Citation: Davies, W. J. 2019. Multiple temperature effects on phenology and body size in wild butterflies predict a complex response to climate change. Ecology 100(4):Abstract. Temperature-induced alterations in phenology and body size are the cumulative outcome of sequential effects impacting development and are universal responses to climate change. Most studies have so far focused on phenological responses to warming in multiple taxa across space and time, or the ontogenetic effects of temperature in the laboratory. I here complement this work by investigating shifts in phenology and body size (wing length) attributable to temperature changes operating over the entire lifespan of the univoltine orange-tip butterfly Anthocharis cardamines in a single wild population over 14 generations. Phenology was affected by temperatures during three discrete periods in the year prior to emergence, corresponding to late larval/early pupal life, the onset of the chilling period required to break pupal diapause, and postdiapause pupal development prior to eclosion. Higher temperatures during late larval/early pupal life and postdiapause pupal development advanced the subsequent emergence of the butterflies, whereas higher temperatures at the onset of the chilling period retarded it. The synchronization of the butterflies' emergence schedule increased when pupae were exposed to milder midwinter temperatures. Wing length increased with warmer temperatures at distinct points in the early and midpupal periods; such direct effects of temperature on body size could complement season length effects in explaining the reversal of the temperature-size rule in univoltine insects. The periods during which temperature affected the phenology of the butterfly only partially overlapped those affecting the first flowering date of its host plants lady's smock (Cardamine pratensis) and garlic mustard (Alliaria petiolata). Observed thermal effects on flowering time, emergence timing, and emergence synchronization indicate that phenological convergence as well as phenological mismatching could affect hostplant availability and diet breadth; thermal effects on body size imply that important population-level processes could be impacted through correlated changes in fecundity and dispersal rate. In general, the combined effects of phenological and ontogenetic responses to temperature changes across the whole lifespan will likely be important in modeling the demographic responses of interacting species to climate change.

focusing on food availability and isolation from predators to maximise the likelihood of attaining levels of productivity and survival that avoid creation of a sink population to the detriment of the overall metapopulation size.

1. The evolution of host range and preference in phytophagous insects is driven by a female's oviposition choice impacting her offspring's fitness. Analysis of the fitness of progeny on different host plants has commonly been restricted to the performance of immature stages. However, since host use can affect adult size, it is important to measure the ongoing effects of host choice on the resulting imagines.2. The orange-tip butterfly, Anthocharis cardamines, shows a strong preference for two host plants in Britain, Alliaria petiolata and Cardamine pratensis, which affect body size. Whilst females exhibit a strong positive size-fecundity relation, the impact of body-size alteration is unknown in males. In this study, fitness effects of host plant choice for male A. cardamines were examined.3. Males reared on C. pratensis were smaller and emerged earlier than those reared on A. petiolata, and early-season males were smaller than late-season ones in the field. Interestingly, regression analysis indicated that the earlier emergence of small males was a host-mediated rather than a size-mediated effect. Small size was associated with reduced male dispersal in a semi-isolated wild population over a 3-year period.4. It is proposed that the earlier emergence associated with C. pratensis has evolved in response to depressed dispersal in isolated/semi-isolated populations associated with this patchily distributed host. We suggest that adult life-history traits are important for the maintenance of host range in this species, and offer a critique of Courtney's earlier hypothesis that host range is maintained by time-limited oviposition behaviour.

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