Institutional Repository of Xishuangbanna Tropical Botanical Garden
| 榕树（Ficus microcarpa）果内榕小蜂物种共存及传粉榕小蜂欺骗性演化的机制 | |
| Alternative Title | The Mechanism of Fig Wasp Coexistence and Cheating Evolution of Pollination on Ficus microcarpa |
| 张 亭 | |
| Thesis Advisor | 彭艳琼 |
| 2020 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 中国科学院西双版纳热带植物园 |
| Degree Name | 理学博士 |
| Degree Discipline | 生态学 |
| Keyword | 榕树，传粉榕小蜂，物种共存，繁殖差异，欺骗性进化 |
| Abstract | 榕树与传粉榕小蜂是动植物互利共生关系的典范，二者在繁殖上互相依赖。大多数的榕树与传粉榕小蜂遵守“一对一”规则，但随着相关研究的深入，一种传粉榕小蜂为多种榕树传粉及一种榕树有多种传粉榕小蜂的实例逐渐增多，正是一种榕树有多种传粉榕小蜂共存，为某种传粉者演化为降低寄主适合度的欺骗者提供了契机。全世界已知约580种传粉榕小蜂，目前已知有3种演化为只产卵、不传粉的欺骗者。第一例欺骗者Ceratosolen galili与传粉者Ceratosolen arabicus共存于分布在非洲的Ficus sycomorus 上，二者亲缘关系很远，寄主转移是导致其欺骗性演化的主要机制。分布于亚洲热带地区高山榕Ficus altissima 上的传粉者Eupristina altissima 和欺骗者Eupristina sp. 是同源姐妹种，欺骗者付出了孕卵量少，后代适合度低的代价，第三种欺骗者是我们近期在榕树（Ficus microcarpa）上发现，也是一种尚未描述的Eupristina属小蜂。已知传粉是维持榕-蜂互利共生系统的关键，寄主惩罚效应降低欺骗者的适合度被认为是维持互利共生系统稳定的重要机制。在互利共生系统中传粉欺骗性极为罕见，其演化机制及如何共存于互利共生系统中一直是生态学中受关注的热点和研究的难点。本论文聚焦原产云南西双版纳热带地区的榕树（Ficus microcarpa）及其榕小蜂系统，通过系统观察榕树繁殖物候、调查其传粉者和欺骗者的发生模式和种群动态，结合人工控制实验全面地比较传粉者和欺骗者的传粉结构、行为及繁殖差异；并整合榕小蜂物种分类、功能性状及系统发育，研究多营养级榕小蜂群落的构建。再通过化学生态学手段收集、分析榕树隐头花序（榕果）释放的挥发物，以及榕小蜂释放的表皮碳氢化合物的成分，探讨榕与蜂及蜂与蜂之间的化学通讯及识别机制。综合分析榕树果内榕小蜂共存，以及传粉欺骗性的演化与稳定共存于榕-蜂互利共生系统中的机制。获得如下主要研究结果：1. 榕树在西双版纳热带地区种群内全年有树结果，通常萌发新叶时开始结果，花期表现树内同步、树间异步，雌花期和雄花期重叠较好，榕树与榕小蜂繁殖物候衔接紧密。榕树结果高峰期出现在雾凉季，但传粉者和欺骗者的繁殖呈现极端的季节变化，传粉者主要发生于高温雨季，同时繁殖更多的种子；而干季大量榕果主要被欺骗者占据，两者发生的高峰期呈现季节性交替，在传粉者表现不佳的季节，竞争减弱促进了欺骗者的发生。西双版地处热带北缘极端的季节变化为欺骗者的演化创造了条件，而传粉者和欺骗者时空生态位的分化有利于维持它们稳定共存。2．榕树的传粉者（Eupristina verticillate）具发达的传粉结构和主动传粉行为，有效生产大量种子；而共存的欺骗者前足基节上花粉刷消失，中胸上的花粉筐退化，没有主动传粉行为，对寄主榕树的种子生产没有贡献，已演化为只产卵不传粉的欺骗者。系统发育关系显示共存于榕树上的传粉者和欺骗者是同源姐妹种关系，两者有相似的个体大小和孕卵量，但无论是单独占据榕果，还是共享同一个榕果的直接竞争中，欺骗者总是比传粉者产下相同或更多的卵，最终与传粉者繁殖后代的适合度相似或更高。对比传粉者带粉与不带粉的4个重复实验结果证实：榕树并未惩罚不带粉的传粉榕小蜂，其繁殖的后代数量与带粉传粉者繁殖的后代数量相似或更多，表明榕树缺乏寄主惩罚效应是导致其传粉榕小蜂欺骗性演化的主要机制。3. 除了传粉者和欺骗者，榕树果内还共存着12种非传粉榕小蜂，它们在榕果发育的不同阶段访果产卵，先到达榕果产卵的小蜂拥有丰富的雌花资源，同一榕小蜂营养级内低营养级的造瘿类榕小蜂之间存在着强烈的生态位优先效应，优先产卵利用雌花直接排斥后到达的榕小蜂。跨营养级时，先到达榕果产卵的低营养级榕小蜂会产生生态位重建效应，造瘿者为后来的高营养级的寄生者提供生态位。榕小蜂群落的物种组成结构很大程度上决定于最先到达榕果产卵的造瘿者，表现为生态过程的随机性；而榕小蜂群落的功能性状和系统发育结构取决于榕果内可用的资源和生态位，即生态过程的决定性。结果支持生态过程的偶然性与必然性共同作用，决定了多营养级榕小蜂群落的构建。4. 榕树不同发育期榕果释放的挥发物，共收集、鉴定出21种化合物，分为脂肪酸衍生物、萜类化合物和芳香族三大类。不同发育期榕果释放的挥发物组分差异明显，雌花期传粉前后的挥发物差异表现为传粉后萜类化合物下降，脂肪酸衍生物增加，特征化合物2-庚酮和3-辛酮消失，D-柠檬烯下降，可巴烯、环己烷和2-己烯醛上升。表明榕树及其传粉榕小蜂的互利共生关系是通过多种化合物的“泛化”策略来维系的。且雌花期榕果对传粉榕小蜂的吸引及雄花期榕果对榕小蜂的趋避作用，形成了榕-蜂之间化学联系的“推拉”的模式。5. 对目前收集到的榕小蜂表皮碳氢化合物进行初步分析，结果显示：来自不同寄主榕树同一属（Ceratosolen）的传粉榕小蜂，它们表皮碳氢化化合物在对叶榕传粉榕小蜂（C. solmsi）、鸡嗉子榕传粉榕小蜂（C. gravayli）和异形花榕传粉榕小蜂（Ceratosolen sp.）三种间较相似，但在木瓜榕传粉榕小蜂（C. emarginatus）和聚果榕传粉榕小蜂（Ceratosolen sp.）两种间差异较大。同种传粉榕小蜂雌性和雄性的表皮碳氢化合物组成相似，但各成分的含量存在差异。共存于高山榕果内的欺骗者与传粉者相比，体表化合物种类更少，存在独特的标志性化合物，并减少自身的表皮碳氢化合物的特征，让欺骗者几乎“透明”地共存于在榕-蜂互利共生系统中。综上所述，通过本研究，掌握了西双版纳热带地区榕树及其榕小蜂的繁殖物候特点，弄清了传粉者和欺骗者的发生规律和共存模式。并在传粉结构、行为和繁殖差异的比较中，阐明了欺骗者演化没有付出明显代价，榕树寄主惩罚效应的缺失是导致其欺骗性演化的主要机制。也从榕小蜂群落组成、种间化学通讯等角度，综合揭示榕树果内榕小蜂共存及传粉榕小蜂欺骗性演化的机制。 |
| Other Abstract | The interaction between Ficus trees and their pollinators (Agaonidae) presents a striking example of mutualism, they only depend on each other for reproduction. Although most Ficus species and their pollinators are strictly species-specific, increasing of studies in depth have reported examples that one pollinating wasp species pollinated several fig trees and one species fig tree host multiple pollinating wasps. Because several pollinating wasps pollinate for one species of fig trees, which gives a chance that some of the mutualistic pollinator become cheater that reduce the fitness of host. Three cases of cheaters in fig-wasp mutualism have been confirmed that lost the pollinating function for their host but only ovipositing on their host. The first case was the cheater Ceratosolen galili and pollinator Ceratosolen arabicus are associated with African Ficus sycomorus, the cheating mechanism is host shift because of their far phylogenetical relationship of pollinator and cheater. The second, cheater Eupristina sp. and pollinator Eupristina altissima from F. altissima are sister species, the cheating pays large cost of lower offspring fitness. The third cheater case, an undescribed Eupristina sp. that recently found on F. microcarpa by our group. It’s known that the pollination is the key to the mutualism, host saction that decrease the fitnees of cheater plays an important role to stabilize the mutualism. Which cause the rarity of the pollination cheating in mutualism, the evolution of cheating has been a foundamental and ecological puzzle. This study focused on the F. microcarpa and it’s related wasps in it’s typical natural distribution area, Xishuangbanna of Yunnan province, the phenological survey was conducted, abundance variation of pollinator and cheater, anatomical, behavioral, phylogenetic, and conducted experiment studies have done to compare the difference of pollinator and cheater systermatically. And the species, functional and phelogenetic diversities of fig wasp community were integrally studied to discover multitrophic community assembly of fig wasps. By means of chemical ecology to extract the fig volatile compounds and the curticular hydrocarbon to explore the communicational mechanism between figs and wasps and the recognition among wasp species. The final aime was to explore comprehensively the mechanism of fig wasp coexistence and the cheating evolution of pollination, as well as how does the cheater coexist in mutulism stably. Results were as following: 1. F. microcarpa initiated figs all year round in Xishuangbanna, usually leaf and fig initiation was synchronous. Fig development phases were synchronous within tree but desynchronized among trees. B phase and D phase figs overlapped significantly and the reproduction of fig-wasp mutualism matched quite well. Pollinators mainly dorminated the hot rainy season with huge seed production, while cheaters dorminated the most figs in hot dry and cool dry season with markedly decreasing of pollinators and seeds. Abundance peak of these two species appeared in turn, during periods of poor performance of pollinator, an opportunity relaxation of competitive exclusion facilitates the coexistence of cheater, periodic rearrangements of mutualism dynamics may due to strongly seasonal environment. Moreover, the relative abundance of the two Eupristina species strongly varied with season and was related to local wind direction. The results indicate spatial heterogeneity in source pools contributes to the dynamic local coexistence between the cheater and pollinator. 2. Eupristina verticillata was a pollinator exhibiting morphologies and active behaviors consistent with observed seed production. Eupristina sp. lacked these traits and pollinating behavior, reduced both female and male reproductive success of the host, and was a “cheater” exploited the mutualism. Phylogenetic analyses suggest that they were sister taxa, they had similar body size and eggloads. Morever, cheater enjoyed a relative fitness advantage the same with or over pollinator, both as individual foundresses in separate figs, with interspecific competition in the same fig or seperated in direct competition with the pollinator and cheater within the same fig. Specifically, the cheater exhibited similar or higher oviposition, larval survival, and overall reproductive success than the pollinator. In contrast to all studies of actively pollinated figs and their pollinators, no fitness reduction of wasps that do not pollinate relative to wasps that do. The results suggest the low to nonexistent host sanctions on wasps that do not pollinate in this region promote the loss of specialized morphologies and behaviors crucial for pollination and the evolution of cheating. 3. The niche-preemption effect among the gallers at the basal (herbivore wasps) trophic level inhibits the co-existing of different galler species, and the niche-modification effect by successfully established galler species (founders) facilitate the establishment of their late-arriving specific consumers (inquilines and parasitoid wasps). Moreover, alternative fig wasp community stated with different species compositions that depended on the founder species (gallers) indicating a role of historically contingency in driving taxonomic community structure.The composition of traits-based functional groups at local fig wasp communities were deterministic due to the similar resources/niches that each fig can provide, highlighting the deterministic processes in shaping functional and phylogenetic community structure in fig wasp system. 4. Totally 21 volatile compounds belonging to fatty acid derivatives, terpenoids and aromatic compounds were identified from the fig. The components of the volatiles apparently differed among the developmental stages. The contents of terpenoids declined, but fatty acid derivatives increased between before and after the pollination. Especially, the characteristic compounds 2-heptanone and 3-octanone before the pollination disappeared, D-limonene decreased after the pollination, but copanene, cyclohexane and 2-hexenal increased. The results of the pollinator choice showed that the pollinator had higher selection to female phase fig than those in other phases especially male phase. The “push-pull” responses by fig wasps to volatiles released by host fig. There were multiple chemical compounds playing the roles in host recognition of E. verticillata. The mutualistic relationship between F. microcarpa and E. verticillata was maintained by the chemical communication of “generalization” strategy. 5. The preliminary analysis of the cuticular hydrocarbons (CHCs) of the fig wasps collected at present showed that the pollinators from the same genus (Ceratosolen) of different host ficus trees, the CHCs composition of C. solmsi, C. gravayli and Ceratosolen sp. were more similar, but those of C. emarginatus and Ceratosolen sp.1 werequite different. The pollinator female and male had similar CHCs composition, but the content of each component was different. Compared with pollinators, the cheater of F. altissima had fewer CHCs compounds, cheater only had 4 unique signature compounds, which reduced the characteristics of it’s species signature, so the cheaters were almost "transparent" existing in the fig- wasp mutualism system. Overall, from characteristics of the reproduction phenology of F. microcarpa and the abundance dynamic of the related pollinator and cheater in the tropical area of Xishuangbanna, with the clarification of occurrence patterns and coexistence patterns of pollinators and cheaters. Comparison of pollination structure, behavior and reproduction differences, this study showed that the evolution of cheatingdidn’t pay a significant cost, the lack of host sanction leadedto the cheating evolution. On another hand, from the perspective of the composition of the wasp community and the chemical communication between species, the mechanism of the coexistence of the wasps within the figs and the cheating evolution of the pollinating was comprehensively revealed. Key Words: Ficus, Agaonidae, Species coexistence, Reproductive difference, Cheating evolution |
| Pages | 140 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | https://ir.xtbg.ac.cn/handle/353005/11705 |
| Collection | 西双版纳热带植物园毕业生学位论文 |
| Recommended Citation GB/T 7714 | 张 亭. 榕树（Ficus microcarpa）果内榕小蜂物种共存及传粉榕小蜂欺骗性演化的机制[D]. 中国科学院西双版纳热带植物园. 中国科学院大学,2020. |
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| 张亭.pdf（5137KB） | 学位论文 | 开放获取 | CC BY-NC-SA | Application Full Text | ||
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