Population structure and mortality of Espeletia hartwegiana Sch.Bip. ex Wedd. in the El Campanario páramo, Colombia

Frailejones (Espeletia spp.) are key components of páramo ecosystems and serve as bioindicators of ecosystem conservation status. However, their populations are increasingly threatened by human activities and climate change, making demographic monitoring essential for conservation. This study aimed to determine the population structure and mortality rates of Espeletia hartwegiana in the El Campanario páramo, Colombia, to identify the most vulnerable age classes and provide baseline demographic information.

Eight permanent transects were established across two elevational zones, where 437 individuals, from seedlings to adults, were marked and monitored. For each individual, total height, necromass height, crown diameter, phenological stage, phytosanitary condition (percentage of herbivory), and reproductive output were recorded. Additionally, 2 × 30 m quadrats were used to estimate population density, age-class structure, and cover. Monitoring data collected between 2024 and 2026 were used to quantify transitions among developmental stages and to perform survival analyses using the Kaplan–Meier estimator and log-rank tests.

Juveniles and adults showed an aggregated spatial distribution, whereas seedlings ranged from random to aggregated. Population density varied between 0.7 and 2.6 individuals/m², and height structure was dominated by the A1 adult size class, with fewer juveniles and seedlings. Overall mortality reached 54% (235 of 437 individuals), with seedlings exhibiting the highest mortality (80.0%), followed by A1 (57.4%), juveniles (50.0%), A3 (49.1%), and A2 (40.5%). Kaplan–Meier analysis confirmed significant differences in survival among age classes (log-rank, p = 0.0069). Most surviving individuals remained in the same developmental stage throughout the study, with few transitions to larger size classes, reflecting the slow growth typical of frailejones.

These findings indicate that early developmental stages are the most vulnerable to mortality, while adults show greater persistence. The population is characterized by an adult-dominated structure and limited recruitment, highlighting potential constraints on long-term population renewal.