Differential water deprivation tolerances of adult Rhagoletis indifferens and Rhagoletis pomonella (Diptera: Tephritidae) as a possible factor affecting their distributional abundances in Washington State, USA.

This article investigates the differential tolerance to water deprivation between two fruit fly species, Rhagoletis indifferens and Rhagoletis pomonella, in relation to their distributions in mesic (moist) versus xeric (dry) regions of Washington State, USA. Rhagoletis indifferens, native to both mesic and xeric habitats in western North America, was found to survive water deprivation significantly longer than the invasive R. pomonella, which originated from mesic eastern North America and was introduced into drier western regions. Experiments showed that while R. pomonella generally survives longer when water is available, R. indifferens exhibits greater desiccation resistance, particularly in younger and female flies, and that populations of R. pomonella in central Washington have adapted to drier conditions compared to western populations. These findings suggest that water availability, rather than temperature alone, influences the relative abundances and establishment success of these species in xeric environments, with implications for understanding invasive insect adaptation to arid climates.