Patterns of arthropod abundance and diversity in an Arabian desert

We captured desert arthropods from sand and gravel substrates at five coastal or inland locations m Abu Dhabi around the new moon once every 28 days for two years Three replicated lines of 20 unbaited pitfall traps were used from two hours before dusk until two hours after dawn We examined the data for spatial and temporal variation, especially in relation to climate Around 53 400 arthropods were caught, 97.3% being insects and the rest arachnids Ants were most common (75.4%), followed by the Thysanura (12%), Coleoptera (8.4%), Araneae (1.5%) and Scorpiones (1.1%) Catches differed significantly among sites, substrates and time of year In general, the number of arthropods caught matched the annual temperature cycle Peak catches also followed the annual rains Summer catches were higher at coastal than inland sites Fewer arthropods were caught at gravel sites than on sand, but the number of taxa did not differ consistently between substrates Community composition was generally less similar among sites than between substrates although this was not always the case Inland communities had fewer taxa and generally fewer individuals than those near the coast Isoptera, Tettigonndae and Carabidae occurred less frequently (if at all) inland We suggest that the higher humidity at sites near the coast allows more taxa to occur and to remain active during the extreme heat of summer Further into the Empty Quarter we would expect a decline in the number of taxa and in the total catch