Habitat characterization and breeding preferences of mosquito larvae in northwestern Spain: abundance, diversity, and species composition.

Abstract

Background: Understanding how environmental variables determine the presence, abundance, and diversity of mosquitoes (Diptera: Culicidae) in their larval habitats is crucial to establish appropriate preventive and control measures against these disease vectors. Although the autonomous community of Galicia (northwestern Spain) is an optimal area for the development of mosquitoes, little is known about their larval ecology.

Methods: The study was performed in 333 sampling points evenly distributed throughout Galicia. Different habitat characteristics (climatic zone, hydroregime, water body type, substrate, surface, depth, degree of insolation, environment type, and land use) and physicochemical parameters of the water (temperature, pH, electrical conductivity, dissolved oxygen, turbidity, salinity, and total dissolved solids) were recorded in each water body. Mosquitoes were collected using the standardized dipping technique between May and October in 2021 and 2022. The relationship between environmental variables with diversity, abundance, and species composition was assessed throughout the Kruskal-Wallis test (K-W), redundancy analysis (RDA), and generalized linear models (GLM). The affinity index between species that shared breeding sites was also analyzed.

Results: A total of 14 mosquito species belonging to the genus Culex (88.1%), Anopheles (7.5%), and Culiseta (4.4%) were identified, with Culex pipiens s.l. being the most abundant in the region (48.1%). The frequency, abundance, and diversity of mosquitoes varied significantly among climatic zones, hydroregime, water body types, substrates, and seasons according to the K-W results (P < 0.05). RDA indicated that water body type, temperature, pH, and the conductivity of the water accounted for the main part of the variation in species composition. GLM revealed that water conductivity, hydroregime, land use, and degree of insolation affect Cx. pipiens s.l. larval abundance. Many species shared breeding sites, but Cx. pipiens s.l. and Cx. torrentium had the highest affinity index (2.58). Both species are competent vectors of West Nile virus (WNV), so their wide presence in Galicia is of interest to public health.

Conclusions: Several environmental variables determine the diversity, abundance, and species composition of mosquitoes at breeding sites. The information presented in this study provides valuable insights into mosquito larval ecology, especially useful for the identification of epidemiological risk areas and the design of vector surveillance and control programs.