FIGURE 1.

(a) Similar to other ectothermic organisms, the life history traits of mosquitoes and the pathogens they transmit typically exhibit non-linear relationships with environmental temperature, where trait performance is constrained by both cool and warm temperatures and optimized at some intermediate temperature. Further, the effect of temperature on these individual traits can vary qualitatively and quantitatively, resulting in different temperature ranges across which trait performance can occur, temperatures that maximize trait performance, and the overall shape of the temperature-trait relationship (e.g., symmetric vs. asymmetric). As a result, predicting the effects of temperature on mosquito fitness, population growth rates or pathogen transmission is complex. (b) Mathematical models of vector-borne pathogen transmission that incorporate these temperature-trait relationships generally predict transmission to also follow a non-linear relationship and to peak at some intermediate temperature, as depicted here with the temperature-dependent relative reproductive number R₀ as a conceptual example. This model incorporates the effects of temperature on traits that drive mosquito population dynamics (e.g., per capita mosquito development rate (MDR), the probability of egg to adult survival (pEA) and the per capita number of eggs females produce per day (EFD)), host-vector contact rates (the per capita daily biting rate of female mosquitoes (a)) and the number of mosquitoes alive and infectious (transmission (b) and infection (c) probabilities, the extrinsic incubation period (1/EIR) and the per capita mosquito mortality rate (μ)). Where the predicted thermal minimum (T_min), maximum (T_max) and optimum (T_opt) for transmission occur will be dependent upon the relative effect of each trait, the nature of the temperature-trait relationship, and how these factors combine to shape the transmission process. Adapted from Mordecai et al. (2017).