Cistus horrens

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.

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[1]

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.           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]