低等六足动物系统学研究进展

低等六足动物包括原尾纲、弹尾纲和双尾纲三个类群,是探讨六足动物起源和进化问题的关键类群,近十年来成为节肢动物系统进化研究中的焦点之一。低等六足动物的系统发育地位以及它们之间的关系一直是备受争论的问题。通过介绍三类低等六足动物最新的分类系统,从经典分类学和系统发育两个方面对低等六足动物近十年来的研究进展进行了综述。迄今,对于三类低等六足动物都建立了比较完备的分类体系,原尾纲划分为3目10科,弹尾纲划分为4目30科,双尾纲划分为2亚目3总科10科。系统发育研究中,大多数的系统发育分析结果不支持传统的缺尾类假说,缺尾纲应摒弃不用。分子数据分析的结果普遍支持原尾纲与双尾纲近缘,但仍需要进一步探讨。线粒体基因组、比较胚胎学和比较精子学的研究结果表明,原尾纲可能经历了长期的趋异进化历史。最近的比较精子学研究支持了双尾纲的单系性。总之,三类低等六足动物系统学研究均取得了长足的发展,但仍然存在诸如研究人员匮乏和研究水平不均衡等问题。系统发育研究中,分子系统学研究成为关注的焦点,而基于核基因和线粒体基因的数据分别建立的系统发育假说存在分歧,亟需开发更优的数据分析方法。此外,需加强低等六足动物比较形态学、比较胚胎学、发育生物学等方面的研究,以便将来进行全证据的系统发育研究。

Progress on the systematic study of basal Heaxpoda

Three basal hexapod groups,Protura,Collembola and Diplura,are important taxa in the research of origin and evolution of Hexapoda and highlighted in the evolutionary studies of Arthropoda.The phylogenetic position of three basal hexapod groups and the relationships between them are hotly debated problems.In this review,the modern classification system of Protura,Collembola and Diplura are introduced,and the progress of the study on the classical taxonomy and phylogeny of basal Hexapoda in recent ten years were summarized.So far,the complete classification systems of three basal Hexapod were constructed,Protura including three orders and ten families,Collembola including four orders and 30 families,and Diplura including two suborders,three superfamilies and ten families.Ellipura was rejected by most of phylogenetical analyses and should be abandoned.Most analyses based on molecular data support a close relationship between Protura and Diplura,however,need further investigations.The results from the studies of mitochondrial genome,comparative embryology and spermology indicate that Protura may be undergone a highly divergent evolution.The recent study on comparative spermology of Diplura support it＇s monophyletic.In summary,the systematic study of three basal hexapod groups has been greatly improved,but some problems still exist,such as researchers reducing and the study level imbalance.In phylogenetic study,molecular phylogeny is the dominant topic,but the phylogenetic hypotheses based on nuclear gene data and mitochondrial gene data are divergent.Therefore,more optimized methods for data analysis are urgent needed.In addition,the comparative studies on morphology,embryology and development of basal hexapods should be strengthened,in order to make a comprehensive phylogenetic study based on the total evidences in the future.