Pollination syndromes in Melastomataceae: pollinator shifts and species richness explain patterns of disparity in an ancestrally buzz-bee pollinated family

Constantin Kopper, Jürg Schönenberger, Agnes Dellinger

Pollination syndromes are defined as suites of floral traits, which have evolved repeatedly across angiosperms in adaptation to distinct functional pollinator groups. Several studies show support for the concept, while others raised concerns about their reliability. The large, pantropically distributed family Melastomataceae is dominated by buzz-bee pollination (95.5 %), where pollen is released from tubular, poricidal anthers through vibrations. In eight (of 23) tribes, shifts to other syndromes have occurred. Shifts among functional pollinator groups, are regarded as a source of increased floral disparity. We recorded 44 functional floral traits across 411 species, spanning the whole family. We used machine learning algorithms to identify pollination syndromes for species with documented pollinators and employed these trained models to predict pollinators for species without observations. We ran ancestral character state estimation to determine directionality in pollinator shifts in Melastomataceae. Furthermore, we contrasted floral disparity among the different syndromes, biogeography, and tribes to evaluate the relative role of pollinator shifts in generating floral disparity. Our results indicate strong support for four well differentiated pollination syndromes within Melastomataceae: “buzz-bee”, “nectar-foraging vertebrate”, “food-body-foraging vertebrate”, and “generalist”. Pollination syndromes in Melastomataceae can be discriminated by six system specific floral traits of which reward type
and pollen release mechanism are the two most important traits. Further, wefound that the “buzz-bee” and “nectarforaging vertebrate” syndromes are highly diverse and pollinator shifts contribute to floral disparity, which is not directly correlated with clade size. Finally, we reconstructed the “buzz-bee” syndrome as ancestral from which all other syndromes evolved repeatedly.

Department für Botanik und Biodiversitätsforschung
ÖFOS 2012
106008 Botanik, 106042 Systematische Botanik, 106012 Evolutionsforschung
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