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Phenology patterns and microhabitat preference of Dixidae (Diptera) on a longitudinal gradient of barrage lake system

Dixidae belong to order Diptera and they are usually associated with clean streams. Larvae are filter feeders, while adults do not feed. During the two-year period (February 2007 – December 2008) the phenology patterns were recorded at 10 sites of the National Park Plitvice. Adults were collected monthly using pyramid-type emergence traps. A total of 736 specimens were collected belonging to five species of the genus Dixa. The species recorded were: Dixa puberula, Dixa submaculata, Dixa nebulosa, Dixa maculata i Dixa nubilipennis which was recorded only with one individual. D. puberula was the most abundant species with 546 specimens recorded at 9 sites. D. submaculata preferred upper and middle parts of Bijela and Crna rijeka streams, while others showed no preference to any type of habitat. The highest diversity was recorded at tufa barrier Kozjak Milanovac in 2007 and the highest number of species (4 species) was found at upper reach of Crna rijeka stream in 2007. The biggest differences in composition and structure of Dixidae assemblages were recorded at site Korana u selu during 2007, as in that year the site completely dried out during the summer months. D. puberula and D. submaculata are univoltine or bivoltine depending on the site and the year. D. nebulosa and D. maculata are univoltine. A statistically significant positive correlation between the abundances and flow velocity of water was found for D. puberula which preferred moss-mats habitats. This study is one of the first studies of Dixidae phenology and microhabitat preference in Europe.

Dixidae, phenology, microhabitats

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