Melanic Forms Research Articles

The colour/pattern polymorphism of Philaenus spumarius (Hemiptera: Cercopidae) in the north-western Black Sea region of Turkey

The heritable elytral colour/pattern polymorphism of Philaenus spumarius in north-western Black Sea region of Turkey was investigated. A total of 2,530 adult spittlebugs, 1,020 females and 1,510 males were collected and analysed in terms of the 11 most common colour forms. Nine different phenotypes, expressed by six different alleles, were determined: populi (POP), typicus (TYP), trilineatus (TRI), marginellus (MAR), flavicollis (FLA), leucocephalus (LCE), gibbus (GIB), albomaculatus (ALB), and leucophtalmus (LOP). The common phenotypes lateralis (LAT) and quadrimaculatus (QUA) of previous studies were not encountered at all. The predominant phenotype was TYP (63%) in females and males followed by POP (31%). TRI (4%) and melanics (5%) were at close proportions. However, only one site had nine phenotypes altogether. The majority of the sites had only the POP and TYP morphs. The melanic forms were found only in females.

Is the Papuan Harrier Circus spilonotus spilothorax a globally threatened species? Ecology, climate change threats and first population estimates from Papua New Guinea

We undertook a 3-week expedition to Papua New Guinea in April-May 2007 to assess the breeding, threats and population densities of the Papuan Harrier Circus spilonotus spilothorax and to determine a first global population estimate for this almost entirely unknown species. Two of the first nests known were discovered in April 2007 with three chicks each, in the eastern lowlands, in rank grass and reeds. The melanistic form of this subspecies was more common in the lowlands (< 1,500 m a.s.l) than in the highlands, but interbreeding of this and the typical form occurred in the lowlands. Movements of identifiable individuals through two highland grasslands indicated up to eight birds per day on passage, corroborating local knowledge that other raptors move into the highlands at the start of the dry season (April). Linear road counts indicated no harriers in the wooded highlands but up to 2.9 harriers 10 km−1 in lowland grasslands. Area counts gave an average of 6.5 harriers 100 km−2 in the grasslands and a breeding density of 1.21 nests 100 km−2. Given that preferred grassland and swamp habitat comprises c. 7% of the forest-dominated island of New Guinea, the global Papuan Harrier population can be no more than c. 3,600 birds and c. 740 breeding pairs. Wildfires peaked at 38 per month in the study area, occur throughout the dry season, and led to the loss of both nests. This suggests that many nests and prey may be lost at critical times and burning may be ultimately detrimental for the species. Grassland fires throughout Indonesia and Papua New Guinea are increasing with climatic warming and ENSO events, so we suggest that the Papuan Harrier may warrant a ‘Vulnerable’ conservation ranking due to small total population size and an accelerated reduction in habitat quality due to ongoing climate change.

Polymorphism in Simyra albovenosa (Lepidoptera, Noctuidae)

The genetics of the melanic forms of Simyra albovenosa (Goeze) were studied by means of laboratory crosses. The forms were classified for the frequency of dark scales on the intravenal regions of the forewing. The uniform black form and the patterned intermediate are controlled by separate loci, the former being completely dominant to pale and epistatic to intermediate, and the latter, partially dominant to pale. The intensity of the whitish to yellowish background colouration is affected by the developing strategy, non-diapausing moths being paler than diapausing.

Differences in biological and behavioural characteristics of Harmonia axyridis (Coleoptera: Coccinellidae) according to colour patterns of elytra

AbstractSamples of overwintering populations of Harmonia axyridis were classified into five colour patterns, succinea 1, succinea 2, conspicua, spectabilis and axyridis. Generally, the succinea 1 colour pattern was dominant at six collecting sites in Daejon and Chungnam provinces of Korea and their occurrence proportion was over 50%. Non‐melanic forms such as succinea 1 and 2 were noted in about 90% of collected individuals. On the other hand, conspicua and spectabilis as melanic forms were dominant in the laboratory. One hypothesis is that the difference between field and laboratory populations is related to non‐random mating and environmental conditions. Practically, in mate‐choice experiments, most colour pattern ladybirds seemed to mate with the melanic form, especially the conspicua form. The body size (length) of H. axyridis in colour patterns was slightly different, but in females, there was no significant difference among colour patterns. However, both lengths of males were significantly different among colour patterns. In reproductive ability (fecundity), there was no difference among colour patterns.

A 'Veiled Blackcap', the partially melanistic form of Blackcap Sylvia atricapilla, on Tenerife, Canary Islands

A 'Veiled Blackcap', the partially melanistic form of Blackcap Sylvia atricapilla, on Tenerife, Canary Islands

A MULTILOCUS PERSPECTIVE ON COLONIZATION ACCOMPANIED BY SELECTION AND GENE FLOW

The colonization of novel habitats involves complex interactions between founder events, selection, and ongoing migration, and can lead to diverse evolutionary outcomes from local extinction to adaptation to speciation. Although there have been several studies of the demography of colonization of remote habitats, less is known about the demographic consequences of colonization of novel habitats within a continuous species range. Populations of the Eastern Fence Lizard, Sceloporus undulatus, are continuously distributed across two dramatic transitions in substrate color in southern New Mexico and have undergone rapid adaptation following colonization of these novel environments. Blanched forms inhabit the gypsum sand dunes of White Sands and melanic forms are found on the black basalt rocks of the Carrizozo lava flow. Each of these habitats formed within the last 10,000 years, allowing comparison of genetic signatures of population history for two independent colonizations from the same source population. We present evidence on phenotypic variation in lizard color, environmental variation in substrate color, and sequence variation for mitochondrial DNA and 19 independent nuclear loci. To confirm the influence of natural selection and gene flow in this system, we show that phenotypic variation is best explained by environmental variation and that neutral genetic variation is related to distance between populations, not partitioned by habitat. The historical demography of colonization was inferred using an Approximate Bayesian Computation (ABC) framework that incorporates known geological information and allows for ongoing migration with the source population. The inferences differed somewhat between mtDNA and nuclear markers, but overall provided strong evidence of historical size reductions in both white sand and black lava populations at the time of colonization. Populations in both novel habitats appear to have undergone partial but incomplete recovery from the initial bottleneck. Both ABC analyses and measures of mtDNA sequence diversity also suggested that population reductions were more severe in the black lava compared to the white sands habitat. Differences observed between habitats may be explained by differences in colonization time, habitat geometry, and strength or response to natural selection for substrate matching. Finally, effective population size reductions in this system appear to be more dramatic when colonization is accompanied by a change in selection regime. Our analyses are consistent with a demographic cost of adaptation to novel environments and show that it is possible to infer aspects of the historical demography of local adaptation even in the presence of ongoing gene flow.

Elytra color as a signal of chemical defense in the Asian ladybird beetle Harmonia axyridis

Carotenoid- and melanin-based colors are valuable indicators of quality in many vertebrates, but their signaling role in invertebrates remains relatively unexplored. The Asian ladybird beetle Harmonia axyridis is an ideal organism for studies of this nature because males and females exhibit highly variable red and black colors on their elytra and are chemically defended with an alkaloid (harmonine). We used digital photography to quantify elytra coloration and absorbance spectrophotometry and gas chromatography mass spectrometry analyses to quantify pigment and alkaloid concentrations, respectively, in wild-caught male and female H. axyridis. We predicted that extensive or intense coloration would be an aposematic signal of high-alkaloid stores. We found that carotenoid pigments largely controlled variation in red elytra coloration. There was no relationship between alkaloid content and either elytra redness or carotenoid pigment concentration in either sex. However, we found a positive correlation between the extent of elytra coloration and alkaloid content. Animals with proportionally more red (or less black) on the elytra were more alkaloid-rich; this relationship was particularly strong in females. We also found that females with lighter black spots had greater amounts of harmonine than those with darker spots. These results suggest that elytra color patterns have the potential to reveal information about chemical defensiveness to mates or predators. Prior studies in this species show that nonmelanic forms are typically less active and yet more sexually attractive than melanic forms, and both results may be explained by the fact that nonmelanics are better chemically defended.

Temporal stability of morph frequency in central European populations of Adalia bipunctata and A. decempunctata (Coleoptera: Coccinellidae)

In central Europe Adalia bipunctata (L.) occurs in two main colour morphs (typical, melanic), and A. decempunctata (L.) occurs in 3 morphs (spotted, chequered, dark). Temporal variation in the relative frequency of morphs was recorded in populations of the Czech Republic where geographic variation in morph frequency is low. Seasonal trends were investigated in samples collected by a light-trap run daily from March to November for 14 years. In A. bipunctata the melanic form was more abundant in autumn than in spring but the difference was not significant. In A. decempunctata morph proportions did not change seasonally. Samples were also collected by sweepnet from stands of many plant species. In both Adalia species the morph proportions did not differ significantly among collections made on different plants. Long-term changes in morph proportions were analysed by pooling annual samples over all host plants. In A. bipunctata, sampled in 15 years between 1971-2004, there was no significant change in proportion of typical (90.1%) and melanic (9.9%) forms. In A. decempunctata, sampled in 12 years between 1976-2004, the proportions of (mean over the years 29.4%), chequered (42.2%) and dark (21.3%) morphs varied between years. There was a trend toward an increasing proportion of the spotted form in the 2000s compared to the 1970s and 1980s.

Molecular data suggest that melanistic ectotherms at the south‐western tip of Africa are the products of Miocene climatic events: evidence from cordylid lizards

AbstractIn the present study the evolutionary relationships among Cordylusniger–oelofseni–cordylus are investigated using molecular sequence data to: (1) estimate the divergence within this group; (2) date the origin of melanism in the clade and to evaluate possible palaeoecological events responsible for its evolution; (3) examine the systematic relationships among the three isolated populations of C. oelofseni that were previously shown to be polyphyletic using allozyme data. The recovered topology for the combined sequence data (16S and NADH dehydrogenase component 2 (ND2)) among C. niger–oelofseni–cordylus suggests that melanism evolved only once in the clade. The application of a molecular clock to the data demonstrates that melanism evolved during the Miocene epoch, 17–15 million years ago. We believe that the development of a cold‐water current and upwelling system along the south‐west coast of Africa during this epoch was instrumental in the evolution of melanism in this lizard clade and possibly also in other ectotherm clades with melanistic forms occurring in the area. The results show that C. oelofseni, as presently construed, is composed of three distinct evolutionary lineages, with no shared haplotypes present and marked sequence divergence. Two of the three lineages represent undescribed species. Cordylus cordylus is composed of two distinct clades, a montane clade and a coastal lowland clade. Cladogenic activity in mountain areas of the Western Cape in South Africa has been particularly pronounced and the systematic diversity of many taxa may have been underestimated.

Frequency of insularia during the decline in melanics in the peppered moth Biston betularia in Britain.

Over the last three decades the frequency of the dark melanic form carbonaria of the peppered moth Biston betularia has declined in Britain. Data have been examined which show the intermediate phenotype insularia, controlled by alleles at the same locus, to have increased or remained level in frequency. Phenotype frequency of insularia does not always track allele frequency accurately because it is recessive to its alternative when carbonaria is common but dominant to the alternative when typical is common. It is shown that if insularia fitness lies between that of carbonaria and typical, and melanics replace typicals or vice versa, there will be a rise and fall in insularia allele frequency during a transitory period. The path followed is strongly affected by initial gene frequencies. During the high melanic period in Britain, differences in insularia frequency between localities may have been influenced by history of arrival of the novel morphs as well as by local selective conditions.

Parallel evolution of the melanic form of the California legless lizard, Anniella pulchra, inferred from mitochondrial DNA sequence variation.

The phylogenetic relationships among populations of the fossorial California legless lizard, Anniella pulchra, were examined by sequencing a 990-bp region of the mitochondrial cytochrome b gene. The mitochondrial DNA gene tree was then compared with the geographic distributions of two currently recognized subspecies: A. p. nigra, a melanic form restricted to two disjunct coastal populations, and A. p. pulchra, a more widely distributed, silvery form. We tested the null hypothesis that all A. p. nigra form a clade that is monophyletic with respect to A. p. pulchra. Our results strongly reject the monophyletic origin of the melanic forms and suggest that the two populations of the nominal subspecies A. p. nigra may have arisen independently from different ancestral populations in a parallel evolutionary response to selection in cool, coastal habitats.

The molecular basis of melanism and mimicry in a swallowtail butterfly.

Melanism in Lepidoptera, either industrial or in mimicry, is one of the most commonly cited examples of natural selection [1] [2]. Despite extensive studies of the frequency and maintenance of melanic genes in insect populations [1] [2], there has been little work on the underlying molecular mechanisms. Nowhere is butterfly melanism more striking than in the Eastern Tiger Swallowtail (Papilio glaucus) of North America [3] [4] [5]. In this species, females can be either yellow (wild type) or black (melanic). The melanic form is a Batesian mimic of the distasteful Pipevine Swallowtail (Battus philenor), which is also black in overall color. Melanism in P. glaucus is controlled by a single Y-linked (female) black gene [6]. Melanic females, therefore, always have melanic daughters. Black melanin replaces the background yellow in melanic females. Here, we show that the key enzyme involved is N-beta-alanyl-dopamine-synthase (BAS), which shunts dopamine from the melanin pathway into the production of the yellow color pigment papiliochrome and also provides products for cuticle sclerotization. In melanic females, this enzyme is suppressed, leading to abnormal melanization of a formerly yellow area, and wing scale maturation is also delayed in the same area. This raises the possibility that either reduced BAS activity itself is preventing scale sclerotization (maturation) or, in contrast, that the delay in scale maturation precludes expression of BAS at the correct stage. Together, these data show how changes in expression of a single gene product could result in multiple wing color phenotypes. The implications for the genetic control of mimicry in other Lepidoptera are discussed.

A bird’s eye view of the peppered moth

Abstract Industrial melanism in Biston betularia is one of the best known examples of the role of natural selection in evolution and has received considerable scrutiny for many years. The rise in frequency of the dark form of the moth (carbonaria) and a decrease in the pale form (typica) was the result of differential predation by birds, the melanic form being more cyptic than typica in industrial areas where the tree bark was darkened by air pollution. One important aspect of early work evaluating the relative crypsis of the forms of B. betularia on tree trunks with different lichen flora was the reliance on human observers. Humans, however, do not have the same visual capabilities as birds. Birds have well-developed ultraviolet (UV) vision, an important component of their colour processing system that affects many aspects of behaviour, including prey detection. We examined the UV characteristics of the two forms of B. betularia and a number of foliose and crustose lichens. In human visible light the speckled form typica appeared cyptic when seen against a background of foliose lichen, whereas the dark form carbonaria was conspicuous. Under UV light the situation was reversed. The foliose lichens absorbed UV and appeared dark as did carbonaria. Typica, however, reflected UV and was conspicuous. Against crustose lichens, typica was less visible than carbonaria in both visible and UV light. These findings are considered in relation to the distribution and recolonization of trees by lichens and the resting behaviour of B. betularia.

Taking the Peppered Moth with a Grain of Salt

H. B. D. Kettlewell's (1955, 1956) classic field experiments on industrial melanism in polluted and unpolluted settings using the peppered moth, Biston betularia, are routinely cited as establishing that the melanic (dark) form of the moth rose in frequency downwind of industrial centers because of the cryptic advantage dark coloration provides against visual predators in soot-darkened environments. This paper critiques three common myths surrounding these investigations: (1) that Kettlewell used a model that identified crypsis as the only selective force responsible for the spread of the melanic gene, (2) that Kettlewell's field experiments alone established that selection for crypsis was the most important factor in the spread of melanic forms, and (3) that Kettlewell's investigations in an unpolluted wood near Dorset constituted a control for his earlier Birmingham studies (contra Hagen 1993, 1996). This analysis further identifies two features that distinguish manipulative experiments in evolutionary biology from experiments in other contexts. First, experiments in evolutionary biology rest on a wealth of information provided by strictly observational ecological studies; in the absence of such information experiments in evolutionary biology make no sense. Second, there is a trade-off between how much control investigators have over the conditions being studied and how informative the results of the experiment will be with regard to natural populations.

Isoenzymes detect variation in populations of Triatoma brasiliensis (Hemiptera: Reduviidae: Triatominae).

Triatoma brasiliensis is one of the most important vectors of Chagas disease in the semiarid zone of the northeast of Brazil. Intraspecific morphological and behavioural variation has been reported for different populations. Results for four distinct populations using eight isoenzymes are reported here. The literature describes three subspecies: T. brasiliensis brasiliensis Neiva, 1911; T. brasiliensis melanica Neiva & Lent, 1941 and T. brasiliensis macromelasoma Galvão, 1956. These subspecies differ mainly in their cuticle colour pattern and were regarded as synonyms by Lent and Wygodzinsky (1979). In order to evaluate whether the chromatic pattern is a morphological variation of different melanic forms within T. brasiliensis or due to interspecific variation, field collections were performed in localities where these three subspecies have been described: Caicó (Rio Grande do Norte), the type-locality for T. b. brasiliensis; Petrolina (Pernambuco) for T. b. macromelasoma and Espinosa (Minas Gerais) for T. b. melanica. A fourth distinct chromatic pattern was found in Juazeiro (Bahia). A total of nine loci were studied. Values of Nei's genetic distance (D) were calculated. T. b. brasiliensis and T. b. macromelasoma are the closest populations with a D = 0.295. T. b. melanica had a D > or = 0.537 when compared to the others, a distance in the range of interspecific variation for other triatomine species.

Parallel Rise and Fall of Melanic Peppered Moths in America and Britain

The moth (Biston betularia) is well known for the rapid rise in the frequency of alleles producing melanic phenotypes correlated with a general blackening of the environment following the nineteenth-century industrial revolution. In recent years the frequency of melanics has been dropping steadily in Britain in apparent response to improved air quality. Some regional American populations of this same species also experienced significant increases in melanics, by 1959 exceeding 90% in southeastern Michigan, but Michigan populations were not reexamined for over 30 years. In 1994 and 1995 we trapped moths in southeastern Michigan and here report that a parallel decline in melanism has occurred in American moths. Furthermore, we document that changes in Michigan's air quality as measured by atmospheric sulfur dioxide (SO2) and suspended particulates also parallel the changes recorded in Britain. The traditional interpretation is that pale phenotypes of moths at rest by day on lichen-encrus ted trees are camouflaged from bird predators; industrial fallout kills lichens and darkens resting surfaces, favoring darker colored moths. However, the changes in allele frequencies in the moth populations we sampled have occurred in the absence of perceptible changes in the local lichen floras. We suggest that the role of lichens has been inappropriately emphasized in chronicles about the evolution of melanism in moths. Industrial melanism in the Lepidoptera ranks among the best examples of observable evolution by natural selection. The most thoroughly documented case is that of the geometrid moth Biston betularia, with the fundamental details of its recent evolutionary history described in virtually every biology textbook. Its common name, peppered moth, describes the appearance of the so-called form or phenotype which is covered with white scales peppered with black over the wings and body. Several other pigmentation phenotypes are known. A melanic form, named carbonaria, is nearly solid black. Intermediates between the pale and fully melanic phenotypes are called insularia. The range in variation from lightest to darkest is continuous, but the phenotypic differences result from multiple alleles at a single locus which exhibit an approximate dominance hierarchy: the carbonaria allele shows complete dominance over the insularia and typical alleles, and

The conservation status of the Saldanha-Langebaan lizard fauna

The conservation status of relic melanistic lizard species occurring in the Saldanha- Langebaan area has been investigated. A contact zone between one melanistic form and a closely related non-melanistic form has been examined in detail. Apart from melanis- tic populations of the girdled lizards, Cordylus niger and C. polywnus, a melanistic morphotype of the Cape legless skink, Acontias meleagris meleagris also occurs in the area. The taxonomic status of this morphotype needs to be investigated. At Mauritz Bay, north of Saldanha, the ranges of C niger and the non-melanistic C cordylus are in contact over a distance of approximately 240 m, with maximum overlap of 70 m. The melanistic populations of C. polyz.onus and A. m. meleagris have relatively large ranges in the Saldanha-Langebaan area and are not threatened by urban development. The C niger population, however, is fragmented into several subpopulations, and those in the Saldanha area, including the contact zone, will be affected if urban development is allowed to continue in the area. As relic populations of other cool-adapted, melanistic invertebrate and lower vertebrate species may also occur in the area, the key areas demarcated by C. niger should be preserved.

A melanic form of the European grape vine moth, Lobesia botrana Den and Schiff (Lepidoptera, Tortricidae), and its genetic basis

Une forme melanique de l'eudemis de la vigne, Lobesia botrana Den et Schiff (Lepidoptera, Tortricidae), et sa base genetique. Nous decrivons une forme melanique de l'eudemis de la vigne, Lobesia botrana, provenant de l'elevage maintenu a l'Inra de Bordeaux, France. A partir de la descendance des croisements avec la forme typique, F 1 , F 2 et retrocroisements, nous montrons que la forme melanique est determinee genetiquement et que l'heredite est controlee par un gene recessif non lie au sexe (Roe). En outre, nous discutons des possibilites d'utilisation pratique du marqueur genetique dans des essais au champ et en laboratoire.

A new crag lizard from the Cape Folded Mountains in South Africa

Abstract A new crag lizard of the genus Pseudocordylus is described from the Western Cape Province, South Africa. It is an archaic melanistic form, occurring in sympatry with other archaic melanistic lizard and mollusc taxa within the mistbelt of the Hottentotsholland Mountains, part of the Cape Folded Mountains. With a maximum snout-vent length of less than 80 mm, it has an exceptionally small body size for a crag lizard. It has a conservative morphology which bridges the morphological gap that exists between Pseudocordylus and Cordylus. It is suspected that this species has a very restricted range in the Hottentotsholland Mountains, and that indiscriminate burning of the veld and collecting of the species may pose a serious threat to its survival.

The cryptic significance of melanism in cordylid lizards: A case study ofCordylus nigerandC. polyzonus

CORDES, I.G., and P. le F. N. MOUTON. 1995. The cryptic significance of melanism in cordylid lizards: A case study of Cordylus niger and C. polyzonus. J. Herpetol. Assoc. Afr. 44: 16–21. The cryptic significance of melanism in two girdled lizard species, Cordylus niger and C. polyzonus, was evaluated by comparing the melanistic forms with closely related, non-melanistic forms. A simple photographic technique involving colour transparencies and a colour densitometer, was used. The degree of correspondence between the integral density of the dorsal body surface of each lizard and its associated substrate was taken as an indication of the degree of background colour-matching. Inland, non-melanistic populations of C. cordylus and C. polyzonus, were significantly more background colour-matched than a population of the melanistic species C. niger and a melanistic population of C. polyzonus, occurring at the coast. A darkly coloured C. cordylus population, occurring 2 km from the coast, was also less background ...