福州大叶榕隐头果内的小蜂群落结构与多样性

吴文珊 Wu Wenshan,刘亮 Liu Liang,陈友铃 Chen Youling,蔡美满 Cai Meiman

doi:10.5846/stxb201101140076

Abstract

对福州2个样地10株大叶榕果内小蜂群落组成和物种多样性进行研究。全年在两个样地267个隐头果内共收集到小蜂13458只。发现大叶榕隐头果内有7种小蜂,隶属小蜂总科Chalcidoidae中的榕小蜂科Agaonidae、金小蜂科Pteromalidae的隐针榕小蜂亚科Epichrysomallinae、锥尾榕小蜂亚科Otitesellinae和延腹榕小蜂亚科Sycoryctinae;广肩小蜂科Eurytomidae、刻腹小蜂科Ormyridae、姬小蜂科Eulophidae,其中榕小蜂科的Platyscapa coronata是大叶榕唯一的传粉者,传粉方式为主动传粉;非传粉榕小蜂的雄性多型现象普遍。传粉与非传粉小蜂的性比明显具有偏雌现象。传粉小蜂性比为0.19±0.07,非传粉小蜂中Camarothorax bismasculinus小蜂性比为0.36±0.10;Walkerella sp.小蜂性比为0.36±0.22,Sycoscapter sp.小蜂性比为0.31±0.22,Sycophila sp.小蜂性比为0.35±0.13。雄性多型现象可能是导致非传粉小蜂性比提高的原因之一。根据各种榕小蜂发生数量及连续性,可将大叶榕隐头果中的榕小蜂分为常见种和偶见种,Platyscapa coronata、Camarothorax bismasculinus、Walkerella sp.、Sycoscapter sp.和Sycophila sp.为常见种,Omyrus sp.和Aprostocetus sp.为偶见种。偶见种的存在对常见种的数量几乎没有影响,偶见种利用的是榕果内未饱和的一部分资源,也可能是榕果为偶见种的发生预留了空间和资源。首次发现姬小蜂科的昆虫寄生在榕果内,且有一定的种群数量,为姬小蜂科昆虫分类及其生物学、生态学特性研究提供了基础资料。在大叶榕小蜂群落结构中,传粉小蜂和非传粉小蜂的种类和数量呈现明显的季节性。冬-春季(12-翌年5月)榕果内小蜂的种类和数量较多,传粉榕小蜂是优势种,其重要值达到0.42,榕果种子结实率高;夏-秋季(6-11月间)小蜂种类和数量略少,Camarothorax bismasculinus和Sycophila sp.是优势种,其重要值分别为0.56和0.28,而传粉小蜂的重要值仅为0.025,此期大叶榕榕果中几乎找不到传粉小蜂,榕果结实率极低,对大叶榕的繁殖利益有较大的负面影响。雨水和高温等不良气候,可能是导致夏-秋季雄花期榕果内的传粉小蜂数量骤减的主要原因。两个实验样地的小蜂群落结构组成没有明显差异,年变化趋势相似。研究结果为城市绿化和热带雨林生物多样性保护提供科学依据。;Ficus virens Ait. var. sublanceolata is a common monoecious landscape trees in Fuzhou. In this study, the structure and biodiversity of fig wasp community inside syconia of F. virens Ait. var. sublanceolata were investigated based on 10 plants at two selected sites in Cangshan and Minhou town of Fuzhou. A total of 13458 fig wasps were collected from 267 syconia in different seasons. Seven fig wasp species were found, which belonged to Agaonidae, Epichrysomallinae, Otitesellinae, Sycoryctinae, Eurytomidae, Ormyridae and Eulophidae of Chalcidoidea, respectively. Among them, only Platyscapa coronata of Agaonidae served as a pollinating agent for F. virens Ait. var. sublanceolata through a way of active pollination. Male polymorphism was common in the non-pollinating fig wasps. Both pollinating and non-pollinating fig wasps showed female-biased sex ratios. The sex ratio of pollinating fig wasps was 0.19±0.07, and the sex ratios of non-pollinating fig wasps Camarothorax bismasculinus, Walkerella sp., Sycoscapter sp. and Sycophila sp. were 0.36±0.10, 0.36±0.22, 0.31±0.22 and 0.35±0.13, respectively. Male polymorphism may be one of the reasons for the increase of sex ratio in the non-pollinating wasps. According to the number and continuity of occurrence, fig wasps could be classified into common species and occasional species. Platyscapa coronata, Camarothorax bismasculinus, Walkerella sp., Sycoscapter sp. and Sycophila sp. were common species, while Omyrus sp. and Aprostocetus sp. were occasional species. The presence of occasional species had little effect on the number of common species. Occasional species might use the unsaturated part of the resources in the fig fruit. It might also be that the fig fruit reserved space and resources for the occurrence of the occasional species. It was the first time that a certain number of Eulophidae parasitic insects were found in fig fruits. This provides the basic data for the taxonomy and the research of biological and ecological characteristics of Eulophidae insect. The wasp community composition and structure differed greatly across seasons. In winter and spring (from December to May of next year), there were more species and higher numbers of fig wasps inside syconia, among which pollinating fig wasps were the dominant species with an importance index up to 0.42. This resulted in a high setting rate of fig seeds. In summer and autumn (from June to November), there were fewer species and lower numbers of fig wasps inside syconia, among which Camarothorax bismasculinus and Sycophila sp. were dominant species with importance indexes up to 0.56 and 0.28, respectively, whereas the importance indexes of pollinating wasps was only 0.025. During this period, it was difficult to find pollinating wasps in the fig. Therefore, the setting rate of fig seeds was lower. The large proportion of non-pollinating had a great negative impact on the reproduction of Ficus virens Ait. var. sublanceolata. Rain and high temperature might be the main causes of the dramatic decrease of the number of pollinating fig wasps inside syconia during the summer and autumn seasons. There were no significant differences in community structure and its annual change between the two sites. The results of this study provide a scientific basis for the urban greening and biodiversity conservation in tropical rain forests.

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