Clinopodium arundanum (Lamiaceae): a long-overlooked and taxonomically misinterpreted serpentinophyte, endemic to the Spanish fir forests of Sierra Bermeja (Andalusia, Spain)

Clinopodium arundanum, a neglected taxon with a name misapplied for over 130 years, is here reinstated as a full species, endemic to the ultramafic Spanish fir (Abies pinsapo) forests of the northern face of Los Reales de Sierra Bermeja (Málaga), in Andalusia. This updated species hypothesis is supported by a critical assessment of all available material and iconography of C. arundanum, and an extensive morphological review of its closely related species in the Western Mediterranean.

Its most noteworthy diagnostic trait is the previously unreported resupinate corolla, associated with a non-resupinate calyx, an exceedingly rare condition in Mediterranean Lamiaceae. We provide an emended description of C. arundanum, together with information on phenology, etymology, geographic distribution, habitat, and potential pollinators. Additionally, we prepared the first photographic plates available for C. arundanum, a synoptic table including four morphologically allied species (C. atlanticum, C. nepeta, C. rouyanum, and C. vulgare), and a preliminary IUCN Red List risk of extinction assessment, in which forest fires are identified as its main threat.

Clinopodium arundanum is evaluated as Critically Endangered [CR B1ab(iii)+2ab(iii)], thus requiring urgent conservation attention, involving adequate forest management and ex situ actions. The rediscovery of this species highlights the exceptional floristic importance of Serranía de Ronda and of ultramafic outcrops.