The use of phenotypic data to delimit species is one of the least explored approaches in systematics. Normal Mixture Models (NMM) provide a useful framework to test for the existence of distinct species based on multivariate phenotypic information. In consequence, functional traits can be used as input data for these models, since they reflect species adaptations to certain environment. Frailejones (Espeletiinae Cuatrec., Asteraceae), which are the most emblematic plant group of the páramo ecosystem, represent an opportunity to apply this approach because they are an example of a recent ongoing adaptive radiation and have high morphological variation. Moreover, as functional traits are inherited characteristics, including them in NMM analyses may provide new insights into group delimitation with phenotypic information. As traits can also be affected by external and/or internal filters, they give additional information on the community assembly process. In this study we aim to determine functional units for frailejones based on functional traits and to understand the filter influence on these units. Four functional traits were measured in five individuals of each morphotype found throughout seven páramo complexes in the departments of Cundinamarca and Boyacá in Colombia. NMM were used to test the existence of different functional groups or units, in these seven páramo complexes. Bayesian Information Criterion (BIC) was used to find the number of functional units with the best empirical support. To evaluate the influence of external and internal filters on the functional units, we used T-statistics. An estimated 29 morphospecies were collected in the seven complexes. However, the model with the highest BIC supported nine functional units. The nine functional units occurred in multiple complexes and were sympatric with other units. Guantiva–La Rusia was the complex with the largest number of coexisting functional units (eight). In most complexes internal filters (e.g., competition, facilitation, microhabitat heterogeneity) had a greater influence on the assembly of functional units than the external filters (e.g., climate, dispersal). The nine functional units did not reflect the currently recognized species, although most of these species are also not supported phylogenetically. Internal and external filters can influence the convergence or degree of niche separation between functional units. Therefore, it is important to understand their contribution in the assembly of functional units and their distribution. There is a need for further studies that address species limits in the Espeletiinae as well as to explore this method and its usefulness within the group.
