基于多个叶绿体基因序列片段重建广义苋科系统发育关系

Phylogenetic Study of Amaranthaceae sensu lato Based on Multiple Plastid DNA Fragments

苋科(Amaranthaceaesensulato)是石竹目(Caryophyllales)第二大科,目前被普遍接受的苋科为其广义概念,含狭义苋科(Amaranthaceae sensu stricto)和藜科(Chenopodiaceae)。然而到目前为止,藜科是否应作为独立的科还存在争议。此外,广义苋科内部各亚科之间的系统关系也尚未厘清。对广义苋科所有13个亚科代表类群进行取样(共59种),基于8个叶绿体序列片段重建其系统发育关系,并结合分子钟估算,对该科及其主要分支的起源与分化时间进行推测。结果表明,广义苋科与狭义苋科都是很好的单系,但藜科并非单系,因此不支持藜科在科级水平的地位,支持广义苋科的观点。除了多节草亚科(Polycnemoideae)之外,其它亚科的系统位置均得到很好的分辨。分子钟估算结果表明,广义苋科于白垩纪晚期约69.9Ma分化出该科的2个主要分支,且该科在白垩纪-古近纪边界附近时期(约66.0Ma)可能发生过快速辐射分化事件。

Amaranthaceae sensu lato,including Amaranthaceae sensu stricto and Chenopodiaceae,is the second largest family in Caryophyllales.However,the family status of Chenopodiaceae is disputable and phylogenetic relationships among all of the subfamilies circumscribed within Amaranthaceae s.l.have not been well resolved to date.In the present study,phylogeny of Amaranthaceae s.l.was reconstructed based on a comprehensive taxonomic sampling of all 13 subfamilies(59 species)circumscribed using eight plastid DNA fragments,and a molecular dating analysis of the family was also conducted.Results revealed that,the monophyly of Amaranthaceae both in broad and narrow sense was strongly supported,but the monophyly of Chenopodiaceae was rejected.Thus the concept of Amaranthaceae s.l.is accepted here.Phylogenetic positions of all subfamilies were all resolved with strong support values,except that the position of the subfamily Polycnemoideae was weakly supported.Additionally,the crown age of Amaranthaceae s.l.was estimated at ca.69.9 million years ago(Ma)in the late Cretaceous,and a period of rapid divergence may have occurred near the Cretaceous-Paleogene(K-Pg)boundary(ca.66.0 Ma).