Testing Darwin´s conundrum in a threatened biome: invasive and non-invasive exotic species have the same phylogenetic field

Exotic and invasive species have been the subject of several studies in the last few decades, due to their negative impact on native species and ecosystems. Despite those efforts, we are yet to definitively solve the question of what makes an exotic species successful in a new environment. Darwin’s conundrum represents that quest, with two contrasting hypotheses regarding exotic species establishment and success. We tested those hypotheses in a threatened biome: Mexican cloud forest (MCF). To do that, we estimated the phylogenetic field of non-invasive and invasive exotic angiosperm species, which allows us to see if they co-occur with more species closely related or distant to them. We also assessed if the phylogenetic field of exotic species is different in species with different growth forms and family representation in the MCF flora. We found that there is no difference between non-invasive and invasive exotic angiosperms’ phylogenetic fields, but there is a tendency for all exotic species to co-occur in assemblages with more closely related species, suggesting the importance for environmental filtering and support for the pre-adaptation hypothesis. Additionally, we did not find conclusive evidence that species with different growth forms had different phylogenetic fields. Finally, exotic species from angiosperm families that have more species on the MCF did not tend to co-occur in clustered assemblages, showing no effect of family representation on the MCF in the exotic species phylogenetic fields.