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

2020 ◽  
Author(s):  
Katja Rönkä ◽  
Janne K. Valkonen ◽  
Ossi Nokelainen ◽  
Bibiana Rojas ◽  
Swanne Gordon ◽  
...  
Keyword(s):  
Large Scale ◽  
Avian Community ◽  
Warning Coloration ◽  
Warning Signals ◽  
Geographic Mosaic ◽  
Frequency Dependent Selection ◽  
Avian Predators ◽  
Morph Frequency ◽  
Predator Community ◽  
Positive Frequency

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 Georgia, where the predator community was the least diverse, whereas in the most diverse avian community in Estonia, hardly any models were attacked. Our results support the idea that spatial variation in predator and prey communities alters the strength or direction of selection on warning signals, thus facilitating a geographic mosaic of selection.

scholarly journals Warning signals are under positive frequency-dependent selection in nature

2016 ◽  
Vol 113 (8) ◽  
pp. 2164-2169 ◽  
Author(s):  
Mathieu Chouteau ◽  
Mónica Arias ◽  
Mathieu Joron
Keyword(s):  
Life History Traits ◽  
Purifying Selection ◽  
Warning Signal ◽  
Warning Signals ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Local Abundance ◽  
Signal Diversity ◽  
Predator Community ◽  
Positive Frequency

Positive frequency-dependent selection (FDS) is a selection regime where the fitness of a phenotype increases with its frequency, and it is thought to underlie important adaptive strategies resting on signaling and communication. However, whether and how positive FDS truly operates in nature remains unknown, which hampers our understanding of signal diversity. Here, we test for positive FDS operating on the warning color patterns of chemically defended butterflies forming multiple coexisting mimicry assemblages in the Amazon. Using malleable prey models placed in localities showing differences in the relative frequencies of warningly colored prey, we demonstrate that the efficiency of a warning signal increases steadily with its local frequency in the natural community, up to a threshold where protection stabilizes. The shape of this relationship is consistent with the direct effect of the local abundance of each warning signal on the corresponding avoidance knowledge of the local predator community. This relationship, which differs from purifying selection acting on each mimetic pattern, indicates that predator knowledge, integrated over the entire community, is saturated only for the most common warning signals. In contrast, among the well-established warning signals present in local prey assemblages, most are incompletely known to local predators and enjoy incomplete protection. This incomplete predator knowledge should generate strong benefits to life history traits that enhance warning efficiency by increasing the effective frequency of prey visible to predators. Strategies such as gregariousness or niche convergence between comimics may therefore readily evolve through their effects on predator knowledge and warning efficiency.

scholarly journals Dominant words rise to the top by positive frequency-dependent selection

2019 ◽  
Vol 116 (15) ◽  
pp. 7397-7402 ◽  
Author(s):  
Mark Pagel ◽  
Mark Beaumont ◽  
Andrew Meade ◽  
Annemarie Verkerk ◽  
Andreea Calude
Keyword(s):  
Natural Populations ◽  
Word Choice ◽  
Random Drift ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Neutral Drift ◽  
Word Use ◽  
New Words ◽  
Core Lexicon ◽  
Positive Frequency

A puzzle of language is how speakers come to use the same words for particular meanings, given that there are often many competing alternatives (e.g., “sofa,” “couch,” “settee”), and there is seldom a necessary connection between a word and its meaning. The well-known process of random drift—roughly corresponding in this context to “say what you hear”—can cause the frequencies of alternative words to fluctuate over time, and it is even possible for one of the words to replace all others, without any form of selection being involved. However, is drift alone an adequate explanation of a shared vocabulary? Darwin thought not. Here, we apply models of neutral drift, directional selection, and positive frequency-dependent selection to explain over 417,000 word-use choices for 418 meanings in two natural populations of speakers. We find that neutral drift does not in general explain word use. Instead, some form of selection governs word choice in over 91% of the meanings we studied. In cases where one word dominates all others for a particular meaning—such as is typical of the words in the core lexicon of a language—word choice is guided by positive frequency-dependent selection—a bias that makes speakers disproportionately likely to use the words that most others use. This bias grants an increasing advantage to the common form as it becomes more popular and provides a mechanism to explain how a shared vocabulary can spontaneously self-organize and then be maintained for centuries or even millennia, despite new words continually entering the lexicon.

scholarly journals Linking the evolution and form of warning coloration in nature

2011 ◽  
Vol 279 (1728) ◽  
pp. 417-426 ◽  
Author(s):  
Martin Stevens ◽  
Graeme D. Ruxton
Keyword(s):  
Mate Choice ◽  
Evolutionary Ecology ◽  
Classical System ◽  
Warning Signal ◽  
Current Understanding ◽  
Warning Coloration ◽  
Warning Signals ◽  
Initial Evolution ◽  
Mechanistic Basis ◽  
Future Work

Many animals are toxic or unpalatable and signal this to predators with warning signals (aposematism). Aposematic appearance has long been a classical system to study predator–prey interactions, communication and signalling, and animal behaviour and learning. The area has received considerable empirical and theoretical investigation. However, most research has centred on understanding the initial evolution of aposematism, despite the fact that these studies often tell us little about the form and diversity of real warning signals in nature. In contrast, less attention has been given to the mechanistic basis of aposematic markings; that is, ‘what makes an effective warning signal?’, and the efficacy of warning signals has been neglected. Furthermore, unlike other areas of adaptive coloration research (such as camouflage and mate choice), studies of warning coloration have often been slow to address predator vision and psychology. Here, we review the current understanding of warning signal form, with an aim to comprehend the diversity of warning signals in nature. We present hypotheses and suggestions for future work regarding our current understanding of several inter-related questions covering the form of warning signals and their relationship with predator vision, learning, and links to broader issues in evolutionary ecology such as mate choice and speciation.

scholarly journals Colour polymorphism torn apart by opposing positive frequency-dependent selection, yet maintained in space

2015 ◽  
Vol 84 (6) ◽  
pp. 1555-1564 ◽  
Author(s):  
Swanne P. Gordon ◽  
Hanna Kokko ◽  
Bibiana Rojas ◽  
Ossi Nokelainen ◽  
Johanna Mappes
Keyword(s):  
Colour Polymorphism ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Positive Frequency

scholarly journals Balanced polymorphisms and their divergence in a Heliconius butterfly

2021 ◽  
Author(s):  
James Ogilvie ◽  
Steven Van Belleghem ◽  
Mathieu Chouteau ◽  
Ryan Range ◽  
Riccardo Papa ◽  
...  
Keyword(s):  
South America ◽  
Selective Pressure ◽  
Interspecific Variation ◽  
Color Patterns ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Selection Regime ◽  
Selective Pressures ◽  
Heliconius Butterflies ◽  
Positive Frequency

The evolution of mimicry in similarly defended prey is well described by Müllerian mimicry theory, which predicts the convergence of warning patterns in order to gain the most protection from predators. However, despite this prediction, we can find great diversity of color patterns amongst Müllerian mimics such as Heliconius butterflies in the neotropics. Furthermore, some species have evolved the ability to maintain multiple distinct warning patterns in single populations, a phenomenon known as polymorphic mimicry. The adaptive benefit of these polymorphisms is questionable since variation from the most common warning patterns is expected to be disadvantageous as novel signals are punished by predators naive to them. In this study, we use artificial butterfly models throughout Central and South America to characterize the selective pressures maintaining polymorphic mimicry in Heliconius doris. Our results highlight the complexity of positive frequency-dependent selection, the principal selective pressure driving convergence amongst Müllerian mimics, and its impacts on interspecific variation of mimetic warning colouration. We further show how this selection regime can both limit and facilitate the diversification of mimetic traits.

scholarly journals Meiotic drive reduces egg-to-adult viability in stalk-eyed flies

2019 ◽  
Vol 286 (1910) ◽  
pp. 20191414 ◽  
Author(s):  
Sam Ronan Finnegan ◽  
Nathan Joseph White ◽  
Dixon Koh ◽  
M. Florencia Camus ◽  
Kevin Fowler ◽  
...  
Keyword(s):  
Side Effects ◽  
Sex Ratio ◽  
Large Scale ◽  
Meiotic Drive ◽  
Adult Survival ◽  
Genetic Element ◽  
Frequency Dependent Selection ◽  
Selfish Genetic Element ◽  
Sex Ratio Bias ◽  
Male Carriers

A number of species are affected by Sex-Ratio (SR) meiotic drive, a selfish genetic element located on the X-chromosome that causes dysfunction of Y-bearing sperm. SR is transmitted to up to 100% of offspring, causing extreme sex ratio bias. SR in several species is found in a stable polymorphism at a moderate frequency, suggesting there must be strong frequency-dependent selection resisting its spread. We investigate the effect of SR on female and male egg-to-adult viability in the Malaysian stalk-eyed fly, Teleopsis dalmanni . SR meiotic drive in this species is old, and appears to be broadly stable at a moderate (approx. 20%) frequency. We use large-scale controlled crosses to estimate the strength of selection acting against SR in female and male carriers. We find that SR reduces the egg-to-adult viability of both sexes. In females, homozygous females experience greater reduction in viability ( s f = 0.242) and the deleterious effects of SR are additive ( h = 0.511). The male deficit in viability ( s m = 0.214) is not different from that in homozygous females. The evidence does not support the expectation that deleterious side effects of SR are recessive or sex-limited. We discuss how these reductions in egg-to-adult survival, as well as other forms of selection acting on SR, may maintain the SR polymorphism in this species.

scholarly journals Human-mediated disturbance in multitrophic interactions results in outbreak levels of North America's most venomous caterpillar

2019 ◽  
Vol 15 (9) ◽  
pp. 20190470 ◽  
Author(s):  
Glen R. Hood ◽  
Mattheau Comerford ◽  
Amanda K. Weaver ◽  
Patricia M. Morton ◽  
Scott P. Egan
Keyword(s):  
Species Interactions ◽  
Large Scale ◽  
Population Level ◽  
Multitrophic Interactions ◽  
Enemy Release ◽  
Ecological Disturbance ◽  
Quercus Virginiana ◽  
Avian Predators ◽  
Live Oak ◽  
Oak Trees

Anthropogenic environmental change is predicted to disrupt multitrophic interactions, which may have drastic consequences for population-level processes. Here, we investigate how a large-scale human-mediated disturbance affects the abundance of North America's most venomous caterpillar species, Megalopyge opercularis . Specifically, we used a natural experiment where netting was deployed to cover the entire canopies of a subset of mature southern live oak trees ( Quercus virginiana ) to exclude urban pest birds (grackles and pigeons), throughout an 8.1 km 2 area encompassing a medical centre in Houston, Texas. We used this experimental exclusion to test the following hypothesis: release from avian predators increases caterpillar abundance to outbreak levels, which increases the risk to human health. Results from a multi-year survey show that caterpillar abundance increased, on average, more than 7300% on netted versus non-netted trees. Thus, increases in caterpillar abundance due to anthropogenic enemy release increase human exposure to this venomous pest, and should be considered a health threat in the area. This study emphasizes the unforeseen consequences of ecological disturbance for species interactions and highlights the importance of considering ecology in urban planning.

scholarly journals How do predators generalize warning signals in simple and complex prey communities? Insights from a videogame

2020 ◽  
Vol 287 (1921) ◽  
pp. 20200014
Author(s):  
Mónica Arias ◽  
John W. Davey ◽  
Simon Martin ◽  
Chris Jiggins ◽  
Nicola Nadeau ◽  
...  
Keyword(s):  
Natural Populations ◽  
Computer Game ◽  
Butterfly Species ◽  
Warning Signals ◽  
Identical Stimulus ◽  
Toxic Species ◽  
Avian Predators ◽  
Colour Patterns

The persistence of distinct warning signals within and between sympatric mimetic communities is a puzzling evolutionary question because selection favours convergence of colour patterns among toxic species. Such convergence is partly shaped by predators' reaction to similar but not identical stimulus (i.e. generalization behaviour), and generalization by predators is likely to be shaped by the diversity of local prey. However, studying generalization behaviour is generally limited to simple variations of prey colour patterns. Here, we used a computer game played by humans as surrogate predators to investigate generalization behaviours in simple (4 morphs) and complex (10 morphs) communities of unprofitable (associated with a penalty) and profitable butterflies. Colour patterns used in the game are observed in the natural populations of unprofitable butterfly species such as Heliconius numata . Analyses of 449 game participants' behaviours show that players avoided unprofitable prey more readily in simple than in complex communities. However, generalization was observed only in players that faced complex communities, enhancing the protection of profitable prey that looked similar to at least one unprofitable morph. Additionally, similarity among unprofitable prey also reduced attack rates only in complex communities. These results are consistent with previous studies using avian predators but artificial colour patterns and suggest that mimicry is more likely to evolve in complex communities where increases in similarity are more likely to be advantageous.

It’s a Matter of Taste: Avian Predators Taste Reject Mimetic Prey in Relation to Signal Reliability

2021 ◽  
Author(s):  
Ruchuan He ◽  
Craig Barnett ◽  
Emilio Pagani-Núñez ◽  
Eben Goodale
Keyword(s):  
Field Experiment ◽  
Associative Learning ◽  
Frequency Ratio ◽  
Visual Signals ◽  
Warning Signals ◽  
Signal Reliability ◽  
Quinine Sulphate ◽  
Avian Predators ◽  
Prey System ◽  
First Time

Abstract Aposematic organisms defend themselves through various means to increase their unprofitability to predators which they advertise with conspicuous warning signals. Predators learn to avoid aposematic prey through associative learning that leads to lower predation. However, when these visual signals become unreliable (e.g., through automimicry or Batesian mimicry), predators may switch from using visual signals to taste sampling prey to choose among them (‘go-slow’ behaviour). In this experiment, we tested this possibility in a field experiment where we released a total of 9600 mealworm prey of two types: (i) undefended prey (injected with water) and (ii) model-mimics (injected with either quinine sulphate [models] or water [mimics]). Prey were deployed at 12 sites, each with a mimic frequency ratio between 0 to 1, at 0.2 intervals. We found that taste rejection peaked at moderate mimic frequencies (0.4 and 0.6), supporting the idea that taste sampling and rejection of prey is related to signal reliability and predator uncertainty. This is the first time that taste-rejection has been shown to be related to the reliability of prey signals in a mimetic prey system.

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