Abstract: Clarifying the mechanisms that determine diversity in communities is a key task in biodiversity conservation. Niche differentiation, dispersal limitation, and stochastic processes are possible causes of variation in community composition, or beta diversity. In this study we quantified variation in ant assemblages related to environmental and spatial factors. We used pitfall traps to sample ant assemblages across a ca. 1200 km transect through arid and semi-arid heterogeneous environments of Iran. We then applied these data to canonical analysis to disentangle the relative importance of environmental and spatial processes. A total of 69 species / morphospecies were collected along the North-South transect. Cataglyphis was the most speciose genus with 12 species, followed by Messor and Monomorium with ten and seven species, respectively. Our parsimonious environmental and spatial models jointly explained 62% of the variation in community composition of ants. Community composition was primarily controlled by environmental factors (45%). Variation in ant species composition was driven by the amount of precipitation and also by its occurrence patterns. A large number of species were highly localized to a certain habitat. The overall findings suggest that mechanisms linked to environmental filtering and niche-based processes may be regulating beta diversity on ants in the Persian semi-deserts and deserts. Environmental factors appear also to control ant dispersal. Future conservation studies on insects should carefully take the temporal pattern of precipitation into account.

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