Intraspecific Color Variation Research Articles

Gymnotiform electric fishes of the Tres Fronteras region of the western Amazon

Gymnotiform electric knifefishes are an important yet undersampled component of the Neotropical aquatic biota. We report on the gymnotiform fauna of the Tres Fronteras region located at the triple border of Brazil, Colombia, and Peru in the biodiverse western Amazon. The presence of at least 33 species of gymnotiforms in the Tres Fronteras region is validated from recent sampling efforts and the review of previously collected materials. A key is provided for the identification of the species that have been collected from the region. We comment on the diversity of habitat utilization and intraspecific colour variation of some species.

Dots in the dark: dorsal polychromatism in the endemic Xingu Freshwater Stingray

AbstractPolychromatism refers to the presence of two or more color patterns within a species. Several species exhibit polychromatic patterns, including some elasmobranchs such as the Xingu Freshwater Stingray (Potamotrygon leopoldi), a threatened, endemic freshwater stingray species that is exploited in the international aquarium trade. Analysis of polychromatic patterns can provide insight into evolutionary mechanisms and be a useful tool for monitoring international trade. In this context, the present study analyzed intraspecific color variation in P. leopoldi. A total of 241 individuals collected in two areas along the Xingu River in Brazil were used for the study. Four dorsal color patterns of P. leopoldi were described. Size differences between color classes were statistically significant, suggesting that these color variations are associated with ontogenetic color changes. In addition, two color morphs specific to each locality were identified and described. Moreover, the occurrence of polychromatic forms in a Potamotrygoninae species may contribute to the understanding of diversification in this group, since some mechanisms of speciation are associated with polychromatism. Analysis of color variation in P. leopoldi is expected to help improve trade monitoring, especially given the existence of look‐alike species.

Ebony underpins Batesian mimicry in melanic stoneflies.

The evolution of Batesian mimicry - whereby harmless species avoid predation through their resemblance to harmful species - has long intrigued biologists. In rare cases, Batesian mimicry is linked to intraspecific colour variation, in which only some individuals within a population resemble a noxious 'model'. Here, we assess intraspecific colour variation within a widespread New Zealand stonefly, wherein highly melanized individuals of Zelandoperla closely resemble a chemically defended aposematic stonefly, Austroperla cyrene. We assess convergence in the colour pattern of these two species, compare their relative palatability to predators, and use genome-wide association mapping to assess the genetic basis of this resemblance. Our analysis reveals that melanized Zelandoperla overlap significantly with Austroperla in colour space but are significantly more palatable to predators, implying that they are indeed Batesian mimics. Analysis of 194,773 genome-wide SNPs reveals an outlier locus (ebony) strongly differentiating melanic versus non-melanic Zelandoperla. Genotyping of 338 specimens from a single Zelandoperla population indicates that ebony explains nearly 70% of the observed variance in melanism. As ebony has a well-documented role in insect melanin biosynthesis, our findings indicate this locus has a conserved function across deeply divergent hexapod lineages. Distributional records suggest a link between the occurrence of melanic Zelandoperla and the forested ecosystems where the model Austroperla is abundant, suggesting the potential for adaptive shifts in this system underpinned by environmental change.

Hooded Grasshopper Teratodes monticollis (Gray, 1832) Morphometric and Intraspecific Colour Variation from Bonai Forest Division, Odisha, India

Hooded grasshopper belongs to the order Orthoptera and the family Acrididae. It is native to India and Sri Lanka. The hooded grasshopper, Teratodes monticollis, was described as Gryllus monticollis by English zoologist George Robert Gray in 1832. The distribution of this species has been recorded in different parts of Burma, Ceylon, and India. The contemporary reports about records of this species from various states of India are very limited. The authors observed the intraspecific colour variation of Teratodes monticollis in Bonai Forest Division, Odisha, India, and presented it here. It might be due to some abiotic stress in the study areas.

Melanin-based plumage coloration is associated with exposure in tawny owls under novel conditions

Intraspecific color variation is often associated with camouflage or protection, but melanin-based color variation is also linked to behavioral and physiological aspects including boldness. In the melanin-based plumage color polymorphic tawny owl (Strix aluco), the grey morph is known to be more cryptic than the brown morph. Using 19 captive tawny owls (11 grey and 8 brown), we tested if these two color morphs that differ in camouflage tend to differently use exposed perches in a familiar environment (home aviary) and a novel environment (experimental aviary), as well as whether their response to predation risk and mobbing cues differs. The two color morphs did not differ in their exposure under known conditions (in their home aviary), but brown tawny owls were more likely to use exposed perches than grey tawny owls after release in a novel environment.Significance statementMelanin-based coloration can be associated with several behavioral traits. However, it is still unknown how predators with genetically-based color polymorphism vary in their efficiency of active background choice and risk-prone behavior while facing predation risk or mobbing harassment. Using captive tawny owls, we investigated predators’ behavior (attention towards the stimulus and use of space) while confronted to mobbing events and predation risk. We showed that tawny owls were using their space differently according to their color morph in a novel environment (experimental aviary) but not in a familiar environment (home aviary).

Association of a single amino acid replacement with dorsal pigmentation in a lizard from the Qinghai-Tibetan Plateau

Reptiles can evolve adaptive colors in different environments, but relatively little is known about the genetic mechanisms. Here, we identified the MC1R gene and its association with intraspecific color variation in the lizard Phrynocephalus erythrurus. Analysis of the MC1R sequence in 143 individuals from dark South Qiangtang Plateau (SQP) and light North Qiangtang plateau (NQP) populations, revealed two amino acid sites that showed significant differences in frequency between two areas. One SNP, corresponding to Glu183Lys residue, was found to be a highly significant outlier and differentially fixed for SQP and NQP populations. This residue is located in an extracellular area in the second small extracellular loop within the secondary structure of MC1R, which represents an “attachment pocket” part of the 3D structure. Cytological expression of MC1R alleles with the Glu183Lys replacement showed a 39 % increase in intracellular agonist-induced cyclic AMP levels and a 23.18 % greater cell surface expression of MC1R protein in the SQP relative to the NQP allele. Further in silico 3D modeling and in vitro binding experiments indicated a higher MC1R-α-MSH binding for the SQP allele, and elevated melanin synthesis. We provide an overview of how a single amino acid replacement leads to fundamental changes in MC1R function, and hence shapes variation in dorsal pigmentation in lizards from different environments.

Differential regulation of the Tor gene homolog drives the red/green pigmentation phenotype in the aphid Myzuspersicae

In some aphid species, intraspecific variation in body colour is caused by differential carotenoid content: whilst green aphids contain only yellow carotenoids (β-, γ-, and β,γ-carotenes), red aphids additionally possess red carotenoids (torulene and 3,4-didehydrolycopene). Unusually, within animals who typically obtain carotenoids from their diet, ancestral horizontal gene transfer of carotenoid biosynthetic genes from fungi (followed by gene duplication), have imbued aphids with the intrinsic gene repertoire necessary to biosynthesise carotenoids. In the pea aphid, Acyrthosiphon pisum a lycopene (phytoene) desaturase gene (Tor) underpins the red/green phenotype, with this locus present in heterozygous form in red individuals but absent in green aphids, resulting in them being unable to convert lycopene into the red compounds 3,4-didehydrolycopene and torulene. The green peach aphid, Myzus persicae, separated from the pea aphid for ≈45MY also exists as distinct colour variable morphs, with both red and green individuals present. Here, we examined genomic data for both red and green morphs of M. persicae and identified an enlarged (compared to A. pisum) repertoire of 16 carotenoid biosynthetic genes (11 carotenoid desaturases and five carotenoid cyclase/synthase genes). From these, we identify the homolog of A. pisum Tor (here called carotene desaturase 2 or CDE-2) and show through 3D modelling that this homolog can accommodate the torulene precursor lycopene and, through RNA knockdown feeding experiments, demonstrate that disabling CDE-2 expression in red M. persicae clones results in green-coloured offspring. Unlike in A. pisum, we show that functional CDE-2 is present in the genomes of both red and green aphids. However, expression differences between the two colour morphs (350–700 fold CDE-2 overexpression in red clones), potentially driven by variants identified in upstream putative regulatory elements, underpin this phenotype. Thus, whilst aphids have a common origin of their carotenoid biosynthetic pathway, two aphid species separated for over 40MY have evolved very different drivers of intraspecific colour variation.

Selective breeding and characterization of a black mealworm strain of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae)

• Black larvae found in the yellow mealworm ( Tenebrio molitor Linnaeus) farms. • The black larvae were identified as T. molitor. • Black larvae of T. molitor were completely fixed by selective breeding. • Yellow and black larvae had no significant differences in growth traits and fecundity. Larvae of Tenebrio molitor Linnaeus are edible insects and are approved as a food ingredient in Korea. They are typically yellow; however, rare black larvae have been found in breeding boxes at insect farms. It is not clear whether black larvae represent a different species that invaded and hybridized with the yellow larvae of T . molitor or whether T . molitor shows intraspecific color variation. In this study, we characterized and identified black larvae for applications in industrial fields as well as accurate breeding and management. First, in a comparative analysis, we did not detect differences in the morphological characteristics of yellow and black larvae and adults, with the exception of larval body color. For accurate species identification, molecular analyses ( p -distances and neighbor-joining) were performed based on partial COI sequences of 33 yellow and seven black larvae. Genetic divergence between yellow and black larvae ranged from 0.0% to 2.1%, revealing intraspecific variation. A neighbor-joining analysis strongly supported the classification of the two morphs as a single species. Black larvae were separated from yellow larvae and maintained by selective breeding. As a result, black larvae were completely fixed in the F2 generation (F1 = 96% and F2 = 100%). Yellow and black larvae showed no significant differences in developmental characteristics and fecundity. These findings improve our understanding of diversity within an important edible insect species and contribute to quality assurance in the food industry based on clear species identification.

Comparative Phylogeography in the Taiwan–Luzon Volcanic Belt Indicates Fast Diversification History of Pachyrhynchus Weevils (Coleoptera: Curculionidae)

Abstract Geological isolation with limited gene flow can shape phenotypic diversification among different populations or species. From Luzon northward to Taiwan lies a series of isolated volcanic islands (the Taiwan–Luzon volcanic belt) where three Pachyrhynchus species [P. sarcitis (Behrens, 1887), P. nobilis (Heller, 1912) and P. semperi (Heller, 1912)] (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) are sympatrically distributed. With intraspecific color variation across different islands, these three weevil species provide a unique opportunity to study genetic divergence associated with geographic isolation and/or phenotypic differences. In this study, genome-wide single nucleotide polymorphism (SNP) data derived from ddRAD-seq was used to reconstruct the speciation history and to delimit species within each of the three species. Our results indicate all three species have ancient diversification histories in southern islands of the Taiwan–Luzon volcanic belt instead of more recent diversification histories in northern islands. Ancestral effective population size estimations also support a scenario of a series of founder colonization events from southern to northern islands in the volcanic belt. Most island populations are monophyletic, and early-divergent populations with deep genetic structures are supported statistically as distinct species. However, color variations could occur between populations with very recent diversification, indicating a fast-evolving rate in the change of coloration, possibly due to müllerian mimicry or founder effects across this region.

Variation in contact chemical cues may mediate differential predator response in the colour polymorphic tortoise beetle,Chelymorpha alternans

AbstractDifferential predation on species with intraspecific colour variation has been explored in various systems and is often implicated as the driving force behind colour polymorphism maintenance.Here, investigation done on whether predation contributes to the maintenance of extensive colour variation in the Neotropical tortoise beetle,Chelymorpha alternans(Chrysomelidae). Recorded predation rates on different colour pattern phenotypes by three common, generalist invertebrate predators, and identified potential chemical signals of unpalatability.Predaceious mantids (Orthoptera, Mantidae) consumed no beetles, regardless of phenotype, whereas the giant orb‐weaving spider (Trichonephila clavipes; Araneidae) consumed all three beetle phenotypes. The carton‐nest ant,Azteca chartifex(Formicidae), displayed differential predation; the rufipennis phenotype ofC. alternanswas sometimes consumed, the metallic phenotype was never consumed, and the veraguensis phenotype was consumed in the first three encounters and subsequently discarded, suggesting a learned avoidance behaviour.Using gas chromatography–mass spectrometry, it was determined that cuticular hydrocarbon profiles were similar between the metallic and militaris‐a phenotypes. The rufipennis phenotype showed pronounced differences and displayed the greatest among‐individual variation in elytral cuticular profiles.Between‐phenotype variation in chemical cues, and differences in how predators receive those cues, may mediate predator response, and play a role in maintaining colour variation in this species.

The Lanternfly genus Pyrops in Vietnam: A new species from Central Vietnam, taxonomic changes, checklist, identification key (Hemiptera: Fulgoromorpha: Fulgoridae)

A new species of the genus Pyrops Spinola, 1839 (Fulgoridae), P. buomvoi sp. nov., is described from Ca Na, Ninh Thuan Province in Central Vietnam. It is attributed to the candelaria group and compared with the other species of the genus. Pyrops lathburii (Kirby, 1818) is proposed as a senior synonym of P. astarte (Distant, 1914), transferred back to the candelaria group from the pyrrhorhynchus group, and recorded from Laos for the first time. The candelaria and pyrorhynchus groups are defined and commented on. Intraspecific variation in the colour of the hind wings is recorded for the first time in Pyrops condorinus (Lallemand, 1960). A checklist of the 12 Vietnamese species of Pyrops and an illustrated key which can also be used for Laos, Cambodia and Southern Continental China, are given. Pyrops buomvoi sp. nov. is the first new species of Pyrops discovered in Indochina for more than 50 years. Intraspecific colour variation in the species of Pyrops is briefly discussed.

Changing How Biologists View Flowers-Color as a Perception Not a Trait.

Studying flower color evolution can be challenging as it may require several different areas of expertise, ranging from botany and ecology through to understanding color sensing of insects and thus how they perceive flower signals. Whilst studies often view plant-pollinator interactions from the plant's perspective, there is growing evidence from psychophysics studies that pollinators have their own complex decision making processes depending on their perception of color, viewing conditions and individual experience. Mimicry of rewarding flowers by orchids is a fascinating system for studying the pollinator decision making process, as rewarding model flowering plants and mimics can be clearly characterized. Here, we focus on a system where the rewardless orchid Eulophia zeyheriana mimics the floral color of Wahlenbergia cuspidata (Campanulaceae) to attract its pollinator species, a halictid bee. Using recently developed psychophysics principles, we explore whether the color perception of an insect observer encountering variable model and mimic flower color signals can help explain why species with non-rewarding flowers can exist in nature. Our approach involves the use of color discrimination functions rather than relying on discrimination thresholds, and the use of statistical distributions to model intraspecific color variations. Results show that whilst an experienced insect observer can frequently make accurate discriminations between mimic and rewarding flowers, intraspecific signal variability leads to overlap in the perceived color, which will frequently confuse an inexperienced pollinator. This new perspective provides an improved way to incorporate pollinator decision making into the complex field of plant-pollinator interactions.

Birds Perceive More Intraspecific Color Variation in Bird-Pollinated Than Bee-Pollinated Flowers.

Pollinator-mediated selection is expected to constrain floral color variation within plant populations. Here, we test for patterns of constraint on floral color variation in 38 bee- and/or hummingbird-pollinated plant species from Colorado, United States. We collected reflectance spectra for at least 15 individuals in each of 1–3 populations of each species (total 78 populations) and modeled perceived color variation in both bee and bird visual spaces. We hypothesized that bees would perceive less intraspecific color variation in bee-pollinated species (vs. bird-pollinated species), and reciprocally, birds would perceive less color variation in bird-pollinated species (vs. bee-pollinated species). In keeping with the higher dimensionality of the bird visual system, birds typically perceived much more color variation than bees, regardless of plant pollination system. Contrary to our hypothesis, bees perceived equal color variation within plant species from the two pollination systems, and birds perceived more color variation in species that they pollinate than in bee-pollinated species. We propose hypotheses to account for the results, including reduced long-wavelength sensitivity in bees (vs. birds), and the ideas that potential categorical color vision in birds and larger cognitive capacities of birds (vs. bees) reduces their potential discrimination against floral color variants in species that they pollinate, resulting in less stabilizing selection on color within bird-pollinated vs. bee-pollinated species.

Colour variation of the intertidal hermit crabClibanarius virescensconsidering growth stage, geographic area in the Indo–West Pacific Ocean, and molecular phylogeny

AbstractMembers ofClibanarius virescensshow considerable intraspecific colour variation, including colouration of the second/third pereopods (green/white) and the dactyls of the second/third pereopods (with or without dark bands/patches). However, factors inducing these colour variations have not yet been elucidated. Here, we investigated the occurrence of colour variation in this species with particular emphasis on change of colouration associated with growth stage and region in specimens from tropical/subtropical to warm temperate areas in the Indo–West Pacific, including evidence from molecular phylogeny based on the cytochrome c oxidase subunit I (COI). We have, then, clarified that the colouration on the pereopod dactyls gradually changed from solid colour (yellow/white) to having dark-coloured area(s) or transverse band(s) as a result of the growth stage. The frequency of occurrence of the solid colour dactyls was higher than those of other colour types in tropical regions. Our results also indicated that the white ambulatory leg type was the colouration type that was frequently seen in juvenile stages. However, significant genetic differences were not detected between each colouration determined by molecular analysis of samples from 14 localities in the Indo-West Pacific region; in contrast, two genetically differentiated regional populations (North Australia; Phuket, Thailand; and Lombok, Indonesia) were detected. The present study, therefore, emphasizes the necessity for further study on the colour variation of marine animals focusing on growth stages and regional differences, with molecular data to facilitate the research on adaptation and/or speciation, especially in geographically widely distributed species.

All the Colors of the Rainbow: Diversification of Flower Color and Intraspecific Color Variation in the Genus Iris.

Floral color plays a key role as visual signaling and is therefore of great importance in shaping plant-pollinator interactions. Iris (Iridaceae), a genus comprising over 300 species and named after the Greek goddess of the colorful rainbow, is famous for its dazzling palette of flower colors and patterns, which vary considerably both within and among species. Despite the large variation of flower color in Iris, little is known about the phylogenetic and ecological contexts of floral color. Here, we seek to resolve the evolution of flower color in the genus Iris in a macroevolutionary framework. We used a phylogenetic analysis to reconstruct the ancestral state of flower color and other pollination-related traits (e.g., the presence of nectar and mating system), and also tracked the evolution of color variation. We further explored weather floral trait transitions are better explained by environmental or pollinator-mediated selection. Our study revealed that the most recent common ancestor likely had monomorphic, purple flowers, with a crest and a spot on the fall. The flowers were likely insect-pollinated, nectar-rewarding, and self-compatible. The diversity of floral traits we see in modern irises, likely represents a trade-off between conflicting selection pressures. Whether shifts in these flower traits result from abiotic or biotic selective agents or are maintained by neutral processes without any selection remains an open question. Our analysis serves as a starting point for future work exploring the genetic and physiological mechanisms controlling flower coloration in the most color-diverse genus Iris.

A new species of Characidium (Characiformes: Crenuchidae) from the rio Madeira basin, Brazil.

This study describes Characidium nambiquara, a new species from the upper rio Guaporé, rio Madeira basin, Brazil. The new species differs from most congeners by the presence of isthmus and area between the contralateral pectoral-fin bases completely naked. From congeners with some degree of scaleless ventral surface of the body C. nambiquara differs by having 10 circumpeduncular scales. The new species is also distinguished from congeners by the spotted colour pattern on body of the large-sized specimens and by having black dashes on all fins and conspicuous midlateral longitudinal dark stripe or conspicuous vertical bars absent. Characidium nambiquara further differs from most congeners by the presence of 34-36 pored scales on the lateral line, 3 horizontal scale rows above the lateral line and 3 horizontal scale rows from the lateral line to the midventral scale series. Remarks on intraspecific colour variation within the genus, not related to sexual dimorphism, are also provided.

Redescription of the enigmatic jellyfish,Crambionella annandalei(Cnidaria: Scyphozoa) from Indian waters

AbstractThe catostylid jellyfish,Crambionella annandaleiwas originally described by Rao (1932) based on a preserved specimen collected from the Andaman Sea. Since then, no detailed taxonomic studies have been conducted and the species is often misidentified. Here, we provide a detailed morphological re-description ofC. annandaleifrom fresh material collected at a variety of locations along the east coast of India. The species can be distinguished from its congeners by a combination of morphological characters, the most important of which are the proportion of terminal club length to oral arm length (0.48 ± 0.031), the proportion of the distal portion of the oral arm to naked proximal portion (7.25 ± 0.268) and the body colour. The occurrence of intra-specific colour variation in fresh specimens was also observed in the present study.

The Diversity of Hornets in the Genus Vespa (Hymenoptera: Vespidae; Vespinae), Their Importance and Interceptions in the United States

AbstractHornets in the genus Vespa (Vespidae, Vespinae) are social wasps. They are primarily predators of other insects, and some species are known to attack and feed on honeybees (Apis mellifera L.), which makes them a serious threat to apiculture. Hornet species identification can be sometimes difficult because of the amount of intraspecific color and size variation. This has resulted in many species-level synonyms, scattered literature, and taxonomic keys only useful for local populations. We present a key to the world species, information on each species, as well as those intercepted at United States Ports of Entry during the last decade. Images of all the species and some of the subspecies previously described are also included.

Variation in some characters of the genus Sceliphron (Hymenoptera: Sphecidae) in the Philippines

The observed morphological and color variations for Sceliphron species in the Philippines are hereby reported. Sceliphron madraspatanum conspicillatum and Sceliphron rufopictum laticinctum have several variations in propodeal maculation pattern and in pronotal collar and petiole of the former. Postmortem color changes were also observed in S. r. laticinctum. A single yellow band on the third tergite of S. r. laticinctum is distinct when it is alive, and an additional yellow band develops on the posterior part of abdominal tergites 2-5 after death. Mandibles may either be sharp or blunt, and clypeus may be lobed or flat for S. r. laticinctum and Sceliphron javanum aemulum. However, newly emerged adults of these species have sharper mandibles and lobed clypeus. DNA barcoding was used to address intraspecific color and morphological variation of the Philippine Sceliphrini, but not all specimens were successfully barcoded because most of the specimens were very old and contaminated by fungi. However, this study came up with a new primer that has successfully barcoded 3% of the specimens.

Paper wasps are darker at high elevation.

High mountains are harsh environments in which colder temperatures and higher levels of UV-B radiation are common. These abiotic conditions strongly affect animals' biology, often constraining their survival and reproduction. As a result, adaptations to live in such habitats are expected to evolve. Body color is thought to be adaptive to the environment that animals experience. Tegument melanization improves heat gain and provides photoprotection. Therefore, at high elevation, ectotherms are expected to be darker (well-melanized). We test this prediction in the paper wasp Agelaia pallipes (Hymenoptera: Vespidae), a species distributed across an elevational gradient in the Colombian Andes. We used Malaise traps and sampled a total of 146 wasps along nine elevations, ranging from 2,600-3,380m above sea level. Standard digital photography was used to measure the body luminance and colour patterning in different body parts of dry-preserved specimens. There was striking variation in body luminance (darker and lighter), color patterning (patched, smoothed, homogeneous) and surface texture (shiny and matte), but the kind and degree of variation depended on the body part examined. Wasps from higher elevations had darker thoraces, confirming our prediction. Besides, at high elevation, the frequency of wasps with a matte rather than a shiny face strongly increased. Overall, our findings support the thermal melanism hypothesis and suggest that intraspecific color variation might be an adaptation to the environment of paper wasps.