Differential predation on the two colour morphs of Nicaraguan Crater lake Midas cichlid fish: implications for the maintenance of its gold‐dark polymorphism

Predation can play an important role in the evolution and maintenance of prey colour polymorphisms. Several factors are known to affect predator choice, including the prey's relative abundance and conspicuousness. In polymorphic prey species, predators often target the most common or most visible morphs. To test if predator choice can explain why in Midas cichlid fish the more visible (gold) morph is also more rare than the inconspicuous dark morph, we conducted predation experiments using two differently coloured wax models in Nicaraguan crater lakes. Contrary to expectations, we observed an overall higher attack rate on the much more abundant, yet less conspicuous dark models, and propose frequency‐dependent predation as a potential explanation for this result. Interestingly, the attack rate differed between different types of predators. While avian predators were biased towards the abundant and less colourful dark morphs, fish predators did not show a strong bias. However, the relative attack rate of fish predators seemed to vary with the clarity of the water, as attack rates on gold models went up as water clarity decreased. The relative differential predation rates on different morphs might impact the relative abundance of both colour morphs and thus explain the maintenance of the colour polymorphism. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 123–131.     

Female‐limited colour polymorphism in the crab spider Synema globosum (Araneae: Thomisidae)

Conspicuous colour variation, caused by the influence of the environment on phenotype or by genetic differences among individuals, is frequently observed in nature. If genetic in origin, colour variation can facilitate the study of mechanisms that contribute to the maintenance of true polymorphisms. Here we describe, for the first time, the female‐limited colour polymorphism in the crab spider, Synema globosum. We looked for associations between life‐history traits and female colour morph, and identified potential agents of selection that could influence the maintenance of the polymorphism. Our results showed that the polymorphism is discrete and heritable, and that differences in colour among morphs are likely to be detectable by honeybees, birds, and conspecifics. We found limited evidence of differences among morphs in morphology and ecology, and found no differences in components of reproduction. Based on the lines of evidence obtained in this study, we suggest that selection exerted by prey, predators, and/or mates is likely to influence the maintenance of the polymorphism observed in S. globosum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 368–383.     

The niche variation hypothesis and the evolution of colour polymorphism in birds: a comparative study of owls, nightjars and raptors

We studied the evolution of colour polymorphism in diurnal raptors, owls and nightjars, the avian taxa in which this trait is most widespread, in relation to species ecological niche width and diet. Two main mechanisms have been put forward to explain the maintenance of polymorphism, namely apostatic selection and disruptive selection. The niche variation hypothesis states that species with broader ecological niches should be more variable compared with those with narrow niches because of the action of disruptive selection; the apostatic selection hypothesis conversely suggests that intraspecific colour variation should be promoted in predators by prey forming an avoidance image for the more common colour morph. Our aim was to determine if colour polymorphism occurrence was associated with broad ecological niches as predicted by the niche variation hypothesis, or with predation on intelligent and sharp‐sighted prey as predicted by the avoidance image hypothesis. Pairwise comparisons were made between pairs of closely related species differing in variables expected to influence the occurrence of polymorphism. We found that polymorphic species of all three groups showed wider and more continuous distribution ranges, frequented many different habitats, both open and closed, and lived in seasonally alternating dry/wet climates. Polymorphic species were more migratory compared with monomorphic ones, and they showed an activity pattern covering both day and night. Conversely, colour polymorphism was not higher in species preying on birds and mammals. All these findings support the hypothesis that colour polymorphism evolved in bird species with wider niche breadth and not in species preying on intelligent prey. Therefore, we propose that disruptive selection may be the main mechanism maintaining colour polymorphism in these bird groups by favouring different morphs in different environmental conditions. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 237–248.     

Body size influences differently the detectabilities of colour morphs of cryptic prey

Body size and coloration may contribute to variation in performance and fitness among individuals; for example, by influencing vulnerability to predators. Yet, the combined effect of size and colour pattern on susceptibility to visual predators has received little attention, particularly in camouflaged prey. In the colour polymorphic pygmy grasshopper Tetrix subulata (Linnaeus, 1758), females are larger than males, although there is a size overlap between sexes. In the present study, we investigated how body size and colour morph influenced detection of these grasshoppers, and whether differences in protective value among morphs change with size. We conducted a computer‐based experiment and compared how human ‘predators’ detected images of large, intermediate or small grasshoppers belonging to black, grey or striped colour morphs when embedded in photographs of natural grasshopper habitats. We found that time to detection increased with decreasing size, that differences in time to detection of the black, grey and striped morphs depended differently on body size, and that no single morph provided superior or inferior protection in all three size classes. By comparing morph frequencies in samples of male and female grasshoppers from natural populations, we also examined whether the joint effects of size and colour morph on detection could explain evolutionary dynamics in the wild. Morph frequency differences between sexes were largely in accordance with expectations from the results of the detection experiment. The results of the present study demonstrate that body size and colour morph can interactively influence detection of camouflaged prey. This may contribute to the morph frequency differences between male and female pygmy grasshoppers in the wild. Such interactive effects may also influence the dynamics of colour polymorphisms, and contribute to the evolution of ontogenetic colour change and sexual dichromatism. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 112–122.     

Predator-prey relationships and the evolution of colour polymorphism: a comparative analysis in diurnal raptors

Genetically based variation in coloration occurs in populations of many organisms belonging to various taxa, including birds, mammals, frogs, molluscs, insects and plants. Colour polymorphism has evolved in raptors more often than in any other group of birds, suggesting that predator–prey relationships was a driving evolutionary force. Individuals displaying a new invading colour morph may enjoy an initial foraging advantage because prey have difficulties in learning the colour of a rare morph (apostatic selection), or because morphs provide alternative foraging benefits allowing differently coloured individuals to exploit distinct food niches (disruptive selection). Plumage polymorphism should therefore have evolved in species that prey upon animals having the physiological ability to distinguish between differently coloured predators but also to flee once a predator has been detected. From this assumption, we can predict that closely related polymorphic and monomorphic species prey upon different animals. They may also differ in morphology, because foraging upon different prey may require different foraging modes, and in turn different morphological structures. We tested these two predictions in a comparative study of raptors. As expected, polymorphic and monomorphic species had a different diet, and there was a difference in wing length between polymorphic and monomorphic species within two genera ( Buteo and Accipiter ). Across all raptors for which phylogenetic relationships are known, polymorphic species preyed more often upon mammals than did monomorphic ones. These two types of raptor did not differ in the frequency of birds, insects and reptiles in their diets. We discuss these results in the light of the hypothesis that predator–prey relationships played a role in the evolution of colour polymorphism. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 565–578.     

Female polymorphism, condition differences, and variation in male harassment and ambient temperature

Female polymorphism is considered to be maintained through negative frequency-dependent selection imposed by costly male harassment. However, few studies have questioned whether male harassment negatively affects female morph success and does so differently for female morphs, especially in the wild. In the present study, we quantified female morph condition (relative body mass and energy reserves) for a colour polymorphic damselfly under natural conditions and evaluated these measures against variation in proxies of male harassment (population density and operational sex ratio) and ambient temperature. Differences in protein content between female morphs were detected and the variation in condition could partly be explained from concomitant variation in proxies of male harassment. Specifically, the relationship between protein content and operational sex ratio differed between morphs in that the negative effect of male harassment was more pronounced in gynomorphs than in andromorphs. In addition, ambient temperature affected the body mass and protein content of female morphs differently, with andromorphs having higher condition values in favourable weather conditions, whereas, for gynomorphs, the patterns tended to be opposite. In conclusion, the results obtained in the present study suggest that male harassment negatively and differentially affects female morph success. Future studies should aim to elucidate whether the observed effects of ambient temperature contribute to the maintenance of the polymorphism.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 545–554.     

Range limits,large‐scale biogeographic variation,and localized evolutionary dynamics in a polymorphic damselfly

Studies of heritable colour polymorphisms allow investigators to track the genetic dynamics of natural populations. By comparing polymorphic populations over large geographic areas and across generations, issues about both morph stability and evolutionary dynamics can be addressed, increasing our understanding of the potential mechanisms maintaining genetic polymorphisms. In the present study, we investigated population morph frequencies in a sex‐limited heritable colour polymorphic damselfly (Ischnura elegans, Vander Linden), with three discrete female morphs. We compared the frequencies of these three female morphs in 120 different populations from ten European countries at differing latitudes and longitudes. There were pronounced differences in morph frequencies both across the entire European biogeographic range, as well as at a smaller scale within regions. We also found considerable between‐population variation at the local scale within regions, particularly at the edges of the range of this species. We discuss these findings in the context of recent models of adaptive population divergence along the range of a species. This polymorphism is thus highly dynamic, with stable morph frequencies at the core of the species range but fluctuating morph dynamics at the range limits. We finish with a discussion of how local interactions and climatic factors can be expected to have a strong influence on the biogeographic patterns in this species and other sexually selected polymorphisms. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 775–785.     

An exuberant, undescribed colour polymorphism in Theridion californicum (Araneae, Theridiidae): implications for a theridiid pattern ground plan and the convergent evolution of visible morphs

An opisthosomal (abdominal) colour polymorphism is described in the North American spider, Theridion californicum , comprising a plain Yellow morph and (at least) ten patterned morphs, which exhibit areas of red or black pigments superimposed on the yellow background, or no pigment (white). The polymorphism appears to be present throughout the species' range. The Yellow morph is the most frequent in populations, with patterned morphs all, individually, being rather rare. Progeny from known mothers were reared and indicate that the polymorphism is genetic and that Yellow is probably recessive to patterned morphs. Similar to other theridiids with well-studied colour polymorphisms, T. californicum occupies an under-leaf habitat and the variation in all these cases might be maintained by sight-hunting predators exerting negative frequency-dependent (apostatic) selection. In T. californicum , blocks of guanine underlying the pigmented hypodermis indicate a segmental patterning, which is not usually apparent in adult spiders. These segments, plus dorso-lateral divisions, permit the dorsal surface of the opisthosoma to be divided up into two mirror-image halves, each comprising 12 compartments. Each compartment can either lack pigment (thus appearing white as a result of underlying guanine) or be yellow, red, or black. All patterns in T. californicum can be derived from this ground plan, as can the morphs of other colour-polymorphic theridiids. It is suggested that selection for polymorphism, combined with constraints imposed by this theridiid ground plan, may have led to the convergent evolution of colour patterns across the family.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 23–34.     

One cost of being gold: selective predation and implications for the maintenance of the Midas cichlid colour polymorphism (Perciformes: Cichlidae)

In the colour‐polymorphic Midas cichlid fish species complex (Amphilophus citrinellus spp.), gold morphs occur at much lower frequencies (< 10%) than dark individuals. This might be surprising because gold coloration is dominant and coded for by a single Mendelian locus. Furthermore, gold individuals are considered to be competitively advantaged over dark ones because they grow faster and win aggressive encounters more often compared to dark individuals of equal size. However, one might expect a cost of being gold in terms of natural selection as a result of predation. We tested whether the Jaguar cichlid (Parachromis managuensis), a major fish predator of Midas cichlids, preys differentially on colour variants of goldfish (Carassius auratus auratus), which were used as a proxy for Midas cichlids because of their similarity in colour. Size‐matched pairs of prey fish (gold and dark) were offered to the predator and the time until the fish were attacked was recorded. The gold morph was attacked first more often (approximately 70%) but not faster than the dark morph. This suggests that the predator perceives the gold individual first, and/or that the predator exhibits a preference or higher motivation to attack the gold prey fish. The increased risk of predation of gold prey fish suggests for the Midas cichlid system that being gold may carry significant costs in terms of natural selection as a result of its major piscivorous predator. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 350–358.     

Apostasy and selection for crypsis in the marine snail Littoraria filosa: an explanation for a balanced colour polymorphism

The marine snail, Littoraria filosa, is polymorphic for shell colour, with yellow, brown, and pink morphs that correspond in both appearance and frequency to the predominant background colours of its habitat. Previous research on this polymorphism has found indirect evidence of apostatic selection and selection for crypsis by unknown agents, probably crabs, and direct evidence of selection for crypsis by the parasitoid fly Sarcophaga megafilosia. In the present study, we report on field experiments to investigate whether S. megafilosia and shell‐crushing predators exert apostatic selection on L. filosa. For S. megafilosia, seven experimental treatments containing yellow and brown snails in the proportions of 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, and 0.9 of each colour were established on mangrove trees and used to separately quantify the proportions of each colour attacked on grey/brown trunks and yellow/green leaves. The results obtained confirmed an earlier finding of selection for crypsis, but only showed slight, but significant, anti‐apostatic selection by S. megafilosia. For shell‐crushing predators, seven experimental treatments containing yellow and brown snails in the proportions of 0.08, 0.17, 0.33, 0.50, 0.66, 0.83, and 0.92 were established on two types of trees that differed in their background proportions of brown and green: (1) trees which had been pruned of approximately 90% of their foliage and (2) unpruned trees. The results obtained showed both selection for crypsis and apostatic selection. Furthermore, a selectively neutral frequency for yellow L. filosa was found for each background, and was less on pruned trees than unpruned ones (and vice versa for brown L. filosa), which can therefore account for the maintenance of a colour polymorphism where the proportions of each morph tend to resemble and correspond in frequency to the colours of the background. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 62–71.     

Testing the role of coadapted genes versus bet-hedging for mating strategies in colour polymorphic pygmy grasshoppers

Recent investigations of mate choice indicate that the genetic effect of sires on offspring fitness may depend on the interaction between maternal and paternal genotypes and the environmental conditions experienced by the offspring. Alternative colour morphs of the pygmy grasshopper, Tetrix subulata , represent ecological strategies that differ in body size, life history, thermoregulatory behaviour, and habitat selection. The hypothesis that selection promotes behaviours maintaining coadapted gene complexes predicts individuals to mate assortatively with respect to colour morph. On the other hand, the bet-hedging hypothesis predicts that the temporal variability of the environment inhabited by these animals may select for disassortative mating behaviour resulting in heterogeneous offspring. To distinguish between these competing hypotheses, we investigated mating behaviours using dual-choice experiments. Our results were not in agreement with the prediction of assortative mating but suggest instead that matings were random with regard to colour morph. Polyandry was common, and females mated with the second male regardless of whether the first mating was assortative or disassortative. Polyandry also was equally frequent among females in triads in which the two males belonged to different colour morphs as in triads where both males belonged to the same colour morph. A field experiment confirmed that polyandry occurred also among free-ranging individuals, and uncovered variation in mating success among male colour morphs, probably due to indirect effects of coloration on activity or habitat use. The consequences of this random and polyandrous mating strategy for the evolutionary dynamics of the colour polymorphism remain to be explored.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 491–499.     

Enhanced colour polymorphisms in island populations of the land snail Euhadra peliomphala

Variations in visible genetic polymorphisms are assumed to decrease in populations on small islands because of intense founder effects, genetic drift and inbreeding. However, we have found evidence of a marked enhancement of colour polymorphisms within populations on small oceanic islands that were colonized from the mainland. The source populations on the mainland of the land snail Euhadra peliomphala in four oceanic islands were estimated by phylogenetic analysis of mitochondrial DNA sequences. Diversity of shell colour was higher in the island populations than in the source populations on the mainland. In addition, the shell colour morphs differed not only among populations from different islands but also between the island populations and the source populations on the mainland. By contrast, no mtDNA variations were found in any of the island populations, even though the source populations possessed high mtDNA diversity. Thus, components of colour morphs changed in the island populations after their colonization, and colour polymorphisms are enhanced in these islands despite the loss of genetic variation. The above findings suggest that ecological mechanisms such as morphological release owing to a release from competition may overcome the tendency toward reduced genetic variation in islands to enhance the colour polymorphism.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 417–425.     

Pro‐opiomelanocortin gene and melanin‐based colour polymorphism in a reptile

Colour polymorphism is widespread among vertebrates and plays important roles in prey–predator interactions, thermoregulation, social competition, and sexual selection. However, the genetic mechanisms involved in colour variation have been studied mainly in domestic mammals and birds, whereas information on wild animals remains scarce. Interestingly, the pro‐opiomelanocortin gene (POMC) gives rise to melanocortin hormones that trigger melanogenesis (by binding the melanocortin‐1‐receptor; Mc1r) and other physiological and behavioural functions (by binding the melanocortin receptors Mc1‐5rs). Owing to its pleiotropic effect, the POMC gene could therefore account for the numerous covariations between pigmentation and other phenotypic traits. We screened the POMC and Mc1r genes in 107 wild asp vipers (Vipera aspis) that can exhibit four discrete colour morphs (two unpatterned morphs: concolor or melanistic; two patterned morphs: blotched or lined) in a single population. Our study revealed a correlation between a single nucleotide polymorphism situated within the 3′‐untranslated region of the POMC gene and colour variation, whereas Mc1r was not found to be polymorphic. To the best of our knowledge, we disclose for the first time a relationship between a mutation at the POMC gene and coloration in a wild animal, as well as a correlation between a genetic marker and coloration in a snake species. Interestingly, similar mutations within the POMC 3′‐untranslated region are linked to human obesity and alcohol and drug dependence. Combined with our results, this suggests that the 3′‐untranslated region of the POMC gene may play a role in its regulation in distant vertebrates. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 160–168.     

Immune function, parasitization and extended phenotypes in colour polymorphic pygmy grasshoppers

Ecological and evolutionary consequences of host–parasite interactions have attracted considerable attention from evolutionary biologists. Previous studies have suggested that immune responsiveness may be genetically or developmentally linked with colour pattern, such that the evolution of animal colour patterns may be influenced by correlated responses to selection for parasite resistance. We studied interactions between the endoparasitic fly Leiophora innoxia (Meigen) (Diptera: Tachinidae) and its colour polymorphic pygmy grasshopper host Tetrix undulata (Sow.) (Orthoptera: Tetrigidae) to test for morph‐specific differences in parasitization and immune defence, and host‐induced variation in parasite phenotypes. Our results revealed that c. 2 and 30% of adult grasshoppers collected from the same natural population in two subsequent years, respectively were parasitized. Parasite prevalence was independent of host sex and colour morph. Pupae were larger if the parasite had developed in a female than in a male host, possibly reflecting host resource value or a physical constraint on larval growth imposed by host body size. Pupal size was also associated with host colour morph, with individuals that had developed in dark morphs being smaller at pupation compared to those that developed in paler morphs. However, immune defence, measured as the encapsulation response to a novel antigen, did not differ among individuals belonging to alternative colour morphs or sexes. Darker morphs warm up more quickly and prefer higher body temperatures than paler ones. Encapsulation was not influenced by maintenance temperature (15 vs. 30 °C), however, suggesting that indirect effects of coloration on parasite resistance mediated via differential body temperature are unlikely. The dependence of parasite body size on host colour morph may thus reflect plasticity of growth and development of the larvae in response to differential host body temperature, rather than variable host immune defence. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 373–383.     

The role of learning by a predator,Rivulus hartii,in the rare‐morph survival advantage in guppies

Negative frequency‐dependent selection (NFDS), where rare types are favoured by selection, can maintain diversity. However, the ecological processes that mediate NFDS are often not known. Male guppies (Poecilia reticulata) exhibit extreme diversity of colour patterning and, in a previous field experiment, rare morphs had a survival advantage. Here, we test the hypothesis that predators impose NFDS because they are efficient at capturing familiar prey morphs, but are less efficient at capturing unfamiliar morphs. Over a series of trials, we presented Rivulus hartii, a natural predator of guppies, with male guppies with the same colour patterning (A trials); then, for a second series of trials, we presented the rivulus with guppies with a new colour pattern (B trials). The success of rivulus at capturing guppies on the first attack increased over successive A trials. First attack success decreased significantly for the early B trials, and then increased during successive B trials, eventually reaching the same level as in the best A trials. This experiment demonstrates that learning, perhaps through long‐term search image formation, plays a role in predation success on familiar vs. unfamiliar prey morphs. These results support the hypothesis that predator learning contributes to the maintenance of the extreme male guppy polymorphism seen in nature.     

Importance of colour in the reaction of passerine predators to aposematic prey: experiments with mutants of Pyrrhocoris apterus (Heteroptera)

Persistent questions concerning the warning coloration of unpalatable insects address whether the bright aposematic colour itself or its combination with a species-specific dark pattern is the key factor in their protection against insectivorous birds, and how chromatic polymorphism originates and is maintained in aposematics. In the present study, these questions were tested experimentally, using the birds Parus major , Parus caeruleus , Erithacus rubecula , and Sylvia atricapilla as predators, and chromatically polymorphic firebug Pyrrhocoris apterus : red wild form, white, yellow, and orange mutants (all four of them with the same black melanin pattern, the mutants differing in colour of pteridine pigments only) and the nonaposematic brown-painted wild form as prey. The results show that a specific colour is essential for the birds to recognize the specific aposematic prey; the melanin pattern is not sufficient. White mutants were no better protected than nonaposematic firebugs; red wild-type and orange mutants were equally well protected against all bird species; and the reaction of birds to yellow mutants was species-specific. An evolutionary scenario of 'recurrent recessive mutations' is formulated to explain the origin of colour polymorphism in some aposematics.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 143–153.     

Lifetime fitness components in female colour morphs of a damselfly: density‐ or frequency‐dependent selection?

In many damselfly species mature females exhibit colour polymorphism: one female morph resembles the conspecific male (androchrome) while the others do not (gynochromes). Hypotheses for the maintenance of such polymorphisms differ mainly as to whether they are based on density- and/or frequency-dependent selection and on the nature of the frequency dependence. We collected lifetime fitness data (individual lifespan, number of copulations and number of ovipositions) for female morphs of the damselfly Ischnura elegans from 15 insectaries differing in population parameters (density, sex ratio and ratio of andro- to gynochromes). Both density and frequency affected a specific set of the studied fitness components. While morph frequency influenced lifespan, sex ratio influenced the number of copulations, and density affected lifespan and the number of ovipositions. Clearly, discrepancies among studies may be generated if the studied fitness components differ. Our final fitness estimate, the number of ovipositions, was only influenced by density, thereby not supporting frequency-based hypotheses. Contrary to expectation under the current density-based hypothesis, androchromes compared to gynochromes had a lower number of ovipositions at high density. We discuss our findings in the light of mechanisms maintaining the female polymorphism.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 515–523.     

Origin of the disjunct distribution of flower colour polymorphism within Limonium wrightii (Plumbaginaceae) in the Ryukyu Archipelago

The sea lavender, Limonium wrightii , has six morphs of flower colour variation. The geographical distribution of flower colour morphs is disjunct; the distribution of the pink flower morph is divided into two subregions, and that of the yellow flower morph intervenes between them. The present study aimed to examine the origin of this apparent distribution pattern of flower colour in L. wrightii . Two main hypotheses (i.e. past dispersal events and phenotypic changes by natural selection and/or stochastic processes) have been proposed to account for the origin of leapfrog distribution patterns. To determine which hypothesis was applicable, we conducted a molecular phylogenetic analysis using sequence variation in chloroplast DNA (three regions of intergenic spacers, trnG - trnfM , trnV - trnM , and psbA-trnH ). We sequenced 58 accessions of L. wrightii frin 28 islands in the Ryukyu Archipelago and the Izu-Ogasawara Islands, located south of the Japanese mainland, and 12 accessions of four congeneric species. Within L. wrightii , we obtained four lineages of ten haplotypes. These lineages and haplotypes did not correlate with the different flower colours. These results indicate that the formation processes of populations are complex. The haplotypes of the pink flower morph did not show a sister relationship between the two disjunct subregions, indicating that the disjunct populations of the pink flower morphs are unlikely to share the pink flower colour as a result of common ancestry. We conclude that the observed leapfrog distribution pattern is caused by natural selection and/or stochastic processes.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 709–717.     

Both novelty and conspicuousness influence selection by mammalian predators on the colour pattern of Plethodon cinereus (Urodela: Plethodontidae)

Predators influence the evolution of colour pattern in prey species, yet how these selective forces might differ among predators is rarely considered. In particular, prey colour patterns that indicate unpalatability to some predator species may not carry the same signal for other predators. We test several hypotheses of selection on patterning between mammal predators and the polymorphic salamander Plethodon cinereus, which, under an avian visual system appears as a mimic of the toxic newt Notophthalmus viridescens. We fit each hypothesis against field observations of mammalian attacks on salamander clay replicas. We then develop a novel analytical procedure that enables the combination of multiple non‐exclusive models in a likelihood framework. We find that mammals do not follow any single hypothesis proposed, including the hypothesis of mimicry. Instead, mammals in this system use visual cues while foraging to avoid unfamiliar, novel prey and attack conspicuous prey. We propose that mammals may help to maintain colour pattern polymorphism within populations of P. cinereus by avoiding novel, unfamiliar colour morphs. Additionally, selective pressures from multiple predators and variation in predator communities among sites may contribute to the maintenance of colour polymorphism within and among localities in this salamander species.     

The detectability of the colour pattern in the aposematic firebug,Pyrrhocoris apterus: an image‐based experiment with human ‘predators’

Crypsis and aposematism are often regarded as two opposite protective strategies. However, there is large variation in prey appearance within both strategies. In this article, we investigated the conspicuousness of the aposematic red‐and‐black firebug, Pyrrhocoris apterus, by presenting images of natural and digitally manipulated phenotypes in their natural habitat on a computer screen to human ‘predators’, and comparing the detection times. We asked whether the natural colour pattern can be made more or less conspicuous by rearranging the spatial distribution of colour elements. Hence, we created a phenotype in which the black colour elements were moved to the body outline to test for a possible disruptive effect. In the ‘black’ and ‘red’ manipulations, we removed one of the two colours, creating two uniform colour variants. We found that some of our manipulations increased, but none reduced, the detection time significantly; this indicates that the naturally coloured firebug is highly conspicuous. The detection time varied among backgrounds and there was a significant relationship between detection time and chromatic similarity between the bug and the background for the natural and black phenotypes. Although background colour composition has an important effect on the signal, we argue that the coloration of P. apterus has evolved for high conspicuousness. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 806–816.