Ants Data from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing coloration and secretes distinct defensive fluids from their thoracic glands and abdomen. We presented the two defensive fluids from lab-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive flui…

Defense against predators incurs high reproductive costs for the aposematic moth Arctia plantaginis

Abstract To understand how variation in warning displays evolves and is maintained, we need to understand not only how perceivers of these traits select color and toxicity but also the sources of the genetic and phenotypic variation exposed to selection by them. We studied these aspects in the wood tiger moth Arctia plantaginis, which has two locally co-occurring male color morphs in Europe: yellow and white. When threatened, both morphs produce defensive secretions from their abdomen and from thoracic glands. Abdominal fluid has shown to be more important against invertebrate predators than avian predators, and the defensive secretion of the yellow morph is more effective against ants. Her…

Geographic mosaic of selection by avian predators on hindwing warning colour in a polymorphic aposematic moth

AbstractWarning signals are predicted to develop signal monomorphism via positive frequency-dependent selection (+FDS) albeit many aposematic systems exhibit signal polymorphism. To understand this mismatch, we conducted a large-scale predation experiment in four locations, among which the frequencies of hindwing warning coloration of aposematic Arctia plantaginis differ. Here we show that selection by avian predators on warning colour is predicted by local morph frequency and predator community composition. We found +FDS to be strongest in monomorphic Scotland, and in contrast, lowest in polymorphic Finland, where different predators favour different male morphs. +FDS was also found in Geo…

Safety in Numbers: How Color Morph Frequency Affects Predation Risk in an Aposematic Moth

Polymorphic warning signals in aposematic systems are enigmatic because predator learning should favor the most common form, creating positive frequency-dependent survival. However, many populations exhibit variation in warning signals. There are various selective mechanisms that can counter positive frequency-dependent selection and lead to temporal or spatial warning signal diversification. Examining these mechanisms and their effects requires first confirming whether the most common morphs are favored at both local and regional scales. Empirical examples of this are uncommon and often include potentially confounding factors, such as a lack of knowledge of predator identity and behavior. …

The price of safety: food deprivation in early life influences the efficacy of chemical defence in an aposematic moth

Aposematism is the combination of a primary signal with a secondary defence that predators must learn to associate with one another. However, variation in the level of defence, both within and between species, is very common. As secondary defences influence individual fitness, this variation in quality and quantity requires an evolutionary explanation, particularly as it may or may not correlate with variation in primary signals. The costs of defence production are expected to play a considerable role in generating this variation, yet studies of the cost of chemical defence have focused on species that sequester their defences, while studies in species that produce them de novo are scarce. …

Evolutionary importance of intraspecific variation in sex pheromones

Sex pheromones in many insect species are important species-recognition signals that attract conspecifics and inhibit attraction between heterospecifics; therefore, sex pheromones have predominantly been considered to evolve due to interactions between species. Recent research, however, is uncovering roles for these signals in mate choice, and that variation within and between populations can be drivers of species evolution. Variation in pheromone communication channels arises from a combination of context-dependent, condition-dependent, or genetic mechanisms in both signalers and receivers. Variation can affect mate choice and thus gene flow between individuals and populations, affecting s…

Not just the sum of its parts : Geographic variation and nonadditive effects of pyrazines in the chemical defence of an aposematic moth

Chemical defences often vary within and between populations both in quantity and quality, which is puzzling if prey survival is dependent on the strength of the defence. We investigated the within- and between-population variability in chemical defence of the wood tiger moth (Arctia plantaginis). The major components of its defences, SBMP (2-sec-butyl-3-methoxypyrazine) and IBMP (2-isobutyl-3-methoxypyrazine), are volatiles that deter bird attacks. We hypothesized that (1) variation in the chemical defences of male wood tiger moths reflects the local predation pressure; (2) observed differences in quantity and quality of defence among populations have a genetic basis; and (3) increasing con…

Reproductive interference in insects

How to fight multiple enemies : target-specific chemical defences in an aposematic moth

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing coloration and secretes distinct defensive fluids from its thoracic glands and abdomen. We presented the two defensive fluids from laboratory-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive…

Bird Data from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing coloration and secretes distinct defensive fluids from their thoracic glands and abdomen. We presented the two defensive fluids from lab-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive flui…

Multimodal Aposematic Signals and Their Emerging Role in Mate Attraction

Chemically defended animals often display conspicuous color patterns that predators learn to associate with their unprofitability and subsequently avoid. Such animals (i.e., aposematic), deter predators by stimulating their visual and chemical sensory channels. Hence, aposematism is considered to be “multimodal.” The evolution of warning signals (and to a lesser degree their accompanying chemical defenses) is fundamentally linked to natural selection by predators. Lately, however, increasing evidence also points to a role of sexual selection shaping warning signal evolution. One of the species in which this has been shown is the wood tiger moth, Arctia plantaginis, which we here put forward…

Diversity begets diversity: A global perspective on gender equality in scientific society leadership.

Research shows that gender inequality is still a major issue in academic science, yet academic societies may serve as underappreciated and effective avenues for promoting female leadership. That is, society membership is often self-selective, and board positions are elected (with a high turnover compared to institutions)—these characteristics, among others, may thus create an environment conducive to gender equality. We therefore investigate this potential using an information-theoretic approach to quantify gender equality (male:female ratios) in zoology society boards around the world. We compare alternative models to analyze how society characteristics might predict or correlate with the …

Supplementary Methods and Results from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Supplementary methods and supplementary results

De novo Synthesis of Chemical Defenses in an Aposematic Moth

Many animals protect themselves from predation with chemicals, both self-made or sequestered from their diet. The potential drivers of the diversity of these chemicals have been long studied, but our knowledge of these chemicals and their acquisition mode is heavily based on specialist herbivores that sequester their defenses. The wood tiger moth (Arctia plantaginis, Linnaeus, 1758) is a well-studied aposematic species, but the nature of its chemical defenses has not been fully described . Here, we report the presence of two methoxypyrazines, 2-sec-butyl-3-methoxypyrazine and 2-isobutyl-3-methoxypyrazine, in the moths’ defensive secretions. By raising larvae on an artificial diet, we confir…

Divergence is not speciation, or why we need females : a comment on Tinghitella et al

Postprint Peer reviewed

Multiple modalities in insect warning displays have additive effects against wild avian predators

Allocation to different components of defence has been suggested as an explanation for the existence of multiple aposematic morphs in a single population. We tested whether there are trade-offs between warning colouration and chemical defence or whether these have an additive effect when combined, using blue tits (Cyanistes caeruleus) as predators and the polymorphic wood tiger moth (Arctia plantaginis) as prey. We used artificial edible models (with and without the moths’ defensive fluids) with paper wings whose colour and pattern properties matched those of real moths. When the models were presented sans defensive fluids or when the fluids were presented without colour cues, we detected n…

Video from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Video in slow motion showing the reaction of a blue tit to the chemical defences of a wood tiger moth

Data from: De novo synthesis of chemical defences in an aposematic moth

Many animals protect themselves from predation with chemicals, both self-made or sequestered from their diet. The potential drivers of the diversity of these chemicals have been long studied, but our knowledge them, and their acquisition mode, is heavily based on specialist herbivores that sequester their defences. The wood tiger moth (Arctia plantaginis, Linnaeus, 1758) is a well-studied aposematic species, but the nature of its chemical defences has not been fully described. Here we report the presence of two methoxypyrazines, 2-sec-butyl-3-methoxypyrazine and 2-isobutyl-3-methoxypyrazine, in the moths’ defensive secretions. By raising larvae on an artificial diet, we confirm, for the fir…

Data from: How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesising that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing colouration and secretes two distinct defensive fluids, from their thoracic glands and abdomen. We presented fluids from lab-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are targe…

Figure S4 from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Differences in composition between the ‘neck’ (a) and abdominal (b) fluids of wood tiger moths. Neck fluids have a richer chemical profile, with their main compounds being carboxylic acids (see Table II in Supplementary Material 5). Photos: Janne Valkonen.

Figure S5 from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Bird (a, b) and ant (c) response to pure pyrazine. Birds ate fewer oats soaked with 2-sec-butyl-3-methoxypyrazine (a; both in a concentration of 1ng/µl (P) and 0.1ng/µl (Pb)). Also, they tended to have longer latencies to approach pyrazine-soaked oats (both concentrations pooled) than control oats (b). Ant response to 2-sec-butyl-3-methoxypyrazine was, in contrast, not different from that to the control sugar solution (c).

Figure S3 from How to fight multiple enemies: target-specific chemical defences in an aposematic moth

Results of GC-MS analysis using Selected Ion Monitoring of ions 124, 138 and 151 of the neck fluid of a single moth. Top row shows total abundance of all three ions.

Response of bird predators for female wood tiger moth chemical defences

Multiple behavioural responses of blue tit predators to the defence fluids of wood tiger moth (Arctia plantaginis) females that were either food deprived or fed ad libitum during development.