Psychrogeton

Farhani, Tayyebeh, Kazempour-Osaloo, Shahrokh, Zare-Maivan, Hassan & Mozaffarian, Valiollah, 2018, Evolutionary history of the tribe Astereae in the Flora Iranica area: Systematic implications, Phytotaxa 379 (1), pp. 95-117 : 110

Psychrogeton

This genus comprises 20 species distributed from western China through Central Asia to Iran ( Nesom & Robinson 2007). The great majority of its members (19 species), including the type species, P. cabulicus Boiss. , were confined to higher elevations in the Flora Iranica area ( Grierson 1967; Grierson & Rechinger 1982; Emadzadeh & Joharchi 2004). Psychrogeton with 11 species is the largest genus of the tribe in Iran. The genus consists of biennial and perennial plants possessing a woody rootstock and a corymbose inflorescence with sterile (functionally male), rarely perfect disc florets, and ligulate or tubular female florets. Analyses of both the nuclear and combined datasets revealed that all 10 sampled Psychrogeton species represented by 23 accessions, except for P. obovatus , are united in a single clade that is well supported. In the chloroplast DNA tree, relationships among these species are not, however, resolved and Psychrogeton species are placed in the large polytomy, due to the low number of informative nucleotide sites. The present analyses are in part consistent with the findings of the nrDNA ITS analysis of Jafari et al. (2015). However, in their analysis, P. pseudoerigeron and two specimens misidentified as P. persicus were placed out of the bulk of the genus. Psychrogeton obovatus is taxonomically one of the most isolated species of the genus, characterized by obovate leaf shape, crenato-dentate leaf margin, foliferous peduncles and fertile achenes, and is distributed in Iran, Iraq and Afghanistan ( Grierson 1967; Grierson & Rechinger 1982). Two analyzed samples of this species were well united with the type species of the newly established genus Neobrachyactis , N. roylei ( Chen et al. 2011) . The morphological characteristics of P. obovatus , including stems branched from the base, subequal phylaries, fertile disc florets and 2-ribbed achenes, are well suited with that of Neobrachyactis . On the basis of all evidence, we treat this species as Neobrachyactis obovata (Benth.) Farhani & Kaz. Osaloo (see Taxonomic treatment). The genus with the inclusion of this new species encompasses four species, distributed in Central, North and South Asia.

The main clade of Psychrogeton is composed of four successive lineages that are largely different from four groups recognized by Grierson (1967) based on vegetative and floral morphology. Psychrogeton pseudoerigeron (Bunge) Novopokr. ex Nevski , represented by two accessions, formed the first diverging branch of Psychrogeton . It is characterized by the perennial habit, taller leafy stems (ca. 20 cm), numerous capitula in corymbose or racemose synflorescences, and prominent ligules of female florets 3.5–4 mm long, and is distributed in Central Asia and Iran. This placement is, however, inconsistent with the result of the previous study ( Jafari et al. 2015), in which it was weakly allied with N. roylei . The next is P. nigromontanus (Boiss. & Buhse) Grierson , distributed in Iran and adjacent countries. It is distinct in having numerous tubular female ray florets with the corolla ½–⅔ as long as the style, and almost oblique lamina. The third lineage contains P. persicus (Boiss.) Grierson , endemic to Iran and Iraq, and P. aucheri (DC.) Grierson , distributed in highlands of western and eastern Iran, represented by 3 accessions from each species, which are common in having tubular female and hermaphrodite flowers, and stem leaves similar to basal leaves ( Grierson 1967; Grierson & Rechinger 1982). The last lineage encompasses two subclades. One is composed of two accessions of P. aellenii (Rech. f.) Grierson , endemic to NE Iran, and two accessions of P. cabulicus . These species are Irano-Turanian elements growing in mountainous regions of Khorasan province and share entire leaves and simple or branched peduncles ( Grierson 1967; Grierson & Rechinger 1982; Emadzadeh & Joharchi 2004). The other comprises P. amorphoglossus (Boiss.) Novopokr. , P. alexeenkoi Krasch. and P. chionophilus (Boiss.) Krasch. They share some traits including dwarf caespitose habit, woody rootstock covered with foliar remains, monocephalic peduncles, and ligulate female flowers. Psychrogeton amorphoglossus is a polymorphic species with the widespread distribution in subnival-nival to subalpine zones of Central and Southwest Asia. Four analyzed samples of this species were placed in different positions in the latter subclade, implying that they have been genetically diversified. Furthermore, a couple of polymorphic nucleotide sites in nrDNA ITS+ETS of the samples were detected, indicating that hybridization might have been occurred within this species several times, that not yet undergone concerted evolution completely. This is consistent with the speculation of Jafari et al. (2015) based on nrDNA ITS sequences.