title: Seasonal changes in predator community switch the direction of selection for prey defences.
abstract: Insect communities consist of aposematic species with efficient warning colours against predation, as well as abundant examples of crypsis. To understand such coexistence, we here report results from a field experiment where relative survival of artificial larvae, varying in conspicuousness, was estimated in natural bird communities over an entire season. This takes advantage of natural variation in the proportion of naive predators: naivety peaks when young birds have just fledged. We show that the relative benefit of warning signals and crypsis changes accordingly. When naive birds are rare (early and late in the season), conspicuous warning signals improve survival, but conspicuousness becomes a disadvantage near the fledging time of birds. Such temporal structuring of predator-prey relationships facilitates the coexistence of diverse antipredatory strategies and helps explain two patterns we found in a 688-species community of Lepidoterans: larval warning signals remain rare and occur disproportionately often in seasons when predators are educated.
authors.affiliation: Centre of Excellence in Biological Interactions Research, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box, 35, Jyväskylä FI- 40014, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Mappes
authors.affiliation: Centre of Excellence in Biological Interactions Research, Department of Evolution, Ecology and Genetics, Research School of Biology, Australian National University, Australian Capital Territory 0200, Canberra, Australia.
authors.forename: Hanna
authors.initials: H
authors.lastname: Kokko
authors.affiliation: Centre of Excellence in Biological Interactions Research, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box, 35, Jyväskylä FI- 40014, Finland.
authors.forename: Katja
authors.initials: K
authors.lastname: Ojala
authors.affiliation: Centre of Excellence in Biological Interactions Research, Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box, 35, Jyväskylä FI- 40014, Finland.
authors.forename: Leena
authors.initials: L
authors.lastname: Lindström
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000818:Animals; D001717:Birds / Q000502:physiology*; D005387:Finland; D020387:Food Chain; D007814:Larva / Q000502:physiology; D007915:Lepidoptera / Q000502:physiology; D009930:Organic Chemicals; D010858:Pigmentation / Q000502:physiology*; D012621:Seasons; D012641:Selection, Genetic; D013045:Species Specificity; D018709:Statistics, Nonparametric
chemical_list: D009930:Organic Chemicals; C056721:plasticine