Mosquito population dynamics is shaped by the interaction among larval density, season, and land use

Abstract

ABSTRACT (English)Understanding how variation in key abiotic and biotic factors interact at ecologically relevant spatial scales is crucial for predicting population dynamics, distributions, and abundances. This is especially true for vectors that transmit human pathogens. However, studies investigating the effects of environmental variation on vectors have typically investigated environmental factors in isolation or in laboratory experiments that examine constant environmental conditions that often do not occur in the field. To address these limitations, we conducted a semi-field experiment in Athens, Georgia using the invasive Asian tiger mosquito (Aedes albopictus). We selected nine sites that varied in impervious surface and vegetation cover to explore effects of natural variation in microclimate (specifically, temperature and relative humidity) on mosquitoes. We manipulated conspecific larval density at each site and repeated the experiment in the summer and fall to further increase the variability in temperature and relative humidity. We then evaluated the original design features (land cover, larval density, and season), and their interactions, on the mean proportion of females emerging, juvenile development time, size upon emergence, and estimated per capita population growth (i.e., fitness). We found significant effects of larval density, land cover, and season on all response variables, including a non-intuitive decrease in development time with increasing larval density in the fall. We repeated these analyses using the hypothesized microclimate drivers of these effects: temperature and relative humidity. In general, the model using the microclimate variables outperformed the model using land use and season, highlighting the roles of temperature and relative humidity and their interactions with density on mosquito traits and dynamics. Our study demonstrates that ignoring the interaction between variation in biotic (e.g., intraspecific competition) and abiotic (e.g., temperature and relative humidity) variables could reduce the accuracy and precision of models used to predict mosquito population and pathogen transmission dynamics, especially those inferring dynamics at finer-spatial scales across which transmission and control occur. ABSTRACT (Spanish)Es crucial comprender como los factores abioticos y bioticos interactuan a escalas ecologicamente relevantes para predecir la dinamica, distribucion, y abundancia de poblaciones. Esto es especialmente cierto para vectores que transmiten patogenos humanos. Sin embargo, la mayoria de estudios han considerado factores ambientales de forma aislada o en condiciones de laboratorio poco realistas. Para superar estas limitaciones, realizamos un experimento de semi-campo en Athens, Georgia, con el mosquito invasor Aedes albopictus. Manipulamos la densidad larval en nueve sitios que variaban en cobertura vegetal y superficie impermeable, y repetimos el experimento en el verano y otono. Luego, evaluamos los efectos de la cobertura del suelo, la densidad larval, y la estacion en la proporcion de hembras adultas emergidas, el tiempo de desarrollo, el tamano al emerger, y el crecimiento poblacional per capita. Encontramos efectos significativos de todas las variables, asi como fuertes interacciones entre estacion y densidad de mosquitos, incluyendo una disminucion no intuitiva del tiempo de desarrollo en el otono con mayor densidad larval. Repetimos los analisis usando factores microclimaticas hipotetizados como impulsores de estos efectos: temperatura y humedad. En general, el modelo que incorpora variables microclimaticas supero al modelo basado en el uso de suelo y estacion, evidenciando la importancia de la temperatura y la humedad, asi como sus interacciones con la densidad larval, en las caracteristicas biologicas y la dinamica poblacional de los mosquitos. Nuestros resultados demuestran que la interaccion entre variacion biotica (competencia intraespecifica) y abiotica (temperatura y humedad), es fundamental para mejorar la precision de los modelos que predicen la dinamica poblacional de mosquitos y la transmision de patogenos a escalas locales de transmision y control.