Premium
Evolution of trichome types and its systematic significance in the genus Phlomoides (Lamioideae–Lamiaceae)
Author(s) -
Eyvazadeh Khosroshahi Elmira,
Salmaki Yasaman
Publication year - 2019
Publication title -
nordic journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.333
H-Index - 33
eISSN - 1756-1051
pISSN - 0107-055X
DOI - 10.1111/njb.02132
Subject(s) - trichome , biology , botany , lamiaceae , genus , phylogenetic tree , taxon , taxonomy (biology) , genetics , gene
Despite a number of recent molecular phylogenetic studies on Phlomoides , in terms of trichome morphology the genus is still among the most poorly studied taxa in the family Lamiaceae. In order to test the utility of trichome characters for delimitation of sections, subsection and species of Phlomoides , we examined trichomes of 64 species representing all recognized sections and subsections using stereomicroscopy and scaning electron microscopy. Two basic types of trichomes could be identified: non‐glandular and glandular. Both trichome types can be simple or branched. The glandular trichomes were sessile, short stalked or long stalked. Different kinds of branched trichomes were observed in most species of P . sect. Phlomoides , i.e. symmetrically stellate, stellate with a central long branch, bi‐ or trifurcate. The species of P . sect. Filipendula were mostly covered by simple trichomes. Moreover, variation in trichome characters appears to have particular value, not only for the classification at sectional or subsectional rank, but also for delimitation of species within each section. For example, all studied species of P . subsect. Fulgentes are characterized by various kinds of stellate trichomes, while the trichome variability in P . subsect. Tetragonae was sufficiently high for species discrimination. An ancestral character state reconstruction was performed in order to investigate the evolution of trichome types and it revealed the following evolutionary trends in trichome characters of Phlomoides : 1) branched trichomes are primitive in Phlomoides as compared to simple ones, 2) long simple non‐glandular trichomes are derived as compared to short simple ones and 3) the presence of stalked glandular trichomes is advanced as compared to subsessile or sessile ones.