Format: ORAL

Thais Vasconcelos1, James Boyko1

1 Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA

The widespread convergence of plant traits in certain environments indicate that generalities exist for how plants diversify in space. However, because evolution and environments are dynamic, not all species are fully adapted to their environment at all times. A consequence of this is that infrequent trait-environment combinations that is, plant traits that appear in environments where they may not be optimalis also a common feature in nature. The presence of these infrequent combinations can be harnessed to test timing of trait evolution in relation to environmental shifts. Specifically, when analyzed in a phylogenetic context they might help indicate whether traits evolve prior to (as in exaptations) or after (as in adaptation) an environmental shift. Here, we demonstrate this in the context of leaf traits and biome shifts in Myrteae (Myrtaceae). We use a subset of 221 species with dry leaf mass/area (LMA g/cm2) data measured from herbarium specimens and trait evolution analyses in a recently generated phylogeny for the group. Biome type and LMA appear correlated, with low LMA lineages being more common in closed-canopy biomes. Low LMA in closed-canopy biomes is recovered as the most likely root state in the group. Transition rates from this state to low LMA in open-canopy biomes are practically zero, meaning that the only route to transition to open-canopy biomes is by evolving high LMA first. Similarly, to transition from open-canopy back to closed-canopy, lineages have to evolve low LMA before a shift. These preliminary results support the idea that trait evolution precedes and may facilitate environmental shifts, at least for this trait and set of species.