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| Aim To investigate the role of alien plants in mutualistic plant–hummingbird
networks, assessing the importance of species traits, ?oral abundance and insu-
larity on alien plant integration.
Location Mainland and insular Americas.
Methods We used species-level network indices to assess the role of alien
plants in 21 quantitative plant–hummingbird networks where alien plants
occur. We then evaluated whether plant traits, including previous adaptations
to bird pollination, and insularity predict these network roles. Additionally, for
a subset of networks for which ?oral abundance data were available, we tested
whether this relates to network roles. Finally, we tested the association between
hummingbird traits and the probability of interaction with alien plants across
the networks.
Results Within the 21 networks, we identi?ed 32 alien plant species and 352
native plant species. On average, alien plant species attracted more humming-
bird species (i.e. aliens had a higher degree) and had a higher proportion of
interactions across their hummingbird visitors than native plants (i.e. aliens
had a higher species strength). At the same time, an average alien plant was vis-
ited more exclusively by certain hummingbird species (i.e. had a higher level of
complementary specialization). Large alien plants and those occurring on
islands had more evenly distributed interactions, thereby acting as connectors.
Other evaluated plant traits and ?oral abundance were unimportant predictors
of network roles. Short-billed hummingbirds had higher probability of includ-
ing alien plants in their interactions than long-billed species.
Main conclusions Once incorporated into plant–hummingbird networks, alien
plants appear strongly integrated and, thus, may have a large in?uence on net-
work dynamics. Plant traits and ?oral abundance were generally poor predic-
tors of how well alien species are integrated. Short-billed hummingbirds, often
characterized as functionally generalized pollinators, facilitate the integration of
alien plants. Our results show that plant–hummingbird networks are open for
invasion
Aim
To investigate the role of alien plants in mutualistic plant–hummingbird networks, assessing the importance of species traits, floral abundance and insularity on alien plant integration.
Location
Mainland and insular Americas.
Methods
We used species-level network indices to assess the role of alien plants in 21 quantitative plant–hummingbird networks where alien plants occur. We then evaluated whether plant traits, including previous adaptations to bird pollination, and insularity predict these network roles. Additionally, for a subset of networks for which floral abundance data were available, we tested whether this relates to network roles. Finally, we tested the association between hummingbird traits and the probability of interaction with alien plants across the networks.
Results
Within the 21 networks, we identified 32 alien plant species and 352 native plant species. On average, alien plant species attracted more hummingbird species (i.e. aliens had a higher degree) and had a higher proportion of interactions across their hummingbird visitors than native plants (i.e. aliens had a higher species strength). At the same time, an average alien plant was visited more exclusively by certain hummingbird species (i.e. had a higher level of complementary specialization). Large alien plants and those occurring on islands had more evenly distributed interactions, thereby acting as connectors. Other evaluated plant traits and floral abundance were unimportant predictors of network roles. Short-billed hummingbirds had higher probability of including alien plants in their interactions than long-billed species.
Main conclusions
Once incorporated into plant-hummingbird networks, alien plants appear strongly integrated and, thus, may have a large influence on network dynamics. Plant traits and floral abundance were generally poor predictors of how well alien species are integrated. Short-billed hummingbirds, often characterized as functionally generalized pollinators, facilitate the integration of alien plants. Our results show that plant–hummingbird networks are open for invasion. | |
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