A floodplain forest mosquito community after man-made moisture changes (Culicidae, Diptera)

Abstract

This paper summarizes data on the response of mosquitoes to changed water regime following extensive water management alterations on the southern Moravian Dyje and Morava rivers. Maximum groundwater level dropped by an average of 90 cm, previous regular floods were prevented, and the area covered by floodplain forests was significantly decreased due to the construction of three reservoirs. The original mosquito community of temporary water bodies (Aedes) is in retreat both quantitatively and, in places, qualitatively. Of the initial number of six species causing plagues, only Ae. vexans has remained (63.3 per cent), the rest occurring at percentages of only 0.1–4.1 per cent. After flood regulation, the breeding grounds of the species developing in temporary water bodies has filled only during periods of sufficiently high groundwater levels and sufficient saturation of soil with rainfall. A prospective group in this area includes mosquito species developing in permanent water bodies (Culex, Anopheles, Culiseta, etc.). This group is increasing in numbers and species richness. After the completion of three reservoirs, Anopheles spp. spread throughout the study area. They develop in the waters accompanying the reservoirs, especially in channels rich in vegetation, in which they attain densities of up to 39.9 larvae per 100 cm2 water surface. The drier environment, and drier and warmer climate prevailing in recent years have probably influenced the occurrence of southern species in the area, notably Culex martinii and Uranotaenia unguiculata. Long-term quantitative collections of mosquitoes enable first note to be made on the possible fluctuation mechanisms, previously obscured by the essential influence of floods on community development.