Page 174 - PC2019 Program & Proceedings

PLANT CANADA 2019

S133. Precarity of American Water Willow (Justicia americana) in Ontario
1
Vasseur, L. ; O. Groff 2
1 Brock University
2 Land Care Niagara

The American waterwillow (AWW) is an aquatic clonal plant, threatened in Canada. Two populations are
found in Ontario and two others in Quebec. This plant grows along the waterbody shores, but habitat loss,
water level fluctuations and presence of invasive species pose as threats. The Niagara populations have
been monitored to understand the ecological factors that may limit its distribution. One priority of the
recovery plan is to reintroduce the species in waterbodies where it was found prior to the construction of
the Welland Canal. The 2014-2018 field surveys showed that, partly due to increased sampling effort, the
number of individual stems has increased from about 20,000 to over 100,000. Seeds pods were collected
for three years and, on average, 1 over 200 pods contained an assumed viable seed. Seed germination
experiments, using direct seeding, cold treatment, and scarification, resulted in no seed germination. In
controlled conditions, plants can survive but require to be maintained with a constant water level.
Genomic analyses have been conducted on the Ontario and one Quebec populations and preliminary
results suggest low polymorphism. As AWW is located at the northern limit of distribution, it is highly
possible that it is affected by founder effect.

Liette Vasseur (lvasseur@brocku.ca)

S134 Integrated metabolic strategy: a framework for predicting the evolution of carbon-water
tradeoffs within plant clades
1
*1
Goud, E. ; J. Sparks ; M. Fishbein ; A. Agrawal
2
1
1 Cornell University
2 Oklahoma State University

The fundamental tradeoff between carbon gain and water loss has long been predicted as an evolutionary
driver of plant strategies across environments. Nonetheless, challenges in measuring carbon-water
tradeoffs in ways that integrate over leaf lifetime have limited our understanding of the variation in and
mechanistic bases of this tradeoff. Here we introduce the concept of ‘integrated metabolic strategy’ (IMS)
to describe the ratio between carbon isotope composition (δ C) and oxygen isotope composition above
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18
source water (Δ O) of leaf cellulose. IMS is a measure of leaf-level conditions that integrate several
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18
mechanisms contributing to carbon gain (δ C) and water loss (Δ O) over leaf lifespan, with larger values
reflecting higher metabolic efficiency and hence less of a tradeoff. We tested how IMS evolves among
closely related yet ecologically diverse milkweed species. Larger IMS values were associated with
species from dry habitats, with larger carboxylation capacity, smaller stomatal conductance and smaller
leaves; smaller IMS was associated with wet habitats, smaller carboxylation capacity, larger stomatal
conductance and larger leaves. The evolution of IMS was dominated by changes in species’ demand for
carbon more so than water conservation. IMS variation among and within species may shed light on
unresolved questions relating to the evolution and ecology of plant ecophysiological strategies.

Ellie Goud (emg244@cornell.edu)

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