title: Variation in Chemical Defense Among Natural Populations of Common Toad, Bufo bufo, Tadpoles: the Role of Environmental Factors.
abstract: Defensive toxins are widespread in nature, yet we know little about how various environmental factors shape the evolution of chemical defense, especially in vertebrates. In this study we investigated the natural variation in the amount and composition of bufadienolide toxins, and the relative importance of ecological factors in predicting that variation, in larvae of the common toad, Bufo bufo, an amphibian that produces toxins de novo. We found that tadpoles' toxin content varied markedly among populations, and the number of compounds per tadpole also differed between two geographical regions. The most consistent predictor of toxicity was the strength of competition, indicating that tadpoles produced more compounds and larger amounts of toxins when coexisting with more competitors. Additionally, tadpoles tended to contain larger concentrations of bufadienolides in ponds that were less prone to desiccation, suggesting that the costs of toxin production can only be afforded by tadpoles that do not need to drastically speed up their development. Interestingly, this trade-off was not alleviated by higher food abundance, as periphyton biomass had negligible effect on chemical defense. Even more surprisingly, we found no evidence that higher predation risk enhances chemical defenses, suggesting that low predictability of predation risk and high mortality cost of low toxicity might select for constitutive expression of chemical defense irrespective of the actual level of predation risk. Our findings highlight that the variation in chemical defense may be influenced by environmental heterogeneity in both the need for, and constraints on, toxicity as predicted by optimal defense theory.
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary. bokony.veronika@agrar.mta.hu.
authors.forename: Veronika
authors.initials: V
authors.lastname: Bókony
authors.affiliation: Department of Pathophysiology, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Ágnes M
authors.initials: ÁM
authors.lastname: Móricz
authors.affiliation: Department of Evolutionary Zoology and Human Biology, University of Debrecen, Egyetem tér 1, H-4032, Debrecen, Hungary.
authors.forename: Zsófia
authors.initials: Z
authors.lastname: Tóth
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.|Agricultural Biotechnology Institute, NARIC, Szentgyörgyi Albert u. 4, H-2100, Gödöllő, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Gál
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Anikó
authors.initials: A
authors.lastname: Kurali
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Zsanett
authors.initials: Z
authors.lastname: Mikó
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Pásztor
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.|Department of Integrative Biology and Evolution, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Savoyenstrasse 1, 1160, Vienna, Austria.
authors.forename: Márk
authors.initials: M
authors.lastname: Szederkényi
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Tóth
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: János
authors.initials: J
authors.lastname: Ujszegi
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.|Department of Integrative Biology and Evolution, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Savoyenstrasse 1, 1160, Vienna, Austria.
authors.forename: Bálint
authors.initials: B
authors.lastname: Üveges
authors.affiliation: Department of Pathophysiology, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Dániel
authors.initials: D
authors.lastname: Krüzselyi
authors.affiliation: Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, 4072, Australia.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Capon
authors.affiliation: Department of Integrative Biology and Evolution, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Savoyenstrasse 1, 1160, Vienna, Austria.
authors.forename: Herbert
authors.initials: H
authors.lastname: Hoi
authors.affiliation: Lendület Evolutionary Ecology Research Group, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Herman Ottó u. 15, H-1022, Budapest, Hungary.
authors.forename: Attila
authors.initials: A
authors.lastname: Hettyey
mesh_terms: D000818:Animals; D018533:Biomass; D002018:Bufanolides / Q000032:analysis / Q000737:chemistry; D002023:Bufo bufo / Q000502:physiology*; D004777:Environment; D007814:Larva / Q000737:chemistry* / Q000502:physiology*; D016014:Linear Models
chemical_list: D002018:Bufanolides; C087925:bufadienolide
keywords: Amphibian toxins; Aquatic community; Bufadienolides; Geographical variation; Pond permanence