Interspecific pollen transport between non-native fennel and an island endemic buckwheat: assessment of the magnet effect

Non-native plant species can disrupt plant–pollinator interactions by altering pollinator foraging behavior, which can in turn affect levels of interspecific pollen transfer between native and non-native plant species. These processes may be amplified in cases where introduced plant species act as m...

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Bibliographic Details
Published in:	Biological invasions Vol. 24; no. 1; pp. 139 - 155
Main Authors:	Etter, K. J., Junquera, G., Horvet-French, J., Alarcón, R., Hung, K. -L. J., Holway, D. A.
Format:	Journal Article
Language:	English
Published:	Cham Springer International Publishing 2022 Springer Nature B.V
Subjects:	Biomedical and Life Sciences Buckwheat Developmental Biology Ecology Eriogonum arborescens Flowers Flowers & plants Foeniculum Foraging behavior Freshwater & Marine Ecology Indigenous plants Indigenous species Insects Interspecific Introduced species Life Sciences Original Paper Plant reproduction Plant Sciences Plant species introduction Pollen Pollinators Stigmas (botany) Santa Cruz Island Heterospecific pollen deposition Conspecific pollen loss Magnet plant effect Pollination
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Summary:	Non-native plant species can disrupt plant–pollinator interactions by altering pollinator foraging behavior, which can in turn affect levels of interspecific pollen transfer between native and non-native plant species. These processes may be amplified in cases where introduced plant species act as magnet taxa that enhance pollinator visitation to other plant species. We investigated these interactions on Santa Cruz Island (Santa Barbara Co., California) between non-native fennel ( Foeniculum vulgare ), a widespread and abundant invader, and the endemic Santa Cruz Island buckwheat ( Eriogonum arborescens ), which broadly overlaps fennel in its local distribution and blooming phenology. A fennel flower removal experiment revealed that this invader acts as a magnet species by increasing insect visitation to adjacent buckwheat flowers. Analysis of the amount of pollen carried on the bodies of insect pollinators (i.e., pollen transport) revealed that 96% of visitors to buckwheat flowers carried fennel pollen and 72% of visitors to fennel flowers carried buckwheat pollen. Pollen transport analyses and visitation rate data further suggest that members of three bee genera (primarily Augochlorella ) may be responsible for the majority of fennel pollen deposited on the stigmas of buckwheat flowers (i.e., pollen transfer) and vice versa. Lastly, fennel pollen transport appeared to occur at a larger spatial scale than the magnet effect that fennel plants exert on floral visitors to neighboring buckwheat plants. The ability of fennel to act as a magnet species, coupled with the fact that it is widespread invader with known allelopathic capacities, suggests that future studies could evaluate if the transfer of fennel pollen adversely affects native plant reproduction in areas where fennel is introduced.
ISSN:	1387-3547 1573-1464
DOI:	10.1007/s10530-021-02626-0