Plant architecture and habitat variation of the exotic ant-plant Ricinus communis Case Mahone Prager
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This study examines the ecology and plant life history strategies of the exotic ant-plant Ricinus communis across a variety of habitats in Costa Rica. Ant-plant protective mutualisms, particularly the less stringent facultative mutualisms, can be heavily influenced by abiotic factors, and consequently vary greatly across landscapes, habitats, and seasons. In this study, R. communis individuals were sampled across four habitat types (charral, roadside, plantation, and forest) in 20 sites. These 20 sites were located in the provinces of San Jose, Heredia, Cartago, Guanacaste, and Alajuela, Costa Rica. Leaf area, percent herbivory, extrafloral nectary (EFN) size and abundance were measured for each individual and three 15 minute temporal transects were run to determine the ant species abundance and diversity at each site. In addition, an ant exclusion experiment was performed to examine the role of defense by ants in this exotic ant-plant species. Plant architecture did vary across habitats, as did ant abundance, along a disturbance regime gradient closely related to the varying habitats. No significant relationship was detected between EFN size nor EFN abundance and herbivory; however, herbivory did increase when both EFN size and EFN count decreased. Furthermore, the ant exclusion experiment revealed no significant difference in herbivory levels between the ant and non-ant treatments. There was, however, a significant difference in the variability of herbivory between the two treatments.