POPULATION ECOLOGY - ORIGINAL RESEARCH Larval life history and anti-predator strategies are affected by breeding phenology in an amphibian Germa ´n Orizaola • Emma Dahl • Alfredo G. Nicieza • Anssi Laurila Received: 16 September 2011 / Accepted: 23 August 2012 / Published online: 14 September 2012 Ó Springer-Verlag 2012 Abstract Seasonal time constraints can pose strong selection on life histories. Time-constrained animals should prioritise fast development over predation risk to avoid unfavourable growing conditions. However, changes in phenology could alter the balance between anti-predator and developmental needs. We studied variation of anti- predator strategies in common frog (Rana temporaria) tadpoles in four populations from the two extremes of a latitudinal gradient across Sweden. We examined, under common conditions in the laboratory, the anti-predator responses and life histories of tadpoles raised with preda- tory Aeshna dragonfly larvae in two consecutive years with a difference of 20 days in breeding time in the north, but no difference in breeding time in the nouth. In a year with late breeding, northern tadpoles did not modify their behaviour and morphology in the presence of predators, and meta- morphosed faster and smaller than tadpoles born in a year with early breeding. In the year with early breeding, northern tadpoles showed a completely different anti- predator strategy by reducing activity and developing morphological defences in the presence of predators. We discuss the possible mechanisms that could activate these responses (likely a form of environmentally-mediated parental effect). To our knowledge, this is the first study to show that a vertebrate modifies the anti-predator strategy of its offspring in response to natural variation in reproductive phenology, which highlights the need to consider phenol- ogy in studies of life-history evolution. Keywords anti-predator defences Á Breeding time Á Climate Á Metamorphosis Á Phenotypic plasticity Introduction Time is a crucial ecological constraint (Dunbar et al. 2009). In species inhabiting seasonal environments, there is often only a short time-window in the annual cycle when condi- tions are suitable for reproduction and growth, and thus the timing of life history events has a strong influence on fit- ness. For example, insects must reach a certain develop- mental stage or reproduce prior to the onset of winter (Gotthard 2001), timing of breeding in birds must match the peak of food abundance for the chicks (Visser et al. 2004), and amphibian larvae must metamorphose before ponds desiccate or temperature falls below levels that prevent further development (Wells 2007). Under the current sce- nario of global warming, studies on the effects of pheno- logical variation are at the forefront of evolutionary and conservation ecology (Forrest and Miller-Rushing 2010; Iba ´n ˜ez et al. 2010). Variation in the seasonal timing of natural events (i.e. phenology) imposes variation in time constraints on life- histories, which favours the maintenance of plasticity in Communicated by Ross Alford. Electronic supplementary material The online version of this article (doi:10.1007/s00442-012-2456-z) contains supplementary material, which is available to authorized users. G. Orizaola (&) Á E. Dahl Á A. Laurila Population and Conservation Biology/Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyva ¨gen 18D, 75236 Uppsala, Sweden e-mail: german.orizaola@ebc.uu.se A. G. Nicieza Ecology Unit, Department of Biology of Organisms and Systems, University of Oviedo, 33071 Oviedo, Spain A. G. Nicieza Research Unit of Biodiversity (CSIC, UO, PA), Oviedo, Spain 123 Oecologia (2013) 171:873–881 DOI 10.1007/s00442-012-2456-z