Sequences of Pitcairnia flammea

Geographic isolation and reduced population sizes can lead to local
extinction, low efficacy of selection, and decreased speciation. However,
population differentiation is an essential step of biological
diversification. In allopatric speciation, geographically isolated
populations differentiate and persist until the evolution of reproductive
isolation and ecological divergence complete the speciation process.
Pitcairnia flammea allow us to study the evolutionary consequences of
habitat fragmentation on naturally disjoint rock outcrop species from the
Brazilian Atlantic Rainforest (BAF). Our main results showed low to
moderate genetic diversity within populations, and deep population
structuring caused by limited gene flow, low connectivity, genetic drift
and inbreeding of long-term isolation and persistence of rock outcrops
populations throughout Quaternary climatic oscillations. Bayesian
phylogenetic and model-based clustering analyses found no clear northern
and southern phylogeographic structure commonly reported for many BAF
organisms. Although, we found two main lineages diverging by approximately
2 Mya during the early Pleistocene, species delimitation analysis assigned
most of the populations as independent evolving entities, suggesting an
important role of disjoint rock outcrops in promoting high endemism in
this rich biome. Lastly, we detected limited gene flow in sympatric
populations although some hybridization and introgression were observed,
suggesting a continuous of speciation processes in this species complex.
Our data not only inform us about the extensive differentiation and
limited gene flow found among Pitcairnia flammea species complex, they
also contain information about the mechanisms that shape the genetic
architecture of small and fragmented populations of isolated rock outcrop
of recently radiated plants.