Arthropod community composition along snowmelt gradients in snowbeds in the Snowy Mountains of south-eastern Australia

Environmental gradients drive variation in community composition across a range of spatial scales. In alpine regions, areas of long-lasting snow ('snow patches') create snowmelt gradients that drive considerable change in vegetation structure and composition over small spatial scales. This study examined whether there is parallel variation in arthropod communities using snowmelt gradients in the Australian Alps. Mites (Acarina) were the most common arthropods in snow patches, followed by springtails while, among the insects, the orders Hymenoptera (primarily Formicidae), Diptera, Coleoptera (primarily Carabidae) and Hemiptera (primarily Cicadellidae) dominated. Along the snowmelt gradient, arthropod assemblages changed from having equal proportions of predators and herbivores in early-melting zones to being predator-dominated in late-melting zones, particularly early in the growing season. This followed a transition in vegetation cover and composition and was driven by higher numbers of predacious carabid beetles in later-melting zones. Overall, however, our results suggest that snowbed arthropod communities in the Australian alpine zone are more sensitive to short-term effects, such as time since snowmelt, than to differences in vegetation structure and composition or long-term patterns of snowmelt. Continued advancement of snowmelt timing due to warmer spring temperatures is therefore likely to have more impact on the seasonality of snowbed arthropod communities than on the overall community composition.