Local trait responses and aquatic microclimates increase projected habitat suitability for field-collected Anopheles stephensi in southern Ethiopia
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Background
Trait-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 Findings
We compared juvenile survival, development, and projected maximal population growth rate, r m , 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 r m as a metric of habitat suitability, and projected r m 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 r m 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 ◦ 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/Significance
This 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 Summary
Anopheles 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.
