Reproductive ecology and isolation of Psittacanthus calyculatus and P. auriculatus mistletoes (Loranthaceae)

Background: Relationships between floral biology and pollinator behavior are important to understanding species diversity of hemiparasitic Psittacanthus mistletoes (c. 120 species). We aimed to investigate trait divergence linked to pollinator attraction and reproductive isolation (RI) in two hummingbird-pollinated and bird-dispersed Psittacanthus species with range overlap.

Methods: We investigated the phylogenetic relationships, floral biology, pollinator assemblages, seed dispersers and host usage, and the breeding system and female reproductive success of two sympatric populations of P. calyculatus and P. auriculatus, and one allopatric population of P. calyculatus. Flowers in sympatry were also reciprocally pollinated to assess a post-mating component of RI.

Results: Hummingbird assemblages differed between calyculatus populations, while allopatric plants of calyculatus opened more but smaller flowers with longer lifespans and produced less nectar than those in sympatry. Baye...