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Cistus horrens
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Malvales
Family:	Cistaceae
Genus:	Cistus
Species:	C. horrens
Binomial name
	Cistus horrens; Demoly

Cistus horrens is a shrubby species of flowering plant in the family Cistaceae, with purple to pink flowers. It is endemic to Gran Canaria in the Canary Islands. First described as a species in 2004, it was previously identified as Cistus symphytifolius, which it resembles.

Description

Cistus horrens generally resembles the more widespread Cistus symphytifolius. Differences include young branches covered with simple hairs; leaf blades grayer and shorter, densely covered with simple, glandular and stellate hairs on the upper surface and with longer simple hairs on the lower surface, with glandular hairs only on the nerves; sepals densely covered with simple hairs; and smaller fruiting capsules with fewer seeds.^[2] The leaves are elliptical to lanceolate, stalked (petiolate) and have netted (reticulate) veins. The stigmas are longer than the stamens.^[3]

Taxonomy and phylogeny

Cistus horrens was first described as a new species by Jean-Pierre Demoly in 2004;^[1] it had previously been treated as C. symphytifolius.^[2] The specific epithet horrens is Latin for "standing erect, bristling".^[4]

A 2011 molecular phylogenetic study placed C. horrens as a member of the purple and pink flowered clade (PPC) of Cistus species, along with some other Canary Island endemics (Cistus asper, Cistus chinamadensis, Cistus ocreatus, and Cistus symphytifolius).^[5]

Species-level cladogram of Cistus species.

Halimium spp.

PPC

Cistus crispus

Cistus heterophyllus

	Cistus albidus

	Cistus creticus

	Cistus asper

	Cistus chinamadensis

	Cistus horrens

	Cistus ocreatus

	Cistus osbeckiifolius

	Cistus palmensis

	Cistus symphytifolius

WWPC

	Cistus clusii

	Cistus munbyi

	Cistus inflatus

	Cistus ladanifer

	Cistus laurifolius

	Cistus libanotis

	Cistus monspeliensis

	Cistus parviflorus

	Cistus populifolius

	Cistus pouzolzii

	Cistus salviifolius

	Cistus sintenisii

Purple
Pink
Clade

White
Whitish Pink
Clade

Species-level cladogram of Cistus species, based on plastid and nuclear DNA sequences.^[5]^[6]^[7]^[8]

Distribution and habitat

Cistus horrens is endemic to Gran Canaria in the Canary Islands,^[3] being found in the south-west sector of the island.^[2] It is typically found at elevations of 300–1,500 metres (1,000–4,900 ft) in pine forests, in semiarid conditions.^[3]

References

^ ^a ^b "Cistus horrens", The Plant List, retrieved 2015-03-02
^ ^a ^b ^c "Cistus horrens Demoly", Jardín Botánico Viera y Clavijo (in Spanish), Cabildo de Gran Canaria, retrieved 2015-03-13
^ ^a ^b ^c Guzmán, Beatriz & Vargas, Pablo (2010), "Unexpected synchronous differentiation in Mediterranean and Canarian Cistus (Cistaceae)", Perspectives in Plant Ecology, Evolution and Systematics, 12 (3): 163–174, doi:10.1016/j.ppees.2009.09.002, p. 167
^ "horreo", Latin Word Study Tool, Tufts University, retrieved 2015-03-14
^ ^a ^b Civeyrel, Laure; Leclercq, Julie; Demoly, Jean-Pierre; Agnan, Yannick; Quèbre, Nicolas; Pélissier, Céline & Otto, Thierry (2011), "Molecular systematics, character evolution, and pollen morphology of Cistus and Halimium (Cistaceae)", Plant Systematics and Evolution, 295 (1–4): 23–54, doi:10.1007/s00606-011-0458-7, S2CID 21995828
^ Guzmán, B. & Vargas, P. (2009). "Historical biogeography and character evolution of Cistaceae (Malvales) based on analysis of plastid rbcL and trnL-trnF sequences". Organisms Diversity & Evolution. 9 (2): 83–99. doi:10.1016/j.ode.2009.01.001.
^ Guzmán, B. & Vargas, P. (2005), "Systematics, character evolution, and biogeography of Cistus L. (Cistaceae) based on ITS, trnL-trnF, and matK sequences", Molecular Phylogenetics and Evolution, 37 (3): 644–660, doi:10.1016/j.ympev.2005.04.026, PMID 16055353
^ Guzman, B.; Lledo, M.D. & Vargas, P. (2009). "Adaptive Radiation in Mediterranean Cistus (Cistaceae)". PLOS ONE. 4 (7): e6362. Bibcode:2009PLoSO...4.6362G. doi:10.1371/journal.pone.0006362. PMC 2719431. PMID 19668338.