Comparing the reproductive success and pollination biology of an invasive plant to its rare and common native congeners: a case study in the genus <Emphasis Type="Italic">Cirsium</Emphasis> (Asteraceae) |
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Authors: | Kristin I Powell Kyra N Krakos Tiffany M Knight |
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Institution: | (1) Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA |
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Abstract: | Previous studies have examined an association between reproductive success and pollination biology of rare versus widespread
species through pair-wise comparisons of native and invasive congeners or rare and common congeners. To determine the importance
of reproductive success and pollination biology for an invasive thistle, Cirsium vulgare, we compared it in its invaded range to five, co-occurring native Cirsium species that range from rare to common. Native study species include C. fontinale var. fontinale, C. andrewsii, C. brevistylum, C. occidentale, and C. quercetorum. We compared all species’ reproductive success, insect visitation rate and composition, autonomous self-pollination, and
level of pollen limitation in multiple populations. Species differed in their reproductive success; the invasive C. vulgare produced more flower heads per plant than most native species. C. vulgare attracted more visitors than its congeners. In addition, reproductive success and insect visitation significantly varied
between populations within species, mainly due to aphid infestation in one population of C. occidentale. Unlike the rare species (C. fontinale and andrewsii), C. vulgare did not require a pollinator for high-levels of seed production. The remaining native species set fewer seeds than C. vulgare without a pollinator. However, differences in insect visitation and autonomous self-pollination did not lead to differences
in pollen limitation across species or between populations. This result suggests that factors other than pollination biology
determine the difference in reproductive success of these species. However, high levels of autonomous self-pollination and
generalist insect visitation may allow the invasive C. vulgare to easily establish new populations from low numbers of propagules. Our study provides one contrast that should build towards
a larger comparative analysis to examine general patterns in the relationship between reproductive success, pollination biology,
rare and invasive species, and our ability to predict biological invasions in introduced species. |
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