Aedes aegypti exhibits a remarkable adaptability to anthropogenic modifications, thriving across a diverse range of environmental conditions. To navigate the challenges posed by these dynamic settings, the mosquito must cope with significant selective pressures. Previous research has highlighted the varied climatic conditions in India (Beck et al. 2018) and their impacts on mosquitoes, influencing their genetics (Sumitha et al. 2023), physiology (Sharma et al. 2023), and morphology (Hounkanrin et al. 2023).
Expanding the existing knowledge, the present study analysed the wing morphometrics of 12 Ae. aegypti populations from five different climatic regions of India to understand the influence of native environmental conditions on wing size and shape. Among the studied populations, Jodhpur, and Sri Ganganagar populations are in the Arid region, marked by dry conditions. Kota and Hoshiarpur populations are situated in the Semi-arid region, which experiences moderately dry climates. Populations from Nagpur, Raipur, Kolkata and Visakhapatnam represents the Tropical wet and dry region. The Srinagar population is located in the Mountain region, defined by mountainous terrain. Lastly, the Lucknow, Guwahati and Itanagar populations are positioned in the Humid sub-tropical region.
Wing size is commonly used as a proxy for overall mosquito size (Dujardin, 2008), and it can influence various physiological and behavioural aspects of mosquitoes (Yeap et al. 2013). Larger mosquitoes, characterized by greater wing size, often exhibit distinct metabolic profiles, enhanced blood-feeding capacities, and improved flight capabilities compared to their smaller size mosquitoes (Yeap et al. 2013). These factors can collectively affect the mosquito's ability to transmit diseases. For example, larger mosquitoes are less susceptible to viral infections, potentially influencing the dynamics of virus transmission within mosquito populations (Alto et al. 2008). Therefore, wing morphometric studies have practical implications for formulating more effective vector management strategies in specific areas, emphasizing the importance of considering local environmental conditions in such interventions. The present study found that mosquitoes from arid region exhibit larger wing sizes (3.95 ± 0.13 mm) compared to those from other regions. This phenomenon can be attributed to the effects of high temperatures, which enhance larval metabolic rates and increase mortality rates. Consequently, the surviving larvae have access to more food, providing sufficient energy and nutrients for growth. This supports the development of larger wings in mosquitoes from arid regions. Conversely, mosquitoes from colder region showed shorter wing size (1.92 ± 0.24 mm). This can be explained as lower temperature slow down the development rate results in prolonged exposure to suboptimal conditions, which can limit growth. Additionally, colder temperature can reduce metabolic efficiency in mosquito larvae, affecting their ability to assimilate and utilize nutrients effectively. However, no significant correlation was found between the centroid size and temperature.
Although wing size offers valuable insights, it is recognized as being more vulnerable to environmental variations (Lorenz et al. 2017). In Thailand, the wing size of Ae. albopictus populations appear to be influenced by climatic conditions, whereas wing shape can reveal heritable intraspecific and regional differences (Vargas et al. 2013). Therefore, caution should be exercised when interpreting wing size data. In contrast, wing shape, as highlighted by research, proves to be more resilient to environmental variations and can predict population structure in certain species (Carvajal et al. 2016, Rodríguez-Zabala et al. 2016, Krtinić et al. 2016). The morphospace analysis, conducted through Canonical Variate Analysis (CVA), reveals statistically significant differences in wing forms among different climatic regions. The Semi-Arid region (SAD) contributed a larger morphospace than the other regions, revealing a greater variety of wing shapes. The cross-validated reclassification results also show that wing shape varies significantly among the regions. Only two of the 25 comparisons had accuracies less than 50% (Mountain and Semi-Arid (47%), and Mountain and Tropical wet and dry (34%)). These findings suggests that these variable climatic conditions contribute significant population structure in Ae. aegypti among the regions.
The Neighbor-Joining (NJ) tree generated in this study reveals two distinct clades, with the Mountain region serving as an outgroup. The first clade comprises the Arid and Semi-Arid regions, indicating that the wing shapes in these climates are highly similar. This similarity is likely driven by common environmental pressures such as high temperatures, sparse vegetation, and the need for efficient flight in open spaces. Whereas, the second clade consists of the Humid Subtropical and Tropical Wet and Dry regions. The species in these climates appear to have evolved wing morphologies that enhance maneuverability and stability in dense vegetation.