Dichodon alborzensis Arabi & Zarre, 2018

Arabi, Zahra, Ghahremaninejad, Farrokh, Rabeler, Richard K., Sokolova, Irina, Heubl, Günther & Zarre, Shahin, 2018, On the taxonomic status of the genus Dichodon (Caryophyllaceae: tribe Alsineae): morphological and molecular evidence reassessed, Phytotaxa 360 (3), pp. 220-236 : 229-230

Dichodon alborzensis Arabi & Zarre , sp. nov. ( Fig. 1 : E–J)

Type:— IRAN. Tehran: North Tehran, Touchal mountains, 3700 m, 15 July 2016, Z. Arabi 47422 (holotype TUH-SZ47422!, isotype M!).

Diagnosis:— Dichodon alborzensis is closely related to D. persicus and D. cerastoides . These two latter species form separate small patches, while D. alborzensis plants are annual or biennial herbs growing as widely scattered individuals, not occurring in clumps. Moreover, D. alborzensis differs from D. cerastoides by the absence of sterile shoots and shallowly incised petals which are equal or slightly exceeding the sepals.

Description:—Annual or biennial plants, glabrous throughout. Taproots slender with fibrous-like lateral roots attached. Stems with rosette of basal leaves, lower internodes short. Leaves succulent, basal ones spatulate, cauline ones lanceolate. Inflorescence terminal, 3-flowered (rarely 1-flowered), lax. Styles 3(4). Bracts similar to leaves, without scarious margins. Pedicels long and deflexed when fruiting. Petals 5, white, slightly longer than sepals, shallowly notched. Stamens 5 or 10. Capsules cylindrical, with 6(‒8) circinate teeth. Seeds many, ovate, 0.80‒0.95 mm, verrucate on surface.

Etymology:— “ alborzensis ” came from Alborz, a mountain range in North Iran where the new species has been discovered at three locations.

Taxonomic notes:—The type specimen of Dichodon alborzensis was collected in the Touchal Mountains in North Tehran. Two other populations of this taxon were found at Azadbar and Damavand at about 4200 m a.s.l. ( Fig. 4 ). In the Damavand area, we recognized three populations of Dichodon representing three species, i.e. D. cerastoides , D. kotschyi and D. alborzensis . The annual/biennial plants from higher elevations of Damavand were morphologically different from the annual ones observed at the lower elevation previously determined as Cerastium schischkinii Grossheim (1950: 9) . Our detailed examination of C. schischkinii confirms major differences between it and D. alborzensis . The specimens distributed in Azadbar and Damavand by earlier workers (cited in Möschl 1988) have been determined as C. viscidus in Flora Iranica ( Möschl 1988) which is inconsistent with the result of the present study.

Conservation status:—Few populations (each with less than 100 individuals, two patches in Demavand, and one in each Azadbar and Touchal) of Dichodon alborzensis were found in meadows close to wet soils in field. We assessed D. alborzensis as endangered (EN) ( IUCN 2017) because the Alborz Mountains are a popular tourist area close to Iran’s capital (Tehran) and is often visited by local people on weekends. In addition, the annual precipitation in this area has decreased significantly in the last few years and the area available for wet meadows is shrinking drastically.

Paratypes:— IRAN. Mazandaran: Polour, Damavand mountain , southern slopes, 4200 m, 29 July 2015, Arabi 47424 ( TUH!) ; Mazandaran: Alborz mountain range, Azadbar , 2500 m, 17 July 2016, Arabi 47420 ( TUH!) .

New record for Iran: — Dichodon kotschyi was found for the first time in Iran. A description of the species based on the Iranian population follows:

Figures

FIGURE 1. Representatives of three Dichodon spp. from Iran in different locations. A–B: D. kotschyi in Prov. Azerbaijan, 2450 m; C–D: D. kotschyi in Prov. Mazandaran, 3450 m; E–F: D. alborzensis in Prov. Mazandaran, 4200 m; G–H: D. alborzensis in Prov.Alborz, 2500 m; I–J: D. alborzensis Tehran, 3700 m; K–L: D. persicus in Prov. Hamedan, 2500 m.

FIGURE 4. Distribution map of Dichodon spp. in Iran. (■) D. alborzensis, (●) D. kotschyi and (▲) D. persicus. Dichodon cerastoides and D. viscidus are widespread in West and North Iran.