Melanic frequencies in three species of moths in post industrial Britain

Changing patterns of morph frequency in three moth species ( Biston betularia , Odontoptera bidentata and Apocheima pilosaria ) have been investigated using data from the Rothamsted Insect Survey. All three exhibited industrial melanism during the period of high atmospheric pollution in Britain. Three historical and habitat types are compared, the old industrial north of England, rural Scotland, Wales and South-West England, and a southern English intermediate region of high human population density but generally low industrialization. Between 1974 and 1999 the carbonaria morph of B. betularia declined in frequency in the industrial region and is nearly absent from rural areas. It is the form which most closely tracks atmospheric change. It is shown that the insularia forms of B. betularia and the melanic morphs in the other two species have decreased in the industrial region, commencing later than carbonaria , but have maintained their presence and possibly reached equilibrium elsewhere. They may be non-industrial polymorphisms. B. betularia is rarer than the other species and all three species are at lower densities in industrial than in non-industrial regions. © 2002 The Linnean Society of London , Biological Journal of the Linnean Society , 2002, 75 , 475–482.     

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.     

Peppered moth revisited: analysis of recent decreases in melanic frequency and predictions for the future

In a recent review article by Mani published in 1990, it was shown that the changes in the frequency of the morph carbonaria can be explained through a migration-selection model and the model is capable of reproducing the decrease in the carbonaria frequency since the enactment of Clean Air Acts. In this paper new data both for carbonaria and for insularia up to 1990 for West Kirby in NW England and for Cambridge are presented. In the earlier review, the data for West Kirby extended to 1987 and for Cambridge to 1985. Data not previously published for the carbonaria and the insularia frequencies at sites in Northwood in Middlesex, Egham in Surrey and Ringwood in Hampshire are also presented. A migration-selection model was used to predict the change in the frequencies of the melanic morphs up to the year 2010. All the data are compared with the predictions of the model. It is encouraging that the data follow the theoretical predictions.     

Pre-adult viability differences of melanic Biston betularia (L.) (Lepidoptera)

Departures from mendelian ratios have been analysed in all published family data for the peppered moth, Biston betularia. No distinction was made between different insularia alleles; thus carbonaria is top dominant while insularia is dominant over typical. Viabilities of five of the six genotypes were calculated by a simple algebraic method; a maximum likelihood method gave viabilities for all six genotypes together with their standard errors. Carbonaria homozygotes (and possibly also insularia homozygotes) have enhanced viability while the viability of insularia/carbonaria heterozygotes is reduced. The significance of these findings is discussed in relation to phenotype frequencies found in the wild.     

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 decline of melanism in the peppered moth Biston betularia in The Netherlands

Melanic forms of the peppered moth Biston betularia were well established in The Netherlands by the end of the 19th century, indeed the first records of the black carbonaria form in 1867 are only about 20 years later than in England. Analysis of extensive sampling data collected by B. J. Lempke for a period of several years beginning in 1969 shows that carbonaria was at a frequency of about 60 to 70% in most of the country where epiphyte communities on trees were reduced due to the effects of air pollution. The pale typica and the three intermediate insularia forms were each at similar, low frequencies. Only in the extreme north and south-east of The Netherlands where epiphyte floras were richer was carbonaria at a lower frequency of less than 40%. Samples collected from seven localities in 1988 show that carbonaria has dramatically declined to a frequency of less than 10%. In contrast to England, the fully black form is being replaced not only by typica but also by the darkest of the insularia phenotypes. The decline in melanism coincides with a period of decreasing levels of sulphur dioxide and of increasing species diversity of lichens on trees.     

Evolutionary dynamics of declining melanism in the peppered moth in the Netherlands

Populations of Biston betularia in the region of The Netherlands around Leiden and Rotterdam were resampled. A comparison of three sets of data for 1969-1973, 1988 and 1999 enabled a further examination of declines in melanism. Unlike parallel changes for the black carbonaria form of this species in urban regions of Britain, those inThe Netherlands involve substantial changes in frequencies of at least two of the intermediate insularia morphs as well as an increase in the non-melanic typica morph. The darkest of the three insularia morphs has shown a transitory pulse of increased frequency in The Netherlands. The dynamics are discussed in relation to the history of air pollution and to straightforward predictions about selection.     

A test of sexual cannibalism models, using a sit-and-wait predator

Sexual cannibalism, the capture and consumption of one sex by the other resulting from sexual interactions, provides an intriguing set of conditional fitness payoffs. Usually these payoffs will only benefit the cannibal, but under certain circumstances advantages might accrue to the cannibalized individual as well. Here I test three models of sexual cannibalism with data from a sit-and-wait predator, the crab spider Misumena vatia , whose lifestyle differs from the species for which these models were generated. The models include both precopulatory mechanisms (no gametes exchanged) and postcopulatory ones (gametes exchanged) perceived to generate adult fitness payoffs and situations in which cannibalism is not adaptive in the adult stage (aggressive spillover). In M. vatia , females sometimes cannibalize males before mating can occur. Precopulatory cannibalism is unlikely to reward female M. vatia significantly because of the diminutive size of the males, but it could be part of a broader syndrome that provides the females with large food payoffs earlier in the life cycle. Although the frequency of cannibalism is low (3.8–7.6%), this level suffices to be an important selective factor, a point accentuated by the extremely cautious behaviour of the males toward the females. I then compare the traits associated with these models to the species for which they were designed and certain others for which adequate data also exist. None of the sets of responses to these traits closely resembles each other in the different species. These results suggest that sexual cannibalism has developed in response to a heterogeneous collection of lifestyles and phylogenetic constraints.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 427–437.     

No evidence for optimal fitness at intermediate levels of inbreeding in Drosophila melanogaster

Optimal outbreeding theory predicts fitness benefits to intermediate levels of inbreeding. In the present study, we test for linear (consistent with inbreeding depression) and nonlinear (consistent with optimal outbreeding) effects of inbreeding on reproductive fitness in male and female Drosophila melanogaster . We found linear declines in fitness associated with increased inbreeding for egg-to-adult viability, but not the number of eggs laid or sperm competitive ability. Egg-to-adult viability was also lower in the progeny of inbred males and females mated to unrelated individuals. However, there was no evidence for optimal fitness at intermediate levels of inbreeding for any trait. The present study highlights the importance of considering biologically realistic levels of inbreeding and cross-generational effects when investigating the costs and benefits of mating with relatives.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 501–510.     

Phototaxis and the evolution of isogamy and 'slight anisogamy' in marine green algae: insights from laboratory observations and numerical experiments

The evolution of anisogamy in marine algae was studied through numerical simulations of gamete mating behaviour in three dimensions, using observed traits of marine green algae as input parameters. The importance of phototaxis became apparent from the numerical experiments: all gametes with phototactic systems are favoured over those without, but this advantage is reduced with increasing tank depth or shorter search times. Phototactic gametes were advantaged over non-phototactic gametes if the water was shallower than about 30–40 mm when the time available for gamete encounter was 1000 time steps (5.55 min). If gametes of both sexes are positively phototactic, slightly anisogamous species are at a disadvantage to isogamous species, which invalidates the sperm-limitation theory as a driver for the evolution of slight anisogamy. Conflicting selection forces of search efficiency and zygote fitness may be needed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 321–327.     

Meiotic drive at the Om locus in wild-derived inbred mouse strains

Meiotic drive is an evolutionary force in which natural selection is uncoupled from organismal fitness. Recently, it has been proposed that meiotic drive and genetic drift represent major forces in the evolution of the mammalian karyotype. Meiotic drive involves two types of genetic elements, Responders and Distorters , the latter being required to induce transmission ratio distortion at the former. We have previously described the Om meiotic drive system in mouse chromosome 11. To investigate the natural history of this drive system we have characterized the alleles present at the distorter in wild-derived inbred strains. Our analysis of transmission of maternal alleles in both classical and wild-derived inbred strains indicated that driving alleles are found at high frequency in natural populations and that the existence of driving alleles predates the split between the Mus spicilegus and M. musculus lineages.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 487–492.     

On the mechanism of floral shifts in speciation: gained pollination efficiency from tongue- to eye-attachment of pollinia in Platanthera (Orchidaceae)

This work explores the mechanism of floral shifts that may result in speciation. The model organisms chosen were the moth-pollinated pollinator-limited orchid species Platanthera bifolia and P. chlorantha . P. bifolia exhibits tongue-attachment of pollinia on pollinators, a character state that has been found previously to be ancestral. The close relative P. chlorantha exhibits the derived state of eye-attachment of pollinia on pollinators. We reasoned that differences between the species in pollination efficiency could give insights into the mechanism of floral shifts and thus cladogenesis. Four populations per species were investigated. In three populations, where the species were growing intermixed and were sharing pollinators, there was significant difference in the pollen export and import efficiency per visit-night (night with pollen export and/or import) between the two species. P. bifolia exported pollinia more efficiently but imported pollen less efficiently than did P. chlorantha . Pollen import was 1.7–4 times faster in P. chlorantha (eye-attachment) than it was in P. bifolia (tongue-attachment). P. chlorantha had a lower risk of interference between pollen import and export. An increase in fitness through greater speed and efficiency of pollen import due to an enlargement of the stigmatic surface and a reduction in the risk of sexual interference may therefore be mechanisms of the floral shift from tongue- to eye-attachment of pollinia on pollinators.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 481–495.     

The lichenicolous Opegrapha species (Roccellaceae, Ascomycota) with 3-septate ascospores on Pertusaria and Ochrolechia

The Opegrapha species with 3-septate ascospores growing on Pertusaria and Ochrolechia are revised. Two species are recognized: Opegrapha anomea (of which O. pertusariae , O. quaternella , O. wetmorei and possibly Leciographa weissii are considered to be synonyms), and O. blakii Ertz & Diederich sp. nov. described from a sterile lichen with an Ochrolechia -like thallus, known from Ecuador and Venezuela. Opegrapha anomea and several related lichenicolous species with roundish or irregular, often multilocular ascomata are morphologically intermediate between Opegrapha and Plectocarpon , and might represent a distinct genus.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144, 235−241.     

Systematic relevance of pollen and orbicule characters in the tribe Hillieae (Rubiaceae)

Pollen and orbicule morphology of 26 species in the tribe Hillieae is described based on observations by light, scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the tribe. Pollen is 3-zonocolporate with a perforate, microreticulate, reticulate or eutectate sexine. In the two species of Blepharidium , however, the pollen has one, four or five apertures. These pollen morphological data were incorporated into an existing macromorphological matrix of the group and cladistically analysed. The resulting phylogenies indicate that it may be appropriate to reduce Cosmibuena to a subgenus of the genus Hillia , while Blepharidium should be removed from Hillieae because of the deviating pollen type that is unique to the Rubiaceae. All species investigated produce orbicules, which are mostly spherical and possess an electron-lucent core that is sometimes characteristically flattened.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 303−321.     

Polyploidy in fishes: patterns and processes

Fishes are the most speciose group of vertebrates, with more than 24 000 species. They are characterized by great diversity in ecology, morphology, life history, behaviour and physiology. Here, the phylogenetic patterns of orders in which polyploidy has been recorded are considered, with special reference to patterns of species richness and hybridization: these orders include such phylogenetically diverse taxa as the Lepidosireniformes (lungfish) and the Perciformes (perch). Examples, predominantly drawn from the Cyprinidae and Salmonidae, are used to illustrate attributes of polyploidy in fishes. It is concluded (i) that polyploidy may have been of considerable importance in the evolution of fishes, and (ii) that fishes, with their diverse life histories, represent a useful model system with which to test theories relating to the origin and consequences of polyploidy that have been derived from work on plants.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 431–442.     

Influence of selfing and maternal effects on life-cycle traits and dispersal ability in the herb Hypochaeris radicata (Asteraceae)

The ecological and evolutionary implications of dispersal are many. Pollination type and maternal effects may affect plant fitness traits, including life-cycle traits as well as dispersal ability. This study investigated the joint influence of pollination type and maternal effects on both life-cycle traits and dispersal ability in the herb Hypochaeris radicata . We conducted experimental crosses to obtain selfed and outcrossed progeny. Individual seeds and their pappuses were measured to determine seed terminal velocity. Seed size was also used to assess maternal effects. Selfing dramatically decreased seed set, indicating that H. radicata is self-incompatible. However, the few selfed seeds produced outperformed outcrossed seeds in seed size and flowering probability, surely as a result of an effective reallocation of resources among selfed seeds. None of the life-cycle traits was affected by seed size, the estimate of maternal effects. Selfed seeds were larger and bore a smaller pappus than outcrossed seeds. As a result, dispersal ability was lower for selfed than outcrossed seeds. Several factors, such as the low proportion of plants that produced selfed seeds, the low number of selfed seeds produced per plant, and the lack of self-fertility mechanisms might act in concert to prevent the evolution of selfing in H. radicata .  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 163–170.     

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.     

Exploring the genomic mysteries of polyploidy in cotton

For several years allopolyploid cottons have been the subject of evolutionary investigations into the genomic mysteries of polyploidy. An array of genomic interactions have been documented, including interlocus concerted evolution, differential rates of genomic evolution and intergenomic sequence transfer. Substantial alterations in gene expression have occurred in response to allopolyploidization, including gene silencing and expression changes that vary by organ. Some of the molecular phenomena occurring in polyploids appear to be non-Mendelian. Many of the genomic and expression alterations have occurred on an evolutionary timescale, whereas others reflect more immediate consequences of genomic merger.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 573–581.     

The role of triploid hybrids in the evolutionary dynamics of mixed-ploidy populations

Theory suggests that the evolution of autotetraploids within diploid populations will be opposed by a minority-cytotype mating disadvantage. The role of triploids in promoting autotetraploid establishment is rarely considered, yet triploids are often found in natural populations and are formed in experimental crosses. Here, I evaluate the effects of triploids on autotetraploid evolution using computer simulations and by synthesizing research on the evolutionary dynamics of mixed-ploidy populations in Chamerion angustifolium (Onagraceae). Simulations show that the fate of a tetraploid in a diploid population varies qualitatively depending on the relative fitness of triploids, the ploidy of their gametes and the fitness of diploids relative to tetraploids. In general, even partially fit triploids can increase the likelihood of diploid–tetraploid coexistence and, in some cases, facilitate tetraploid fixation. Within the diploid–tetraploid contact zone of C. angustifolium , mixed populations are common (43%), and often (39%) contain triploids. Greenhouse and field studies indicate that triploid fitness is low (9% of diploids) but variable. Furthermore, euploid gametes produced by triploids can be x , 2 x or 3 x and contribute the majority (62%) of new polyploids formed in each generation (2.3 × 10⁻³). Although triploid bridge, alone, may not account for the evolution of autotetraploidy in C. angustifolium , it probably contributes to the prevalence of mixed-ploidy populations in this species. Therefore, in contrast to hybrids in homoploid species, triploids may actually facilitate rather than diminish the fixation of tetraploids by enhancing the rate of formation.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 537–546.