DIONYSIA SPLENDENS (PRIMULACEAE), A NEW SPECIES FROM THE FARS PROVINCE OF IRAN

Dionysia splendens Alipour, Mehregan & Lidén, sp. nov., from Fars, Iran, is a unique species that cannot be easily accommodated in any hitherto recognised section of the genus and is immediately recognised by its large flowers and pectinate leaves with very broad pale and thick midvein. It agrees with Dionysia cespitosa Duby (Boiss.) in the small flat leaves, stalked inflorescence with large bracts, and few large ellipsoid seeds, but differs in the tubular calyx and large purplish-blue corolla. It is also somewhat reminiscent of Dionysia viva Lidén & Zetterl. in growth habit and inflorescence structure, but that species has large irregularly dentate leaves, yellow corolla and numerous small angular seeds. Dionysia splendens is so far known from a single locality with c.200 mature individuals. An updated key to Dionysia species in the Zagros mountains is provided.


Introduction
The genus Dionysia Fenzl is endemic to the Irano-Turanian floristic region, from Southeast Anatolia and the Zagros mountains of Iran east to Afghanistan and Tadjikistan, with a southern outlier in Northeast Oman.All species are cliff-dwellers, often confined to vertical or even overhanging rocks.Dionysia is a well-characterised monophyletic taxon, but recognising it at generic rank leaves Primula L., as traditionally circumscribed, polyphyletic (see Lidén et al., 2021, for further discussion).
Dionysia splendens was discovered by the first author in May 2020, southwest of the village of Kaftar in the Fars province in Southwest Iran, in a place that is difficult to access, which explains why this remarkable plant has escaped notice.It is a unique species that cannot be immediately accommodated in any hitherto recognised section of the genus, and is easily recognised from all other Dionysia by its pectinate rosette leaves with very broad pale and thick midvein, and its large flowers.It agrees with Dionysia cespitosa (Duby) Boiss. in its small flat leaves, stalked inflorescence with large bracts, and few large ellipsoid seeds, but differs (in addition to the unique leaves) in its tubular calyx and very large purplish-blue corolla.It is also somewhat reminiscent of Dionysia viva Lidén & Zetterl. in growth habit and inflorescence structure, but that species has large irregularly dentate leaves, much smaller yellow corolla, and numerous small angular seeds.
The only other Dionysia species with stalked several-flowered inflorescenses with purplish flowers are D. involucrata Zaprjag.and D. hedgei Wendelbo, from Tajikistan and Afghanistan, respectively, both belonging to sect.Dionysiastrum subsect.Involucratae Wendelbo.They are very different in pubescence, as well as leaf and seed morphology.According to DNA data (Trift et al., 2004), the eastern taxa form a separate clade from the Zagros taxa, but neither Dionysia splendens nor D. viva was included in that study.Ecology.On west-facing limestone cliffs.
Phenology.Flowering in May.
Distribution.Known only from the type locality.Dionysia splendens, a new species from Fars, Iran Key to species of Dionysia in the Zagros mountains All species detailed in the key, except Dionysia viva and D. splendens (both currently incertae sedis) belong in sect.Dionysopsis (Pax) Melchior.Section Dionysia (see couplets 3 and 7) is not detailed.Species described since Lidén's synopsis (2007)
Calyx 8-11 mm, divided to c.4/5 into linear acute erect lobes; pubescence like that of bracts and peduncle.Corolla tube 16-18 mm long, pale yellowish, conspicuously ridged, ± densely pubescent with glandular hairs up to 0.5 mm long, often farinose.Limb pinkish purple to pale purplish blue, often paler towards the centre, but without a marked eye, 20-24 mm in diameter, cut into obovate, narrowly and shallowly emarginate lobes, sometimes with a few apical teeth.Style in longistylous flowers usually slightly exserted; style of brevistylous flowers reaching halfway through the tube.