苏铁类植物自二叠纪晚期以来在地球植被更替和演化过程中扮演了重要的角色,在历史上经历了漫长的兴衰过程。经过系列的气候变化和地质变迁,大部分苏铁类植物已经灭绝,仅剩少部分类群残存分布在热带和亚热带的一些区域(Osborne,2002)o在...苏铁类植物自二叠纪晚期以来在地球植被更替和演化过程中扮演了重要的角色,在历史上经历了漫长的兴衰过程。经过系列的气候变化和地质变迁,大部分苏铁类植物已经灭绝,仅剩少部分类群残存分布在热带和亚热带的一些区域(Osborne,2002)o在系统发育上,现存苏铁类植物与银杏互为姐妹群,是整个裸子植物的最早分支(Wu et al.,2013;Li et al.,2017),对研究种子植物的起源与早期演化具有极为重要的价值。展开更多
Discocephalids and pseudoamphisiellids are possibly two of the most confused groups among hypotrichous/euplotid ciliates regarding their systematic position and phylogenetic relationships.The former were often regarde...Discocephalids and pseudoamphisiellids are possibly two of the most confused groups among hypotrichous/euplotid ciliates regarding their systematic position and phylogenetic relationships.The former were often regarded as related to euplotids while the latter,in the absence of molecular data,were mostly assigned to the urostylid-like hypotrichs.In the present work,the small subunit rRNA genes of several rarely observed discocephalid and pseudoamphisiellid genera were analyzed to obtain insights into the phylogenetic relationships of these highly ambiguous Spirotrichea.Four different tree reconstruction algorithms yielded nearly identical topologies,which indicated both groups belong to the same assemblage.This assemblage is clearly isolated as a deep-branching clade and invariably positioned between Euplotida and Hypotricha.The sister group relationship of the Pseudoamphisiellidae and Discocephalidae supports the previous suggestion that they might represent an ordinal taxon,the Discocephalida.Both morphological and morphogenetic features indicate that the pseudoamphisiellids should be placed in the order Discocephalida but as a sister group to other typical discocephalids.Thus we propose establishing a new suborder,Pseudoamphisiellina subord.n.The new taxon is diagnosed by the following characteristics:(i) two distantly separated midventral rows that are morphogenetically formed with an urostylid mode;(ii) absence of the "frontoterminal row",which is formed from the posterior-most frontoventral-transverse cirral anlage in all other typical urostylids;(iii) numerous caudal cirri that derive from each of the dorsal kinety anlagen;(iv) right marginal row that has a unique de novo origin;and (v) inhabiting periphytic communities.The validity of the suborder Pseudoamphisiellina is firmly supported by molecular data.展开更多
基金The Third Phase of the Innovation Program in the Chinese Academy of SciencesGrants from the National Natural Science Foundation of China (Grant Nos.30670242 and 30500056)the Major Program from the Natural Science Foundation,Beijing(6081002)
文摘苏铁类植物自二叠纪晚期以来在地球植被更替和演化过程中扮演了重要的角色,在历史上经历了漫长的兴衰过程。经过系列的气候变化和地质变迁,大部分苏铁类植物已经灭绝,仅剩少部分类群残存分布在热带和亚热带的一些区域(Osborne,2002)o在系统发育上,现存苏铁类植物与银杏互为姐妹群,是整个裸子植物的最早分支(Wu et al.,2013;Li et al.,2017),对研究种子植物的起源与早期演化具有极为重要的价值。
基金supported by the National Natural Science Foundation of China (Grant Nos. 40906065 and 31030059)
文摘Discocephalids and pseudoamphisiellids are possibly two of the most confused groups among hypotrichous/euplotid ciliates regarding their systematic position and phylogenetic relationships.The former were often regarded as related to euplotids while the latter,in the absence of molecular data,were mostly assigned to the urostylid-like hypotrichs.In the present work,the small subunit rRNA genes of several rarely observed discocephalid and pseudoamphisiellid genera were analyzed to obtain insights into the phylogenetic relationships of these highly ambiguous Spirotrichea.Four different tree reconstruction algorithms yielded nearly identical topologies,which indicated both groups belong to the same assemblage.This assemblage is clearly isolated as a deep-branching clade and invariably positioned between Euplotida and Hypotricha.The sister group relationship of the Pseudoamphisiellidae and Discocephalidae supports the previous suggestion that they might represent an ordinal taxon,the Discocephalida.Both morphological and morphogenetic features indicate that the pseudoamphisiellids should be placed in the order Discocephalida but as a sister group to other typical discocephalids.Thus we propose establishing a new suborder,Pseudoamphisiellina subord.n.The new taxon is diagnosed by the following characteristics:(i) two distantly separated midventral rows that are morphogenetically formed with an urostylid mode;(ii) absence of the "frontoterminal row",which is formed from the posterior-most frontoventral-transverse cirral anlage in all other typical urostylids;(iii) numerous caudal cirri that derive from each of the dorsal kinety anlagen;(iv) right marginal row that has a unique de novo origin;and (v) inhabiting periphytic communities.The validity of the suborder Pseudoamphisiellina is firmly supported by molecular data.
