Table 1.
Wild habitats and microhabitats of triatomine bugs, with a few examples.
Fig 1.
The microhabitats of Triatoma brasiliensis: Human dwellings, rocky outcrops, and shrubby cacti.
The lower panel illustrates the hypothesis that microhabitat quality varies along a gradient running from top-quality dwellings through high-quality rock microhabitats (the primary habitat of the species) to lower-quality cacti (most likely secondary habitat); alternatively, a small minority of cacti may also represent high-quality habitat (white asterisk).
Fig 2.
The microhabitat-quality hierarchy hypothesis: Predictions about habitat and drought effects.
Arrows in the plots emphasize drought-associated changes predicted by the microhabitat-quality hierarchy hypothesis. Note that we illustrate two alternatives for bug crowding in cacti–either it declines with the drought, suggesting that virtually all cacti are low-quality for the bugs (darker orange), or it increases, suggesting that a few cacti are high-quality and can act as ‘safe havens’ that sustain relatively large colonies (lighter orange, with a white asterisk emphasizing the link with Fig 1).
Fig 3.
Rainfall in the study area, 2000–2018.
Total annual and mean annual rainfall for the pre-drought (2000–2011, blue), drought (2012–2016, orange), and post-drought (2017–2018, grey) periods. Blue–orange gradation indicates that drought effects were barely perceptible in 2012, and orange–grey gradation that drought effects were still at its peak in early 2017. Lighter-blue bars indicate pre-drought years with rainfall below the overall mean (713 mm; empty bar in the right-hand panel). Pre-drought field trips are indicated by green arrowheads, and drought field trips by red arrowheads, along the x-axis. The graphs summarize daily rainfall data from the Russas rainfall station (Fundação Cearense de Meteorologia e Recursos Hídricos; data available at http://www.funceme.br/).
Table 2.
Descriptive and exploratory analyses: Microhabitat infestation by Triatoma brasiliensis, bug density, and bug crowding.
Table 3.
Microhabitat and drought effects on Triatoma brasiliensis: Models and hypotheses.
Fig 4.
Observed microhabitat infestation by Triatoma brasiliensis, bug density, and bug crowding.
Summary metrics by microhabitat (dwellings = triangles; rocks = squares; cacti = circles) both before (‘pre-drought’, blue) and during the drought (‘drought’, orange), with 85% confidence intervals (CI). Note that y-axes are on log10 scale.
Fig 5.
Microhabitat and drought effects on wild and synanthropic Triatoma brasiliensis populations: Model-averaged slope-coefficient estimates and confidence intervals (CI).
Microhabitat effects are represented in yellow, drought effects in red, and microhabitat × drought interactions in orange; intercepts (grey) are included for reference; the dashed horizontal line at zero indicates no effect.
Table 4.
Infestation models: Structure and performance.
The only competitive model (ΔAICc < 2.0) is in bold typeface.
Table 5.
Top-ranking infestation model (im13; wi = 0.882): Structure and numerical estimates.
Table 6.
Bug density models: Structure and performance.
Competitive models (ΔAICc < 2.0) are in bold typeface.
Table 7.
Competitive density models (ΔAICc < 2.0; ∑wi = 0.892): Structure and numerical estimates.
Table 8.
Bug crowding models: Structure and performance.
Competitive models (ΔAICc < 2.0) are in bold typeface.
Table 9.
Competitive crowding models (ΔAICc < 2.0; ∑wi = 0.566): Structure and numerical estimates.