Biology subjects

Huxley, P. J.

Publications and source records attributed to Huxley, P. J..

7 recordsLinked to original sources

bioRxiv2026

Local trait responses and aquatic microclimates increase projected habitat suitability for field-collected Anopheles stephensi in southern Ethiopia

BackgroundTrait-based models of mosquito environmental suitability commonly use global thermal performance curves compiled from laboratory studies. These curves may misrepresent suitability when local populations or larval habitats differ from globally synthesised expectations. This issue is particularly relevant for Anopheles stephensi, an urban malaria vector expanding in the Horn of Africa, where artificial aquatic habitats may generate microclimates poorly represented by global trait datasets or gridded air-temperature products. Methodology/Principal FindingsWe compared juvenile survival, development, and projected maximal population growth rate, rm, using locally measured data from field-collected Ethiopian An. stephensi and a global comparator combining pub-lished juvenile trait data. We fitted thermal performance curves for juvenile survival and development, used these curves to estimate temperature-dependent rm as a metric of habitat suitability, and projected rm across two matched temperature inputs: logger-measured larval habitat water temperature and ERA5-Land 2 m air temperature. Local juvenile trait responses produced higher projected rm than the global comparator across monitored habitats. Measured aquatic temperatures were warmer than ERA5-Land air temperatures, with a mean daily water-air offset of 3.26{whitebullet}C, and were more spatially heterogeneous among habitats. ERA5-Land resolved only two unique temperature series across the six monitored habitats. Sensitivity analyses showed that the Local-Global difference was robust for logger-measured water temperatures, whereas the ERA5-based difference was partly amplified by cooler temperatures below the local experimental range. Conclusions/SignificanceThis study provides the first locally derived juvenile thermal performance curves and temperature-dependent population growth estimates for field-collected An. stephensi in Africa, demonstrating that locally measured juvenile traits consistently predict higher habitat suitability than globally synthesised trait data. These find-ings highlight the importance of incorporating local mosquito trait data and aquatic microclimate measure-ments into predictive models to improve assessments of An. stephensi establishment, spread, and malaria risk in newly invaded urban environments. Author SummaryAnopheles stephensi is an invasive malaria mosquito that is rapidly spreading in urban areas of Africa. Pre-dicting where this species can establish is difficult because many models use mosquito temperature-response data from long-maintained laboratory colonies rather than from recently collected African populations. We measured juvenile survival and development in An. stephensi collected from Ethiopia, and compared pro-jections based on these local data with projections based on published laboratory-colony data. We also compared field-measured larval habitat water temperature with ERA5-Land air temperature. We found that local juvenile trait responses produced higher projected population growth than the global comparator across monitored habitats. Field-measured water temperatures were warmer and more variable among habitats than gridded air temperatures, which reduced habitat-level differences. These findings show that local mosquito biology and larval habitat microclimate measurements can change fine-scale estimates of suitability. This matters for surveillance and control because urban water containers may create suitable conditions that are poorly represented by broad climate datasets.

ecology↗

bioRxiv2026

Humidity shapes the thermal niche of Anopheles stephensi,an invasive malaria vector

Vector-borne pathogens cause 17% of all human infectious diseases, and rising global temperatures are shifting the distribution and abundance of mosquito vectors. Because mosquitoes are ectotherms, temperature strongly governs biological rates and physiology; however, mosquitoes also experience other environmental factors that may interact with temperature to shape the thermal performance of traits driving population dynamics. Here, we use a factorial life-table experiment spanning five relative humidities (30-90%) and seven temperatures (16-38{whitebullet}C) to show that humidity modifies the thermal performance of key fitness traits in adult Anopheles stephensi, an invasive urban malaria vector. When integrated into a demographic model, humidity markedly reshapes projections of population fitness relative to temperatureonly models, suppressing growth and contracting year-round suitability in hot, arid regions while enhancing fitness in more humid or high-elevation climates characteristic of South Asia and Africa. Together, these results highlight the need to integrate multiple environmental drivers into projections of climatic suitability, as temperature-only approaches may mischaracterize both the magnitude and spatial structure of mosquito population fitness. More broadly, our findings demonstrate how moisture availability reshapes thermal niches, population fitness, and climate-driven projections of vector distributions.

ecology↗

bioRxiv2025

Beyond temperature: Relative humidity systematically shifts the temperature dependence of population growth in a malariavector

Understanding ectotherm responses to environmental change is central to coping with many of humanitys current and future challenges in public health, biodiversity conservation, and food security. Complex relationships between abiotic and biotic factors can influence ectotherm abundance and distribution patterns by introducing stage-specific variation in fitness trait responses. Variation in temperature, rainfall, competition, and habitat have all been considered in previous attempts to understand how environmental factors can interact and vary in their relative influence on species maximal population growth rates, rm. However, the combined effects of temperature and humidity on this fundamental metric are poorly understood. We show that variation in relative humidity can influence juvenile trait responses and rms temperature dependence in Anopheles stephensi, an important malaria vector. Our climate suitability maps show that the interactive effects of temperature x humidity on juvenile traits have important implications for predicting how environmental change will influence arthropod-mediated systems.

ecology↗

bioRxiv2024

Divergence of discrete- versus continuous-time calculations of the temperature dependence of maximum population growth rate in a disease vector

O_LIThe temperature dependence of maximal population growth rate (rm) is key to predicting how organisms respond and adapt to natural and anthropogenic changes in climate. For organisms with complex life histories, discrete-time matrix projection models (MPMs) can be used to calculate temperature-dependent rm because they directly capture variation in empirically-observed life-history trait values as well as the time delays inherent in those traits. C_LIO_LIHowever, MPM calculations can be laborious and do not capture the continuous nature of time. Temperature-dependent rm calculated from more complex approaches based on delay-differential equation and integral projection models are more accurate but are notoriously difficult to parameterise. Ordinary differential equation-based models (ODEMs) offer a relatively tractable alternative of intermediate complexity but it is largely unknown whether ODEM-based calculations and MPMs broadly agree when the effects of time delays and altered juvenile survival trajectories on temperature-dependent rm are introduced by environmental variation. C_LIO_LIHere we investigate differences in the predicted temperature dependence of rm obtained from an ODE-based model with those calculated from MPMs using high-resolution temperature- and resource dependent life-history trait data for the globally-distributed disease vector, Aedes aegypti. C_LIO_LIWe show that the level of agreement between discrete- and continuous-time representations of temperature-dependent rm can vary with resource availability, and is extremely sensitive to how juvenile survival is characterised. This finding suggests that analytic rm models can consistently provide comparable rm predictions to standard methods except for under severe resource constraints. C_LIO_LIOur study also suggests that all formulations of the intrinsic growth rate of a population may not be equally accurate for all types of organisms in all situations. Furthermore, this studys findings raise questions relating to whether existing mathematical models can be used to predict and understand population-level effects of environmental change. C_LI

ecology↗

bioRxiv2024

bayesTPC: Bayesian inference for Thermal Performance Curves in R

1O_LIReliable predictions of arthropod responses to climatic warming are important because many of these species perform important roles that can directly impact human society. C_LIO_LIThermal performance curves (TPCs) provide useful information on the physiological constraints that limit the capacity of temperature-sensitive organisms (like arthropods) to exist and grow. C_LIO_LINLS pipelines for fitting TPCs are widely available, but these approaches rely on assumptions that can yield unreliable parameter estimates. C_LIO_LIWe present bayesTPC, an R package for fitting TPCs to trait responses using the nimble language and machinery as the underlying engine for Markov Chain Monte Carlo. bayesTPC aims to support the adoption of Bayesian approaches in thermal physiology, and promote TPC fitting that adequately quantifies uncertainty. C_LI

ecology↗

bioRxiv2021

Competition in depleting resource environments shapes the thermal response of mosquito population fitness

The temperature-dependencies of life history traits are increasingly being used to predict how climatic warming will affect vector-borne disease dynamics, partially by affecting the abundance dynamics of the vector population. Such predictions generally arise from mathematical models that incorporate the temperature dependence of traits measured under laboratory conditions. These temperature-trait relationships are typically estimated from juvenile populations reared under optimal resource conditions, even though natural populations experience intermittent resource depletion. Using laboratory experiments on the mosquito Aedes aegypti, combined with a stage-structured population model, we show that resource depletion in the juvenile habitat can significantly depress the vectors maximal population growth rate (rm) across the entire temperature range, cause it to peak at a lower temperature, and narrow its thermal niche width. Our results provide compelling evidence for future studies to consider resource depletion when predicting the effects of global change on vector-borne disease transmission, disease vectors and other arthropods.

ecology↗

bioRxiv2020

The effect of resource limitation on the temperature dependence of mosquito population fitness

Laboratory-derived temperature dependencies of life history traits are increasingly being used to make mechanistic predictions for how climatic warming will affect vector-borne disease dynamics, partially by affecting abundance dynamics of the vector population. These temperature-trait relationships are typically estimated from populations reared on optimal resource supply, even though natural populations of vectors are expected to experience variation in resource supply, including intermittent resource limitation. Using laboratory experiments on the mosquito Aedes aegypti, a principal arbovirus vector, combined with stage-structured population modelling, we show that low-resource supply significantly depresses the vectors maximal population growth rate across the entire temperature range (22-32{degrees}C) and causes it to peak at a lower temperature than at high-resource supply. This effect is primarily driven by an increase in juvenile mortality and development time, combined with an exaggerated decrease in adult size with temperature at low-resource supply. Our study suggests that projections of vector abundance and disease transmission based on laboratory studies are likely to substantially underestimate how resource supply can modulate the temperature-dependency of population-level fitness through its influence on juvenile survival and development time. Our results provide compelling evidence for future studies to consider resource supply when predicting the effects of climate and habitat change on disease vectors and transmission.

ecology↗