Impact of urbanization and temperature on local abundance of Drosophila repleta Wollaston (1858) in the Western Himalayas

With rising global temperatures and expanding urbanization, rapid species abundance shifts and local extinctions may occur. We have observed a notable increase in the local population of Drosophila repleta, a species adapted to warmer environments, which was never documented at higher altitudes in the Western Himalayas before 2003. This change can be attributed to the recent acceleration of urbanization and the effects of climate change. To understand the species' response to temperature variations, we conducted a comparison of life-history traits at two different temperatures: 17 °C and 25 °C. These temperatures were chosen to simulate the variations experienced in 2003 and 2017, respectively. Our findings revealed a significant decrease in trait values at 17 °C, indicating a lower evolutionary capacity for adapting to colder and drier habitats. Additionally, we simultaneously examined the performance of life-history traits in response to different food resources, which corresponded to the levels of urbanization (carbohydrate-rich vs. protein-rich). The results showed a significant increase in fecundity, viability, and the percentage of adult emergence in flies reared on protein-rich food. This suggests that D. repleta possesses the ability to survive by utilizing the available food resources in the newly urbanized habitats. Considering the projected rise in global temperatures and further urbanization in the near future, D. repleta is likely to become even more abundant in urban environments. However, this could potentially pose a health risk due to the species' ability to transmit disease-causing organisms.