Evidence that phylogenetically novel non-indigenous plants experience less herbivory |
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Authors: | Steven Burton Hill Peter M Kotanen |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Toronto at Mississauga, 3359 Mississauga Road N, Mississauga, ON, L5L 1C6, Canada |
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Abstract: | The degree to which biotic interactions influence invasion by non-indigenous species may be partly explained by the evolutionary
relationship of these invaders with natives. Darwin’s naturalization hypothesis controversially proposes that non-native plants
are more likely to invade if they lack close relatives in their new range. A possible mechanism for this pattern is that exotics
that are more closely related to natives are more likely to share their herbivores, and thus will suffer more damage than
phylogenetically isolated species. We tested this prediction using exotic plants in Ontario, Canada. We measured herbivore
damage to 32 species of exotic plants in a common garden experiment, and 52 in natural populations. We estimated their phylogenetic
distances from locally occurring natives in three ways: as mean distance (age) to all native plants, mean distance to native
members of the same family, and distance to the closest native species. In the common garden, the proportion of leaves damaged
and the average proportion of leaf area damaged declined with mean phylogenetic distance to native family relatives by late
summer. Distance to native confamilials was a better predictor of damage than distance to the closest native species, while
mean distance to the entire native plant community failed to predict damage. No significant patterns were detected for plants
in natural populations, likely because uncontrolled site-to-site variation concealed these phylogenetic trends. To the extent
that herbivory has negative demographic impacts, these results suggest that exotics that are more phylogenetically isolated
from native confamilials should be more invasive; conversely, native communities should be more resistant to invasion if they
harbor close familial relatives of potential invaders. However, the large scatter in this relationship suggests that these
often are likely to be weak effects; as a result, these effects often may be difficult to detect in uncontrolled surveys of
natural populations. |
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Keywords: | Biological invasions Biotic resistance Community phylogenetics Enemy release Natural enemies |
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