Localized industrial melanism in the spittlebug Philaenus spumarius (L.) (Homoptera: Aphrophoridae) in Cardiff docks, south Wales

Twenty-four large adult samples of the meadow spittlebug, Philaenus spumarius , were collected from within a 4 times 3 km area containing Cardiff docks, south Wales. All samples are highly polymorphic for colour and pattern and show marked geographic variation in the combined frequency of the eight melanic morphs (from <15% to > 75%). Maximum melanic phenotype frequencies in both sexes coincide with dock wharfs currently containing large accumulations of pulverized coal and these samples are heavily contaminated with small coal particles. However, interpretation of this association is complicated by the existence, until 1976, of a smokeless fuel factory causing local air pollution immediately adjacent to the area of highest melanic frequency. It is suggested that the association of high levels of melanism in P. spumarius with areas heavily contaminated with particulate pollutants is due to direct selective effects of small particles favouring melanies.     

Genetic control of colour /pattern polymorphism in British populations of the spittlebug Philaenus sputnarius (L.) (Homoptera: Aphrophoridae)

The results of breeding experiments designed to determine the genetic control of the colour/pattern polymorphism in Philaenus spumarius in certain British populations are described and contrasted to previously published results for material taken from populations in southern Finland. The 11 principal phenotypes are controlled by seven alleles at a single autosomal locus, with complex patterns of dominance and co-dominance. In Finland, and most of the rest of the species' extensive range, the eight melanic morphs are wholly or substantially limited to the females, in which they are dominant to the typical form. Previously, this sex limitation has been explained in terms of reduced penetrance of melanic alleles in males and/or dominance reversal between the sexes, such that the eight melanic phenotypes (controlled by five alleles which are adjacent in the dominance heirarchy) are dominant to typical in the females but recessive in the males. Published data on morph frequencies in S Finland and on breeding experiments using material collected from these populations are re-examined and it is shown that neither theory accounts adequately for all the evidence. By contrast, in most British populations there is greatly increased penetrance in males of the melanic morphs which are strictly female-limited elsewhere. Breeding experiments, using P. spumarius taken from selected British populations, provide clear evidence that melanics are dominant to typical in both sexes. This difference in genetic control is entirely consistent with the balance of morph frequencies between the sexes in the populations from which the breeding material for the two separate studies was taken. Experimental material for this study was taken from populations in the Cynon Valley in south Wales, which have the highest melanic frequencies in the species' range and show particularly clear expression of melanic phenotypes in males. Both of these features are strongly correlated with severe aerial pollution from a local smokeless fuel factory. Selection for melanism in these populations is clearly strong, which probably accounts for the high level of penetrance and the dominance of melanics to typical in both sexes. Although further experiments are needed, it is suggested that regulatory loci, controlling the penetrance and expression of melanic alleles in males, could account for the observed differences in genetic control between populations in Britain and Finland.     

Geographic variation in the colour/ pattern polymorphism of British Philaenus spumarius (L) (Homoptera: Aphrophoridae) populations *

Geographic variation in the frequency of colour/pattern morphs of Philaenus spumarius is described at 48 localities in England and Wales. The sites have been divided into four broad environmental categories, two urban and two rural. There is a distinction between the urban and rural groupings in the relative proportions of the colour morphs; in urban localities there is a higher combined frequency of the eight ‘melanic’ morphs. Differences also exist between locality groupings, and between the sexes, in the relative frequencies of the eight morphs within the ‘melanic’ phenotypic category. Morphs limited to the female sex in some other parts of the species range occur among males in British populations. It is suggested that the different dominance hierarchy between the sexes which exists in Fennoscandian populations may not be characteristic of British populations.     

Industrial and non-industrial melanism in the peppered moth, Bistort betularia (L.)

Abstract. 1. Estimates of the relative crypsis of the melanic and typical morphs of B.betularia have been made at fifty-two sites in southern England and south Wales and these estimates were compared with melanic frequencies in samples from these sites.
2. The decrease from east to west in the frequency of the melanic form, carbonaria , and increase in the frequency of a second melanic form, insularia , across the southern part of England and Wales is largely independent of changes in smoke concentration, sulphur dioxide concentration or relative crypsis.
3. When all the available information on the distribution of the melanics of B.betularia is considered, sulphur dioxide concentration is correlated with the geographic variation in carbonaria frequency. This, together with evidence of the close relationship between carbonaria crypsis and sulphur dioxide levels, indicates that outside southern England and south Wales, either selective predation, or some direct selective effect of pollutants, is of major importance in determining the variation in carbonaria frequency.
4. Some features of the pattern of the spread of carbonaria in England and Wales during the last century give reasons for expecting non-industrial selective factors to be of greater importance in determining the distribution of melanics of B.betularia in southern England and south Wales than in the rest of Britain.     

The costs of colour: plasticity of melanin pigmentation in an outbreaking polymorphic forest moth

Outside the context of industrial melanism, little is known about the physiological and ecological importance of genetic melanic polymorphisms in moths. Melanin pigments are synthesized from amino acid precursors and should therefore be costly to produce in nitrogen‐limited insects. A genetic melanic polymorphism is present in adult Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), a widespread forest moth with outbreaking population dynamics. We test the hypotheses that melanin‐based colouration is physiologically costly in M. disstria, that expression of melanin‐based colouration is a plastic trait which varies with population density and nutrition, and that the genetically based melanic phenotype is disadvantaged under nutritionally poor conditions. Two experiments were used to test these hypotheses. A field study compared pigmentation and phenotypic frequencies in moths collected from high‐ and low‐density populations. A laboratory experiment investigated the effects of larval nitrogen availability on adult pigmentation and phenotypic frequencies. High population density and nitrogen limitation reduced pigmentation and size of all moths, but phenotypic frequencies were not affected in either experiment. The effects of diet on both pigmentation and size were stronger for melanic moths than for typical moths. Our results show that adult melanism in M. disstria is physiologically costly, that colour expression is plastic despite its genetic component, and that the melanic phenotype may be disadvantaged under poor conditions but favoured under good conditions. We suggest that temporal variation in selection and trait plasticity help maintain polymorphism stability.     

Industrial melanism in the moths, Diurnea fagella (Oecophoridae) and Allophyes oxyacanthae (Caradrinidae)

Comparative studies of melanism in the two cryptic moth species, Diurnea fagella (Denis & Schiffermüller) and Allophyes oxyacanthae (L.), have been carried out in southern England and south Wales. Estimates of the relative crypsis of the melanic and typical forms of both these species have been made at a number of sites and these were compared with the melanic frequencies in samples from these sites. These comparisons showed that selective prédation could be a major factor in the variation of melanic frequencies of both of these species. A consideration of the spread of melanism in these species suggests that non-visual selection may favour the melanics of D. fagella in urban areas and that non-visual selection, not closely associated with urban conditions, may be responsible for the restriction of melanics in A. oxyacanthae to Britain. The results for these two species are discussed in relation to investigations of melanism in other moth species.     

A survey of the macro-fauna of the River Cynon, a polluted tributary of the River Taff (South Wales)

(1) A survey of the macro-invertebrates and fish in the River Cynon, a trout stream in south-east Wales receiving industrial and domestic wastes, and nine of its tributaries, was carried out in the summer of 1970. Its principal purpose was to describe the structure of these communities before waste treatment facilities, in course of construction, reduce the degree of pollution. (2) The macro-invertebrate communities changed dramatically at station C4, there being a very varied fauna upstream and one dominated by chironomids and oligochaetes downstream, principally Nais barbata., Cricotopus bicinctus and Syncricotopus rufiventris. It seems likely that coal particles, influencing the substrate, are largely responsible for this change. Further downstream, and below substantial organic discharges, tubificids and the enchytraeid, Lumbricillus rivalis, became increasingly abundant. The total density of macro-invertebrates increased from about 2000/m2 in the headwaters to over 20,000/m2 in the lower reaches. (3) The fauna of the clean tributaries, Hir (C16) and Wenallt (C19) was similar to that ofthe unpolluted upper reaches ofthe Cynon (C1-C3) whereas that of tributaries affected by coal particles was similar to the fauna of the Cynon downstream of C4. (4) Six species of fish were recorded (bullhead, eel, minnow, trout, stickleback and stoneloach) of which tbree (bullhead, eel and trout) were confined to reaches upstream (C8 and above) of industrial eflluents at Abercwmboi. For 0–8 km downstream of these effluents the river was fishless and further downstream, to the confluence with the River Taff, fish density and biomass were reduced. (5) In the upper Cynon and its tributaries the density and biomass of trout were within the range recorded elsewhere in the British Isles. The growth rate of trout in the catchment is low. Diflerences in growth rate and shape of trout in the main river and tributaries suggest that there is little interchange between these areas, except perhaps with very young fish. 0 + * * The convention of referring to fish in their first year as 0+, in their second year as 1 + and so on is adopted here.
fish were only caught in abundance at two tributary stations and their numbers, even if widely distributed, could not permanently support the current density of older fish throughout the upper catchment. (6) Stone loach and minnow reached a very large size and individuals caught of the latter species approached the maximum recorded length for the British Isles.     

The rise and fall of the Carbonaria form of the peppered moth

The evidence for change in frequency of the melanic carbonaria morph in the peppered moth Biston betularia (L.) (Lepidoptera: Geometridae) in England and Wales is reviewed. At mid-20th century a steep cline of melanic phenotype frequency running from the north of Wales to the southern coast of England separated a region of 5% or less to west from 90% or more to northeast. By the 1980s the plateau of 90% frequency had contracted to northern England. The frequency has since continued to drop so that the maximum is now less than 50% and in most places below 10%. There have been similar declines in Europe and North America. Evidence from surveys and from two-point records shows the change to require 5% to 20% selection against the melanic. The melanic is more disadvantageous in regions where its frequency was initially high than in regions where it was low. Experiments to investigate predation by birds show a net advantage to carbonaria morphs in regions where typical frequencies were low at the time of the experiment, and a disadvantage where typical frequencies were high. This would be expected if environment and frequency were associated, and selective predation played a part in generating the association. The cryptic advantage of carbonaria was large in areas of heavy pollution where typical frequencies were 20% or less. The moth usually has a low density but is relatively highly mobile. The ability of present information to explain the patterns has been tested in simulations. They indicate a system under strong selection that has always been in a dynamic state without equilibria.     

A Narrow Heliconius cydno (Nymphalidae; Heliconiini) Hybrid Zone With Differences in Morph Sex Ratios1

In the western cordillera of the Cauca valley, Colombia, there is a narrow hybrid zone between two races of Heliconius cydno, one of which is polymorphic. Three large broods show that most of the phenotypic variation observed can be explained by four loci of major effect, named Sb, Yb, L, and K. Two further loci, G and Wo, were identified that control more minor phenotypic variation. Sb, Yb, and Wo are linked and the latter is differentially expressed between the sexes. The transition between H. c. cydnides in the north and H. c. weymeri to the south occurs over approximately 15 km. Collections from a single site near the center of the hybrid zone show that gene frequencies have been stable over the 10 yr from 1991 to 2001 and that color‐pattern genes are in Hardy–Weinberg equilibrium, with little evidence for linkage disequilibrium. This suggests that mating is random between color‐pattern forms. Nonetheless, there is evidence for variation in the sex ratio, with parental phenotypes and the most melanic hybrid phenotypes showing a fairly even sex ratio compared to a strong male bias observed in the remaining hybrids. We hypothesize that this might be explained by differential selection between sexes and phenotypes, phenomena that could have important implications for hybrid zone analysis and the evolution of Müllerian mimicry.     

A study of nonrandom mating in a British population of the two-spot ladybird with a high frequency of the melanic morph

In some studies of the two-spot ladybird (Adalia bipunctata), melanic males have been found in excess over the typical morph in matings. Data suggest that a genetic female mating preference is responsible. The mating advantage of melanic males may be important in maintaining a polymorphism between melanic and typical ladybirds in many populations in the United Kingdom (U.K.). It has been reported that preference frequency varies linearly with melanic frequency throughout most of the U.K. One particular population ofAdalia bipunctata near Aberdare, South Wales, is noted for its high frequency of melanic individuals. It has been suggested that local environmental factors account for the high melanic frequency in this population. It is also possible, however, that a female mating preference may be at least partly responsible for the high frequency of melanics (as has been proposed for the rest of the U.K.). In this study, experiments have been performed to determine the level of female mating preference in the Aberdare population. No evidence was found for any mating advantage to melanic males. There was inconsistent and unexpected evidence that melanic females were overrepresented in matings, but the cause for this was unclear. Female mating preference does not appear, therefore, to be responsible for the high melanic frequency in the population ofAdalia bipunctata near Aberdare. There is not a simple association between mating preference and melanic frequency in U. K. populations of the two-spot ladybird.     

Spread and potential distribution of Senecio madagascariensis Poir. (fireweed) in Australia

Abstract The potential distribution of the herbaceous weed Senecio madagascariensis Poir. (fireweed) in Australia was estimated using the Bioclimate Prediction System, BIOCLIM. Climate profiles for S. madagascariensis predicted that suitable areas occurred only in the south-eastern region of Australia. Its potential to spread outside these areas was assessed by comparing the present African and South American distributions of this species with that observed in Australia. The rate of spread of S. madagascariensis in New South Wales was exponential, although in some regions, such as the Gloucester River Valley, the rates had decreased because all farms had become infested. The results indicate that S. madagascariensis may spread and increase in abundance along the far south coast of New South Wales and in south-eastern Queensland. Coastal areas in eastern Victoria and as far north in Queensland as the Tropic of Capricorn may be invaded.     

Polymorphism of Philaenus spumarius L. (Hemiptera: Cercopidae) in the Samsun (Mid-Black Sea Region) populations of Turkey

Variation in the frequency of colour/pattern phenotypes of Philaenus spumarius (L.) is studied in the three local populations of Samsun (Mid-Black Sea Region), Turkey. The data, obtained from the 91 samples including 10,427 adult spittlebugs, 5,340 females and 5,087 males were analysed according to phenotype distributions in the study sites. The adult spittlebugs were collected during eleven months except with April. The mean sample size was 114.6±19.9 (Mean±S.E.) for 91 samplings. Eight different phenotypes of P spumarius were detected in the Samsun populations. Of these, four were non-melanic and four were melanic phenotypes with the lack of the “O” group. In females, non-melanic frequency was over 95%, which TYP (typicus) was the predominant phenotype, but POP (populi) in males. However the phenotype frequency distributions were not different between the sites studied. Although, frequency of females reached up to 85% in some samples, the overall sex ratio did not differ from the 1:1.     

The molecular basis of the plumage colour polymorphism in the Tahiti reed‐warbler Acrocephalus caffer

The endemic Tahiti reed‐warbler Acrocephalus caffer occurs in two distinct morphs, a typical or ‘yellow’ morph and a melanic or ‘dark’ morph, which are found together in the valleys of the eastern and central parts of the island of Tahiti (Society Islands, French Polynesia). We investigated the molecular basis of the plumage colour polymorphism in this species using sequences of the melanocortin‐1 receptor (MC1R), a gene often found associated to melanism in birds. We found that the MC1R genotype was perfectly associated with plumage colour in the Tahiti reed‐warbler, with the same nonsynonymous substitution that showed a correlation with phenotype in the Caribbean bananaquit Coereba flaveola. An heterozygous reed‐warbler at this site presented a melanic phenotype, suggesting that the melanic allele is dominant. All other Polynesian reed‐warbler species, which do not have a melanic morph, shared the ‘yellow’ nucleotide at this position. These results suggested that the same mutation point was linked to a melanic polymorphism in two unrelated passerine birds.     

Temperature and the colour polymorphism of Philaenus spumarius (Homoptera: Aphrophoridae)

ABSTRACT.

• 1 The spittle bug, Philaenus spumarius (L.), has eleven distinct elytral colour pattern morphs in Britain, of which three are designated non-melanic and eight melanic. Frequencies of different morphs vary between populations.
• 2 The role of thermal factors in the maintenance of the balanced polymorphism was investigated by measurements of dorsal reflectance and body temperature when artifically irradiated.
• 3 Non-melanic forms had higher reflectances and showed lower temperature excesses when irradiated. There was considerable variation in reflectance for the populi–typicus morph group, and trilineatus is therefore the only true‘non-melanic’morph.
• 4 For samples along altitudinal transects in three Scottish glens, trilineatus frequencies were found to be negatively and populi-typicus and melanic frequencies positively correlated with altitude.
• 5 Thermal considerations do therefore play some role in the broad and complex selection regime of P.spumarius.

     

The Genetics of Melanism in MALACOSOMA DISSTRIA HUbner (Lepidoptera: Lasiocampidae)

The forest tent caterpillar is polymorphic for two melanic genes affecting wing color of moths. These are the first genetically determined morphological traits reported for the genus. Dark (D) is a sex-limited, autosomal dominant with a phenotype of dark brown males. Frequencies in population samples varied from 8 to 44%. Characteristics of Dark and nonmelanic males were compared. Larval development times, larval survival and pupal weights were not significantly different, but mean fecundity was higher for females with Dark progeny. Band (b), a darkened area across the forewings, occurred in low frequency in both sexes.     

Industrial melanism in Mesopsocus unipunctatus (Müll.) (Psocoptera) in northern England

Abstract. 1. The light and melanic morphs of M.unipunctatus are described, their genetic inheritance considered, and their geographic distribution over a pollution gradient in Yorkshire is examined.
2. There is an obvious colour dimorphism. The light forms are disruptively patterned while the melanic forms are uniformly dark.
3. Genetic crosses indicate that the melanic character is inherited as a Mendelian dominant and that separate alleles, linked on the same chromosome, control the respective melanisms of the head-thorax and of the abdomen.
4. In Yorkshire, there is a decrease in the frequency of melanics from the industrial south to the rural north.     

Geographic variation of color polymorphism in two sibling ladybird species,Harmonia yedoensis and H. axyridis (Coleoptera: Coccinellidae)

Geographical variation of elytra color pattern in two sibling ladybird species, Harmonia yedoensis and H. axyridis (Coleoptera: Coccinellidae), was examined. The two species are distributed sympatrically in central Japan; however, only H. yedoensis and H. axyridis occur in the Ryukyu Islands (southern Japan) and Hokkaido island (northern Japan), respectively. The frequency of elytra color patterns was significantly different between the two species in all sympatric locations and our results were inconsistent with the classical theory on Müllerian mimicry. The most dominant pattern of H. axyridis was the least dominant of H. yedoensis in all sympatric populations. Furthermore, the frequency of the non‐melanic form (red ground color with or without black spots) increased towards the south in H. yedoensis. This tendency was in contrast to the known geographical cline in H. axyridis in which the melanic form (black ground color with red spots) was gradually displaced with the non‐melanic form northwards in the Japanese archipelago. We discuss possible selective factors including predator avoidance, thermal adaptation and reproductive character displacement, all of which might contribute to the maintenance of the color polymorphism in the two Harmonia species.     

Three divergent lineages within an Australian marsupial (Petrogale penicillata) suggest multiple major refugia for mesic taxa in southeast Australia

Mesic southeastern Australia represents the continent's ancestral biome and is highly biodiverse, yet its phylogeographic history remains poorly understood. Here, we examine mitochondrial DNA (mtDNA) control region and microsatellite diversity in the brush‐tailed rock‐wallaby (Petrogale penicillata; n = 279 from 31 sites), to assess historic evolutionary and biogeographic processes in southeastern Australia. Our results (mtDNA, microsatellites) confirmed three geographically discrete and genetically divergent lineages within brush‐tailed rock‐wallabies, whose divergence appears to date to the mid‐Pleistocene. These three lineages had been hypothesized previously but data were limited. While the Northern and Central lineages were separated by a known biogeographic barrier (Hunter Valley), the boundary between the Central and Southern lineages was not. We propose that during particularly cool glacial cycles, the high peaks of the Great Dividing Range and the narrow adjacent coastal plain resulted in a more significant north–south barrier for mesic taxa in southeastern Australia than has been previously appreciated. Similarly, located phylogeographic breaks in codistributed species highlight the importance of these regions in shaping the distribution of biodiversity in southeastern Australia and suggest the existence of three major refuge areas during the Pleistocene. Substructuring within the northern lineage also suggests the occurrence of multiple local refugia during some glacial cycles. Within the three major lineages, most brush‐tailed rock‐wallaby populations were locally highly structured, indicating limited dispersal by both sexes. The three identified lineages represent evolutionarily significant units and should be managed to maximize the retention of genetic diversity within this threatened species.     

Melanism in a Chinese Population of Harmonia axyridis (Coleoptera: Coccinellidae): A Criterion for Male Investment with Pleiotropic Effects on Behavior and Fertility

In Beijing, China, females of Harmonia axyridis are promiscuous but prefer typical (succinea form) males to melanic ones in the spring generation, ostensibly due to the thermal disadvantages of melanism during summer. We used laboratory observations to test whether males invested differentially in females according to their elytral color, and whether male behavior was phenotype-dependent. Video-recording was used to monitor no-choice mating tests between virgin adults in all phenotype combinations and females were isolated post-copula to observe their egg retention times and reproduction over 5 days. Females tended to wait longer before using the sperm of melanic males, and melanic females delayed longer than succinic females. Melanic males spent longer in copula with succinic than melanic females and the latter received fewer bouts of male abdominal shaking that correlate with sperm transfer, regardless of the phenotype of their mate. Although melanic males abandoned melanic females faster than did succinic males, they remained in copula with females of both phenotypes for a longer period after shaking, suggesting a larger investment in mate guarding by the less-preferred male phenotype. Although female fecundity did not vary among phenotype combinations, egg fertility was lower for females mated to melanic males, suggesting a pleiotropic effect of melanism on male fertility in addition to its effects on male mating behavior.     

Fitness of insularia morphs of the peppered moth Biston betularia

In recent years the industrial melanic carbonaria morph in the moth Biston betularia (L.) has decreased rapidly in frequency in Britain as air pollution has decreased. The intermediate melanic insularia has shown a variable response. We have estimated the fitness of insularia, compared with the other two morphs, for several data sets. As a rule its fitness lies between that of carbonaria and typical, but nearer to typical and sometimes very close to it. The intermediate position is expected if fitness relates directly to phenotype. The results suggest that insularia may continue polymorphic while carbonaria is likely to disappear. The past high frequency of insularia in South Wales may have been due to an initial increase in insularia frequency before carbonaria reached the region. Differences in dynamics of frequency change in insularia and carbonaria are evidence against induction, which has sometimes been invoked to explain the spread of melanism in this species.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 359–366.