Repeated evolution of pollination syndromes in a highly diverse bromeliad lineage is correlated with shifts in life form and habitat

Abstract

Mutualistic plant-pollinator interactions play a critical role in the diversification of flowering plants. The spatiotemporal correlates of such interactions can be understood in a phylogenetic context. Here, we generate ddRAD-seq data for the highly diverse Vriesea-Stigmatodon lineage to test for correlated trait evolution among pollination syndromes and life form, habitat type, and altitude. Our results show that pollination syndromes are correlated with changes in life form and habitat type. The ancestor of the Vriesea-Stigmatodon lineage was likely bat pollinated, rock dwelling and inhabited open, mid-elevation forests. Transitions from bat to hummingbird pollination are correlated with transitions to the epiphytic life form in shaded habitats, whereas bat pollination is correlated with the rock-dwelling life form and open habitats. Our dated phylogenetic tree reveals independent origins of hummingbird pollination, occurring twice in Vriesea at c. 5.8 and 5.4 Mya. The timing for the shifts in pollination syndrome coincides with geological and environmental transformations across the Serra do Mar Mountain Chain, which increased habitat heterogeneity where Vriesea and their mutualists diversified. The phylogenetic tree reinforces the non-monophyly of taxonomic sections within the genus Vriesea previously defined by flower morphology, indicating that some lineages should be treated as species complexes. This study identifies synergetic drivers of speciation in a tropical biodiversity hotspot.