Patchily distributed but not necessarily isolated populations of Deuterocohnia meziana: a threatened bromeliad from rock outcrops

The movement of organisms or genes among resource patches is fundamental to the persistence of natural populations over time. Species occurring in rock outcrops may have difficulty maintaining genetic connectivity due to the natural disjunct distribution of these formations, which may lead to genetic differentiation. In this study, we tested the hypothesis of genetic isolation among populations of Deuterocohnia meziana on rock outcrops in Brazil. We evaluated genetic diversity and structure, number of migrants, and the contribution of pollen and seed to dispersal. Additionally, we used niche modelling to estimate the potential distribution of D. meziana and combined this with genetic data to identify potential dispersal routes under different climatic scenarios from the Quaternary. Deuterocohnia meziana showed high diversity and moderate genetic structure, low number of migrants and more efficient dispersal by pollen. Only populations separated by > 70 km showed genetic differentiation. Dispersal routes varied mainly in the intensity of the environmental suitability and indicated the present scenario as the most favourable for gene flow in D. meziana. Our findings contribute to the understanding of processes related to the connectivity and isolation of naturally fragmented populations, highlighting the role of biotic and abiotic drivers for genetic differentiation.