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Habitat and population structure of rare and endemic Andean Espeletia pycnophylla subsp. llanganatensis (Asteraceae) in an Ecuadorian biodiversity hotspot

Abstract:

High-elevation neotropical environments of the Andes include the Páramo, a biodiversity hotspot with fast speciation rates. The genus Espeletia is distinctive of this ecosystem in the northern Andes. Its southern distribution limit lies in Ecuador, with the endemic E. pycnophylla subsp. llanganatensis being the only known representative south of the equator. This study presents the distribution, population structure and co-occurring flora of the subspecies llanganatensis in the Valle de los Frailejones (VFL), Cordillera de los Llanganates. Four clusters totalling ~ 20 ha could be identified at elevations of 3400–3550 m above sea level. Espelatia pycnophylla subsp. llanganatensis occurred amidst the sub-Páramo upper elevational limits of montane forests and within transitional areas between forest margins and waterlogged terrains. This habitat preference was a distinguishing ecological difference to the nearest (200 km) congener, E. pycnophylla subsp. angelensis. Plants (N = 781 measured) were skewed towards the smallest size classes ≤ 20 cm (28% of the population, including 17% recruits ≤ 10 cm) and reaching a total plant height of 900 cm. Synflorescences were observed in specimens ≥ 110 cm and in 51% of the mature population. The oldest specimens grew on terrains with higher edaphic stability. While local recruitment appears healthy, geographic distribution is limited suggesting vulnerability to local extinction. Co-occurring vegetation encompassed ~ 70 species, with grasses (Poaceae) and mosses (Bryophyta) dominating the ground cover, resulting in homogenous vegetation. Although E. pycnophylla subsp. llanganatensis is currently not exposed to direct human disturbance, clandestine mining activities intruding the region pose a potential threat to the survival of this Ecuadorian endemic.