La Naturaleza de las Especies de Frailejones: Un Experimento de Jardín Común en Sumapaz

Species are considered basic units of study and management in several areas of biology, despite a persistent debate about whether different organisms, and in particular plants, form discrete units that correspond to species. This debate is particularly relevant when taxonomic divisions at the species level are used for practical purposes of broad interest. Such is the case of the taxonomic species of “frailejones” (Espeletiinae, Asteraceae), a monophyletic group of plants that is important for the functioning of high mountain ecosystems in northern South America and, at the same time, is quite vulnerable to global change. Previous studies suggest that frailejones from the Sumapaz region, in the Colombian Eastern Cordillera, form a syngameon: a group of species that are morphologically distinct despite exchanging genes through hybridization and introgression. This hypothesis has not been formally tested, but it predicts that morphological groups differ in their ecological niche. The aim of this study was to examine this prediction in terms of a facet of the ecological niche: recruitment and growth during early ontogeny. To achieve this aim, a common garden experiment was carried out in a nursery at 3400 m of elevation, in the Sumapaz region, where 100 seeds of each of 43 mother plants belonging to four morphological groups were sown. The recruitment and growth of the progeny from each mother plant were measured during four years. The morphological groups of mother plants did not form distinct groups of recruitment in the common garden. However, one morphological group showed a lower growth rate than the others. These results only partially supported the syngameon hypothesis, because concordance between morphological groups and groups according to growth was low, albeit statistically significant. Potential causes of demographic exchangeability among “frailejones” are discussed, along with implications of the results for their propagation in the context of ex situ conservation and restoration programs.