Search results for "Aposematism"
showing 10 items of 124 documents
Hairiness and warning colours as components of antipredator defence: additive or interactive benefits?
2008
To deter predator attack, aposematic prey species advertise their unprofitability with one or more conspicuous warning signals that, in turn, enhance the avoidance learning of predators. We studied the costs and benefits of multicomponent signalling in Parasemia plantaginis moths. The hairy moth larvae have an orange patch on their otherwise black bodies. The patch varies phenotypically and genetically in size. We studied whether the detection risk associated with patch size varied against two backgrounds (green or brown) with two different predators: naive chicks, Gallus gallus domesticus, and experienced great tits, Parus major. We also evaluated the signal value of different defence trai…
Can aposematic signals evolve by gradual change?
1999
Aposematic species, which signal conspicuously of their unprofitability to predators, have puzzled evolutionary biologists for over a century1,2. Although conspicuousness of unpalatable prey improves avoidance learning by predators3,4,5, it also involves an evolutionary paradox: with increasing detectability4,6,7,8 the deviant aposematic prey would suffer high predation initially from naive predators. Here we test a neglected idea7,8,9,10,11 that aposematic coloration may evolve by gradual change rather than by major mutations. Weak signals did not suffer high initial predation, but predators (great tits, Parus major) did not learn to separate them from cryptic palatable prey. Furthermore, …
Strong antiapostatic selection against novel rare aposematic prey
2001
The evolution of aposematism, a phenomenon where prey species conspicuously advertise their unprofitability to predators, is puzzling. How did conspicuousness evolve, if it simultaneously increased the likelihood of an inexperienced predator to detect the prey and presumably kill it? Antiapostatic selection, where rare prey is predated relatively more often, is considered as another major difficulty for aposematism to evolve. However, the risk of being conspicuous in low frequencies has not been experimentally tested. We designed an experiment to test how frequency (4%, 12%, 32%) of conspicuous aposematic prey and its dispersion type (solitary vs. aggregated) affect an initial predation ri…
Relative importance of taste and visual appearance for predator education in Müllerian mimicry
2006
Mullerian mimicry, by definition, is the visual resemblance between two or more aposematic prey species. According to classical Mullerian mimicry theory, comimics draw mutual benefits from the resemblance because predators have to learn to avoid only one colour pattern. In contrast, the relatively untested quasi-Batesian mimicry theory suggests that, because of differences in unpalatablility, the less toxic mimic acts like a parasite on the more defended prey, decreasing its fitness. We tested predation pressures on artificial mimicry complexes in which comimics varied both in visual similarity and in taste. Both signal and taste were important for the survival of comimics. Predators learne…
A tale of 2 signals: signal mimicry between aposematic species enhances predator avoidance learning
2010
Mullerian mimicry, where 2 or more unrelated aposematic species resemble one another, is predicted to reduce the per capita mortality of co-mimics by allowing them to share the cost of educating nao ¨ve predators about their unpalatability. However, the specific assumptions and predictions of Muller's theory of shared resemblance have been previously unsupported; some authors have suggested that the benefits of signal similarity are undetectable or at best very small. We demonstrate clearly and un- ambiguously that mimicry between 2 defended forms can provide substantial protection from uneducated predators in the manner proposed originally by Muller. By utilizing prey signals that were des…
Can experienced birds select for Müllerian mimicry?
2008
Field experiments have shown that avian predators in the wild can select for similarity of warning signals in aposematic prey (Müllerian mimicry) because a common signal is better protected than a signal that is novel and rare. The original theory of Müllerian mimicry assumes that the mechanism promoting mimicry is predator learning; by sharing a signal, the comimic species share the mortality that is due to sampling by inexperienced predators. Predation events have not been observed in the wild, and learning experiments with naive bird predators in a laboratory have not unambiguously shown a benefit of a uniform signal compared with different signals. As predators in the field experiments …
Multiple benefits of gregariousness cover detectability costs in aposematic aggregations
2001
Understanding the early evolution of aposematic (warning) coloration has been a challenge for scientists, as a new conspicuous morph in a population of cryptic insects would have a high predation risk and would probably die out before local predators learnt to avoid it1,2,3,4. Fisher5 presented the idea of aggregation benefit through the survival of related individuals; however, his theory has been strongly debated6,7,8 as the mechanisms that favour grouping have never been explored experimentally with the incorporation of detectability costs. Here we create a comprehensive ‘novel world’ experiment with the great tit (Parus major) as a predator to explore simultaneously the predation-relate…
Do avian predators select for seasonal polyphenism in the European map butterfly Araschnia levana (Lepidoptera: Nymphalidae)?
2012
Seasonal polyphenism in animal colour patterns indicates that temporal variation in selection pressures maintains phenotypic plasticity. Spring generation of the polyphenic European map butterfly Araschnia levana has an orange–black fritillary-like pattern whilst individuals of the summer generation are black with white bands across the wings. What selects for the colour difference is unknown. Because predation is a major selection pressure for insect coloration, we first tested whether map butterfly coloration could have a warning function (i.e. whether the butterflies are unpalatable to birds). In a following field experiment with butterfly dummies we tested whether the spring form is bet…
Disentangling composite colour patterns in a poison frog species
2008
A phylogenetic approach was performed to infer whether variation in conspicuous colour-patterns of a poison frog (Dendrobatidae: Dendrobates tinctorius) has evolved neutrally or under selection. Colour and pattern were split into components that were separately analysed and subsequently re-grouped via principal component analysis. This revealed four different ‘displayed’ factors on the dorsal and lateral views versus one ‘concealed’ factor on the ventral view. Based on the assumption that current patterns of trait variation contain information about the evolutionary history of the phenotype, we correlated these trait components to a neutrally evolving gene fragment (cytochrome b). The conce…
From deception to frankness: Benefits of ontogenetic shift in the anti-predator strategy of alder moth Acronicta alni larvae
2014
Abstract Animals can avoid prédation by masquerading as objects that are not food to their predators. Alder moth Acronicta alni larvae go through an impressive ontogenetic change from masquerade to highly conspicuous appearance: early larval stages resemble bird droppings but in the last instar the larval coloration changes into striking yellow-and-black stripes. We hypothesized that such a change may be driven by differential prédation favoring dissimilar anti-predator strategies in different life stages. We show with a series of laboratory assays that larvae are distasteful to birds regardless of their developmental stage, suggesting that ontogenetic color change is not driven by the diff…