稻纵卷叶螟幼虫寄生性天敌的种群特征与多样性分析(英文)

水稻卷叶螟的田间种群包括三个种,即稻纵卷叶螟(Cnaphalocrocis medinalis),和 MarasmiaPatnalis,M.exigua。1989年雨季在菲律宾吕宋岛上两个点进行的试验共分别记录了15(内湖省)和12(中吕宋)个种的幼虫寄生性天敌,它们分别攻击寄主卵～幼虫、幼虫和幼虫～蛹期,这些寄生性天敌分属于外寄生或内寄生,单寄生或多寄生,这种生物学特征上的差异为寄生性天敌提供了降低寄主种群的广大的机会。进一步的调查显示,那些攻击低龄寄主的种类具有高繁殖力的小个体的特征,而攻击高龄寄主的种类具有较宽的寄主范围且常常发育历期较短。多数天敌寄生于2或3龄幼虫,将寄主杀死于5龄之前,优势种及寄生率随寄主密度和水稻的生长期不同而变化。 根据Hill(1972)的多样性序列指数分析指出,当以N_2为标准时,在内湖省的整个水稻生育期内始终仅有2—3个种为极优势种,其数据适于用几何或对数序列进行描述。两个点的寄生性天敌种群多样性(N_2)接近于常数3—4,均匀度(E_5)与寄主幼虫密度呈负相关。因此,幼虫的寄生作用可被认为是一个抑制并稳定水稻卷叶螟田间种群的关键因子。

THE POPULATION DIVERSITY OF LARVAL PARASITOIDS ATTACKING RICE LEAFFOLDERS (RLF) (LEPIDOPTERA:PYRALIDAE)

Field population of RLF in the Philippines composed of a complex of three species, Cnapholocrocis medinalis, Marasmia patnalis, and M. exigua. Experiments conducted in two locations during the wet season of 1989 recorded total of 15 (Laguna) and 12 species (N. Ecija) of parasitoids, which attack the egg-larval, larval, and larval-pupal stages of the RLF. They are either monoor poly-phagous, and either ecto or endo-parasitoids. Such a larger variety of the species provides wide opportunities for parasitoids to reduce the RLF population. The species attacking early stages trended to have a high reproductive capacity with a smaller body size, those attacking old larvae shown a broader host range and usually have a short pre-mature period. Most of larvae were parasitized at 2nd or 3rd instar and killed before 5th instar. The dominant species and percentage of parasitism varied with plants stages as well as host larva density.Diversity analysis based on the Hill's numbers indicated that only 2 - 3 of parasitoids were rated to very abundant species (N2) over plant growing stages and the data fitted well with geometric or log series. The richness (N0) and diversity (N2) were nearly constant around 3 - 4. The evenness (E5 ) was negatively correlated with host larval density. Larval parasitization of RLF can be considered as a key factor in suppressing and stabilizing the RLF field population.