Bert Wim, Leliaert Frederik, Vierstraete Andy R, Vanfleteren Jacques R, Borgonie Gaetan
Nematology Section, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Ghent, Belgium.
Mol Phylogenet Evol. 2008 Aug;48(2):728-44. doi: 10.1016/j.ympev.2008.04.011. Epub 2008 Apr 14.
Tylenchina are a morphologically and functionally diverse group of nematode species that range from free-living bacteriovores, over transitory grazing root-hair feeders to highly specialized plant-parasites with complex host associations. We performed phylogenetic analyses of small subunit rDNA sequences from 97 species including an analysis that account for the RNA secondary structure in the models of evolution. The present study confirms the sister relationship of the bacteriovore Cephalobidae with the predominantly plant-parasitic Tylenchomorpha. All analyses appoint the fungal-feeding Aphelenchidae and Aphelenchoididae as being polyphyletic but the morphology based hypothesis of their monophyly could not be significantly rejected. Within the Tylenchomorpha, the families that exclusively parasitize higher plants are joined in a single clade. However, only the monophyletic position of the (super)families Hoplolaimidae and Criconematoidea were supported; Anguinidae, Tylenchidae, Belonolaimidae and Pratylenchidae appeared to be paraphyletic or polyphyletic. Parsimony and likelihood ancestral state reconstruction revealed that burrowing endoparasitism and sedentary endoparasitism each evolved, respectively, at least six and at least three times independently, mostly from migratory ectoparasitic ancestors. Only root-knot nematodes have evolved from burrowing endoparasitic nematodes. Traditional classifications are partially misled by this convergent evolution of feeding type and associated morphology. Contrastingly, mapping attributes of the gonoduct cellular architecture, including newly obtained data of 18 species belonging to the Aphelenchoidea, Criconematoidea, Anguinidae and Panagrolaimidae, revealed a broad congruence of the gonoduct characters and the molecular phylogenetic hypothesis. Yet, the presence of an offset spermatheca and proliferation of uterus cells has evolved multiple times, the latter associated with derived endoparasitic feeding specialization and resulting reproduction mode. Ancestral state reconstruction further revealed that the gonoduct of the morphologically and ecologically dissimilar tylenchid and cephalobid nematodes evolved from a common ancestor.
垫刃总科线虫是一类形态和功能多样的线虫物种，其范围从自由生活的食细菌线虫，到短暂取食根毛的过渡性线虫，再到具有复杂寄主关系的高度特化的植物寄生线虫。我们对97个物种的小亚基核糖体DNA序列进行了系统发育分析，其中包括一项在进化模型中考虑RNA二级结构的分析。本研究证实了食细菌的头叶科与主要为植物寄生的垫刃形亚目之间的姐妹关系。所有分析都表明，取食真菌的滑刃科和滑刃亚科是多系的，但基于形态学的它们单系性的假设不能被显著否定。在垫刃形亚目内，专门寄生于高等植物的科聚在一个单一的分支中。然而，只有螺旋线虫科和环线虫总科的单系地位得到了支持；粒线虫科、垫刃科、长针线虫科和短体线虫科似乎是并系或多系的。简约法和似然法祖先状态重建表明，钻蛀性内寄生和定居性内寄生分别至少独立进化了六次和至少三次，大多起源于迁移性外寄生祖先。只有根结线虫是从钻蛀性内寄生线虫进化而来的。传统分类在一定程度上受到了取食类型和相关形态的这种趋同进化的误导。相反，绘制生殖管细胞结构的属性，包括属于滑刃亚目、环线虫总科、粒线虫科和杆线虫科的18个物种的新获得数据，揭示了生殖管特征与分子系统发育假设的广泛一致性。然而，偏斜受精囊的存在和子宫细胞的增殖已经多次进化，后者与衍生的内寄生取食特化和由此产生的繁殖方式有关。祖先状态重建进一步表明，形态和生态不同的垫刃科和头叶科线虫的生殖管是从一个共同祖先进化而来的。
