| Carex L.,with about 2000 species worldwide,is one of the most diverse genera of angiosperms,and distributed on all continents except Antarctica.Carex sect.Graciles,is mainly distributed in East Asia（China and Japan）,and 21 species recorded in China.In the past,the classification methods of sect.Graciles were relatively single,the delimitation of related species were relatively confused,and there were differences on section definition and species division.This study adheres to the concept of population,based on reviewing and collating a large number of literature and specimens,and synthesizes molecular phylogenetic evidence,micromorphological evidence of utricles and nutlets,morphological evidence to explore the phylogeny,taxonomy of this section and controversial species attribution under section.The main results are as follows:Morphological and micromorphological characters of utricles of 18 species（39samples）in sect.Graciles were compared.The results showed that the utricles in sect.Graciles were mostly elliptic,rarely suborbicular or narrowly elliptic,plano-convex or biconvex,base stipitate,several veined,hispidulous on veins.Only 7 species,viz.C.gentilis,C.ereica,C.henryi,C.longipes,C.omeiensis,C.orbicularinucis and C.sinodissitiflora,were subglabrous,medium-sized beak,orifice 2-toothed.The morphology and micromorphology of utricles were stable among different populations within the species.The shape,length,surface coat,beak length,ratio of beak length/utricles length,basal morphology and orifice morphology were of systematical and taxonomic value,while utricles color were of little significance.Morphological and micromorphological characters of nutlets of 18 species（39samples）in sect.Graciles were compared.The results showed that nutlets in sect.Graciles were mostly elliptic,rarely ovate,suborbicular or narrowly elliptic,plano-convex or biconvex,base shortly stipitate or estipitate,style base slightly thickened,stigmas 2.The epidermal cells were 5 to 7 gonal,rarely 4 or 8,the anticlinal wall was straight or microwave,and silica platform was flat,with a central silica body but without satellite bodies.The morphology and micromorphology of nutlets within this section were stable and consistent,and the shape,length,basal morphology and epidermal cell shape of nutlets were of taxonomic value for distinguishing species within sect.Graciles.Phylogenetic studies on 20 species and 1 variety（58 samples）of sect.Graciles were conducted based on five gene segments of nr DNA（ITS and ETS）and cp DNA(trn L-F,rpl32 UAG-trn L and mat K).The results showed that sect.Graciles defined by traditional morphology was not a monophyletic group.Carex longipes,C.sinodissitiflora and C.ereica did not form a clade with members of sect.Graciles.While C.longipes,C.sinodissitiflora embedded in Indica clade,and C.ereica in a branch composed of sect.Secalinae,C.kitaibeliana,C.negrii,sect.Alliiformes and sect.Grallatoriae,the rest formed a large branch with well-support.The sect.Graciles and sect.Albae were sister groups of each other.The interpopulation and interspecific variation of morphological characters of 5closely related species（46 populations,93 individuals）of C.stipitinux complex and C.brunnea complex were analyzed.The results showed that C.stipitinux and C.autumnalis were two independent species with discontinuous variation in brown sheath length and utricles number/density in each spike,which were effective in distinguishing the two species.In C.brunnea complex,C.sendaica differs from C.brunnea and C.bodinieri in culm height and stolons.C.brunnea and C.bodinieri could be distinguished by utricles size,surface coat and epidermal cell shape of nutlets.Based on the concept of morphological-biological species,we agree that C.stipitinux,C.autumnalis,C.brunnea,C.bodinieri and C.sendaica are independent species.Integrating molecular phylogenetic,morphological and micromorphological evidences,19 species and 4 varieties where recognized in Carex sect.Graciles in China.Carex longipes,C.sinodissitiflora and C.ereica did not belong to this section. |
