LARSON, KATHERINE C. Dept. of Biology, Univ. of Central Arkansas, Conway, AR 72035. - Lack of pollinators limits fruit set in the exotic Lonicera japonica.
The non-indigenous invasive, Lonicera japonica, is a woody vine
with a well-documented capacity for vegetative spread. Few data exist
on its potential for establishment by seed, but anecdotal reports span
the range from abundant seed reproduction to little seed reproduction.
Atypical for an invasive alien, L. japonica is
biotically-pollinated and xenogamous, requiring pollen from a
genetically distinct individual for fruit set. I addressed the
question of whether the services provided by the locally-available
pollinator community were adequate for fruit set of L. japonica
within its naturalized range. Hand-pollinations indicated that fruit
set of L. japonica in Arkansas was pollinator limited.
Naturally-pollinated control shoots produced fruit from 17.4% of their
flowers, but the hand-pollinated flowers had a fruit set of 78.7%, an
increase of over 4.5 times. As expected for a plant reported to be
biotically pollinated and xenogamous, the shoots with pollinators
excluded set fruit on only 2.1% of the flowers. In a survey of seven
different sites along the western edge of the naturalized range of
L. japonica, we found an average fruit set on primary shoots of
11.5+1.4% (mean+SE), while the secondary shoots averaged 20.1+2.8%.
These results indicate that sexual reproduction by L. japonica
is limited along the western edge of its naturalized range, and that
the invasive character of L. japonica in this area is largely
due to its prolific vegetative spread. Because this is one of the few
empirical data sets on sexual reproduction by this important plant
within its naturalized range, we do not extend our conclusions to
other areas of the US, but instead emphasize the importance of
documenting geographic differences in the reproductive potential of
Key words: fruit set, invasive plant, Lonicera japonica, pollination