Strong impact of temperature and resource specialisation on patterns of voltinism within an oak-associated insect community

Abstract

Insect phenology consists of the timing of life events, as well as the number of generations (voltinism). While several studies have focused on the impact of climate on the timing of seasonal events, or the voltinism of single species, we have few insights into the factors that shape patterns of voltinism within ecological communities. Importantly, voltinism can have a major impact on population growth, species interactions, and rate of evolution. We investigated the relative importance of spatial variation in temperature and species traits in shaping patterns of voltinism within an herbivore community feeding on deciduous oaks across a temperature gradient in Europe. Voltinism increased with temperature, where the probability for a species to be univoltine decreased with temperature, whereas the probability for a species to be strictly multivoltine increased with temperature. The relative abundance of the first and subsequent generations of multivoltine species did not significantly change along the temperature gradient. Resource specialisation affected voltinism, where oligophagous and polyphagous species were more likely to be strictly multivoltine than narrow oligophagous species. Overwintering stage and body size did not affect voltinism, and there was no evidence that species traits influenced the relationship between temperature and voltinism. Our findings highlight that temperature and species traits shape variation in voltinism within an herbivore community associated with oak trees. These temperature-induced shifts in voltinism within the oak-associated herbivore community may have profound effects on the synchrony within and between trophic levels, and consequently for food web structure and outbreak dynamics.