Conspicuous Colour Patterns Research Articles

Colour pattern diversity and evolution in Oriental velvet ants (Hymenoptera: Aculeata: Mutillidae)

Abstract The Mutillidae (Hymenoptera: Aculeata) are a family of solitary ectoparasitoid wasps, famous for their sting and conspicuous coloration. The occurrence of Müllerian mimicry complexes has been demonstrated in both Africa and North America. Müllerian mimicry is the resemblance between several harmful species, advertising their defence to would-be predators by sharing a conspicuous colour pattern. Various colour patterns are known to occur in Oriental (Asian) velvet ants, but potential Müllerian mimicry complexes have not yet been inferred. We analysed the coloration of the females of 283 Oriental velvet ant species (52 genera), characterized by 12 phenotypic traits, and we identified shared colour patterns. Morphological differences between groups were tested using non-metric multidimensional scaling and permutational multivariate analysis of variance. We also inferred the geographical range of these colour patterns, and we investigated whether the shared patterns are the result of convergent evolution or common ancestry. We identified six distinct shared colour patterns, of which four can be associated with Müllerian mimicry. We also studied the position and shape of metasomal markings, and we found no association with mimicry rings. Our results improve the understanding of colour evolution in Oriental velvet ants and extend the previously described Müllerian mimicry complex to the south Asiatic landmass.

Family resemblance in color-patch size is not affected by stress experience in a cichlid fish.

Animal body coloration is often linked to social dominance and mating success. This is because it can carry information on an animal's body condition and competitive ability by reflecting the genetic quality of individuals or by responding to their current or past living conditions. The present study investigates genetic and environmental effects on a conspicuous color pattern of the cichlid fish Tropheus sp. black "Ikola," in which the size of a carotenoid-based yellow area on the body co-varies with social dominance. To examine environmental plasticity of the color pattern, we tested for effects of early-life stress, induced by reduced feeding of juveniles prior to color pattern formation, as well as effects of a stress treatment administered to fully colored adult fish. None of the stress treatments affected the color pattern as quantified by the width of the yellow bar. However, offspring bar width was correlated to parental values in mid-parent-mid-offspring regression analyses, and animal models estimated significant additive genetic effects on bar width, indicating heritability of the trait. Depending on the random effects structure of the animal models (i.e., whether including or excluding maternal and brood effects), narrow-sense heritability estimates for bar width ranged between 0.2 and 0.8, with the strongest statistical support for the highest estimate. In each of the alternative models, a large proportion of the total variance in bar width was explained by the included random effects, suggesting that bar width is strongly determined by genetic factors or shared maternal and brood environments, with limited scope for environmental influences later in life.

A New Species of the Shrimp Genus Salmoneus Holthuis, 1955 (Malacostraca: Decapoda: Alpheidae) from the Exposed Shores of Eastern and Southern Oman

Salmoneus sultanus sp. nov. is described based on several specimens collected on the exposed shores of Masirah Island and Dhofar, Oman, a region characterised by seasonal upwellings cooling water temperature to less than 23 °C. The new species is compared with the morphologically most similar congeners present in the north-western Indian Ocean, e.g., S. latirostris (Coutière, 1897), S. cristatus (Coutière, 1897), S. serratidigitus (Coutière, 1897), and S. chadwickae Ďuriš and Horká, 2016; the latter species is recorded for the first time from Oman. The conspicuous colour pattern of S. sultanus sp. nov. appears to be diagnostic, differing greatly from that of S. latirostris, S. cristatus, S. serratidigitus, and S. chadwickae.

Five new ocellus-bearing species of the cusk-eel genus Neobythites (Ophidiidae, Ophidiiformes) from the West Pacific, with establishment of three new species groups.

Five new West Pacific species of the cusk-eel genus Neobythites (Ophidiidae) from the lower shelf and upper slope of the Solomon Sea, off Okinawa, Japan, and off Fiji are described. The descriptions are based on nine specimens from three fish collections and unvouchered fresh colour photographs showing three specimens taken shortly after being caught. The new species all bear at least one ocellus on the dorsal fin, a conspicuous colour pattern consisting of a dark spot surrounded by a contrasting white or pale ring. Fifteen ocellus-bearing congeners are rather similar with at least one of the new species, requiring detailed comparisons based on a large set of morphometric, meristic, colour and otolith-shape data from over 300 specimens. To facilitate the comparisons among the 20 Neobythites species in total and the preparation of identification keys, three new taxonomic species groups, the australiensis, kenyaensis and longiventralis groups, are established. Also, the steatiticus species group which had been previously established, is slightly updated. A key for identification of each of these four groups is prepared. The most important characters for distinction among groups are the presence and number of preopercular spines, the number and position of ocelli, and pelvic-fin length. For each of the three new groups, species accounts including new species descriptions, within-group comparisons, and identification keys are prepared. For the steatiticus group, only the description of the new species, N. pako n. sp., and an updated account of the Atlantic N. monocellatus are provided, considering previously published accounts of the other seven species in comparisons with those two species and the identification key. The results are shortly discussed, emphasizing the finding of a unique ocellus structure in N. superocellatus n. sp. (australiensis species group) and the need for taxonomic studies of the remaining 10 ocellus-bearing species of Neobythites together with additional, non-ocellus-bearing congeners.

A distinctive new species of the coral shrimp genus Microprosthema Stimpson, 1860 from the Atlantic coast of Florida and Honduras (Decapoda: Stenopodidea: Spongicolidae).

A new species of the spongicolid coral shrimp genus Microprosthema Stimpson, 1860 is described on the basis of three specimens collected by hand while scuba diving off the Atlantic coast of southern Florida, with additional photographic records from Roatan, Honduras. Microprosthema dimitrisorum sp. nov. can be separated from all presently known species of the genus by a unique combination of morphological characters, and most easily, by its highly diagnostic and conspicuous colour pattern consisting of large red spots on most of the body and appendages.

Contribution of visual stimuli to mating and fighting behaviors of Drosophila prolongata

AbstractThe importance of visual stimuli in a given behavior is often different, even between closely related species. Species of the genus Drosophila have been categorized into three classes according to their reproductive dependency on vision. Class I and II species reproduce in the darkness, whereas class III species never reproduce without vision. Therefore, in class III species, mutants at the white locus that are deprived of normal visual function are not able to be established as homozygous stocks. Drosophila prolongata is a species with a conspicuous body color pattern, suggesting that an increased importance of visual stimuli underlies the evolution of this species. In this study, to examine the behavioral dependency on visual stimuli in D. prolongata, we generated white gene‐knockout (w−) mutants using the CRISPR/Cas9 system and examined their mating and fighting behaviors in light and dark conditions. The courtship and fighting activities of w− males were extremely reduced regardless of the light condition. Furthermore, wildtype males did not perform any courtship or fighting behaviors in dark conditions. Our results showed that D. prolongata is a class III species that strongly relies on visual stimuli in both behaviors.

Body colourations affect predation risk from fish in fiddler crabs

Many animals show conspicuous colour patterns that inform potential predators about their unprofitability due to their toxicity or unpalatability (aposematism). However, no systematic work has evaluated the colouration of crabs in terms of aposematism, even though many species exhibit conspicuous colouration. We conducted a laboratory study to compare predation risk from a fish predator, the barred mudskipper (Periophthalmus argentilineatus), in two sympatric fiddler crab species with different body colour patterns: Austruca perplexa with brownish-white colourations and Paraleptuca crassipes with red-and-black colour patterns. Fiddler crabs and mudskippers are active on tidal flats during low tides. A predation trial by stocking one crab and one mudskipper in a test arena was repeated five times for each species–sex combination. The animal behaviour was video recorded for 24 h, and crabs were confirmed to be alive or dead after 72 h. A. perplexa females were most vulnerable to predation from mudskippers. The attack intensity from mudskippers was stronger during the nighttime than daytime against P. crassipes females and males and A. perplexa males, suggesting that mudskippers may avoid them by visually detecting the body colouration in P. crassipes and the body structure in males of both species (i.e. a large weaponry claw) during the daytime. Mudskippers eventually preyed on and consumed some individuals in both species–sexes. Mudskippers are known to shift their main food components from small crustaceans through polychaete worms to crabs, such as fiddler crabs, and unpalatable polychaete worms tend to be brightly coloured. We suggest that the red colouration of P. crassipes may be incidental mimicry of the unpalatable red/orange-coloured polychaete worms that mudskippers might have learned to avoid.

The evolution of conspicuousness in frogs: When to signal toxicity?

Many organisms use conspicuous colour patterns to advertise their toxicity or unpalatability, a strategy known as aposematism. Despite the recognized benefits of this anti-predator tactic, not all chemically defended species exhibit warning coloration. Here, we use a comparative approach to investigate which factors predict the evolution of conspicuousness in frogs, a group in which conspicuous coloration and toxicity have evolved multiple times. We extracted colour information from dorsal and ventral photos of 594 frog species for which chemical defence information was available. Our results show that chemically defended and diurnal species have higher internal chromatic contrast, both ventrally and dorsally, than chemically undefended and/or nocturnal species. Among species that are chemically defended, conspicuous coloration is more likely to occur if species are diurnal. Our results also suggest that the evolution of conspicuous colour is more likely to occur in chemically defended prey with smaller body size. We discuss potential explanations for this association and suggest that prey profitability (related to body size) could be an important force driving the macroevolution of warning signals.

Evidence of attack deflection suggests adaptive evolution of wing tails in butterflies.

Predation is a powerful selective force shaping many behavioural and morphological traits in prey species. The deflection of predator attacks from vital parts of the prey usually involves the coordinated evolution of prey body shape and colour. Here, we test the deflection effect of hindwing (HW) tails in the swallowtail butterfly Iphiclides podalirius. In this species, HWs display long tails associated with a conspicuous colour pattern. By surveying the wings within a wild population of I. podalirius, we observed that wing damage was much more frequent on the tails. We then used a standardized behavioural assay employing dummy butterflies with real I. podalirius wings to study the location of attacks by great tits Parus major. Wing tails and conspicuous coloration of the HWs were struck more often than the rest of the body by birds. Finally, we characterized the mechanical properties of fresh wings and found that the tail vein was more fragile than the others, suggesting facilitated escape ability of butterflies attacked at this location. Our results clearly support the deflective effect of HW tails and suggest that predation is an important selective driver of the evolution of wing tails and colour pattern in butterflies.

Captivating color: evidence for optimal stimulus design in a polymorphic prey lure

Abstract Many species – humans included – employ color as an instrument of deception. One intriguing example of this resides in the conspicuous abstract color patterns displayed on the bodies of female orb weaving spiders. These displays increase prey interception rates and thereby function at least as visual lures. Their chromatic properties however vary extensively, both across and within species, with discrete forms often co-existing in the manner of a stable polymorphism. Variation is principally expressed in terms of signal hue (color per se), but it is unclear how attractiveness scales with this property and if extant morphs are maximally attractive relative to a graded range of potential alternatives. We examined these questions by assessing catch rates among color-manipulated females of the dimorphic jeweled spider Gasteracantha fornicata in their natural webs. The manipulation altered dorsal appearance in a manner akin to adding six new variants of their existing white/yellow phenotypes. This magnified the natural variation in stimulus hue independently of chroma (saturation) across a range spanning most of the color spectrum. Catch rate varied across treatments in simple accordance with how greatly stimulus hue deviated from either of the two extant spider phenotypes. Predictions based on fly-perceived chromatic and achromatic background contrast were clearly unsupported despite dipterans constituting ~60 % of identifiable prey. This study supports the importance of signal coloration per se in G. fornicata and suggests that extant lure phenotypes reside in a broadly optimal spectral range for stimulating their aggregate prey community.

Uncovering the effects of Müllerian mimicry on the evolution of conspicuousness in colour patterns

Variation in the conspicuousness of colour patterns is observed within and among defended prey species. The evolution of conspicuous colour pattern in defended species can be strongly impaired because of increased detectability by predators. Nevertheless, such evolution of the colour pattern can be favoured if changes in conspicuousness result in Müllerian mimicry with other defended prey. Here, we develop a model describing the population dynamics of a conspicuous defended prey species, and we assess the invasion conditions of derived phenotypes that differ from the ancestral phenotype by their conspicuousness. Such change in conspicuousness may then modify their level of mimicry with the local community of defended species. Derived colour pattern displayed in this focal population can therefore be either exactly similar, partially resembling or completely dissimilar to the local mimicry ring displaying the ancestral colour pattern. We assume that predation risk depends 1) on the number of individuals sharing a given colour pattern within the population, 2) on the occurrence of co‐mimetic defended species and 3) on the availability of alternative edible prey. Using a combination of analytical derivations and numerical simulations, we show that colour patterns that are less conspicuous than the ancestral one are generally favoured within mimicry rings, unless reduced conspicuousness impairs mimicry. By contrast, when a mutation affecting the colour pattern leads to a shift toward a better protected mimicry ring, a more conspicuous colour pattern can be favoured. The selected aposematic pattern then depends on the local communities of defended and edible prey, as well as on the detectability, memorability and level of mimicry of the colour patterns.

Aculeate Hymenopterans as Aposematic and Mimetic Models

Aposematism and mimicry are complex phenomena which have been studied extensively; however, much of our knowledge comes from just a few focal groups, especially butterflies. Aposematic species combine a warning signal with a secondary defense that reduces their profitability as prey. Aculeate hymenopterans are an extremely diverse lineage defined by the modification of the ovipositor into a stinger which represents a potent defense against predators. Aculeates are often brightly colored and broadly mimicked by members of other arthropod groups including Diptera, Lepidoptera, Coleoptera, and Araneae. However, aculeates are surprisingly understudied as aposematic and mimetic model organisms. Recent studies have described novel pigments contributing to warning coloration in insects and identified changes in cis-regulatory elements as potential drivers of color pattern evolution. Many biotic and abiotic factors contribute to the evolution and maintenance of conspicuous color patterns. Predator distribution and diversity seem to influence the phenotypic diversity of aposematic velvet ants while studies on bumble bees underscore the importance of intermediate mimetic phenotypes in transition zones between putative mimicry rings. Aculeate hymenopterans are attractive models for studying sex-based intraspecific mimicry as male aculeates lack the defense conferred by the females’ stinger. In some species, evolution of male and female color patterns appears to be decoupled. Future studies on aposematic aculeates and their associated mimics hold great promise for unraveling outstanding questions about the evolution of conspicuous color patterns and the factors which determine the composition and distribution of mimetic communities.

Aposematic coloration from Mid-Cretaceous Kachin amber.

Aposematic coloration is among the most diverse antipredator strategies, which can signal unpleasantness of organisms to potential predators and reduce the probability of predation. Unlike mimesis, aposematic coloration allows organisms to warn their predators away by conspicuous and recognizable colour patterns. However, aposematism has been a regular puzzle, especially as the long-term history of such traits is obscured by an insufficient fossil record. Here, we report the discovery of aposematic coloration in an orthopteran nymph from Mid-Cretaceous Kachin amber (99 million years old). It is attributed to the extinct family Elcanidae and erected as a new genus identified by conspicuous dark/light-striped coloration, four apical spurs on the metatibia, a two-segmented metatarsus and unsegmented stylus. It represents the first fossil orthopteran preserved with aposematic coloration from the Mesozoic, demonstrating that orthopterans had evolved aposematism by the Mid-Cretaceous. Our findings provide novel insights into the early evolution of anti-predator strategies among orthopterans. Together with mimesis, debris-carrying camouflage and aposematism previously reported, our findings demonstrate the relative complexity of prey-predator interactions in the Mesozoic, especially in the Mid-Cretaceous Kachin amber forest. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.

Mimicry can drive convergence in structural and light transmission features of transparent wings in Lepidoptera.

Müllerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal. In Lepidoptera, aposematic species typically harbour conspicuous opaque wing colour patterns with convergent optical properties among co-mimetic species. Surprisingly, some aposematic mimetic species have partially transparent wings, raising the questions of whether optical properties of transparent patches are also convergent, and of how transparency is achieved. Here, we conducted a comparative study of wing optics, micro and nanostructures in neotropical mimetic clearwing Lepidoptera, using spectrophotometry and microscopy imaging. We show that transparency, as perceived by predators, is convergent among co-mimics in some mimicry rings. Underlying micro- and nanostructures are also sometimes convergent despite a large structural diversity. We reveal that while transparency is primarily produced by microstructure modifications, nanostructures largely influence light transmission, potentially enabling additional fine-tuning in transmission properties. This study shows that transparency might not only enable camouflage but can also be part of aposematic signals.

Evolution and diversification of the Southern Chilean genus Ceroglossus (Coleoptera, Carabidae) during the Pleistocene glaciations

AbstractThe Quaternary glaciations affected the evolution and current distribution of taxa in southern Chile, including the emblematic and endemic genus Ceroglossus Solier. This genus of ground beetles has fascinated a great number of entomologists due to their conspicuous colour patterns, but despite this attention their taxonomy has remained controversial, with a large amount of taxa described based on unclear or variable morphological characters. In this work, we carry out a phylogenetic analysis of the 10 described species of Ceroglossus, based on mitochondrial and nuclear markers, and perform a species delimitation analysis using different algorithms, to clarify the backbone of their evolutionary tree and to lay the basis for a comprehensive and integrative taxonomic revision of this genus. Our results show that Ceroglossus is divided in five main lineages, composed of 13 putative phylogenetic species. The five lineages diverged before the Quaternary, while the divergence of the species within each lineage occurred during the glaciations and followed a parallel pattern among the different lineages. Additionally, we carry out an evolutionary interpretation of the revised available chromosomal data to shed light on the mechanisms that promoted their diversification.

Potential role of sensory bias in plumage pattern evolution: termite-eating and polka-dots in estrildid finches

Conspicuous colour patterns of animals, such as dots or stripes, can function as sexual and/or social signals. Their evolution is often explained by honest indicator mechanisms or the sensory exploitation hypothesis. In birds, however, the latter scenario has been scarcely tested. According to the sensory exploitation hypothesis, prey-like colour patterns can evolve when they contribute to attracting opposite-sex conspecifics by hitchhiking pre-existing sensory systems (sensory bias) that help foraging. Even without cheating scenarios, visual systems can serve as an underlying factor that facilitates the evolution of both foraging behaviours and colour patterns on the body. To test this idea, we examined the relationship between bird plumage patterns and diet using phylogenetic comparative approaches. Specifically, we focused on white polka-dot plumage patterns in estrildid finches and tested whether such patterns evolved for visual sensory systems that help foraging termites and other gregarious whitish small round prey items. Although we predicted that white polka-dots exist in termite-eater species, and that termite-eating evolved before the white polka-dot pattern, ancestral reconstruction did not reveal clear ancestral states for termite-eating. However, the phylogenetic regression model showed that species with conspicuous white polka-dots tended to be termite-eaters. We also found that estrildids with white polka-dots were likely to become termite-eaters, while those without white polka-dots were likely to become non-termite eaters, according to evolutionary transition analysis. These results are in contrast to the prediction of sensory exploitation hypothesis, wherein diet is believed to trigger the evolution of plumage patterns. However, the results presented here suggest that pre-existing sensory bias for white dots may have promoted the evolution of both termite-eating and white polka-dot plumage patterns in estrildids.

A new species of spiny driftwood catfish Spinipterus (Siluriformes: Auchenipteridae) from the Amazon basin.

An expedition to the middle Rio Purus basin uncovered a remarkable new species of the genus Spinipterus. The new species has a very distinct and conspicuous colour pattern resembling a jaguar and it is almost four times larger than Spinipterus acsi, a small specimen (32 mm LS ) from Caño Santa Rita, a right bank tributary of Río Nanay in Peru and a second specimen was reported from Rio Juruá, Amazonas State, Brazil. Although the new species is more similar in size and colour pattern to Liosomadoras, it shares the synapomorphies for Spinipterus. The new species differs from the congener by the following characters: (a) colour pattern with large black rosette-like spots over a light yellow to brown background (v. brown background with small dark blotches over the body); (b) adult body size reaching 104.5 mm LS (v. maximum known size 37.1 mm LS ); (c) posterior process of cleithrum short, never reaching vertical through the dorsal-fin origin (v. posterior process long, surpassing vertical through the dorsal-fin origin); (d) seven soft pectoral-fin rays (v. six); (e) caudal fin truncated (v. caudal fin rounded).

Male guppies differ in daily frequency but not diel pattern of display under daily light changes

Sexually signalling animals must trade off the benefits of attracting mates with the consequences of attracting predators. For male guppies, predation risk depends on their behaviour, colouration, environmental conditions and changing intensity of predation throughout the day. Theoretically, this drives diel patterns of display behaviour in native Trinidadian populations, where males display more under low-light conditions when their most dangerous predator is less active. Here, we observed Australian guppies in a laboratory setting to investigate their diel display pattern, and if this pattern is controlled by ambient light intensity. We also quantified individual variation in both the daily frequency and diel pattern of displays, and if such variation relates to body size, colouration and a non-sexual behaviour. Under a typical daily light regime, male guppies displayed mostly in the first hour of observation. Extending the duration of dawn-like lighting, however, resulted in an extended period of high display, demonstrating that light intensity per se is an important cue for this behaviour. These findings mirror those obtained for Trinidadian populations, suggesting that male courtship timing is likely shaped by broad, potentially generalizable features of guppy ecology. The effect of acclimation to captive conditions on male behaviour is also discussed. Whereas the temporal pattern of display appeared consistent, individuals varied in their daily display frequency, and this was correlated with variation in colour phenotype and a measure of non-sexual risk acceptance behaviour. Such relationships pose promising avenues for integrating behavioural and sensory ecology with contemporary work on behavioural syndromes and animal personality. To limit the costs of their conspicuous colour patterns, male guppies should alter their behaviour to avoid predation. However, our understanding of how different individuals deal with this problem is lacking. Following individuals in the laboratory, we demonstrated individual variation in the daily frequency of male displays, and this was correlated with variation in colour phenotypes and non-sexual behaviour. However, all male guppies displayed more in the early hours of the day and extending the period of low lighting also extended this period of elevated display. These findings replicate and expand experiments on native populations, suggesting that male courtship timing is likely shaped by broad, potentially generalizable features of guppy ecology.

Age, growth, reproductive biology, color pattern, and ontogenetic divergence of two closely related rockfishes (Sebastes koreanus and S. nudus) off the coasts of the Shandong Peninsula, China

The live-bearing genus Sebastes is renowned for its outstanding species richness and color diversity, and its speciation has been a point of interest. This study investigated the age, growth, reproductive biology, color pattern and ontogenetic divergence of a pair of closely related rockfishes from the coasts of the Shandong Peninsula, namely, Sebastes koreanus (n=879) and S. nudus (n=257). Marginal increment analysis of sectioned otoliths showed that annulus formation occurred once a year between June and July in both species. The sex-pooled growth curves of S. nudus and 3 populations of S. koreanus differed significantly from each other. No apparent latitudinal cline in growth parameters was found in S. koreanus. For both species, the peak parturition periods were from April to May, and the peak copulation periods were from November to December. S. nudus has a highly variable and conspicuous color pattern while S. koreanus has a stable and dull color pattern. This difference, together with the overlapping distribution and the close relationship, make S. koreanus and S. nudus an ideal model to investigate the color-driven speciation of the Sebastes. We confirmed that S. nudus changes its body color with age and season and fully expresses the carotenoid-based nuptial coloration when the fish reaches first maturity. Moreover, our comparisons of morphological traits that are likely related to survival and quality of these fishes suggested that S. nudus may suffer higher predation risk and foraging difficulty beginning at age 3. In light of the ontogenetic development of the color pattern in S. nudus, we suggested that the full expression of nuptial coloration most likely triggers the strong selective pressure to enhance swimming performance, anti-predator defense and foraging capacity of S. nudus through predator-prey interactions. By understanding all these details, we further inferred a hypothesis that both color pattern and bathymetric segregation play key roles in facilitating the speciation of demersal rockfishes.

The Kei Islands Monitor Lizard (Squamata: Varanidae: <i>Varanus</i>: <i>Euprepiosaurus</i>) as a Distinct Morphological, Taxonomic, and Conservation Unit

We describe a new species of the Varanus indicus group (subgenus Euprepiosaurus ) from the Kei Islands, Indonesia, which differs from its close relative V. indicus by a light tongue, a conspicuous color pattern composed of distinct yellowish ocelli on a blackish ground color and by some scalation characters. From its more distantly related, but morphologically similar relative V. finschi it differs by its midbody scale count and by some peculiarities of its scale microstructure. The new taxon, endemic to the Kei Islands, is also discussed in the light of conservation problems for many Indonesian island endemics.