细叶榕榕小蜂群落结构及动态变化

细叶榕为桑科榕属植物,雌雄异株,广泛分布于印度-澳大利亚(Asia-Australasia)榕树植物分布中心区,它既是热带雨林的主要树种,也是庭院和行道绿化的常见树种。通过全年定时、定点、定株观察与采集,对福州2个样地19株细叶榕隐头果内小蜂群落结构及其动态进行研究。全年在两个样地530个隐头果内共收集到小蜂26318只。发现细叶榕隐头果内有17种小蜂,隶属小蜂总科Chalcidoidae中的榕小蜂科(Agaonidae)、隐针榕小蜂亚科(Epichrysomallinae)、金小蜂科(Pteromalidae)、广肩小蜂科(Eurytomidae)和刻腹小蜂科(Ormyridae),其中榕小蜂科的Eupristina verticillata是细叶榕唯一的传粉者,传粉方式为主动传粉,其性比为0.16,具明显偏雌现象;非传粉小蜂中,有翅雄蜂的榕小蜂(Odontofroggatia galili,O.quinifuniculus,O.corneri,Sycophila sp.1,Sycophila sp.2,Meselatus bicolor)的性比(0.46—0.55)较高,无翅雄蜂的榕小蜂(P.taiwanensis,Sycoscaptergajimaru,W.microcarpae)的性比(0.31—0.37)较低,而既具有翅雄蜂又具无翅雄蜂的非传粉榕小蜂(P.okinavensis)性比(0.47)居中。榕小蜂的性比可能与其交配行为策略有关。在细叶榕小蜂群落结构中,传粉小蜂E.verticillata的重要值占绝对优势,非传粉小蜂O.galili和Sycophila sp.2的重要值仅次于传粉小蜂。根据榕小蜂发生数量及连续性,可将细叶榕隐头果中的榕小蜂分为常见种和偶见种,E.verticillata、Odontofroggatia galili、Walkerella microcarpae、Sycophila sp.1、Sycophila sp.2和Philotrypesis okinavensis为常见种,其余11个种为偶见种。传粉小蜂和非传粉小蜂的种类和数量呈现明显的季节性变化。2月至6月期间,每月出现的榕小蜂种类较少,仅3—4种,单果内平均有传粉小蜂48.88只,非传粉小蜂13.64只;7月至翌年1月间,每月出现的榕小蜂种类较多,达6—13种,单果内平均有传粉小蜂24.38只,非传粉小蜂18.89只,表明,7月—翌年1月单果内传粉小蜂数量比较于2—6月极显著降低(P<0.001),而单果内非传粉小蜂数量极显著提高(P=0.001),同时种类也显著增加。雄花期榕小蜂的种类与数量取决于雌花期产卵榕小蜂的种类与数量,而雨量、气温以及雌花期花序果数量对产卵小蜂的数量,以及小蜂产卵行为都可能产生影响。本研究结果可为城市绿化和热带雨林生物多样性保护提供科学依据。

Community structure and dynamics of fig wasps in syconia of Ficus microcarpa Linn. f. in Fuzhou

Ficus microcarpa Linn. f. (Ficus, Moraceae) is a common monoecious tree, which is widely distributed in the fig center area of Asia-Australasia. It is both a main tree species in the tropical forest and a common tree species planted in the courtyard and street. In this study, we investigated the structure, biodiversity and dynamics of fig wasp community in syconia of 19 F. microcarpa plants at two selected sites by observation on and collection from the specific trees at specific time and season all year around. A total of 26,318 fig wasps were collected from 530 syconia in different seasons. Seventeen fig wasp species belonging to Agaonidae, Epichrysomallinae, Otitesellinae, Sycoryctinae, Eurytomidae and Ormyridae of Chalcidoidea were collected. Among them, only Eupristina verticillata of Agaonidae served as a pollinator for F. microcarpa through a way of active pollination. The sex ratio in this pollinating fig wasp species was 0.16, with a very strong female-bias phenomenon. In the non-pollinators, the sex ratio is higher (0.46-0.55) in the species with winged male wasps (Odontofroggatia galili, O. quinifuniculus, O. corneri, Sycophila sp.1, Sycophila sp. 2 and Meselatus bicolor), lower (0.31-0.37) in the species with wingless male wasps (Philotrypesis taiwanensis, Sycoscapter gajimaru, Walkerella microcarpae), and medium (0.47) in the species with both winged and wingless male wasps (Philotrypesis okinavensis). The results suggested that the sex ratio of fig wasps may be related to the strategy of mating behavior. In the structure of fig wasp community in F. microcarpa, the importance index was dominant in the pollinating fig wasps, but was much smaller in non-pollinating species O. galili and Sycophila sp. 2. According to the number and continuity of occurrence, fig wasps could be classified into common species and occasional species. E. verticillata, Odontofroggatia galili, Walkerella microcarpae, Sycophila sp. 1, Sycophila sp. 2 and Philotrypesis okinavensis were common species, while the remaining 11 were occasional species. The composition and structure of wasp community differed greatly across seasons. From February to June, there were fewer (only 3-4) species inside syconia, with 48.88 pollinating wasps and 13.64 non-pollinating wasps in a single fig on average, respectively. From July to January of next year, there were more (as many as 6-13) species inside syconia, with 24.38 pollinating wasps and 18.89 non-pollinating wasps in a single fig on average, respectively. The results suggested that the number of pollinating wasps in the latter period reduced greatly compared with that in the former period (P<0.001); whereas for the non-pollinating wasps, both the number of species and that of wasps were significantly increased (P=0.001). The species and the number of fig wasps in the male-flower phase depended on the species and the number of spawning wasps in the female-flower phase. However, the rainfalls, temperature and the number of syconia in the female-flower phase may affect on the number of spawning wasps and the spawning behavior of wasps. The results of this study provide a scientific basis for urban greening and biodiversity conservation in tropical rain forests.