A bromeliad living in the city: a case of a native species resilient to urbanization in South Brazil

In an era of increasing urbanization across the planet, understanding how urbanization affects biodiversity and whether or not species will be able to adapt quickly enough to urban environments is critical to conserving biodiversity. We studied the effects of urbanization on genetic diversity, genetic structure, and local adaptation in Tillandsia aeranthos, an epiphytic self-incompatible bromeliad with a high ability to colonize urban habitats. We sampled T. aeranthos along two transects comprising urbanization gradients in South Brazil. We used AFLP markers to genotype 200 individuals and we obtained 971 fragments, of which 100% were polymorphic. We found high levels of genetic diversity and a greater proportion of genetic variation found within populations. We did not find a decrease in genetic diversity with increasing urbanization, as expected if the effects of genetic drift were greater in those urbanized habitats. In each transect, the urban populations were genetically clustered with the non-urban populations, indicating that dispersion by pollen or seed may occur between urban and non-urban populations. The lack of correlation between the outlier loci detected and the index of urbanization found in our study corroborates with other indices of genetic diversity not being affected by urbanization. Our results suggest that gene flow via pollen and seed, combined with high rates of outcrossing, are major determinants of the maintenance of genetic diversity in urban populations of T. aeranthos.