Marrubium eriocephalum (Lamiaceae); a species new to the flora of Turkey, with contributions to its taxonomy

Abstract Marrubium eriocephalum (Lamiaceae) is described as a new record for the Flora of Turkey (B9 Van). A detailed morphological description, photographs, distribution map, and pollen and nutlet morphology of this new record are given.


Introduction
Th e genus Marrubium L. includes annual and perennial herbs. Although species of this genus are mainly distributed in the Irano-Turanian and Mediterranean phytogeographic regions, some members are naturalized in Australia and America. Th e genus comprises about 40 taxa (Akgül et al. 2008). In Turkey, the genus is represented by 21 taxa, of which 12 are endemic to Turkey (Cullen 1982, Davis et al. 1988, Aytaç et al. 2012. Th is endemism rate (57%) shows that Turkey is an important centre of diversity for the genus. Bentham (1834Bentham ( , 1848 fi rst revised the genus and divided it into sections Lagopsis and Marrubium. Later, many who studied the genus divided it into several sections (Briquet 1986, Boisser 1879, Seybold 1978; however, in Turkey, Marrubium was not divided into sections in recent treatments by Cullen (1982) and Akgül (2004).
A detailed pollen morphological study of Turkish Marrubium species was undertaken by Akgül et al. (2008), where the pollen features of 19 Turkish taxa were examined and the pollen grains were divided into 3 groups: 1) the exine is psilate-perforate, psilate-foveolate and the pollen shape is prolate spheroidal, oblate-spheroidal; 2) the exine is granulate-perforate; and 3) the exine is reticulate, rugulate-reticulate and the pollen shape is prolate-spheroidal.
Lamiaceae nutlet surfaces are also taxonomically signifi cant; they have diff erent sizes and colours, so the nutlet morphology is used not only between the genera but also between subsections and subspecies (Husain et al. 1990). Marrubium nutlet surface morphology also has a systematic signifi cance (Brochmann 1992, Hedge 1992.
Marrubium eriocephalum pollen grains were studied using LM and SEM. Th e voucher specimens are listed in (Table 1). For the LM, the pollen grains were fi rst treated with 70% alcohol and allowed to evaporate, and then embedded in glycerine jelly (Wodehouse 1935). Th e polar axis (P), equatorial axis (E), colpus length (Clt), colpus width (Clt), exine thickness (Ex), intine thickness (I), and apocolpium diameter (Ap) were measured from at least 30 fully developed grains per sample under an Olympus BX21 microscope (1000×). For the SEM analyses, pollen grains obtained from each specimen were transferred onto stubs and coated with gold (JEOL JSM 7001-F). Th e methods of Henderson et al. (1968), Faegri and Iversen (1989), and Punt et al. (2007) were those mainly followed.

Palynological investigation
Th e pollen grains were measured and photos were taken with an Olympus BX21 light microscope. Th e pollen type, exin surface ornamentation, and SEM microphotography were recorded. Th e seed sizes were measured and the surface ornamentation was scrutinized with SEM microphotography.

Nutlet morphology
Th e nutlet morphology of Marrubium eriocephalum was studied herein for the fi rst time. Nutlet of the species were large, brown, and eliptic. Th e average nutlet size was 2.5-3.48 × 1.18-2.10 mm. Th ere were polygonal cells in the nutlet epicarp and the ornamentation was verrucate.

Discussion
Th e Marrubium eriocephalum was fi rst collected from the Kurdistan region of Iraq by Ali-al-Rawi & Serhang, and described as a new species by Seybold (1978). Diff erences based on observations and measurements during 2-year fi eld trips and herbarium studies, between type specimens and our material, are shown in Table 2. Specifi cally, Seybold described the species as having purple fl owers; however, our fi ndings showed that the species has yellowish fl owers with purple upper lips. We believe that this error was due to the fact that the observations by Seybold were based solely on herbarium material. However, the author of Marrubium eriocephalum, Seybold (1978) claimed that Marrubium astracanicum is a species close to Marrubium eriocephalum, yet our fi ndings showed that Marrubium vanense Hub.-Mor. is closer to Marrubium eriocephalum according to Flora of Turkey (Table 1, Fig. 3) in stem height, bracteole length and leaf indumentum. Our palynological fi ndings were compared with those of the study of Akgül et al. (2008) and according to their classifi cation, Marrubium eriocephalum is classifi ed as the third type. Due to its oblate-spheroidal pollen grains, psilate-reticulate ornamentation, and tricolpate aperture, our pollen showed similarities with Marrubium vanense and Marrubium catariifolium Desr. However, Marrubium catariifolium is different from M. eriocephalum in being an annual, with white fl owers in 5-8 fl owered verticilasters Cullen (1982).
In Flora of Turkey, the nutlet features of Marrubium vanense and Marrubium catariifolium are described. Both species have oblong, brown-dark brown nutlet with verrucate ornamentation. Our investigation showed similarities with the nutlet features of Marrubium vanense, Marrubium catariifolium, and Marrubium eriocephalum, which are oblong, brown, and verrucate in ornamentation.