Altitudinal and seasonal variation in the family-level assemblages of flies (Diptera) in an Australian subtropical rainforest: One hundred thousand and counting!

Abstract

Many surveys around the world have examined the altitudinal or seasonal variation of invertebrate biodiversity but few have concentrated on the fly fauna because of difficulties with the amount of material and identification. We examined family-level assemblages of flies collected in Malaise traps from rainforest at Lamington National Park, south-east Queensland across altitude and seasons. We found significant effects of both season and altitude on the overall abundance of other Diptera (without lower Diptera), with a significant interaction effect so that abundances in summer were much higher than those in winter, but only at mid to high altitudes. We also found significant effects of both season and altitude on the family richness of other Diptera, and again the interaction of these factors was significant. A clear seasonal influence was noted at mid to high elevations with a progressive decline in the number of fly families captured from summer to Spring to winter together with a decline with increasing altitude, at least in Spring and winter. Within each altitude, all seasonal fly assemblages were significantly different, with the exception of those from summer and autumn at 500 m a.s.l. However, the altitudinal responses of fly assemblages were less strong and not consistent between seasons. Six families were most strongly correlated with these patterns; Asilidae, Chloropidae, Dolichopodidae, Empididae, Muscidae and Phoridae. Asilidae, Dolichopodidae and Empididae declined in abundance with increasing altitude. Only Chloropidae and Muscidae appeared to increase in abundance with altitude, at least between 700 and 1100 m but only in summer. Dolichopodids and muscids progressively declined in abundance as the sampling period became cooler, while asilids were captured throughout the transect in summer, were collected from only the two lowest elevations in Spring, and were completely absent in winter. All families had a limited presence at higher altitudes during July, the coldest and driest month. The Empididae, Phoridae, Chloropidae, and Drosophilidae appear to be able to survive at lower altitudes in winter, and become more abundant at higher cooler altitudes in summer. Generalist behaviours, lack of host specificity, larvae within the protected soil or leaf litter habitat, and ability as adults to fly considerable distances may provide many fly families with the capacity to cope with climate change, as they have in the past. © The State of Queensland (Queensland Museum) 2011.