Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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DOES POLYEMBRYONY CONFER GREATER COMPETITIVE ABILITY IN THE NON-
NATIVE INVASIVE VINE, PALE SWALLOW-WORT? M.L. Blanchard, A. DiTommaso,
K.M. Averill, C.L. Mohler, and J.N. Barney, Cornell Univ., Ithaca, NY.
ABSTRACT
Pale swallow-wort (Vincetoxicum rossicum (Kleopow) Barbar) is a non-native
invasive vine in the Asclepiadaceae that has colonized natural systems in many
Northeastern States and several Canadian provinces. It is a twining herbaceous
perennial vine that can spread vegetatively, but reproduces primarily by seeds, some of
which exhibit polyembryony (i.e., a condition where a single seed can produce multiple
seedlings). Polyembryony occurs in a significant percentage of pale swallow-wort
seeds, and may allow the plant to more effectively colonize areas as well as
outcompete other plants for resources. Little is known about how polyembryony in this
invasive plant affects competitive outcomes. Thus, the effect of polyembryony in pale
swallow-wort on intra- and inter-specific competition was evaluated in a greenhouse
experiment using a modified replacement series design. Pale swallow-wort plants from
three polyembryonic classes; singles, doubles, and triples (i.e., one, two, and three
seedlings per seed, respectively) were grown with each other in all combinations and
with the native species, Canada goldenrod (Solidago canadensis L.) and common
milkweed (Asclepias syriaca L.). A total density of 2 plants per pot was used. The height
and number of nodes (rosette width for goldenrod) were recorded for pale swallow-wort
and milkweed plants every two weeks for 10 weeks, and then 4 weeks later at the end
of the experiment. After this 14-wk period, all plants were harvested and above- and
below-ground biomass determined. In general, pale swallow-wort plants consisting of
one seedling (singles) had significantly lower total biomass when competing with pale
swallow-wort plants having two or three seedlings and with goldenrod and milkweed
than with other single-seedling swallow-wort plants. These reductions in growth of
single-seedling plants were most evident for belowground biomass. There was no
significant difference between goldenrod and milkweed in their negative effect on pale
swallow-wort. These findings suggest that the production of more than one seedling via
polyembryony in pale swallow-wort may be advantageous in competitive environments.
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