Abstract
Advances in phenology (the annual timing of species’ life-cycles) in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions. Here, we show that phenology advances combine with the number of reproductive cycles per year (voltinism) to shape abundance and distribution trends in 130 species of British Lepidoptera, in response to ~0.5 °C spring-temperature warming between 1995 and 2014. Early adult emergence in warm years resulted in increased within- and between-year population growth for species with multiple reproductive cycles per year (n = 39 multivoltine species). By contrast, early emergence had neutral or negative consequences for species with a single annual reproductive cycle (n = 91 univoltine species), depending on habitat specialisation. We conclude that phenology advances facilitate polewards range expansions in species exhibiting plasticity for both phenology and voltinism, but may inhibit expansion by less flexible species.
Highlights
Advances in phenology in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions
We found that phenology advances led to positive abundance trends for multivoltine species, but not for univoltine species (likelihood ratio test (LRT), χ2 = 8.23, d.f. = 1, P = 0.004; Table 1)
We found that phenology advances did not directly correlate with change in the distribution size (LRT, χ2 = 0.07, d.f. = 1, P = 0.792) or change in range margin latitude (LRT, χ2 = 1.29, d.f. = 1, P = 0.256)
Summary
Advances in phenology (the annual timing of species’ life-cycles) in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions. Lepidoptera include species that are obligately univoltine (i.e., all individuals pass a winter in diapause), and species in which every individual makes a plastic developmental ‘decision’ whether to undergo diapause or to directly develop, based on environmental cues Populations of such species may undergo multiple generations per year depending on the length of the local growing season annually, and in cooler regions may be functionally univoltine. Many Lepidoptera have advanced their phenology, with adults emerging earlier in recent, warmer years[16] because the growth rate of immature stages increases at warmer temperatures ( photoperiod may regulate phenology in some species[17]) Such phenology advances could be either detrimental or beneficial to species, depending on the outcomes of longer or more favourable growing seasons[18,19,20,21] and potential temporal decoupling from host–plants or natural enemies[22,23,24]. Phenology advances do not correlate with abundance trends or range expansions in species with a single annual reproductive cycle (i.e., univoltine species), and are associated with abundance declines in the subset of univoltine species that are habitat specialists
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