The physicochemical parameters of water, such as pH, salinity, conductivity, and total dissolved solids, can influence mosquito larval development, survival, and abundance. Therefore, it is important to elucidate how these factors influence mosquito occurrence. We hypothesized that the occurrence and community composition of immature mosquito species are driven not only by the availability of suitable aquatic habitats, but also by the physicochemical factors of these habitats. The primary objective of this study was therefore to investigate the influence of the physicochemical parameters of water in different types of aquatic habitats on the occurrence of mosquito species in two remnants of Atlantic Forest in the city of São Paulo, Brazil. Collections of immature mosquitoes and assessment of the physicochemical characteristics of the water in the collection sites were carried out for twelve months. The variation in species composition and occurrence with the measured physicochemical parameters and the type of breeding site was assessed using constrained ordination methods. The results indicate that there was a statistically significant difference in species composition as a function of the different types of aquatic habitats, and that pH had an influence on species occurrence even when the variance explained by the type of aquatic habitat was removed from the analysis. There was a statistically significant association between mosquito species occurrence and pH and salinity, and the former had a significant influence on the mosquito species collected regardless of the type of aquatic habitat, showing that the pH of the breeding site water is an important factor in driving mosquito population dynamics and species distribution.

Culex coronator Dyar and Knab and Culex usquatus Dyar belong to the Coronator Group of the subgenus Culex. Culex coronator and Cx. usquatus are widespread and sympatric throughout their distribution range, which includes Brazil. Morphological identification of these species is based primarily on the characteristics of the male genitalia; females are indistinguishable using the qualitative characteristics employed in identification keys. The primary objective of this study was to distinguish females of Cx. coronator from those of Cx. usquatus employing both wing geometric morphometrics, and DNA sequences (NADH5, COI, Hunchback, and CAD). Additionally, we employed the isolation with migration model (IMa) to evaluate: 1) the migration rates and 2) the divergence time, between Cx. coronator and Cx. usquatus. Specimens were captured in Pariquera-Açu and Cananéia south-eastern São Paulo, Ribeira Valley, Brazil. Canonical variate analysis (CVA) demonstrated two groups in the morphospace. The accuracy of species recognition was moderate (82.6%) for Cx. coronator and low (60.8%) for Cx. usquatus. Bayesian analyses of concatenated gene sequences recovered from specimens of Cx. coronator separated the species into three lineages (herein referred to as Culex coronator A, B, and C), whereas Cx. usquatus specimens clustered into a single lineage. Lineages A and B of Cx. coronator intermixed with specimens of Cx. usquatus, and one specimen of Cx. coronator clustered into the Cx. usquatus lineage. The IMa analysis indicated that the divergence of Cx. coronator and Cx. usquatus is a slow process, with some degree of gene flow between the two species.

Temperature is a major driver of arbovirus transmission, and a changing climate is expected to affect this process significantly. Most experimental studies rely on constant temperatures and overlook realistic daily temperature fluctuations that impact vector-pathogen interactions. The nonlinear relationship between temperature and vector traits responsible for pathogen transmission suggests that daily fluctuating temperatures produce phenotypes important for transmission distinct from those at constant temperatures. Here, we tested whether realistic variations in mean temperature and diurnal temperature range (DTR) influence West Nile virus (WNV) transmission. We experimentally infected colonized Culex tarsalis with WNV-infectious blood meals and maintained them under constant and fluctuating temperature regimes. We quantified how temperature, DTR, and incubation time shaped several outcomes (infection, dissemination, infectiousness, WNV loads in mosquito saliva and mosquito survival). We also integrated survival and infectiousness probabilities to infer implications for transmission. We observed strong effects of temperature on the WNV infection dynamics, viral loads and mosquito survival. Although the probability of initial infection was similar among all temperature regimes, dissemination and infectiousness were constrained by temperature. Dissemination and infectiousness were highest at 26C and reduced at cooler (22C) and warmer (30C) temperatures. Fluctuating temperatures significantly decreased infection and dissemination probabilities, while the probability of becoming infectious was driven primarily by mean temperature rather than DTR. Mosquito survival probability was temperature dependent, and fluctuating regimes increased mortality risk by 1.95-fold. Integrating mosquito survival and infectiousness dynamics demonstrated that, although at higher temperatures the extrinsic incubation period is shorter, reduced mosquito lifespan can limit viral transmission. Together, these results indicate that overall WNV transmission is affected by temperature-dependent viral dynamics and host physiological constraints. Fluctuating temperature regimes significantly delay viral dissemination within the host, especially at the optimal temperature (26C). Measurement of infection outcomes under constant temperatures treatments may lead to over/under estimation of transmission parameters in epidemiological models, therefore integrating fluctuating temperature treatments into mechanistic models of transmission can improve estimates of when and where WNV transmission is most likely to occur.