Research Article |
Corresponding author: Barış Özüdoğru ( barisozudogru@gmail.com ) Academic editor: Karol Marhold
© 2016 Barış Özüdoğru, Mehmet Fırat.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Özüdoğru B, Fırat (2016) Arabis watsonii (P.H.Davis) F.K.Mey.: An overlooked cruciferous species from eastern Anatolia and its phylogenetic position. PhytoKeys 75: 57-68. https://doi.org/10.3897/phytokeys.75.10568
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Arabis watsonii (P.H.Davis) F.K.Mey. was initially reported as Thlaspi watsonii P.H.Davis in Flora of Turkey. Although F.K.Meyer transferred this species to Arabis L., this species has been overlooked and treated as Thlaspi L. in relevant literature for Flora of Turkey. In this study this species was evaluated using molecular (nuclear ITS and plastidic trnL-F sequences) and morphological data. Results clearly show that A. watsonii is sister to the A. hirsuta aggregate and its relatives. In conclusion, our results increased the number of known Arabis species in Turkey to 23. Furthermore, detailed description and distribution of the species are given and a new IUCN threat category for A. watsonii is proposed.
Arabis watsonii , Arabis hirsuta aggregate, Arabideae , Brassicaceae , phylogeny
The genus Arabis L. is represented by ca. 60 species and distributed in temperate regions of the northern hemisphere (
After the first revision of J.
Arabis watsonii (P.H.Davis) F.K.Mey. (Fig.
To verify Meyers’s treatment of Arabis watsonii, plant material was collected from type locality and nearby areas. Collected specimens were evaluated morphologically and molecularly to analyse 1) is A. watsonii a member of Arabis and 2), which main clade does it belong? We carried out morphological and molecular phylogenetic studies of A. watsonii plus representatives of Arabis and other Arabideae and combined this data with climatic and biogeographic data.
The present study includes for the first time sequences of nuclear ribosomal ITS1, ITS2 and 5.8 S rRNA (hereafter ITS) and trnL(UAA) intron/trnL-trnF intergenic spacer sequence data (hereafter trnL-F) for Arabis watsonii (Voucher: M. Fırat 32513 at
50 specimens belonging to five populations were used for extending description of A. watsonii. The vouchers were deposited at Hacettepe University Herbarium (
Total genomic DNA was isolated using DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) following the manufacturer’s instructions. ITS and trnL-F regions were amplified using primers ITS1 and ITS 4 (
Firstly, to determine whether A. watsonii belongs to tribe Arabideae, the phylogenetic tool in Brassibase (
Sequence evolution models were selected by the Akaike information criterion (AIC) implemented in MEGA v.6 (
The GTR + G + I model was selected for ITS and GTR + I for trnL-F and a Yule process of speciation was used as the tree prior. Two independent Markov Chain Monte Carlo (MCMC) runs for each data set were conducted with 10 million generations and sampled every 1000 generations. Each run was checked using TRACER v1.6 (http://beast.bio.ed.ac.uk/Tracer) and then log and trees files were combined in LOGCOMBINER (
A total of 20000 trees were obtained and 10% (2000) of these were discarded as burn-in. 18000 post-burn-in trees were used in the program TREEANNOTATER v.1.7.5 to obtain a single posterior probability and maximum clade credibility tree as visualized using FIGTREE v1.3.1.
To redescribe morphological features of A. watsonii ca. 50 individuals from five populations were investigated. In order to evaluate the IUCN thread category of A. watsonii, occurrence data were obtained from both field and Yüzüncü Yıl University, Science faculty herbarium (
Basionym: Thlaspi watsonii P.H.Davis (in
Turkey B9 Van: Çuh pass, Halanduran Da. and Güzeldere 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.
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 (
In Van province, indigenous people use name ‘Nançûk’ for Arabis species (
Field observations and records taken from relevant herbaria indicate that A. watsonii has two distinct populations (Fig.
The basic climatic requirements of A. watsonii, annual main temperature and annual precipitation were calculated as 5.7 °C and 583 ml respectively.
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 A. 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
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 = A. hirsuta aggregate, red=the closest relatives of the A. hirsuta aggregate, blue = A. watsonii. Clade names follow
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 = A. hirsuta aggregate, red=the closest relatives of the A. hirsuta aggregate, blue = A. watsonii. Clade names follow
In this study, we used evidence from nuclear ITS and plastidic trnL-F sequences to determine the phylogenetic and taxonomic position of the overlooked Anatolian endemic A. watsonii. In addition, morphological and climatic data were used to better understand ecological and evolutionary relationships of A. watsonii with representatives of the well-defined A. hirsuta aggregate and its relatives.
The differences in the phylogenetic placement of A. watsonii in relation to its sister position to A. cretica, according to ITS and trnL-F analyses, indicates possible chromosome capture /ancient hybridization. These processes are well known in the A. hirsuta aggregate and its relatives (
A recent study of A. hirsuta aggregate recognised eight European species including A. hirsuta (L.) Scop., A. sagittata (Bertol.) DC., A. planisiliqua (Pers.) Rchb., A. nemorensis (Wolf ex Hoffm.) W.D.J. Koch, A. allionii DC., A. sudetica Tausch, A. sadina (Samp.) Coutinho, and A. juressi Rothm. The historical definition and circumscription of such an aggregate depends on different authors (see
As indicated above, the ITS phylogeny supports a clear monophyly between A. watsoni and Greece endemic A. cretica Boiss. & Heldr. Whereas this relationship does not supported by trnL-F, both species seems to be at a basal position for A. hirsuta aggregate and its relatives. This results is somewhat expected because the Western Irano-Turanian and the East Mediterranean regions have already been suggested as diversity centres for almost all Arabideae clades (
Morphologically A. watsonii is smilar to A. hirsuta and A. sagittata, therefore specimens were treated under these names in some herbaria. However A. watsonii differsfrom A. hirsuta and A. sagittata in having glabrous stems and relatively large petals.
Finally, distribution in the alpine zone and perennial life cycle of A. watsonii is concordant with general trends of the tribe Arabideae (
This study was supported by Hacettepe University Scientific Research Projects Coordination Unit (Projects no. 014D01601015-489). We thank Çağaşan Karacaoğlu for helping us to use DIVAGIS and İsmail Kudret Sağlam for correcting style and grammar.