Abstract
Orchid bees compose an exclusive Neotropical pollinators group, with bright body coloration. Several of those species build their own nests, while others are reported as nest cleptoparasites. Here, the objective was to evaluate whether the inclusion of a strong biotic interaction, such as the presence of a host species, improved the ability of species distribution models (SDMs) to predict the geographic range of the cleptoparasite species. The target species were Aglae caerulea and its host species Eulaema nigrita. Additionally, since A. caerulea is more frequently found in the Amazon rather than the Cerrado areas, a secondary objective was to evaluate whether this species is increasing or decreasing its distribution given South American past and current climatic conditions. SDMs methods (Maxent and Bioclim), in addition with current and past South American climatic conditions, as well as the occurrences for A. caerulea and E. nigrita were used to generate the distribution models. The distribution of A. caerulea was generated with and without the inclusion of the distribution of E. nigrita as a predictor variable. The results indicate A. caerulea was barely affected by past climatic conditions and the populations from the Cerrado savanna could be at least 21,000 years old (the last glacial maximum), as well as the Amazonian ones. On the other hand, in this study, the inclusion of the host-cleptoparasite interaction complex did not statistically improve the quality of the produced models, which means that the geographic range of this cleptoparasite species is mainly constrained by climate and not by the presence of the host species. Nonetheless, this could also be caused by unknown complexes of other Euglossini hosts with A. caerulea, which still are still needed to be described by science.
Highlights
Associations between host and parasitic species among Neotropical orchid bees (Hymenoptera: Apidae: Euglossini) have been mostly established based on casual and fortuitous reports
This model had an omission rate of 0.03, what means that the presences are being perfectly predicted) and a lower discriminative power than the climatic models, with a training AUC equal to 0.70. It has a high predictive power in the test sample, with AUC equal to 0.85. These results indicate that the relative likelihood of both models is similar, and statistically, no distinction of the best model solution can be made
The predictions of the potential distribution of a host-parasite complex of South American orchid bees were assessed when the host species distribution was included as a predictor variable of the parasitic bee, in the current and past climatic conditions for the LGM event
Summary
Associations between host and parasitic species among Neotropical orchid bees (Hymenoptera: Apidae: Euglossini) have been mostly established based on casual and fortuitous reports (revised by [1,2]). Besides field observations of cleptoparasitism, such behavior can be inferred from particular morphological features of females of the parasitic species, such as the lack of corbiculae, a synapomorphic character shared by females of all non-parasitic Apini, Bombini, Euglossini and Meliponini, used in harvesting pollen and returning it to the nest or hive [4]. Species belonging to these two genera, Aglae and Exaerete, are known to be cleptoparasites on the nests of Eufriesea Cockerell and Eulaema Lepeletier species (revised by [2]). The aforementioned new occurrences for A. caerulea in savannic areas in Central Brazil raised doubts whether its populations are expanding their ranges towards central South America or are retreating their distribution backwards to the Amazon after several expansion and contraction events of this forest formation in previous moments of South America climatic history [17,18,19,20,21,22,23]
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