Arabis watsonii (P.H.Davis) F.K.Mey (in Meyer 2006 p.187)

Oezuedogru, Baris & Firat, Mehmet, 2016, Arabis watsonii (P. H. Davis) F. K. Mey.: An overlooked cruciferous species from eastern Anatolia and its phylogenetic position, PhytoKeys 75, pp. 57-68 : 61-65

Arabis watsonii (P.H.Davis) F.K.Mey (in Meyer 2006 p.187)

Arabis watsonii Basionym: Thlaspi watsonii P.H.Davis (in Davis et al. 1988 p. 235)

Type.

Turkey B9 Van: Çuh pass, Halanduran Da. and Guezeldere Tepe , dry stony slopes, locally common, 2800 m, flowers white, vi 1966, Albury, Cheese & Watson 1438 (holo. K photo!) .

Slender perennial herb. Stem erect, nearly glabrose, 13-30 cm high. Basal leaves up to 30 mm, oblong - obovate, petiolate, leaves on sterile shoots completely covered by branched trichomes, fertile shoot with branched trichomes on the leaves margin. Stem leaves narrowly oblong, very shortly auriculate, tapering to subacute apex, 5-32 × 2.5-10 mm with marginal trichomes. Sepals white-purplish, inner sepals saccate, 3-3.2 × 1-1.8 mm, outer sepals smooth, 2.7-3 × 1-1.5 mm. Petals white, 5.5-7 mm long, 1.5 mm broad above, tapering below into 1.5-2 mm claw. Stamens 6, long filaments 4, 3- 4 mm, short filaments 2, 2.5 - 3 mm long, anther yellow, 0.8 - 1 × 0.3-0.4 mm. Pedicel up to 7-8 mm in fruit. Fruit ± constricted between seeds, 4-14 × 0.8-1.2 mm, with 6-8 seeds, style ca. 1 mm. Seeds brown, ovate-oblong, 0.9-1.1 × 0.5-0.7 mm.

Fl. and fr: 4-6. Alpine damp places, dry stony slopes, steppe. 1980-2800 m.

Distribution:

Endemic. Irano -Turanian element (Fig. 2 )

Specimens examined.

TURKEY. B9 Van: Gürpınar district, from Güzeldere pass to Çuğ pass, damp places, 2495 m, 38°09'57"N, 43°57'47"E, 19 May 2015, M. Fırat 32513 (herb. M. Fırat); ibid M. Fırat 32572 (HUB, herb. M. Fırat) 11 June 2015; Bahcesaray district , from Ulubeyli village to Hizan, damp steppe, 2265 m, 38°07'46"N, 42°40'53"E, 19 May 2014, M. Fırat 30870 (HUB, herb. M. Fırat); ibid M. Fırat 30989 (HUB, herb. M. Fırat) 21 June 2014; Bahçesaray, between Liçan Village and Kavuşşahap Mountains ( Deve Mountain ), humid steppe, 1980 m, 04.04.1999. M. Fırat 1077 (herb. M. Fırat); Bahçesaray, Altindere Village Kavussahap Mountains , damp places, 2300 m, 17.05.2000, M. Fırat 2122 (herb. M. Fırat); Bahçesaray, between Cevizlibelen Village and Arnos Mountain, humid steppe, 2400 m, 23.06.2000, M. Fırat 2729 (herb. M. Fırat); between Güzelsu ( Hoşap) and Başkale, Güzeldere pass, meadows, 2550-2650 m, 10.06.2001, M. Armağan 1073 (VANF); between Güzelsu ( Hoşap) - Başkale, Güzeldere Pass, Güzeldere Hill, moist meadows, slopes, steppe, 2700-2800 m, 07.06.2002, M. Armağan 2423 (VANF); between Güzelsu ( Hoşap) and Başkale, Güzeldere pass, from Güzeldere gendarmerie station to Başkale, slopes, steppe and moist meadows, 2600-2730 m, 19.05.2001, M. Armağan 1130 (VANF) .

Vernacular name.

In Van province, indigenous people use name ‘Nançûk’ for Arabis species ( Fırat 2013).

Field observations and records taken from relevant herbaria indicate that Arabis watsonii has two distinct populations (Fig. 2 ). A large population growing around Bahçesaray district and a second population occurring in the Gürpınar district especially around the Güzeldere pass. Therefore total distribution areas for these populations were estimated separately. The area around Bahçesaray was calculated as 108.99 km2 and the second area around Gürpınaras 2.69 km2. In summary, to propose IUCN threat categories of Arabis watsonii , these two population groups and calculated areas were considered. The occupancy area (AOO) of Arabis watsonii was calculated as 111.68 km2 in which about 1000 individuals in each population were estimated to occur. Overgrazing and reaping activities by the local people were observed in field studies. Therefore, in accordance with the criteria of the IUCN (2016), Arabis watsonii is assessed here as “Vulnerable” [(VU) (B2a, C2a(i))], because distribution area of the species is severely fragmented and the species is currently known from no more than ten localities occupying less than 2,000 km2, (although it was considered “Endangered” (EN) according to Ekim et al. (2000)).

The basic climatic requirements of Arabis watsonii , annual main temperature and annual precipitation were calculated as 5.7 °C and 583 ml respectively.

Phylogeny.

The aligned ITS and trnL-F data matrices included 91 species. The ITS data set was 642 bp, of which 236 were variable and 168 parsimony informative, whereas the trnL-F data set incorporates 855 bp, of which 181 were variable and 108 parsimony informative.

The query of ITS sequences of Arabis watsonii in BrassiBase (version 1.1) supported its phylogenetic placement within tribe Arabideae and clearly matching Arabis . The outcome of Bayesian phylogenetic analyses using ITS and trnL-F data sets (Figs 3 , 4 ) were congruent with each other in regard to the placement of Arabis watsonii . In both analyses Arabis watsonii falls into the main Arabis clade as sister to Arabis hirsuta (L.) Scop. aggregate and its relatives outlined in Karl and Koch (2014). Whereas Arabis watsonii forms a monophyletic lineage with Arabis cretica (Bayesian posterior probability (pp) = 0.98) in ITS analysis (Fig. 3 ), this sister relationship was not supported by trnL-F analysis (Fig. 4 ) and chloroplast data shows that Arabis watsonii , the Arabis hirsuta aggregate, its relatives plus non -European Arabis species are linked to this aggregate (including Arabis georgiana R.M.Harper, Arabis pycnocarpa M.Hopkins and Arabis borealis DC.) forming a monophyletic clade (pp=1.00).

Figures

Figure 2. Distrubution of Arabis watsonii (red dots). Map was taken from Firat (2016).

Figure 3. ITS-based phylogenetic backbone of Arabideae that focuses on the placement of Arabis watsonii. Shown is the Bayesian maximum clade credibility tree with posterior probability values> 0.5. Highlighted part of the tree, (magnified on the left), is the Arabis hirsuta aggregate and its relatives. Color codes: Green = Arabis hirsuta aggregate, red = the closest relatives of the Arabis hirsuta aggregate, blue = Arabis watsonii. Clade names follow Karl and Koch (2013).

Figure 4. trnL-F-based phylogenetic backbone of Arabideae that focuses on the placement of Arabis watsonii. Shown is the Bayesian maximum clade credibility tree with posterior probability values> 0.5. Highlighted part of the tree, (magnified on the left), is the Arabis hirsuta aggregate and its relatives. Color codes: Green = Arabis hirsuta aggregate, red = the closest relatives of the Arabis hirsuta aggregate, blue = Arabis watsonii. Clade names follow Karl and Koch (2013).