Range size positively correlates with temperature and precipitation niche breadths but not with dietary niche breadth in triatomine insects, vectors of Chagas disease

Abstract

Ecological theory predicts that species that can utilise a greater diversity of resources and, therefore, have wider niche breadths should also occupy larger geographic areas (the 'niche breadth-range size hypothesis'). Here, we tested this hypothesis for a blood-sucking group of insects of medical significance: the Triatominae (aka 'kissing bugs') (Hemiptera: Reduviidae). Given that niches can be viewed from different perspectives, we tested this hypothesis based on both dietary and climatic niches. We assembled the most complete dataset of triatomine feeding patterns to date by reviewing 143 studies from the literature up to 2021 and tested whether the niche breadth-range size hypothesis held for this group for both dietary and climatic components of the niche. Temperature and precipitation niche breadths were estimated from macro-environmental variables, while diet breadth was calculated based on literature data that used PCR and/or ELISA to identify different types of hosts as blood sources per triatomine species. Our results showed that temperature and precipitation niche breadths, but not dietary breadth, were positively correlated with range sizes, independent of evolutionary history among species. These findings support the predictions from the range size-niche breadth hypothesis concerning climate but not diet, in Triatominae. It also shows that support for the niche breadth-range size hypothesis is dependent upon the niche axis under consideration, which can explain the mixed support for this hypothesis in the ecological literature.

Fig 1. Overview of the hypotheses tested.

(A). Occurrence points from each studied species are plotted. World country polygons were plotted using “rnaturalearth” v.1.0–1 R package [35]. (B). Phylogeny reconstructed in our study, with bar charts indicating the range size, species-level diet breadth, temperature niche breadth, and precipitation niche breadth. To facilitate visualisation, variables were scaled to 1. Coloured points at the tips of the phylogeny represent the occurrences of the species in (A). DBR = “Diet niche breadth”, TNB = “Temperature niche breadth”, PNB = “Precipitation niche breadth”.

Fig 2. Proportions of each host family used as diet by each triatomine species.

Only the names of the three families with the higher proportions are shown. Colours correspond to the host families used by each triatomine.

Fig 3. Relationships between the predictor and response variables analysed using diet breadth at the species level.

The natural log of the range size was used as the response in a multivariate regression, whereas the natural log of the diet breadth (first column) and square root transformed temperature (second column) and precipitation (third column) niche breadths were used as predictors. Each row corresponds to the analyses for the entire dataset and divided by triatomines’ habitat. Linear trend lines were added to facilitate interpretation according to the intercept and slope from the regression calculations. Dashed lines represent non-significant relationships, whereas solid lines are statistically significant. Coloured points correspond to the species exclusive of the respective habitat.