Impacts of introduced species on specialized mutualisms: A case study on the oil reward pollination network in southern Florida

Background/Question/Methods

Plant and pollinator interactions are important drivers that shape community diversity. Studies quantifying the trajectory and strength of these interactions in the face of increasing human-mediated species exchange can help us understand and predict future community assemblages. Recently in southern Florida an introduced oil bee, Centris nitida, native to Central America and Mexico, has been identified as a novel participant in an endemic specialized mutualism between Byrsonima lucida (locust berry), a native oil producing plant, and Centris errans, its native oil bee pollinator. The native oil bee also plays a major role in pollinating the rare native cowhorn orchid, Cyrtopodium punctatum. Also present in the landscape are several other introduced floral-oil producing plants (Malpighiaceae), some of which originate from the same region as the introduced oil bee. In this study we examine the impacts of the introduced oil bee and oil plants on the native specialized pollination interactions by quantifying interaction intensity among the native and introduced oil bees and plants, and creating a specialized pollination web among the studied plants and bees. We hypothesize that interaction intensity will be highest between species that share prior evolutionary histories. We predict the native oil bee will prefer to visit the native oil plant, and the introduced oil bee will preferentially visit non-native oil plants.

Results/Conclusions

Data from two seasons’ observation indicated that our predictions were partially correct. Consistent with our prediction, the native oil bee indeed had stronger interaction intensity with the native oil plant than with the introduced oil plants. To the contrary of our prediction, the interaction intensity of the introduced oil bee was also strongest toward the native oil plant than with the introduced oil plants. The introduced oil bee was not attracted to the native cowhorn orchid, a possible oil plant mimic. These asymmetric interactions indicate that the impacts of introduced species may be limited, and could even be beneficial to this the already threatened and pollen limited native plant species.