TY - JOUR

T1 - Variation in Chemical Defense Among Natural Populations of Common Toad, Bufo bufo, Tadpoles

T2 - the Role of Environmental Factors

AU - Bókony, Veronika

AU - Móricz, Ágnes M

AU - Tóth, Zsófia

AU - Gál, Zoltán

AU - Kurali, Anikó

AU - Mikó, Zsanett

AU - Pásztor, Katalin

AU - Szederkényi, Márk

AU - Tóth, Zoltán

AU - Ujszegi, János

AU - Üveges, Bálint

AU - Krüzselyi, Dániel

AU - Capon, Robert J

AU - Hoi, Herbert

AU - Hettyey, Attila

PY - 2016/4/8

Y1 - 2016/4/8

N2 - 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.

AB - 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.

KW - Animals

KW - Biomass

KW - Bufanolides/analysis

KW - Bufo bufo/physiology

KW - Environment

KW - Larva/chemistry

KW - Linear Models

U2 - 10.1007/s10886-016-0690-2

DO - 10.1007/s10886-016-0690-2

M3 - Article

C2 - 27059330

VL - 42

SP - 329

EP - 338

JO - Journal of Chemical Ecology

JF - Journal of Chemical Ecology

SN - 0098-0331

IS - 4

ER -