Surrounded by concrete: genetic isolation of Tillandsia recurvata L. in an urban landscape in southeastern Brazil

Increasing urban expansion has resulted in the decline of many natural and seminatural communities globally. However, the connectivity and genetic structure of species that survive in these urban landscapes have received little attention, especially with regard to epiphytic plants. This study aimed to describe and evaluate the connectivity and genetic structure of populations of Tillandsia recurvata, a highly abundant and widely distributed atmospheric epiphyte, amongst urban green spaces within a city. A total of 288 T. recurvata individuals were sampled across 65 trees throughout the city of Alfenas in South-East Brazil. We designed seven novel microsatellite markers and used four cross-amplified loci to determine the basic genetic structure of T. recurvata. All populations showed high global spatial genetic structure, which indicated low connectivity between urban populations. The findings of this study, as well as evidence from previous assessments of T. recurvata genetic structure, suggest that the combined effects of genetic drift, breeding system, and dispersal may have dictated the connectivity of these urban populations. This study represents an important step towards understanding epiphyte population structure within urban landscapes. Low connectivity across urban landscapes is likely to benefit epiphytes such as T. recurvata, due to their adaptability and high tolerance; this suggests a bleak future for many other more sensitive epiphytic species under predicted urbanization globally.