植食性哺乳动物与植物协同进化研究进展

从动物-植物协同进化模式,植物对动物采食反应及动物对植物防卫的适应对策等方面综述了以植物次生化合物为媒介的植食性哺乳动物-植物协同进化的研究进展,动物与植物的协同进化模式包括成对协同进化,扩散协同进化,躲避-辐射协同进化,多样性的协同进化,平行分枝进化,互惠进化等模式,植物不仅以超补偿反应,物理防卫作为对植食性动物采食的应答,延长植食性动物的觅食时间,降低植食性动物的觅食效率,更能以其派生的次生化合物抑制动物的摄食,进而影响其消化,代谢及生长等生理生态特征,动物通过改变觅食行为,调整对各食物项目的相对摄入量,减少次生化合物的摄入量,动物还通过氧化,还原,络合,改变消化道内环境,形成相应的降解酶,改变代谢率等途径降低次生化合物对其的负作用。     

植物化学防卫与植食性哺乳动物的适应对策

植物化学防卫与植食性哺乳动物的适应是动物—植物系统协同进化研究的重要内容。植物次生化合物可降低动物的食物摄入量及消化率、蛋白质可利用率。某些次生化合物还影响植食性哺乳动物的正常繁殖活动。单宁是动物的重要觅食阻遏剂之一。动物在学习食物选择的过程中,通过认知过程和感知过程处理食物信息,选择食物项目。幼体在胚胎期和哺乳期能从母体获得食物信息,或向有觅食经验的同胞伙伴学习处理食物的经验。动物亦可通过形成络和物,改变体内环境,通过微生物降解、氧化还原、基础代谢率等降低生理对策,以降低植物次生化和物的影响。     

植物的防卫

植物对动物的防卫大体可分为机械防卫和化学防卫两大类。机械防卫主要表现在植物体表具刺、毛和高度角质化与发达的韧皮纤维的产生。化学防卫,即植物体内次级代谢物质的产生。次级代谢物质虽然与植物本身生长发育没有多大关系但它对动物的防卫面广量大,远较物理防卫重要。本文除了介绍物理防卫的一般情况外,重点介绍了次级代谢物的分布,对动物的影响,和昆虫对它的利用。     

植食性哺乳动物食物选择的生态学意义及行为机制

综述了植食性哺乳动物食物选择行为机制的研究进展。植食性动物的食物选择是觅食生态学研究最为活跃的领域,动物食物选择对策主要有营养选择、植物次生化合物假设、营养平衡假设、最优觅食理论和条件性气味回避假设。动物学习食物选择的行为过程中,觅食个体能通过其认知过程和感知过程来处理食物信息、学习选择食物项目是一种可塑性行为方式,有利于动物获得适应栖息地的行为模式。幼体通过社会学习自母体学习的觅食经验,在幼体一生的食物选择中均具有重要的作用。在环境条件相对稳定条件下,幼体可模仿成体的食物选择模式;在环境剧烈变化的条件下,动物通过试错学习选择的食物项目可能较模仿成体所摄取的食物项目营养含量更丰富。     

植物对动物的化学防卫

化学防卫是植物防止动物采食的方法之一。植物组织可能产生一些次生物质来防止动物的采食,这些物质可能是苦的、有毒的、有难闻气味或具有对抗营养物质吸收的作用。酚类化合物对生命有广泛的毒性,萜类化合物与酚类化合物一样,以其难以忍受的味道和致毒作用对植食动物有很强的防护作用。单宁又叫鞣质或鞣酸,是一类分子量比较大的水溶性的多元酚类衍生物的总称。单宁广泛存在于植物界中,尤其在高等植物中更多,例如我们常吃的柿子中就富含单宁。单宁能使蛋白质变性,当动物摄食含单宁的植物时,单宁使动物唾液中的蛋白质沉淀,因此,动物会感觉到这…     

植食性哺乳动物觅食的功能反应及其模型

章主要介绍植食性哺乳动物觅食功能反应与模型的研究进展。植食性哺乳动物觅食的摄入率与其食物可利用性的功能反应是动物觅食生态学过程的基础。可利用植物的生物量密度、植物密度、植物大小、以及动物觅食的口量是影响动物觅食功能反应的潜在变量集。这些变量的差异导致动物功能反应格局的复杂化。生物量密度和植物密度对动物摄入率无明显影响,而植物大小对动物摄入率则有显影响。有食物密集的斑块条件下,以植物大小代替动物     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0％单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

饥饿和食物单宁酸对东方田鼠(Microtus fortis)食物摄入量和觅食行为的影响

实验室条件下,测定饥饿和食物单宁酸对东方田鼠食物摄入量和觅食行为的影响。结果表明,饥饿使实验个体的食物总摄入量增加,食物摄入率及口量大小随饥饿强度的增大而增加,而觅食频次则无显著改变,实验个体每取食回合的觅食时间呈缓慢增加的趋势,与对照组比较,觅食时间差异不显著。东方田鼠优先选择0%单宁酸食物,次为3%单宁酸食物,而对6%单宁酸食物的摄入量最少。在饥饿条件下,东方田鼠食物摄入率的增加主要源于其口量大小,觅食频次和觅摄食时间对食物摄入量增加的贡献不显著。在饥饿条件下,植食性小哺乳动物并未通过延长觅食时间,降低用于防卫、繁殖活动时间来增加食物摄入量,而是通过增加口量大小,提高其食物摄入率来满足其营养需要。验证了饥饿与植物次生化合物共同作用引起田鼠类动物生理的改变,能影响其食物摄入量及觅食行为的假设。     

植物次生物质对于植物生存的重要作用

植物次生物质在植物生存中抵御动物和微生物的侵害,参与同其他植物的生存竞争以及进行植物间化学通讯等方面具有重要的作用。植物次生物质的产生是植物化学保护的必然结果。简要介绍植物次生物质的合成途径。     

脊椎动物传播植物肉质果中的次生物质及其生态作用

在种子植物-动物的互惠关系中,植物果实成熟后需要吸引种子传播者取食果实,传播其种子至适宜萌发的生境,同时又要防御种子捕食者过度消耗种子。果实内的次生物质(如:配糖生物碱、大黄素、辣椒素)在此过程中起到重要的调控作用。依赖脊椎动物传播的肉质果中往往含有与植物茎、叶内相同的次生物质,其种类繁多,主要分为含氮化合物、酚类化合物和萜类化合物。未成熟果实内富含次生物质(如:单宁、大黄素),主要保护未成熟种子不被潜在的捕食者和食果动物取食,这些次生物质的含量通常随果实成熟而降低;其它次生物质(如:脱辅基类胡萝卜素)的含量随果实成熟而增多,可能起到吸引食果动物的作用。在对脊椎动物捕食的抵御中,果实内不同类型的次生物质促使成熟果实对所有脊椎动物都有毒性(专毒性)或者仅对种子捕食者有毒性(泛毒性)。肉质果内的次生物质对植物-食果动物相互关系的调控作用,还可以通过调节动物取食频次和数量、抑制和促进种子萌发、改变种子在肠道的滞留时间、吸引传播者等生态作用而实现。某种次生物质往往集多种生态作用于一身。目前对肉质果内次生物质与脊椎动物相互关系的探讨还不够深入。未来研究需要综合考虑植物次生物质与果实生理生化、形态学等特征对食果者的综合调控机理;次生物质在种子传播后的调控作用对植物种群或群落结构和分布格局的影响;从动植物协同进化角度探讨植物次生物质的产生、防御和吸引策略与脊椎动物对果实的选择和消费之间的关系等。开展脊椎动物传播肉质果实中次生物质的研究,对完善种子传播机制、植物繁殖和更新格局,丰富动植物相互作用、协同进化理论具有重要的意义。     

Diversity of plant–animal interactions: Possibilities for a new plant defense indicator value?

The interactions between herbivores and plants are of general interest in ecology. Even though the extensive research carried out during the last decades has culminated in many theories, additional studies are necessary to validate these findings. In particular, the hypotheses dealing with the complex interrelations of plant defense mechanisms and herbivores continue to be debated.In this paper, we develop a new indicator value that quantifies the defense mechanisms of Central European woody plants against large mammalian herbivores. The indicator value is based on three plant-specific traits: chemical defense (toxic compounds, digestion inhibitors), mechanical defense and leaf size. Our validation of the newly established indicator shows that evergreen woody plants have a significantly higher indicator value than deciduous woody plants. Moreover, plant defense is correlated with growth height: woody plants growing in the browsing zone preferred by large mammalian herbivores have significantly higher levels of defense compared with woody plants capable of growth high above the reach of large herbivores.We conclude that the new plant defense indicator value is a valuable tool for the validation of existing hypotheses and habitat calibration on a statistical basis. The quantification of plant mechanisms of defense against large herbivores produces a significantly better understanding of the multifaceted nature of plant–animal interactions and should contribute positively to future studies.     

Mechanisms of plant defense against insect herbivores

Plants respond to herbivory through various morphological, biochemicals, and molecular mechanisms to counter/offset the effects of herbivore attack. The biochemical mechanisms of defense against the herbivores are wide-ranging, highly dynamic, and are mediated both by direct and indirect defenses. The defensive compounds are either produced constitutively or in response to plant damage, and affect feeding, growth, and survival of herbivores. In addition, plants also release volatile organic compounds that attract the natural enemies of the herbivores. These strategies either act independently or in conjunction with each other. However, our understanding of these defensive mechanisms is still limited. Induced resistance could be exploited as an important tool for the pest management to minimize the amounts of insecticides used for pest control. Host plant resistance to insects, particularly, induced resistance, can also be manipulated with the use of chemical elicitors of secondary metabolites, which confer resistance to insects. By understanding the mechanisms of induced resistance, we can predict the herbivores that are likely to be affected by induced responses. The elicitors of induced responses can be sprayed on crop plants to build up the natural defense system against damage caused by herbivores. The induced responses can also be engineered genetically, so that the defensive compounds are constitutively produced in plants against are challenged by the herbivory. Induced resistance can be exploited for developing crop cultivars, which readily produce the inducible response upon mild infestation, and can act as one of components of integrated pest management for sustainable crop production.     

Seasonal variation in the secondary chemistry of foliar and reproductive tissues of Delphinium nuttallianum

Plant secondary compounds are critical in affecting interactions between plants and their herbivores. The norditerpene alkaloids are secondary compounds in Delphinium (larkspur) species which are divided into two classes: the N-(methylsuccinimido) anthranoyllycoctonine (MSAL-type) and non MSAL-type, and are known to be toxic to herbivorous insects and livestock. Alkaloid concentrations were measured in a whole plant context in vegetative and reproductive tissues in Delphinium nuttallianum at different stages of plant maturity at two locations to explore how plant maturity affected alkaloid concentrations within a growing season. Alkaloid concentrations differed between vegetative and reproductive tissues, with vegetative tissues having significantly lower alkaloid concentrations than reproductive tissues. However, no systematic differences in alkaloid concentrations were observed at different plant maturity stages across the growing season. Based on the data we suggest that alkaloid allocation in different plant parts of D. nuttallianum is influenced by life history of the plant, consistent with plant defense theory. At one location, as pods mature the qualitative alkaloid composition changed through structural diversification of the alkaloids present. The ecological significance of this structural diversification awaits further exploration.     

The defense hypothesis of elemental hyperaccumulation: status,challenges and new directions

Elemental hyperaccumulation may have several functions, including plant defense against natural enemies. A total of 34 studies, including 72 experimental tests, have been conducted to date. At least some tests have demonstrated defense by hyperaccumulated As, Cd, Ni, Se and Zn, but relatively few plant taxa and natural enemies have been investigated. Defense by hyperaccumulated Ni has been shown for most leaf/root chewing herbivores and pathogens tested (20 of 26 tests) but not for herbivores of other feeding modes (1 of 8 tests). Most tests (5 of 6) using Ni concentrations below accumulator levels found no defensive effect, and the single test using plants in the accumulator range also found no effect. For Zn, mixed results have been reported for both hyperaccumulator (3 of 6 tests showed defense) and accumulator levels (3 of 4 tests showed defense). These tests have focused exclusively on leaf chewing/scraping herbivores: no herbivores of other feeding modes, or pathogens, have been tested. Both hyperaccumulator and accumulator concentrations of Se generally have shown defensive effects (12 of 14 tests). Most (75%) of these positive results used plants with accumulator Se concentrations. The three tests of Cd showed defensive effects in two cases, one for hyperaccumulator and one for sub-accumulator Cd concentrations. Arsenic has been tested only once, and was found effective against a leaf-chewing herbivore at a concentration much less than the hyperaccumulator level. Defense studies have used a variety of experimental approaches, including choice and no-choice experiments as well as experiments that use artificial diet or growth media. Investigations of hyperaccumulation as a defense against natural enemies have led to two emerging questions. First, what is the minimum concentration of an element sufficient for defense? Evidence suggests that plants other than hyperaccumulators (such as accumulators) may be defended by elements against some natural enemies. Second, do the effects of an element combine with the effects of organic defensive compounds in plants to produce enhanced joint defensive effects? Recent investigation of this “joint effects hypothesis,” using Ni and secondary plant compounds in artificial insect diet, has demonstrated joint effects. Initial answers to both these questions suggest that defensive effects of elements in plants are more widespread than previously believed. These results also suggest an evolutionary pathway by which elemental hyperaccumulation may have evolved from accumulation. In this “defensive enhancement” scenario, defensive benefits of elevated levels of elements may have led to stepwise increases in element concentrations that further magnified these benefits. This series of steps could have led to increased accumulation, and ultimately hyperaccumulation, of elements by plants.     

植物次生代谢物对植食性哺乳动物营养和生理生态特征的影响

植物次生代谢物对植食性哺乳动物的营养和生理生态效应是动植物相互关系研究中的一个重要方面。本文简要介绍了植食性哺乳动物处理植物次生代谢物的一般途径,着重阐述了植物次生代谢物对植食性哺乳动物的营养和生理特征的限制方式,并对决定植食性哺乳动物处理植物次生代谢物能力差异性的相关因素进行了探讨。最后,结合国际上的研究趋势,论述了国内开展此类研究的方向和重点。     

Selection Mosaic Exerted by Specialist and Generalist Herbivores on Chemical and Physical Defense of Datura stramonium

Selection exerted by herbivores is a major force driving the evolution of plant defensive characters such as leaf trichomes or secondary metabolites. However, plant defense expression is highly variable among populations and identifying the sources of this variation remains a major challenge. Plant populations are often distributed across broad geographic ranges and are exposed to different herbivore communities, ranging from generalists (that feed on diverse plant species) to specialists (that feed on a restricted group of plants). We studied eight populations of the plant Datura stramonium usually eaten by specialist or generalist herbivores, in order to examine whether the pattern of phenotypic selection on secondary compounds (atropine and scopolamine) and a physical defense (trichome density) can explain geographic variation in these traits. Following co-evolutionary theory, we evaluated whether a more derived alkaloid (scopolamine) confers higher fitness benefits than its precursor (atropine), and whether this effect differs between specialist and generalist herbivores. Our results showed consistent directional selection in almost all populations and herbivores to reduce the concentration of atropine. The most derived alkaloid (scopolamine) was favored in only one of the populations, which is dominated by a generalist herbivore. In general, the patterns of selection support the existence of a selection mosaic and accounts for the positive correlation observed between atropine concentration and plant damage by herbivores recorded in previous studies.     

Plant breeding: importance of plant secondary metabolites for protection against pathogens and herbivores

Summary Chemical protection plays a decisive role in the resistance of plants against pathogens and herbivores. The so-called secondary metabolites, which are a characteristic feature of plants, are especially important and can protect plants against a wide variety of microorganisms (viruses, bacteria, fungi) and herbivores (arthropods, vertebrates). As is the situation with all defense systems of plants and animals, a few specialized pathogens have evolved in plants and have overcome the chemical defense barrier. Furthermore, they are often attracted by a given plant toxin. During domestication of our crop and food plants secondary metabolites have sometimes been eliminated. Taking lupins as an example, it is illustrated that quinolizidine alkaloids are important as chemical defense compounds and that the alkaloid-free varieties (sweet lupins), which have been selected by plant breeders, are highly susceptible to a wide range of herbivores to which the alkaloid-rich wild types were resistant. The potential of secondary metabolites for plant breeding and agriculture is discussed.     

Plant volatiles as method of communication

Plants emit volatile compounds that can act as a communication method to insects, neighboring plants and pathogens. Plants respond to leaf and root damage by herbivores and pathogens by emitting these compounds. The volatile compounds can deter the herbivores or pathogens directly or indirectly by attracting their natural enemies to kill them. The simultaneous damage of plants by herbivores and pathogens can influence plant defense. The induced plant volatiles can also make neighboring plants ready for defense or induce defense in parts distant from the damaged area of the same plant. Belowground root herbivory can alter the defense response to aboveground leaf herbivory. In addition, most plants normally emit volatile compounds from their flowers that directly attract foraging mutualistic insects for nectar, which in turn perform the very important function of pollination for subsequent reproduction. The volatile compounds emitted from the floral and vegetative parts of plants belong to three main classes of compounds: terpenoids, phenylpropanoids/benzenoids, and C6-aldehydes (green-leaf volatiles). The volatile phytohormones methyl salicylate and methyl jasmonate serve as important signaling molecules for communication purposes, and interact with each other to optimize the plant defense response. Here we discuss and integrate the current knowledge on all types of communication between plants and insects, neighboring plants and pathogens that are mediated through plant volatiles.     

Detoxification rates of wild herbivorous woodrats (Neotoma)

The detoxification systems of mammalian herbivores are thought to have evolved in response to the ingestion of plant secondary compounds. Specialist herbivores consume high quantities of secondary compounds and are predicted to have faster rates of Phase 1 detoxification compared to generalist herbivores. We tested this hypothesis by comparing the performances of a specialist (Neotoma fuscipes) and generalist (Neotoma lepida) herbivore using hypnotic state assays. Herbivores foraging in nature were live trapped and injected with hexobarbital (100 mg/kg). We measured the length of time in the hypnotic state as the time in which the animal was unable to right itself twice in 30 s. The specialist metabolized hexobarbital 1.7 times faster than the generalist (F(1, 19) = 9.31, P = 0.007) as revealed by its significantly shorter time spent in the hypnotic state (56+/-9 min vs. 87+/-8 min, respectively). The results are consistent with the hypothesis that specialists have faster rates of Phase 1 detoxification. This is the first evaluation of the detoxification capability of mammalian herbivores foraging under natural conditions. Hypnotic state assays have broad potential applications to the study of vertebrate-plant interactions.