Merianieae (Melastomataceae) as a model for studying Neotropical plant diversification

Merianieae are a tribe of ca. 300 species in the large tropical plant family Melastomataceae, and distributed from lowland rainforests to high-elevation cloud forests and páramos in the Andes. As in many other tropical lineages, the natural history of Merianieae was poorly understood when I started working on the group and broad generalizations for hundreds of species were based on a handful of studied taxa only. 

In recent projects, I have conducted in-depth investigations of the pollination biology of more than 25 Merianieae species to establish a solid baseline of knowledge for the group. In extensive field expeditions, I discovered a completely novel passerine pollination system and rodent pollination in the páramos of Southern Ecuador. Through collaborative efforts (Darin Penneys (University of North Carolina Wilmington), Fabián Michelangeli (New York Botanical Garden)), I have further produced a molecular phylogeny for the group. This setup now allows us to take a broad, comparative approach, integrating microevolutionary (ecological) patterns into a macroevolutionary (phylogenetic) framework to better understand the role of pollinators and other agents in driving plant diversification.

Pollination syndromes and floral trait evolution

Despite decades of research on pollinator-mediated selection, the mechanisms and processes by which flowers evolve and diversify remain elusive. Are there floral traits which are evolutionarily more labile than others? Do certain floral traits evolve independently of other floral traits? Do developmental/functional constraints restrain flowers from converging into traditional pollination syndromes?

Merianieae harbour an exceptional diversity of different pollination strategies, including bees, passerine birds (tanagers, flowerpiercers), hummingbirds, rodents and bats. Much of my recent research has revolved around tracing recurrent floral adaptations to these distinct pollinator groups (pollination syndromes) and analysing floral trait evolution from a multivariate, geometric-morphometric perspective. I am combining extensive field observations (mainly in Ecuador, Colombia and Costa Rica) with morphological lab work. Current work focuses on testing pollination syndromes established for Merianieae through empirical field observations and across the family Melastomataceae.

Buzz-pollination – investigating an adaptive plateau

Buzz-pollination refers to a functionally highly specialized pollination strategy where bees apply vibrations to flowers to extract pollen rewards. Pollen is concealed in tubular anthers which only open by a small, apical pore. Buzz-pollination has evolved in more than 65 plant families independently and is considered as an evolutionarily highly successful strategy (adaptive plateau). Although Melastomataceae represent the largest radiation of buzz-pollinated flowers, functional aspects of buzz-pollination in this group remain poorly understood.

I have recently started investigating the structural and functional properties of buzz-pollinated flowers using High-Resolution X-Ray Computed Tomography technologies (collaboration with Jürg Schönenberger, University of Vienna) and am testing a variety of hypotheses related to the adaptive success of buzz-pollination using artificial vibrations (collaboration with Mario Vallejo-Marín, University of Stirling).

Drivers of diversification in the Neotropics

Andean uplift, climatic perturbations as well as biotic and abiotic niche shifts have contributed to the extraordinary biodiversity found in the Neotropics. I have recently been funded by the Austrian Science Fund to investigate the relative contribution of historic, climatic and biotic factors in driving diversification in Merianieae (in collaboration with Stacey Smith, University of Colorado, Boulder; Laura Lagomarsino, Louisiana State University).

I am further using experimental and population genomic approaches (in collaboration with Ovidiu Paun, University of Vienna) to studying the impact of environmental and geographic factors on population-level processes such as pollen limitation and outcrossing. These microevolutionary approaches ultimately improve our understanding of macroevolutionary processes, i.e. whether and how environmental factors may drive pollinator shifts.

Combining the abiotic and biotic niche for understanding plant evolution

Environmental niche modelling (ENM) provides a powerful tool for characterizing the multivariate nature of a species’ niche. Too often, however, ENM focuses on abiotic (climatic) factors only, disregarding biotic interactions. This is particularly cumbersome given the crucial role biotic interactions such as pollination and seed dispersal have played in the diversification of angiosperms.

I am combining ENM with data on plant reproductive strategies to understand how biotic and abiotic niche shifts or niche conservatism may influence plant evolution and adaptation (in collaboration with Stefan Dullinger, University of Vienna). I am particularly interested in analysing how niches change and shift along altitudinal gradients both in the tropical Andes and in the European Alps.