Predator selection on phenotypic variability of cryptic and aposematic moths

Colour variation in crocodilians is associated with size, environment and genetic structure, but little is known about colour variation in the genus Paleosuchus (Alligatoridae). Different genetic lineages of Paleosuchus palpebrosus (Dwarf caiman) occupy different environments throughout the species extensive distribution, and all are cryptically coloured. We captured 187 P. palpebrosus and recorded their head colour from four genetically distinct geographic clades between 2008 and 2019. Additionally, we determined the jaw and belly spot pattern of a subsample of 95 individuals (22–109 cm snout-vent length). PERMANCOVA was used to investigate the relationships between head colour and spot patterns, to the caiman size, sex, and geographic lineage, as well as ambient temperature. Variation in head colour, and jaw and belly spot patterns, were related to genetic lineage, snout-vent length and temperature, but the model explained only ∼45.4% of the variance in the data. Sex was not significantly related to the head colour, or jaw and belly spot patterns. Dwarf caimans inhabiting cooler climates tend to be darker than individuals from warmer areas, and individuals from the “Cerrado-Pantanal” and “Bolivia” lineages generally darker than the “Amazon” and “Madeira” lineages. However, individuals of a given size in different lineages overlap greatly in colour patterns and colour alone could not be used to distinguish lineages. The Natterer’s hypothesis of head-colour as diagnose from “Cerrado-Pantanal” lineage, cannot be completely accepted according our quantitative analysis, although there are a variation in the geographic distribution of these phenotypic traits, and the “Cerrado-Pantanal” lineage had been the most distinct among the lineages.

Treating color patterns in a geometric morphometrics framework reveals rapid rates of color evolution that are explained by a combination of intrinsic organismal features (color variation among patches) and geography within a cosmopolitan radiation of birds.

The green and black poison-dart frog Dendrobates auratus exhibits high intraspecific variation in hue color and pattern throughout its range, making it a very popular species in the pet trade. We analyzed the corre- spondence between color variation and molecular variation of D. auratus from Costa Rica using RAPD analysis. Twenty-six random primers were analyzed for variation in 99 individuals from seven populations. Color pattern was scored from digital images of the dorsal and ventral views. In general, frogs from the Caribbean coast had significantly more light coloration than black color but cannot be grouped by population based only on hue pat- tern. Only 3 RAPD primers were found to be polymorphic, representing a total of 16 loci. Most of the molecular variation encountered here occurs within populations, thus making unclear the degree of population structure and differentiation. Further examination of COI mtDNA sequences from our samples also supports these results. Partial Mantel correlations suggested that the pattern of molecular variation is not congruent with the variation in color pattern in this species, an outcome that is discussed in terms of phenotypic evolution. Rev. Biol. Trop.

The variation and inheritance of juvenile shell color and pigmentation pattern in the freshwater mussel, Hyriopsis cumingii, were reported in 1‐yr‐old progeny of eight families. There were three distinctive phenotypes of shell color and pigmentation patterns observed, including a greenish‐brown shell with radial rays, yellowish‐brown shell with radial rays, and yellowish‐brown shell without radial rays. There were no greenish‐brown individuals without radial rays. The shell color phenotypes showed variation with the growth in juvenile Stage I (1–3 cm in shell length), and the percentage of individuals with radial rays increased once they reached a shell length of 11 mm and then stabilized after reaching 20 mm in shell length. Shell color differentiation became more apparent at a shell length of 26 mm. Results of chi‐square tests of the segregation ratio of shell color or ray phenotypes obtained from eight families at juvenile Stage II (6–9 cm in shell length) suggested that greenish‐brown is controlled by a dominant allele (G) and yellowish‐brown‐shell phenotype is by a recessive allele (y); the ray pattern phenotype is controlled by a recessive (r) and a dominant allele (R) at a single locus. Shell color phenotypes may be a useful genetic marker for future selective breeding of triangle pearl mussels.

We determined whether body colour patterns of the narrow-headed Formica exsecta ant can serve as a marker of adaptative strategies in heterogenous environments. The variations in colour were studied in two populations of F. exsecta in central and north western areas in European Russia. A generalised colour scheme of the head and three thorax segments is developed based on a comparative analysis of the colouration of F. exsecta and red wood ants (Formica s. str.). The scheme consists of 23 variants. We found that the colouration of different parts of the body varies independently to a large extent, although a pale (less melanized) head and three thoracic segments often co-occur with paler other parts of the body. We also show that the relationship between colour pattern and body size vary significantly in different complexes. We suggest that these colour variants can be used to study the spatial-temporal phenotypic differentiation of populations and adaptation of ants to microhabitats. The proposed scheme can be used as a convenient tool in future studies to quantify the variation in colour patterns. This scheme should be further tested for its applicability for other species of the subgenus Coptoformica.

Variation in color pattern between populations of cryptic animals is common and typically attributed to selection pressures from visual predators combined with variation in substrate composition. However, little is known about how cryptic color pattern relates to varied rates of predation, and few studies simultaneously analyze patterns of escape behavior and microhabitat use along with variation in color pattern, even though these traits evolve in tandem. Here, we use a combination of calibrated photographs and spectrometry to examine the influence of spatial heterogeneity in rates of predation on dorsal brightness in the Florida scrub lizard (Sceloporus woodi), a cryptic and sexually dimorphic species. Simultaneously, we analyze patterns of escape behavior and microhabitat use measured in the field. The results of this study indicate that populations inhabiting environments of increased predation have less color variation and more closely match the color of local substrate than populations sampled in environments of relaxed predation. Populations exposed to increased predation also show more pronounced escape behavior and are more selective in their use of microhabitat. Interestingly, geographic variation of dorsal brightness, escape behavior, and microhabitat use were greater for females than for males. Our results not only provide empirical evidence for theories of adaptive coloration, but suggest that sexual dichromatism can be maintained by selection pressures related to predation.

Identifying the genetic changes driving adaptive variation in natural populations is key to understanding the origins of biodiversity. The mosaic of mimetic wing patterns in Heliconius butterflies makes an excellent system for exploring adaptive variation using next-generation sequencing. In this study, we use a combination of techniques to annotate the genomic interval modulating red color pattern variation, identify a narrow region responsible for adaptive divergence and convergence in Heliconius wing color patterns, and explore the evolutionary history of these adaptive alleles. We use whole genome resequencing from four hybrid zones between divergent color pattern races of Heliconius erato and two hybrid zones of the co-mimic Heliconius melpomene to examine genetic variation across 2.2 Mb of a partial reference sequence. In the intergenic region near optix, the gene previously shown to be responsible for the complex red pattern variation in Heliconius, population genetic analyses identify a shared 65-kb region of divergence that includes several sites perfectly associated with phenotype within each species. This region likely contains multiple cis-regulatory elements that control discrete expression domains of optix. The parallel signatures of genetic differentiation in H. erato and H. melpomene support a shared genetic architecture between the two distantly related co-mimics; however, phylogenetic analysis suggests mimetic patterns in each species evolved independently. Using a combination of next-generation sequencing analyses, we have refined our understanding of the genetic architecture of wing pattern variation in Heliconius and gained important insights into the evolution of novel adaptive phenotypes in natural populations.

The taxonomic status of B. terricola Kirby and B. occidentalis Greene has long been questioned. However recent COI gene sequence data suggests that B. occidentalis and B. terricola do represent good biological species. In this paper we test the hypothesis that B. terricola and B. occidentalis are conspecific by using independent morphometric and genetic (RAPD) data. For comparison we also analyzed one consubgeneric species, B. moderatus (now B. crytptarum), and one non-consubgeneric species B. (Pyrobombus) perplexus. Discriminant function analysis of wing morphometric data correctly classified over 85% of the specimens of B. occidentalis and B. terricola. Analysis of molecular variance of the RAPD data showed a significant difference (P < 0.0001) between B. occidentalis and B. terricola. Colour variation from laboratory reared colonies of B. occidentalis suggests that probably two gene locus inheritance is likely but that hybridization as the sole basis for the colour variation seen in the nominate taxon B. occidentalis can be excluded. We conclude that B. terricola and B. occidentalis should be regarded as distinct species which have recently diverged, and that they can be distinguished by wing morphometrics and RAPD genotypes. Where they are sympatric (e.g. in Alberta) colour pattern variation is confined to B. occidentalis.

Species identification using the characteristics of developmental stages is challenging. However, for insect taxonomy the coloration of larval stages can be an informative feature. The use of live specimens is recommended for this because the color fades in preserved specimens. In this study we examine the possibility of using variation in coloration and color pattern of larvae in order to distinguish between twoground beetlesspecies Epomis dejeani (Dejean, 1831) and Epomis circumscriptus (Duftschmid, 1812). We present an atlas and describe the coloration and body size of the three larval stages of the above species based on live specimens. An identification key is given for the three larval instars of the two Epomis species.The first instar larvae of the two Epomis species can be easily distinguished based on their color. From the second instar on, the variability in coloration and color patterns increases, creating an overlap in these attributes between larvae of the two species. Except for minor differences in color of the antennae and the base of the mandibles, larvae of the two species are indistinguishable at the second and third larval stages. To the best of our knowledge this is the first attempt to use variation in coloration and color pattern in live larvae in order to identify coleopterans. The color atlas of the larvae enables simple separation of the two Epomis species without requiring sophisticated magnifying devices, although it is less straightforward at the second and third larval stages.We found similar body lengths between the two species for all developmental stages, except for third instar larvae prior to pupation. In the two species the difference in larval body length before pupation positively correlated with that of the adult beetles. More than 70% of the adults’ length can be explained by the length of the late third-instar larva; i.e. the large larvae develop into large adults. The larger specimens are the females.

Migrating to butterflies

A hallmark trait of the lizard genus Anolis is the presence of remarkable interspecific variation in dewlap color patterns. Yet, considerable intraspecific variation also occurs in many Anolis species. In Florida different populations of the Green Anole (Anolis carolinensis) exhibit red, pink, magenta, and even greenish-gray dewlaps. To date, comparisons of color variation in this species have used subjective techniques based on human color perception. Instead, we used an objective method—reflectance spectrometry—to quantify A. carolinensis dewlap and body color variation along a transect from northeastern to southwestern Florida. Reflectance readings of local vegetation allowed us to calculate contrast of the lizards with their visual backgrounds. By incorporating local ambient light and A. carolinensis spectral sensitivity into additional calculations, we were able to estimate lizard-background contrast from the perspective of the lizards. Results revealed dewlap and dorsum spectra to differ si...

The presence of persistent polymorphisms within natural populations elicits the question of how such polymorphisms are maintained. All else equal, genetic drift and natural selection should remove genetic variants from populations. Disassortative mating and overdominance are potential mechanisms for maintaining variation within populations. Here, we consider the potential role of these mechanisms in maintaining variation in colour pattern in the tortoise beetle, Chelymorpha alternans. Five colour morphs distinguished by elytral and pronotal coloration are largely determined by a single locus of large effect with four segregating alleles. As many as four morphs co-occur in natural populations. We first assessed whether disassortative mating might maintain this polymorphism. To test for assortative and disassortative mating, we paired females with two males, one with the same colour pattern as the female and one with a different colour pattern and examined the colour patterns of the offspring. We found strong evidence for random mating as a function of colour pattern. We next assessed whether differences in offspring survival among assortative and disassortative male-female pairs maintain colour variation. Crosses involving disassortative pairings had significantly higher offspring survival during development and resulted in more adult progeny. This result is consistent with the effects of overdominance, whereby outcrossed individuals have higher fitness than their homozygous counterparts. Overall, differences in offspring survival appear to play a greater role in maintaining polymorphisms than nonrandom mating in species.

Evolutionary developmental biology has encouraged a change of research emphasis from the sorting of phenotypic variation by natural selection to the production of that variation through development. Some morphologies are more readily generated than others, and developmental mechanisms can limit or channel evolutionary change. Such biases determine how readily populations are able to respond to selection, and have been postulated to explain stasis in morphological evolution and unexplored morphologies. There has been much discussion about evolutionary constraints but empirical data testing them directly are sparse. The spectacular diversity in butterfly wing patterns is suggestive of how little constrained morphological evolution can be. However, for wing patterns involving serial repeats of the same element, developmental properties suggest that some directions of evolutionary change might be restricted. Here we show that despite the developmental coupling between different eyespots in the butterfly Bicyclus anynana, there is great potential for independent changes. This flexibility is consistent with the diversity of wing patterns across species and argues for a dominant role of natural selection, rather than internal constraints, in shaping existing variation.

Theory posits that species with inter-individual variation in colour patterns should be less vulnerable to extinction, compared with species that do not vary in colour. To evaluate this prediction, we explored whether differences in colour pattern diversity was associated with extinction risk, using red-list status for more than 350 species of noctuid moths in Sweden. We also evaluated six other species characteristics that have been proposed to influence extinction risk namely: host plant niche breadth, habitat type, area of occupancy, body size, overwintering life-history stage and length of flight activity period. We found that species with variable colour patterns had reduced extinction risk overall compared with species having non-variable colour patterns, and that this difference was pronounced more strongly among species having smaller areas of occupancy. There were also significant associations with host plant niche breadth and habitat type, extinction risk being lower on average in polyphagous species and in generalist species that occupied different habitat types. These findings represent the first evidence for insects that variable colouration is associated with reduced extinction risks. Information on colour pattern variation is readily available for many taxa and may be used as a cost-effective proxy for endangerment in the work of halting national and global biodiversity loss.

THE famous African butterfly Papilio dardanus Brown is highly polymorphic in the female, while the males are monomorphic and non-mimetic1. The species has been divided taxonomically into a number of sub-species, mainly on the basis of quantitative variation in wing pattern of the males2–4. Several of these races are isolated from all others on islands and mountainous areas. However, five named races are not geographically isolated from their neighbours and the male wing pattern, since it tends to show a clinal distribution, is unsatisfactory for delimiting their exact distributions. The western race (dardanus) might be thought to be more distinct than the others, because of the morphology of the male genitalia4. In the eastern races there is a long spine on the inner surface of the valve; the western race usually has no spine (Fig. 1). In a narrow zone north of Lake Victoria where the races meet, both types are found, together with intermediates with very short spines, which in west Africa are known only as rarities.