巴氏小新綏蟎 (蟎蜱亞綱：植綏蟎科) 與近緣種形態變異之探討

Abstract

植綏蟎 (捕植蟎) 屬於節肢動物門 (Arthropoda)、蛛形綱 (Arachnida)、蟎蜱亞綱 (Acari)、寄蟎總目 (Parasitiformes) 、中氣門蟎目 (Mesostigmata)、植綏蟎科 (Phytoseiidae)。全世界記錄超過 2,700 種，臺灣已記錄 58 種。植綏蟎食性複雜，部分種類為肉食者，另外也有許多種類能取食真菌、植物汁液與花粉。部分種類的植綏蟎具捕食葉蟎、粉蝨、薊馬及蚜蟲等小型害蟲之能力，故被作為生物防治之捕食性天敵。植綏蟎的重要鑑定特徵為背板形態、背毛相、腹板形態、腹板毛式、足毛式、螯肢齒數及交尾囊形態等。種內變異 (intraspecific variation) 係指因遺傳性狀或受環境條件等因子影響，而造成同一物種在形態上發生改變。本研究以巴氏小新綏蟎 (Neoseiulus barkeri) 為例，探討植綏蟎在形態與分子層面之種內變異。首先進行雌雄性形態重新描述，特別加上往昔描述缺少之背面孔與足毛相。並記錄巴氏小新綏蟎標本之毛相變異，如缺毛、多毛、嵌入、位移等。此外以 56 個形態測量特徵 (長度) 進行主成分分析 (轉換的) ，探討巴氏小新綏蟎的物種界線及其與真桑小新綏蟎 (N. makuwa)、溫氏小新綏蟎 (N. womersleyi)、N. agrstis 與其他 19 種近緣種之分群。巴氏小新綏蟎與真桑小新綏蟎分為兩群，其兩物種間無重疊；7 種近緣種與巴氏小新綏蟎及真桑小新綏蟎呈明顯分群。巴氏小新綏蟎、真桑小新綏蟎、溫氏小新綏蟎為近緣種，以ITS 分子序列建構鄰位歸併樹 (Neighbor joining)、最大似然樹 (Maximum likelihood) 及貝氏親緣譜系樹 (Bayesian inference)，結果顯示各親緣樹有相同樹形，其分群與形態分群的結果一致，但與 Chant and McMurtry 以形態特徵提出的分群關係不同；另外亦探討巴氏小新綏蟎與近緣種之遺傳距離，巴氏小新綏蟎的遺傳距離在不同國家的樣本中最遠遺傳距離為 0.002，巴氏小新綏蟎與真桑小新綏蟎最近遺傳距離為 0.025。本研究預期能由形態與分子角度探討植綏蟎的種內變異，瞭解物種界線並重新檢視現行以形值分析探討近緣種的研究方法。

Phytoseiidae is a mite family belongs to subclass Acari, superorder Parasitiformes, order Mesostigmata. More than 2,700 species of Phytoseiidae have been reported in the world, whereas fifty-eight species in Taiwan. Phytoseiid mites have diverse feeding habits, some of them are carnivorous, but they also feed on fungi, plant exudates and pollen. Some species are considered as natural predators for phytophagous pests involving spider mites, whiteflies, thrips and aphids. They have received considerable attention because of their biological control potential for phytophagous mites and other small arthropods. Current classification of phytoseiids is based on morphological characteristics, including dorsal shield, chaetotaxy of idiosomal setae, sternal shield, genital shield, ventrianal shield, chaetotaxy of legs, cheliceral dentition and spermatheca shape. The aim of present study was to investigate the morphological and molecular intraspecific variations of Neoseiulus barkeri (Hughes). The morphological characteristics of N. barkeri were recognized and re-described, especially for dorsal pores and chaetotaxy of legs which have not been described yet. The setal variations can be further divided into the following categories: additional, absent, deviated and lengthened setae etc. Transformation-based principal component analysis (tb-PCA) was used to determine how the differences in the 56 morphological characteristics can be associated with species delimitation. The result revealed N. barkeri and N. makuwa belong to two distinct groups; and the seven closely species also belong to different group with N. barkeri. In molecular analyses, internal transcribed spacer (ITS) molecular markers were used to construct phylogenetic trees among closely related species based on Neighbor Joining (NJ), Maximum likelihood (ML), and Bayesian inference (BI). The phylogenetic trees show convergent topologies but differ from previous result of Chant and McMurtry based on morphological characters. In addition, genetic distances among N. barkeri and closely related species were also evaluated. The farthest genetic distance observed within N. barkeri is almost 0.002, and the closest genetic distance between N. barkeri and N. makuwa is 0.025. This study will approach intraspecific variation and species delimitation of phytoseiids on morphological and molecular aspects.