Abstract
Bird pollination is relatively common in the tropics, and especially in the Americas. In the predominantly Neotropical tribe Myrteae (Myrtaceae), species of two genera, Acca and Myrrhinium, offer fleshy, sugary petals to the consumption of birds that otherwise eat fruits, thus pollinating the plants in an unusual plant-animal interaction. The phylogenetic position of these genera has been problematic, and therefore, so was the understanding of the evolution of this interaction. Here we include new sequences of Myrrhinium atropurpureum in a comprehensive molecular phylogeny based on a balanced sample of two plastid and two nuclear markers, with the aim of providing the historical framework of pollination by frugivorous birds in Myrteae. We developed 13 flower and inflorescence characters that comprehensively depict the macroscopic morphological components of this interaction. Bayesian and parsimony phylogenies concur in placing both Acca and Myrrhinium in a clade with Psidium species; with Myrrhinium sister to Psidium. Mapping of morphological characters indicated some degree of convergence (e.g., fleshy petals, purplish display) but also considerable divergence in key characters that point to rather opposing pollination strategies and also different degrees of specialization in Acca versus Myrrhinium. Pollination by frugivorous birds represents a special case of mutualism that highlights the evolutionary complexities of plant-animal interactions.
Highlights
A wide array of evidence supports a strong association between specific floral traits and functional groups of pollinators that exert similar selective pressures on key aspects of the plant reproductive biology (Fenster et al, 2004)
While more species of Acca and Psidium need to be included in future analyses, it is clear from the support values that we report, that the taxa pollinated by frugivorous birds are not sister to each other
The South American myrtaceous genera Acca and Myrrhinium are known to share several characters that make them attractive as food bodies eaten by otherwise typical frugivorous birds
Summary
A wide array of evidence supports a strong association between specific floral traits and functional groups of pollinators that exert similar selective pressures on key aspects of the plant reproductive biology (Fenster et al, 2004). Most cases likely represent parallel origins of ornithophily from bee-pollinated ancestors (Cronk & Ojeda, 2008) This type of pollination is characterised by a passive pollen transport; nectar is the primary reward for pollinating birds (Stiles, 1981; Proctor, Yeo & Lack, 1996; Armbruster, 2011). Both groups of birds (hovering and perching) visit flowers of different morphologies and inflorescences that present diverse architectures (Rocca & Sazima, 2008; Rocca & Sazima, 2010)
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