Co-occurrence or dependence? Using spatial analyses to explore the interaction between palms and triatomines (Chagas disease insect vectors)

Abstract

BackgroundTriatomine kissing bugs are responsible for the vectorial transmission of the parasite Trypanosoma cruzi, etiological agent of Chagas disease, a zoonosis affecting 10 million people and with 25 million at risk of infection. Triatomines are associated with particular habitats that offer shelter and food. Several triatomine species of the Rhodnius genus have close association with palm crowns, where bugs can obtain blood from the associated fauna. The Rhodnius - palm interaction has been reported in several places of Central and South America. However, the association in the distributions of Rhodnius species and palms has not been quantitatively determined.Methodology/Principal FindingsBroad distributions of eight Rhodnius species and 16 palm species with Rhodnius-infestation reports were estimated using Ecological Niche Models. Rhodnius species distributions in their total range were compared to their distributions in areas with palms. Rhodnius species presence was found to be higher in areas with palms. However, that tendency notoriously depended on palm species. Rhodnius species presence increased several times in areas with particular palm species. Moreover, a possible relationship was found between Rhodnius and palm species richness, indicating the Amazon region as the convergent region where several Rhodnius and palm species intersected. Finally, palm distribution was evaluated as predictor of Rhodnius species distributions, but their inclusion in the distributions models did not improve their performance.Conclusions/SignificanceThe distributions of some Rhodnius and palm species showed a high spatial association, which can be based on species interaction or niche similarity. Based on distribution convergence, the Amazon region appear to be the origin of the Rhodnius-palm association. The direct relationship between palms and Rhodnius species richness could be based on the habitat heterogeneity offered by different palm species. Despite spatial association, palm presence would not be a relevant predictor of Rhodnius species distributions in comparison to other environmental variables. Inclusion of other input data as hosts’ distribution could help to increase model predictability.Author summaryThe infestation of palms with Rhodnius genus kissing bugs (Chagas disease vectors) is important from the public health perspective, since insects living in palms can infest nearby houses. The migration of these bugs to households could threaten vector control programs since reinfestation of treated dwellings can occur. Association between Rhodnius and palms species distributions has been previously suggested but never quantitatively determined. The strong association between one palm species and one Rhodnius species can be used as a factor to predict the presence of Rhodnius bugs in definite areas. In this study, we estimated by models the distributions of eight Rhodnius species and 18 Rhodnius-infested palm species. Rhodnius distributions models showed a biased presence toward areas with certain palm species. That specific association was very strong in some cases; however, the presence of associated palm species was used in Rhodnius distributions models, but that did not improve the predictability of the models. Palm presence appear to be not essential for the Rhodnius current distribution because they could inhabit other habitats; but that association could be relevant to the Rhodnius evolutionary and biogeographic history.