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Interactions among nectar robbing, floral herbivory, and ant protection in Linaria vulgaris
Author(s) -
Newman Daniel A.,
Thomson James D.
Publication year - 2005
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1111/j.0030-1299.2005.13885.x
Subject(s) - nectar , biology , ecology , herbivore , mutualism (biology) , ant , pollen
Nectar robbers are often assumed to be plant antagonists; however, empirical data show that the impacts of these animals range from negative to positive depending on the system and ecological conditions. We experimentally evaluated the combined effects of nectar robbing and ant visitation on three indices of reproductive fitness in Linaria vulgaris in the Colorado Rocky Mountains, via indirect effects on flower‐ and seed‐eating beetles ( Brachypterolus pulicarius and Gymnaetron antirrhinni ). Nectar robbing Bombus occidentalis leave holes in the nectar spurs, effectively creating “extra‐floral nectaries” that attract ants. In a paired‐plant experiment, ants were significantly more abundant on robbed than on unrobbed plants. Manipulation of ant access and nectar robbing showed that ant exclusion increased beetle attack and decreased female fitness. There was a significant ant‐by‐robbing interaction on flower damage. Patterns in the other two indices were suggestive of ant‐by‐robbing interactions, but these were not statistically significant. We also found correlations between spider occupancy on some plants and the mean number of ants (marginally negative) or beetles (significantly positive). Although the effect we report in this study may be highly dependent on spatial and temporal distributions of several interacting species, we discuss its potential role in mitigating the costs of floral parasitism, and its importance to the study of nectar robbing in general.