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Alexandra Harmon-Threatt

Alex observing pollinators
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Are non-native species more pollen limited than native species?
Research by Alexandra Harmon-Threatt and Tiffany Knight
The spread of exotic weeds has caused significant economical and
ecological problems. The focus of much research is to predict which
exotic plants will become pests, and to control existing pests. While
there has been much work done on the role of plant enemies, the role of
mutualists such as pollinators on seed production and spread of exotic
species has been virtually ignored. Many non-native plants require
pollinators for sexual reproduction, but occur without their co-evolved
pollinators in their introduced range. Thus, we hypothesize that the
reproduction of non-native plants will be more limited by pollinators than
the reproduction of native plants. We compared native and exotic species
in the same plant family. Using pairs of species with similar
phylogenetic histories means that species will be similar in many aspects
except for their native/exotic status. We experimentally determined the
breeding system of these plants, observed pollinators, and tested for
pollen limitation using a pollen supplementation experiment. We find that
in outcrossing species, non-native plants were more pollen limited than
there native counterparts. However, there is evidence that
self-compatibility is more prevalent in non-native plants, making them
less reliant on pollinators.
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