Data from: Plant responses to light competition: Does evolutionary history matter?

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.
To fill this knowledge gap, we performed a common-garden experiment that
examined shade avoidance and tolerance responses of the winter 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. In most of the studied traits, including those related to
shade avoidance, such as vertical elongation, or to shade tolerance, such
as photosynthetic efficiency, we found no evidence for differences among
H. circinnatus populations in the extent of their shade avoidance or
tolerance responses to light competition. 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. Moreover, we found differences among
populations in mean values of some of the studied traits across
treatments, particularly in the onset of flowering and internode length,
which are related to aridity adaptations to the shorter and unpredictable
growth season in the more arid sites. The little divergence we found in
light-competition responses across populations along the climatic gradient
might reflect low costs of plasticity in these traits in H.
circinnatus. Moreover, our results indicate that procumbent plants such as
H. circinnatus might respond more to lateral competition cues that
indicate neighbor density than to vertical cues that indicate neighbor
height, thus highlighting the need to incorporate the two types of cues
when studying plastic responses of plants to competition.