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Environmental variables as indicators of Triatominae geographic distribution

Because of their hematophagous habit, Triatominae species are generally associated either with their blood sources and/or specific habitats where there is a significant chance of finding a blood meal. Some species are host-specific and others are

habitat-specific. As an example, T. delpontei is exclusively found in M. monachus colonial nests. The nest is occupied over several years, and individual nests are added every year to the colonial structure. During this time, the triatomine population has a relatively stable population of M. monachus to feed upon. A closely related species to T. delpontei, T. platensis, is associated with nests of various species of furnariid birds, which are only occupied during the breeding season when the species has the opportunity to feed on brooding adults and chicks. During the nonbreeding season, birds abandon the nest, and this nest is eventually occupied by other birds and/or mammals (especially rodents) that will become hosts for the tria- tomines. Rhodnius species are well-known generalists among the triatomines that occupy palm tree crowns. Different Rhodnius species are associated specifically (or preferentially) with a palm species, where the triatomines will feed on the rich fauna of birds and mammals nesting in the crown (e.g., R. brethesi with L. piassaba). Habitat availability for sylvatic populations of particular triatomine species strongly depends on the community structure and environmental conditions. Given this close association between habitat and Triatomine species, a number of studies have used sets of environmental variables at continental and subcontinental scales to analyze the geographic distribution of Triatominae species. The basic hypothesis of these studies investigates if places with similar environmental conditions would potentially represent places of additional occurrence of the species based on other areas with known occurrence of a particular Triatominae species. The idea is mainly applicable to studies on the geographic distribution of species at regional scales, where extrinsic factors of the studied populations are more important than intrinsic factors (i.e., climate variables and vegetation versus intra/interspecific competition and predation). For these types of studies, discriminant analysis and ecological niche modeling were used. The distribution of Triatominae species was studied using climate variables data that were collected at the ground level by meteorological stations available at continental scales (i.e., Worldclim database) and land cover and climate variables data recorded by earth observation satellites. Studies showed that environmental variables are good indicators of the geographic distributions of sylvatic, peridomes- tic, and domestic species of Triatominae.

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