1) Prof. Michal Gruntman

Plants can respond to light-competition cues with sets of plastic responses that provide either shade avoidance or tolerance and were suggested to match these strategies to the competition scenarios they experience. However, little is known about the effect of plants’ evolutionary history on their ability to shift between these strategies. We performed a common-garden experiment that examined shade avoidance and tolerance responses of the annual plant Hymenocarpos circinnatus to a variety of simulated light-competition scenarios, including different heights and densities of surrounding vegetation. These responses were compared across plants originating from six populations along a climatic gradient; from a semi-arid region, where light competition is relatively weak and homogenous, to a mesic-Mediterranean region, where light competition is stronger and more heterogenous. We found little evidence for divergence along the climatic gradient in the responses of H. circinnatus to light competition, which might reflect low costs of plasticity in these traits. Interestingly however, regardless of their evolutionary history, H. circinnatus were more responsive to cues of neighbor density rather than height in both shade tolerance and avoidance traits. These results suggest that procumbent plants such as H. circinnatus might respond more to lateral competition cues than vertical ones, thus highlighting the need to incorporate the two types of cues when studying plastic responses of plants to competition.