Biologists have long debated the processes responsible for generation of diversity within and among species. The genetic structure of plant species can be shaped by both geographic and ecological factors that limit gene flow among populations. Geographically, populations can become fragmented and isolated by distance or by physical barriers, such as rivers or mountain ranges. Ecologically, populations can become isolated as a result of many diverse ecological processes, including pollinator driven genetic differentiation. Pollinators are important drivers of angiosperm evolution at both micro- and macroevolutionary scales. Diversity in floral traits of the bromeliad genus Vriesea has been driven largely by pollination by either hummingbirds or bats. Yet, a taxonomical quandary has arisen in the Vriesea, with some species originally described and grouped based upon pollinator type and others based upon floral morphology alone. This classification led to the controversial taxonomic placement of some Vriesea species with mixed floral traits.
In their new study published in AoBP, Neves et al. test whether floral traits (morphology, colour, scent, rewards and phenology) can accurately predict hummingbird and bat pollinators in the Atlantic Forest bromeliad genus Vriesea. They also test if genetic structure in Vriesea is mainly shaped by geography (latitudinal and altitudinal heterogeneity) or ecology (pollination syndromes). The genetic groupings of species were found to closely match the two pollinator types. The authors did identify species with intermediate genetic position which differed morphologically from the typical hummingbird and bat-pollinated Vriesea flowers by their mixed floral traits. These likely represent a window into shifts between bat pollination and hummingbird pollination, and vice-versa. The authors suggest that pollinators of this genus have roles in driving ecological isolation in Vriesea clades and highlight a morphological-genetic continuum that may be typical of ongoing pollinator-driven speciation in biodiversity hotspots.
Beatriz Neves received her PhD from the Museu Nacional of the Federal University of Rio de Janeiro, Brazil and is currently a post-doc researcher at the University of Gothenburg, Germany. Her research focusses on taxonomy, morphology, phylogenetics and pollination ecology of bromeliads (the pineapple family Bromeliaceae). She is currently studying floral shape evolution under pollinator-mediated selection.