的物理属性、营养物质含量和化学防御属性,以降低未来可能受到的虫食伤害。研究结果显示：展叶阶段早期受到思茅新木蛾(Neospastos simaona)幼虫取食的木荷叶片,与对照组幼叶相比,表现出更高的硬度和单宁含量,但含水量和含氮量低于对照组叶片；同时,受早期虫食伤害的叶片在试验期间的虫食率也明显低于对照组。以上研究结果表明,食叶昆虫在展叶早期对木荷叶片的取食减低了叶片的营养含量并提高了叶片的防御能力,降低了叶片作为昆虫食物的质量并影响了昆虫的取食行为,从而降低了昆虫的进一步取食。4.叶片的营养和防御属性限制了食叶昆虫的多样性、生长和发育,并影响到食叶昆虫对天敌的防御本文通过对福建梅花山及浙江天童常绿阔叶林植物上食叶昆虫的多样性、取食行为、生活史过程和对天敌防御属性的研究,探讨了幼叶质量对食叶昆虫的影响及两者的相互适应关系。研究结果显示：1)昆虫与植物存在时空一致性,春季植物叶片昆虫密度最高,夏季密度虽然有所降低,但仍保持较高水平,进入秋季后由于昆虫密度快速降低,明显低于春、夏两季。2)植物叶片的营养和防御属性会影响到食叶昆虫幼虫的取食偏好性和生长率,以幼叶为食的幼虫生长率高于以成熟叶为食的幼虫(F1,43=13.50,p<0.001)。由于快速展叶植物叶片的高含氮量和含水量,幼虫生长速率与叶片展叶速率呈正相关(r2=0.64,p<0.001)。专食性幼虫的相对生长速率相对于广食性昆虫在以幼叶和成熟叶为食时分别提高了1.8倍和4.2倍。3)幼虫的防御属性与叶片质量相关,生长速度较慢的广食性昆虫由于发育历期长增加了暴露给天敌的风险,对天敌的防御能力比专食性昆虫更强。以上研究结果表明,食叶昆虫的多样性、生长和发育受到了叶片质量的限制,食叶昆虫为了获得最优的食物资源其发生的时间要与寄主植物物候保持一致,叶片的营养含量会对幼虫的生长速度和发育历期产生影响,进而影响到食叶昆虫对天敌的防御能力。本论文主要创新：(1)亚热带常绿阔叶林分布地区不仅气候条件和变化格局不同于温带与热带地区,植物的物种组成和群落结构具有明显的多样性和自身特点,本论文从时间和空间尺度上研究了亚热带常绿阔叶林植物叶片虫食规律。(2)研究综合野外跟踪观测、叶属性测定、室内培养、人工控制模拟等多种手段,系统研究了植物与食叶昆虫之间的相互关系,这种综合多种方法的系统研究尚不多见。(3)从群落水平总结归纳出亚热带常绿阔叶林植物幼叶对食叶昆虫的防御对策,是对现有植物防御对策理论的发展和补充。(4)本论文以常绿阔叶林代表植物木荷和栲树为研究对象,研究植物防御对策的影响因素,从而对亚热带常绿阔叶林植物的防御对策能够较为全面的认识和了解。(5)本论文结合植物叶片的营养和防御属性,分析测定食叶昆虫在多样性、取食行为、生长发育等方面与植物的相互适应,能够对亚热带常绿阔叶林种植物和食叶昆虫的关系有更为深刻的理解。更多还原

【Abstract】 Plants and insect herbivores are integral to the forest ecosystem. They formed close relationships through a long term evolution process. They connect with primary production and consumption and play a major role on nutrient cycling and energy transfer in forest ecosystem. Young leaves are preferred by herbivores because they are more nutritious and tender in comparision with the mature leaves. The majority of damage occurs during the short window when leaves are young and expanding. Although young leaves are ephemeral, they are key for understanding the interaction relationship between plant and herbivore. We ask how the young leaves protect themselves from feeding by leaf-feeding insects?Before answering this problem, we need to address the following questions:(1) What are the herbivory patterns of young leaves? (2) Facing herbivory pressure, do young leaves present similar suits of traits that characterize defense sydromes and what are these syndromes? (3) What factors influence plant defense? (4) How do leaf defense syndromes affect insect herbivores? And how the insect herbivores adapt to it?Evergreen broad-leaved forest is the regional vegetation of subtropical area in eastern China, and differs from tropical and temperate forests in both species diversity and community structure. To understand the plant-insect interactions, the study was conducted in Mt. Meihuashan, Fujian province (116°45’25"-116°57’24" 25°15’24"-25°35’44") and Tiantong National Forest Park, Zhejiang province (29°48’N,121°47’E). Through field monitoring, traits analyzing, artificial simulating and leaf-feeding insect larvae feeding, herbivory pattern diversity, leaf phenology, leaf traits, insect diversity, larvae growth and defense traits were record. We analyzed the characteristics of leaf herbivory, plant defense syndromes and the effects of plant quality on leaf-feeding insects. The results and conclusions were as follows:1. The leaf damage of leaves in evergreen broad-leaved forest is between those in tropical rain forest and temperate deciduous forest. The majority of damage occurs during the short window when leaves are young and expanding. To determine the patterns of herbivory in subtropical evergreen broad-leaved forest, the study investigated herbivory rate and frequency on leaves of 76 evergreen plant species in Mt. Meihuashan, Fujian province and Tiantong National Forest Park, Zhejiang province. In this study, herbivory on leaves was 7.21% and herbivory frequency was 32.95%. Leaf herbivory rate in shrub species (7.52%) was significantly higher than that of tree species (7.02%). With herbivory frequency between 10% and 60%, herbivory rates of most species were less than 10%. Herbivory rate on leaves of companion species (7.23%) was higher than dominant species (6.94%), there were no significant difference between them (p>0.05). Over 60% of the lifetime damage occurs during the few weeks that leaves are expanding. More herbivory occurs at lower latitudes. The herbivory rate of young leaves in the same specie decrease along latitudinal gradient.The results indicated that, the leaf damage of leaves in evergreen broad-leaved forest is between those in tropical rain forest (11.1%) and deciduous forest (7.1%). Life form and dominance affected herbivory on leaves. Rates of leaf damage reduced with the rising of latitude and altitude gradient. The majority of damage occurs during the short window when leaves are young and expanding.2. Young leaves have traits against herbivory that may occur together and increase defense efficiency. The plant defense traits grouped into three syndromes for plants.To test whether there are defense syndomes in evergreen broad-leaved forest, we measured defense traits and leaf herbivory on 38 plants in Tiantong, Zhejiang province. Our research showed that most pairwise correlations of traits were complementary. The defense syndromes of these species clusters in evergreen broad-leaved forest are associated with either low nutritional quality, or a balance of higher nutritional quality coupled with defense or escape:(1) The small area species with lower leaf nutrients content and water content might employ’low nutritional quality’strategy to reduce leaf losses. (2) The large area species that leafed out later with higher leaf nutrients content, low chemical defense and toughness but high leaf expansion rate might employ’escape’strategy to reduce insect attack. (3) The species that leafed out with larger area, higher leaf nutrients content and higher defense material and lower leaf expansion rate, might employ’nutrition and defense’strategy to reduce leaf losses.The results suggested that, plant defense are composed of multiple traits, they might be organized into coadapted complexes. The defense syndromes of these species clusters in evergreen broad-leaved forest are associated with’low nutritional quality’,’nutrition and defense’or’escape’.3. Defense strategies of young leaves were influenced by ontogenetic stages, expansion stages and early-season insect attack.Many factors may influence the defense of young leaves against leaf-feeding insects. We carried out studies on the typical evergreen broad-leaved forest plants—Schima superba and Castanopsis fargesii to understand the effect factors of plant defense.(1) Leaf traits influencing plant quality as food and/or shelter for herbivores may change during plant ontogeny, and as a consequence, influence the amount of herbivory that plants receive as they develop. To assess plant ontogenetic differences in foliage quality as food for herbivores, nutritional and defensive traits were evaluated in saplings and reproductive trees of S. superba. Herbivore density was 1.52 times higher and herbivory was significantly greater in saplings than in reproductive trees (p<0.01). Accordingly, concentrations of total foliar phenols were higher in reproductive trees than in saplings (44%-April;29.7%-August), whereas leaf toughness, water and nitrogen concentration did not vary between ontogenetic stages. The results indicated that ontogenetic changes in traits influencing plant defense capability. With increasing defense capability, leaf damage was lower for reproductive trees than for saplings (p<0.01).(2) In this study, we measured damage throughout the whole leaf expansion to understand the herbivory pattern and the defense strategy on young leaves of C. fargesii. Leaf herbivory frequency and herbivory rate on young leaves in unfolded stage were significantly higher than in folded stage (F1,32=8.97, p=0.0054;F1,32=12.38, p=0.0014). The herbivory of leaves in folded stage consisted with large amount of low proportion herbivory, while the leaves in folded stage were mainly occupied by high proportion herbivory. Leaves were intensively grazed in the nighttime (t=2.51, p=0.017), which accounted for about 85% of the total leaf herbivory. Young leaves of C.fargesii might follow different strategies in the two expansion stages.(3) Induced defense is a principal response of plants to herbivory. Induced responses to herbivory are physical, nutritional, and chemical traits that change in plants following damage or stress, and that reduce the performance of herbivores. The result showed that young leaves that were damaged by Neospastos simaona in the beginning of the leaf expansion had higher toughness and concentration of tannins, but lower water content and nitrogen content when compared with the control leaves. As a result, the damaged shoots had lower rates of herbivory than control shoots. The results may imply that early-season herbivory on the leaves of S. superba reduced the nutritional quality of leaves and increased the amount of secondary compounds, therefore influencing later-season herbivory through the induction of plant responses that may act to reduce plant quality as food for herbivores.4. Diversity, growth and defensive traits of caterpillars were correlated with the nutritional and defensive traits of their hosts.A survey of leaf-feeding insect larvae feeding on plants was carried out in Tiantong, Zhejiang province. The results showed that:(1) There were temporal and spatial consistence on insects and young leaves. The greatest caterpillar density related to high leaf quality on spring, and maintained high density during summer. Then insect density decreased rapidly form autumn. (2) Growth and defensive traits of caterpillars were correlated with the nutritional and defensive traits of their hosts. Growth rates were faster on young than mature leaves (F1,43=13.50, p<0.001), reflecting the higher nitrogen and water content of the former. Growth was also positively correlated with leaf expansion rate (r2=0.51, p<0.001), because of higher nitrogen and water contents of fast-expanding young leaves. Specialists grew faster than generalists, with average growth of 1.8 times on young leaves and 4.2 on mature leaves. Generalists with low growth rate had more defense traits than specialists. Because slow growth for caterpillars increased their risk to natural enemies, generalists had more defense traits than specialists. These results suggested that diversity, growth and defensive traits of caterpillars were limited by leaf quality of host plants. For getting appropriate food resource, it is crucial for caterpillars to be synchronized with their host plants phenology. Growth and larva period of caterpillars were correlated with the nutritional and defensive traits of their hosts, which influenced the defensive traits against natural enemies indirectly.Innovations of this PhD dissertation are mainly:(1) Evergreen broad-leaved forest is the regional vegetation of subtropical area in eastern China, and differs from tropical and temperate forest in both species composition and community structure. We summarized the patterns of leaf herbivory in subtropical evergreen broad-leaved forest from space and time level.(2) Interactions between plant and leaf-feeding insects were studied systemically by field investigating, leaf traits analying, insects rearing and artificial simulating. The research system of multiple methods is rare.(3) Defense syndromes of young leaves were studied at the community level. It could be useful to add further insights to defense syndrome theory.(4) The factors which affect defense syndromes of young leaves were evaluated in the two typical evergreen broad-leaved forest plants—Schima superba and Castanopsis fargesii. Thus defense syndromes of young leaves in subtropical evergreen broad-leaved forests can be comprehensive known and understanded.(5) The relationships how host nutrition and defense traits affect in herbivore diversity, growth rates and defenses against natural enemies were determined. It is capable of deeper understanding on the interaction relationship between plant and leaf feeding insects更多还原