ABSTRACT

In hot deserts, low, but highly variable precipitation drives resource availability, resulting in dramatic fluctuations of many consumer populations. However, the timeframes over which species respond to resource influxes are poorly understood. We pitfall-trapped ants in winter and spring over a twenty-two year period (1992–2013) in the Simpson Desert, central Australia. We asked: over what time-scale does ant activity (abundance and species richness) respond to climate (temperature and precipitation) and vegetation (plant species richness, cover and plant resources: flowering and seeding)? We considered both ‘standard lags’, i.e., the conditions at time i prior to sampling, and ‘cumulative lags’, i.e., the conditions prevailing over the entire period since time i. Ant species richness in samples responded positively to high winter temperatures, but negatively to high summer temperatures during the year prior to sampling. Short-term responses to precipitation were idiosyncratic, but longer-term responses were positive, peaking at fourteen months and probably driven indirectly through precipitation impacts on plant production. Responses to resource availability over long time frames (cumulative lags) were relatively stable, while short-term responses (standard lags) were stronger, but highly idiosyncratic, indicating that high cumulative resource availability promotes ant abundance and diversity, while short-term pulses in resource availability have less predictable impacts. The social structure of ants may allow greater flexibility in short-term responses to resource fluctuations, imparting greater long-term stability than non-social species.

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