Morphological characteristics of Teucrium species: Generative morphology

Abstract

The generative morphology related with corolla and calyx construction, pollen, inflorescence type and nutlets are of great importance in Teucrium L. These characters are the basis for the classic systematic and recent classifications. Teucrium has a corolla usually 1-lipped or 2-lipped (bilabiate). Spartothamnella Briq., Oncinocalyx F. Muell., and Teucridium F. Hook, closely related to Teucrium, present a corolla 5-lobed in the upper half, lobes slighty spreading, 4 posterior ± similar, anterior lobe larger than the others and not concave. The calyx in these genera is actinomorphic. This is an exceptional corolla conformation in Teucrium and only found in these species. The main difference between Spartothamnella and Teucrium is that the former has drupaceous fruit and between Teucrium and Teucridium is the ovary form. Oncinocalyx differs from Teucrium in the conspicuously hooked calyx lobes. Teucrium Sections Pycnobotrys Benth., Stachyobotrys Benth., Scorodonia (Hill) Schreb., and Teucriopsis Benth., have weakly 2-lipped corolla and zygomor-phic calyx. Species of section Teucrium have 1-lipped spurred corolla and actinomorphic calyx except for the Australian species with non-spurred corollas. Teucrium show a great diversity in floral phenotypic diversity and adaptive significance to pollination and dispersal. Functional redundancy is found in the gullet-shaped corollas with nectar guides and nototribic pollination of the sections Chamaedrys (Mill.) Kästner, lsotriodon Boiss., subsection Scordium (Mill.) Kästner, Montana Lazaro Ibiza and subsection Pumila (Lazaro Ibiza) Rivas Mart. Teucrium is the only genus within the sub family Ajugoideae with two derived pollen characteristics, granulate or verrucate sculpturing and operculate colpi and with a considerable variation in pollen sculpturing. Nototribic pollination of the gullet-shaped corollas with closed gullet mechanism (by a palate of hairs associated to a slight pouch in the corolla tube) are exclusive of the section Teucrium. The sternotribic pollination of the brush-shaped corollas closed by a tuft of hair in the entrance of the corolla tube (base of the anterior lobe), are specific of the ginodioecious species of section Polium (Mill.) Schreb. Resupinate flag-shaped corollas with sternotribic pollination is present in subsection Spinularia (Boiss.) Kästner and Stachyobotrys. The main dispersal modes in section Chamaedrys, Isotriodon and Polium is the semachory. Sections Teucrium and Teucriopsis are wind-dispersal by pogonospores, subsection Spinularia, section Scorodonia and Teucrium betonicum and Teucrium abutiloides L'Hér from section Teucriopsis are ballospores.