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Showing papers in "Biological Journal of The Linnean Society in 1983"


Journal ArticleDOI
TL;DR: Overall little evidence was found that balancing selection is responsible for maintenance of the polymorphisms studied in M. edulis, and the pattern of geographic variation in gene frequencies in Mytilus in the British Isles is discussed in relation to variation in the south and north of Europe and North America.
Abstract: Starch gel electrophoresis was used to study variation at 11 loci in mussels sampled mainly from British coastal sites. Two types of mussel were identified, Mytilus edulis, the common mussel and its southern relative Mytilus galloprovincialis. Several partially diagnostic loci were used to map the distribution of the two forms. Mytilus edulis was present at all sites sampled in Britain and Ireland but was at low frequency in SW England; M. galloprovincialis was detected in SW England, the south and west of Ireland. Scotland and NE England, but was absent from south Wales, the Irish sea coasts of Wales and Ireland, and SE England. Apart from the occurrence of M. galloprovincialis in NE England, this distribution conforms with the results of studies using morphological characters and parallels the distribution of many other southern species in Britain. At the microgeographical level, M. edulis was found to prefer more sheltered and estuarine conditions than M. galloprovincialis. Analysis using the best diagnostic loci showed that hybridization is occurring between M. edulis and M. galloprovincialis at all localities where they occur sympatrically but that the extent of hybridization varies considerably between localities. The distribution of localities having high proportions of hybrid individuals is best interpreted by assuming that hybrids have higher fitness than parental types at these localities. A study was made of variation within and between those localities where only M. edulis individuals were observed. Little significant geographic variation in allele frequency was detected, but significant deficits of heterozygotes compared with Hardy-Weinberg expectations were seen for most loci. Analysis suggests that the Wahlund effect is not involved and that the most likely cause of the deficit is low frequencies of null alleles. In M. edulis no differences in phenotypic variance in shell height and width were observed between samples of multiply heterozygous and multiply homozygous individuals and no genetic differences were found between juveniles and adults. Overall little evidence was found that balancing selection is responsible for maintenance of the polymorphisms studied in M. edulis. The pattern of geographic variation in gene frequencies in Mytilus in the British Isles is discussed in relation to variation in the south and north of Europe and North America. It is concluded that steep clines in gene frequencies in M. edulis observed by other workers in the Baltic and in Long Island Sound cannot be attributed to the presence of M. galloprovincialis.

227 citations


Journal ArticleDOI
TL;DR: Old World phytophagous bats (Megachiroptera: Pteropodidae) number 173 species of which 79% are Asian and 21% African, and both bat-flower and bat-fruit syndromes are commonly recognized.
Abstract: Old World phytophagous bats (Megachiroptera: Pteropodidae) number 173 species of which 79% are Asian and 21% African. Bats arose, presumably monophyletically, in the early Tertiary, the Megachiroptera soon diverging from the Microchiroptera. By the Cretaceous-Tertiary boundary the major groups of modern angiosperms were present, some of these probably being pollinated nocturnally by large insects and non-flying mammals and others with seeds dispersed by terrestrial vertebrates. Early bats were perhaps initially attracted to such flowers and fruit by the insects found around them, later finding the plants themselves nutritious. Megabats today feed upon floral resources, fruit and leaves from a total of at least 188 plant genera in 64 families. They may effect both pollination and seed-dispersal, and both bat-flower and bat-fruit syndromes are commonly recognized. Individual species are generally catholic in their feeding, favoured food varying with locality and season. Depending upon roosting habits and season, megabats may travel considerable distances each night to feed and may undertake seasonal migrations. Their feeding in orchards may sometimes require their control, but the future of certain species is more seriously threatened by slaughter for food and particularly by habitat destruction.

180 citations


Journal ArticleDOI
TL;DR: It is concluded that the patterns that emerge from an analysis of 10 kinds of mutualistic symbiosis strongly support predictions that sex is usually reduced in inhabitants in comparison to related free-living taxa, although it remains widespread in exhabitants.
Abstract: It has previously been proposed that sex is selected for in organisms living in antagonistic biotic environments. Here, the contrasting case of mutualistic biotic environments is considered. In these environments, it is argued that there should be selection against sex and an accompanying low rate of genetic change. This proposition is tested on mutualistic symbioses with substantial histories of co-evolution in which one partner, the inhabitant, lives partly or wholly inside the other, the exhabitant. This asymmetry between the partners means that inhabitants should exhibit a reduction in sex in comparison to related free-living taxa and a lower rate of genetic change than exhabitants. The patterns that emerge from an analysis of 10 kinds of mutualistic symbiosis strongly support these predictions. Where adequate information is available, sex is usually reduced in inhabitants in comparison to related free-living taxa, although it remains widespread in exhabitants. Inhabitants are also represented by a much smaller taxonomic diversity than exhabitants. Various alternative reasons for these patterns are considered but it is concluded that they are best explained by the mutualistic environment in which the inhabitants live.

165 citations


Journal ArticleDOI
TL;DR: The orchid-male euglossine bee interaction does not appear to represent a mutually obligatory relationship and the orchids may have exploited a preexisting behavioural phenomenon of the bees, and reciprocal evolutionary responses may not have occurred.
Abstract: Seasonal and geographic relationships, and host pollinator specificities are examined for indications of interdependency in the orchid-euglossine bee interaction The orchids are dependent on the bees for pollination, and their flowering seasonality corresponds well with peak activity of their pollinators However, there is little evidence that the bees are dependent on these fragrance hosts The orchids tap the majority of euglossine species and individuals for pollinator services during any given season, but most of those bee species that temporarily lack orchid fragrance hosts persist in the area, continually emerge from nests, and seek floral fragrance compounds Pollinator specificity occurs in less than half of the orchids, and host specificity is rare Geographic distributions of nearly all orchid-pollinator pairs are not mutually inclusive Moreover, nearly a third of the local male euglossine bee species censused are not pollinators of any fragrance orchids in the area Local alternative fragrance sources occur The orchid-male euglossine bee interaction does not appear to represent a mutually obligatory relationship The orchids may have exploited a preexisting behavioural phenomenon of the bees, and reciprocal evolutionary responses may not have occurred

152 citations


Journal ArticleDOI
TL;DR: The jaw mechanism of carnivores is studied using an idealized model that makes the following predictions: in carnivores with carnassial teeth the resultant force of the jaw muscles will be positioned approximately 60% of the way from the jaw joint to the tooth—this arrangement delivers the maximum bite force possible together with a reasonably wide gape.
Abstract: The jaw mechanism of carnivores is studied using an idealized model (Greaves, 1978). The model assumes: (i) muscle activity on both sides of the head, and (ii) that the jaw joints and the carnassial teeth are single points of contact between the skull and the lower jaw during carnassial biting. The model makes the following predictions: (i) in carnivores with carnassial teeth the resultant force of the jaw muscles will be positioned approximately 60% of the way from the jaw joint to the tooth—this arrangement delivers the maximum bite force possible together with a reasonably wide gape (remembering that bite force and gape cannot both be maximized); (ii) in an evolutionary sense, if greater bite force is required at the carnassial tooth, either the animal will get larger so as to deliver an absolutely larger bite force or the architecture of the muscles may change, becoming more pinnate, for example, but jaw geometry (i.e. the relative positions of the jaw joints, the carnassial tooth, and the muscle resultant force) will not change; (iii) if greater gape is required, the animal will get larger so as to have longer jaws and therefore an absolutely wider gape or change its muscle architecture allowing for greater stretch while the geometry remains unchanged; and (iv) in animals with a longer shearing region (e.g. the extinct hyaenodonts) the shearing region will be approximately 20% of jaw length and the muscle resultant force will be positioned approximately 60% of the way from the jaw joint to the most anterior shearing tooth.

115 citations


Journal ArticleDOI
TL;DR: All the Aphelinidae in which conspecific males and females have different host relationships, i.e. those that have divergent ontogenies, are here designated heteronomous parasitoids.
Abstract: A classification of the different types of divergent male ontogeny in Aphelinidae is proposed to replace the little known and cumbersome systems previously published. All the Aphelinidae in which conspecific males and females have different host relationships, i.e. those that have divergent ontogenies, are here designated heteronomous parasitoids. Females of these species are primary endoparasitoids of Homoptera. The males of (i) diphagous parasitoids are primary ectoparasitoids of the same host species exploited by their females, (ii) heteronomous hyperparasitoids develop hyperparasitically, and (iii) heterotrophic species are endoparasitoids of lepidopterous eggs. Heteronomous hyperparasitoids can be classified further as obligate autoparasitoids, facultative autoparasitoids or alloparasitoids. All the species of heteronomous aphelinids whose biologies are known are listed according to the new classification, and the evolutionary sequence of these unusual host relationships is discussed.

104 citations


Journal ArticleDOI
TL;DR: Refinement of Markovian branching hypotheses to include the possibility of multiple furcations, differential speciation and extinction rates for different groups of organisms as well as for a single group through geological time, hybrid speciation, introgression, and lineage fusion will be necessary to produce realistic models of lineage diversification.
Abstract: Three hypotheses that predict probabilities associated with various tree shapes, or topologies, are compared with observed topology frequencies for a large number of 4, 5, 6 and 7-member trees. The united data on these n-member trees demonstrate that both the equiprobable and proportional-to-distinguishable-types hypotheses poorly predict tree topologies, while all observed topology frequencies are similar to predictions of a simple Markovian dichotomous branching hypothesis. Differences in topology frequencies between phenetic and non-phenetic trees are observed, but their statistical significance is uncertain. Relative frequencies of highly asymmetrical topologies are larger, and those of symmetrical topologies are smaller, in phenetic than in non-phenetic trees. The fact that a simple Markovian branching process, which assumes that each species has an equal probability of speciating in each time period, can predict tree topologies offers promise. Refinement of Markovian branching hypotheses to include the possibility of multiple furcations, differential speciation and extinction rates for different groups of organisms as well as for a single group through geological time, hybrid speciation, introgression, and lineage fusion will be necessary to produce realistic models of lineage diversification.

79 citations


Journal ArticleDOI
TL;DR: The following areas are discussed with respect to how seed and pollen movement compare: ability of parent plant to assess success; gene flow; dependency of animals on seeds, pollen and bait; disruption by animal loss; secondary movements; fate of most seeds and pollen; syndromes; selection for maximization of movement.
Abstract: Seed dispersal and pollen movement by animals have very much in common, though we know so little of either that it is hard to be specific. The focus has been on animals at the fruit crop rather than the seed shadows that they generate (and the fate of those seeds), and on the animals that arrive at flowers rather than where they take the pollen obtained or whence came the pollen they are carrying. ‘Seed dispersal’ is a word that does not imply the fate of the seed; ‘pollination’ relates to the fate of the pollen grain, and therefore the two words are not of parallel meaning. In like manner, seeds (the zygote contained within, are different individuals from the parents while pollen is much more like the parent. The following areas are discussed with respect to how seed and pollen movement compare: ability of parent plant to assess success; gene flow; dependency of animals on seeds, pollen and bait; disruption by animal loss; secondary movements; fate of most seeds and pollen; syndromes; selection for maximization of movement; exclusion of ‘unwanted’ animals; adjustments to the needs of the animals; seeds and pollen as contaminants; necessity of dispersal and outcrossing. We need much more knowledge of what actually is happening in nature with seed and pollen shadows, and improved ability to think like a plant.

65 citations


Journal ArticleDOI
TL;DR: It is confirmed that the mediterranean mussel occurs on the mainland coast of Japan, and investigation of some early Japanese literature suggests that mussels did not occur in this area earlier this century, and M. galloprovincialis may have been introduced to the region of Kobe, around 1930–1935.
Abstract: Mussels (Mytilus sp) from Sanriku Bay, NE Honshu, Japan were examined using morphological characters and electrophoretically detectable enzyme polymorphisms Using both sets of criteria, the mussels were identified as M galloprovincialis, the mediterranean mussel This confirms an earlier opinion, which was based on morphological criteria alone, that the mediterranean mussel occurs on the mainland coast of Japan Investigation of some early Japanese literature suggests that mussels did not occur in this area earlier this century, and M galloprovincialis may have been introduced to the region of Kobe, around 1930–1935 The present-day distribution of M edulis and M galloprovincialis in the Japanese archipelago may be explained by sea-surface temperatures in the region

62 citations


Journal ArticleDOI
TL;DR: Measurements on the skull and dentition of 159 specimens of 22 species of recent felid were analysed using multivariate statistical methods (principal components analysis and correspondence analysis).
Abstract: Measurements on the skull and dentition of 159 specimens of 22 species of recent felid were analysed using multivariate statistical methods (principal components analysis and correspondence analysis). The resulting patterns were considered in the light of recent work on the systematics of felids (large cats and small cats were clearly differentiated). Within each group there are subgroups. In the small cat group one subgroup was found to consist of the species Lynx lynx, L. rufus, L. pardina, L. canadensis and possibly Felis manul. Another subgroup consisted of the species F. bengalensis, F. rubiginosa, F. planiceps and F. viverrina. These two subgroups agree well with other work on felid systematics. Subgroups which do not agree so well with other work were also found, and the reasons for this are considered. Within the large cats there are two species, F. concolor and Neofelis nebulosa, which are clearly deviant from the norm. The reasons for this deviation are also considered.

50 citations



Journal ArticleDOI
TL;DR: The fossil molluscs complement information provided by the biology of extant fishes and invertebrates and emphasize the importance of these lakes in the study of evolution in living and extinct populations.
Abstract: The present-day faunas of the great African lakes present some of the world's best examples of ‘explosive speciation’. Lakes Victoria and Malawi each probably have several hundred endemic species of cichlid fishes. Much can be inferred about the evolution of these fishes from morphology, behaviour and intra-lacustrine distribution and from the fact that they include taxa ranging from local races, through sibling species, to forms that display extensive differentiation. The time taken to acquire specific distinctness can sometimes be accurately defined, but fossil lineages are unknown. A recent study of a fossil sequence of molluscs in the Turkana basin throws new light on the history of African lake faunas. It also claims to have resolved events during speciation. While critical analysis based on our knowledge of living molluscs in this area fails to substantiate this claim, the fossil molluscs complement information provided by the biology of extant fishes and invertebrates and emphasize the importance of these lakes in the study of evolution in living and extinct populations.

Journal ArticleDOI
TL;DR: It is postulated that the modern Nucella lapillus is a combination of several genetically distinct populations, some of which show the full range of variation and may respond to the selective effects of crabs and waves, and some ofWhich do not and show little variation.
Abstract: In Nucella lapillus there is usually a progressive gradation in mean shell shape from short squat individuals on exposed headlands to more elongated ones in shelter. This pattern has been attributed to the differential selective effects of wave action and crab predation, although it would almost certainly be an oversimplification to imagine these as the only significant forces involved, especially near the limits of the species' distribution. However, whilst this pattern of shell-shape variation with exposure is generally true over most of the animal's range in both Europe and North America, there are exceptions. There are occasional enclaves with much more elongated shells than would normally have been expected. Sometimes these are so abundant, as in the Severn Estuary, that all dog-whelk enclaves are unusually elongated, regardless of the exposure of their habitat. In other areas, such as south-eastern England, the Solway Firth and the area around the mouth of the Conway the shells are not unusually elongated, but the enclaves show very little variation: a normal sheltered-shore form is seen wherever the species occurs. Shetland samples appear to be a combination of this pattern (predominating) with the ‘normal’ one showing the full range of shellshape variation. Nucella appears in the Atlantic fossil record at the end of the Pliocene without any antecedent forms. It is assumed to have colonized from the Pacific and exploited the vacant niche before the onset of the Ice Age. Successive advances and retreats of the ice, with attendant changes in sea level, will have served to break up and recombine those dog-whelk populations that were not eliminated. It is postulated that the modern Nucella lapillus is a combination of several genetically distinct populations, some of which show the full range of variation and may respond to the selective effects of crabs and waves, and some of which do not and show little variation.

Journal ArticleDOI
TL;DR: A field experiment is reported in which differential survival of seeds and seedlings in response to fine-scale heterogeneity is tested as a possible mechanism of plant co-existence in species-rich plant communities.
Abstract: A field experiment is reported in which differential survival of seeds and seedlings in response to fine-scale heterogeneity is tested as a possible mechanism of plant co-existence in species-rich plant communities. Eight hundred seeds each of three pairs of congeneric species were sown into grassland micro-sites with variable amounts of leaf cover and their fate determined by weekly censuses over a three month period. Seeds of Leontodon spp. and Plantago spp. germinated significantly better in micro-sites with low leaf cover but difference between species in the same genus were not apparent. Differential seeding survival of two Centaurea species was observed and a transitory difference in seedling survival between Leontodon species in different micro-sites was also observed.

Journal ArticleDOI
John Turner1
TL;DR: Melpomene is used to suggest that two currently popular controversies are similarly futile: the allopatric and parapatric models of race formation are considered to be the extremes of what in nature is a continuum of populations showing varying degrees of partial isolation.
Abstract: The horns of a dilemma are usually on the same bull–Spanish proverb. A plague o' both your houses–Veronese imprecation. Although some hypotheses explain the world better than others, making ‘pluralism’ an untenable position, it is the case that scientists frequently set up as alternative hypotheses, one of which must be rejected, models which are merely compatible aspects of some other valid hypothesis that embraces them both. For example, Miillerian mimicry was once supposed to evolve either by a single large change or by gradual convergence (the assumption of gradualism is such that the second alternative has usually been regarded as correct). Yet our genetical research with Heliconius indicates that both processes take place, one after the other, when Miillerian mimicry evolves. A reconstruction of the most plausible route, through time and space, for the evolution of mimicry in Heliconius erato and H. melpomene is used to suggest that two currently popular controversies are similarly futile: the allopatric and parapatric models of race formation are considered to be the extremes of what in nature is a continuum of populations showing varying degrees of partial isolation (ecological change rather than stoppage of gene flow being the driving force in race formation); and it is shown that jerky evolution of the type now interpreted as evidence for ‘punctuated equilibria’ and ‘hopeful monsters’ can be produced by changes in the frequencies of major but ordinary gene mutations in response to changing ecological conditions, a phenomenon well accounted for in neo-Darwinian theory.

Journal ArticleDOI
TL;DR: Sedentary reef-organisms such as sponges, colonial coelenterates, bryozoans and compound ascidians produce repeated modules (aquiferous systems, polyps, zooids) as they grow to alleviate constraints on biomass imposed by mechanical and energetic factors that are functions of the surface area to volume ratio.
Abstract: Sedentary reef-organisms such as sponges, colonial coelenterates, bryozoans and compound ascidians produce repeated modules (aquiferous systems, polyps, zooids) as they grow. Modular construction alleviates constraints on biomass imposed by mechanical and energetic factors that are functions of the surface area to volume ratio. Colonies thus may grow large whilst preserving optimal modular dimensions. Among corals, optimal polyp size is smaller in the more autotrophic than in the more heterotrophic species. Modular construction allows flexibility of growth form, which can adapt to factors such as water currents, silting, light intensity and proximity of competitors. Modular colonies have great regenerative capacities, even separated fragments may survive and grow into new colonies. All fragments from a parental colony are genetically identical and large branching corals frequently undergo clonal propagation through fragmentation during storms. Soft corals can also fragment endogenously. By spreading the risk of mortality among independent units, the generation and dispersal of fragments lessens the likelihood of clonal extinction. In spite of their ability to propagate asexually, most benthic colonial animals also reproduce asexually. The selective advantages of the genetic diversity among sexually produced offspring seem not to be linked with dispersal, but probably lie in the biological interactions with competitors, predators and pathogens in the parental habitat. Age at first sexual maturity and the proportional investment of resources in sexual reproduction are related to colonial survivorship. Small branching corals on reef flats grow quickly, attain sexual maturity within 1–4 years, planulate extensively, but reach only small sizes before dying. Massive corals are longer lived and have the opposite characteristics of growth and reproduction. Most sessile reef organisms compete for space, food or light. Faster growers can potentially outcompete slower growers, but are often prevented from doing so by several forms of aggression from competitors and by the damage inflicted by storms. Competitive interactions among sedentary organisms on coral reefs are unlikely to be linear or deterministic, and so the co-existence of diverse species is possible.

Journal ArticleDOI
TL;DR: It is concluded that phenotype must play an important role in determining the behavioural responses of the snails to their environment.
Abstract: Two population cage experiments which examined the mortality and behaviour of artificial and natural morphs of the landsnail C. nemoralis (L.) are described. In the first experiment artificial ‘morphs’ were manufactured from one genetically homogeneous founder group of snails by painting the shells black or white. Differences in behaviour and mortality between these two ‘morphs’ were observed during the course of the experiment. Daylight and weather conditions were important in determining the activity patterns of the two types of snail. In the second experiment naturally occurring brown and yellow colour morphs were used. These exhibited very similar behaviour patterns to those of their artificial ‘mimics’ and it is concluded that phenotype must play an important role in determining the behavioural responses of the snails to their environment. Thermal relationships are suggested as causal factors for the differences between the experimental morphs.

Journal ArticleDOI
TL;DR: The majority of invertebrates so far studied are more efficient converters of absorbed food energy to gametes than they are, as adults, to somatic tissues, but the fact that the metabolic processes associated with gamete production are distinct from those associated with the production of somatic tissue has implications for the theory of life-cycle evolution.
Abstract: The majority of invertebrates so far studied are more efficient converters of absorbed food energy to gametes than they are, as adults, to somatic tissues. Indeed, reproductive conversion efficiencies sometimes better the best conversion efficiencies associated with somatic production (usually in juveniles). Depending on species, this is achieved either by an increase in absorption relative to respiratory losses, or a reduction in respiratory losses relative to absorption, or by supplementing the energy absorbed from the food with that obtained from somatic stores and tissues, or by a combination of these. The fact that the metabolic processes associated with gamete production are distinct from those associated with the production of somatic tissues has implications for the theory of life-cycle evolution.

Journal ArticleDOI
TL;DR: An extensive allozyme survey in populations of the alpine grasshopper Podisma pedestris shows that the chromosomal change is not correlated with gene frequency changes at any of the 21 loci studied, consistent with recently developed theory concerning the strength of the barrier to gene flow posed by a hybrid zone.
Abstract: We have made an extensive allozyme survey of 21 enzyme and protein loci in populations of the alpine grasshopper Podisma pedestris. This species occurs in two races, differing by a chromosomal fusion which separates the ancestral XO/XX race from a derived neo-XY race. These races also differ in DNA content, and hybrids between them have reduced viability. Electrophoresis reveals that the amount of genetic differentiation between these races is no greater than the variation among populations within each race. Both larger-scale surveys and a detailed survey of an area where the races hybridize, show that the chromosomal change is not correlated with gene frequency changes at any of the 21 loci studied. These findings are consistent with recently developed theory concerning the strength of the barrier to gene flow posed by a hybrid zone with characteristics such as those measured experimentally in Podisma. It is argued that hybrid zones in other species which involve allozymic differences do so because of stronger selection against hybrids rather than through mating isolation.

Journal ArticleDOI
TL;DR: Darwin's studies on barnacles, begun to satisfy his curiosity about specimens from the Beagle, but later extended to the large collections of other naturalists, lasted for 8 years and produced a set of definitive monographs, which had considerable influence on the development of his theories about natural selection.
Abstract: Darwin's studies on barnacles, begun to satisfy his curiosity about specimens from the Beagle, but later extended to the large collections of other naturalists, lasted for 8 years and produced a set of definitive monographs. Darwin was particularly troubled over the taxonomy of two groups of acorn barnacles, Balanus tintinnabulum and B. amphitrite, which he ultimately classified as clusters of wellmarked varieties. Recent studies, based on established taxonomic methods or on statistical treatment of morphometric data, suggest these are clusters of full species and that the ‘intermediate’ forms are just phenotypic variants. Darwin was also troubled by the small chthamalid intertidal barnacles, which he eventually grouped as varieties of a world-wide species, Chthamalus stellatur. Gel electrophoresis and morphometrics now show this to be a heterogenous assemblage of distinct species, some very different, others closer together, all with restricted geographical range, but all showing extreme variability in the characters normally used for classification. Darwin's difficulties with the classification of the highly varying barnacles, and his anatomical studies on these peculiar animals, must have had considerable influence on the development of his theories about natural selection, more than is usually acknowledged by writers on evolution. These ‘lost years’ were in fact a period of intense zoological enquiry, and Darwin's change in attitude with regard to species and variation in nature underwent a big change, as can be seen from the letters and from the differences between the early drafts written before the barnacle work and the later Natural Selection and The Origin. Whether we regard the difficult groups of Balanus as clusters of species or clusters of varieties, they still draw attention to evolutionary processes as in Darwin's day.

Journal ArticleDOI
TL;DR: Allozymic variation in proteins encoded by 29 loci was analysed electrophoretically in 364 adult specimens representing 12 populations and five species of the landsnail Sphincterochila in Israel along a north-south general transect of increasing aridity and suggests that climatic selection plays a conspicuous role in allozymics morphological differentiation into ecologically adaptive patterns.
Abstract: Allozymic variation in proteins encoded by 29 loci was analysed electrophoretically in 364 adult specimens representing 12 populations and five species of the landsnail Sphincterochila in Israel along a north-south general transect of increasing aridity. In addition, geographic variation in three morphological body variables of these snails was also studied. The results indicate that: (i) most loci (86%) are strongly polymorphic; (ii) most loci (65%) display fixation of alternative alleles either within or between species; (iii) most of the variant alleles (51%) are not widespread, and genie differentiation is very high (66%) between populations and species, indicating sharp local and regional geographic differentiation; (iv) clinal patterns are rare or nonexistent; (v) populations of Sphincterochila display average estimates of mean alleles per locus,A=1.53; polymorphism, P (5% criterion) = 0.31; heterozygosity, H=0.07; and genie diversity, He= 0.11; (vi) wide geographic variation within and between species is displayed in A= 1.18-2.07; P=0.11–0.61; H=0.02-0.15, and He = 0.042-0.22. Wright's fixation index, F, ranges from 0.03 to 0.65. (vii) Genie diversity, He, increases southwards with aridity from 0.051 to 0.145. (viii) A differential amount of variation in different functional classes of enzymes follows the Gillespie-Kojima hypothesis, (ix) Coefficients of genetic distance, D, between populations are high, D= 0.34, range 0.09-0.58, and between species, D= 0.27, range 0.12-0.40. D's within species may be higher than between species. Likewise, D's increase clinally southwards, (x) Deviations from Hardy-Weinberg equilibria were found in several loci in some populations and species, (xi) A statistically significant (P< 0.001) amount of morphological variation of body variables exists within and between species. Size between three species increases eastwards and southwards with aridity, (xii) P, H, He, and allozymic variation in several gene loci are significantly correlated with, and predictable by, climatic variables, primarily those related to the moisture index, (xiii) Allozymic and morphological variations are partly correlated, (xiv) Significant microgeographical climatic differentiation was found in three critical tests. The pattern of genetic variation within and between species suggests that: (a) climatic selection plays a conspicuous role in allozymic morphological differentiation into ecologically adaptive patterns; (b) the environmental variation model seems to be a good predictor of genetic variation in Sphincterochila; (c) adaptive radiation of the five species of Sphincterochila in Israel occurred during Pleistocene times in accord with climatic differentiation and apparently involved few changes of structural genes.

Journal ArticleDOI
TL;DR: There was a general tendency for the frequency of recapture to increase with increasing age in both morphs and Habitat selection resulting from different behaviour of different morphs of A. arbustorum is discussed.
Abstract: The behaviour of morphs of Arianta arbustorum has been investigated using a new technique involving a paint which fades in daylight. The technique was used to study the response of different morphs to exposure to sunlight at a homogeneous woodland habitat and a heterogeneous open habitat. The yellow morph showed a significantly higher rate of fading than the brown morph. A mark, release and recapture programme was used to analyse the association between frequencies of different morphs recaptured and not recaptured. In both habitats, there was a general tendency for the frequency of recapture to increase with increasing age in both morphs. Habitat selection resulting from different behaviour of different morphs of A. arbustorum is discussed. Morph frequencies can be related to habitat, the brown morphs of A. arbustorum are significantly less frequent in the open habitat. The behavioural responses of Cepaea hortensis, present with A. arbustorum in two other populations, to the exposure of sunshine were also studied. Climatic selection by solar energy associated with different morphs, species and habitat are also discussed.

Journal ArticleDOI
TL;DR: The level of compatibility of these populations is similar to that found when different populations of Lepidoptera species are crossed, and quite different from the incompatibility revealed by studies of interspecific hybridization.
Abstract: Spanish and Swedish populations of Helophorus lapponicus are shown on fossil evidence to have been isolated from one another for about 10 000 years, since the end of the Pleistocene. When cross-bred they show some evidence of heterosis in the F1, with reduced viability in the F2 and back-cross generations. The level of compatibility of these populations is similar to that found when different populations of Lepidoptera species are crossed, and quite different from the incompatibility revealed by studies of interspecific hybridization. The degree of evolutionary stability revealed is consistent with the apparent absence of evolution revealed by studies of Pleistocene fossil Coleoptera.

Journal ArticleDOI
TL;DR: Though Darwin did not include the dioecious parasitic group, the Rhizocephala, in his studies, he recognized the wide repertoire of sexual arrangements from hermaphroditism todioecy which now provides challenging material to the authors' further understanding of sex allocation, control and evolution.
Abstract: Darwin's magnificent study of the stalked, sessile and fossil barnacles, perhaps his greatest work, was started not many years after the systematic position of cirripedes within the class Crustacea had been accepted. It was completed at a time when histology and microtomy were not developed and when living specimens could only be seen on occasional visits to the seaside. Yet 130 years later it remains the standard text. It was on a visit to Tenby that he observed that barnacles were sensitive to vibration and, in seeking an acoustic organ, he mistakenly seized upon the oviducal gland. This led to an ever increasing series of misinterpretations of the female generative mechanism. Associated with this error was the belief that the ovary and cement glands were homologous in both cyprid and adult. He later confessed to “having blundered terribly over the cement glands”, but it was probably his search for examples of organs changing their function during evolution that led to this blunder. Similarly, he convinced himself mistakenly that the ovigerous fraena, which hold fast the egg masses to the mantle lining in stalked barnacles, became modified to gills in sessile barnacles. Darwin's interest in barnacle reproduction led to his discovery of complemental males attached to hermaphrodite individuals. He proved that they were dwarf cirripedes and not parasites. His knowledge that male and hermaphrodite flowers could co-exist helped him to accept that these apparently unnecessary beings could be present also in barnacles. We now know that complemental males are not confined to stalked barnacles but are also present in certain balanids. Though Darwin did not include the dioecious parasitic group, the Rhizocephala, in his studies, he recognized the wide repertoire of sexual arrangements from hermaphroditism to dioecy which now provides challenging material to our further understanding of sex allocation, control and evolution. Since Darwin dealt mainly with dried or preserved specimens he did not describe any of the details of the liberation of nauplii or the searching behaviour of the cyprid. Current investigators have shown that the former involves a prostaglandin which activates the embryos. Searching cyprids have been shown to be able to recognize their own and other species. Charles would have seen in this phenomenon a relevance both to survival and to the evolution of epizoic barnacles. Despite Charles' belief that his barnacle work would be “for ever unapplied” it has in fact been the foundation on which all studies of commercially important barnacle fouling have been based.

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TL;DR: Yellows are more active than browns at high humidities, but less active at low, and are likely to be behaviourally more responsive than Browns in an environment of fluctuating humidities.
Abstract: The noctural activities of the phenotypic shell colour morphy and age classes (adults and juveniles) of Arianta arbustorum were recorded 1 day week-1 for 4 weeks in several laboratory microclimatic conditions. Six constant temperatures between 3 and 18dC and four levels of relative humidities between 34 and 98% were maintained. A light regime of 16 h light: 8 h dark was used. There are highly significant differences in activity at different levels of adaptation temperature and relative humidity. The interaction between these factors is significant. There are no significant differences in nocturnal activity between the two phenotypic shell colours nor between the two age classes, but the interaction between morph and relative humidity is significant. The interaction between age classes and relative humidity is also significant. Yellows are more active than browns at high humidities, but less active at low. They are therefore likely to be behaviourally more responsive than browns in an environment of fluctuating humidities. This result is discussed in relation to the maintenance of the polymorphism.

Journal ArticleDOI
TL;DR: The ontogeny of migratory potential of male and female Drosophila subobscura has been quantified using tethered flight in the laboratory and there is an intervening peak in the potential of males, which may result from an increased rejection-rate by inseminated females.
Abstract: The ontogeny of migratory potential of male and female Drosophila subobscura has been quantified using tethered flight in the laboratory. In both sexes there is an increase in the few days immediately after eclosion, and a decline before the flies cease reproductive activity. There is an intervening peak in the potential of males, which may result from an increased rejection-rate by inseminated females. The migratory potential generally appears greater than that usually utilized in the field. Such extended migration extracts a significant cost from female flies in terms of reduced fecundity.

Journal ArticleDOI
TL;DR: In this paper, shell-shape variation in samples of the dog-whelk/dog-winkle, ucella lapillus, from the southern half of its North American range, between 41 and 46N, and compares it with the pattern seen in Europe.
Abstract: This paper considers shell-shape variation in samples of the dog-whelk/dog-winkle, ucella lapillus, from the southern half of its North American range, between 41 and 46N, and compares it with the pattern seen in Europe. At the extreme southern limit of its American range, to the south of Cape Cod, the species exhibits features to be expected in an animal close to an environmental limit. It is generally rare and has a patchy distribution. There is little variation in the shell: almost all adult individuals have rather large, thick, white, elongated shells. This contrasts sharply with the situation in Portugal, at the southern limit in Europe, where the animals have small thin, coloured shells of intermediate shape. Away from the marginal situation, north of Nahant (42CN) in America, the species shows much the same range of variability in shell size, shape and colour on both sides of the Atlantic. Most populations appear to show the same pattern of shape variation in asociation with the exposure of their habitat to wave action. Animals from exposed sites tend to have shorter, squatter shells than their compatriots in shelter. However, in America as in some parts of Europe, there are occasional enclaves which do not fit the usual pattern. It is interesting to note that the form normally associated with extremely exposed shores from Brittany to Faroe in Europe is found in Atlantic Canada but is apparently absent from southern populations in both the U.S.A and the Iberian Peninsula.

Journal ArticleDOI
TL;DR: No entirely satisfactory explanation has yet been given for the persistence of all-female broods in the Xymphalid butterfly Hypolimnas bolina, and the status of H, bolina as a mimic of species of Euploea is less assured as the result of the survey.
Abstract: In the Xymphalid butterfly Hypolimnas bolina (L.) H. W. Simmonds in 1921 demonstrated, by breeding experiments, the occurrence on the islands of West Fiji of all-female broods, and he compared their frequency with that of normal bisexual broods in the same localities. In two areas he found only unisexual families (14 of them in Suva and one on Vanua Levuj, in one island (Ovalau) only a single bisexual brood and in the other two islands, Taveuni and Kandavu, one bisexual and one of each type respectively. Nearly 60 years, and probably at least 150 generations later, we found that all-female broods were still present in four of the five islands re-investigated, and breeding showed that in these four (which included Suva) the proportion of the two types of female was approximately equal. In the fifth island only a bisexual family was bred. The only marked change between 1921 and 1980 was in the Suva area, where Simmonds found far more unisexual females than we did. By carrying out spermatophore counts in many of our wild females we found that almost all of them had been mated, the majority of them on one occasion only. Though the data are scanty, they suggest that there is no wastage of females and that the population in 1980 was stable for the two types of brood. Reasons for our findings are discussed, particularly in the light of the Heuch model, but we conclude that no entirely satisfactory explanation has yet been given for the persistence of all-female broods. Again, there is so far no explanation of the mechanism though we favour a cytoplasmic factor. We feel that the status of H, bolina as a mimic of species of Euploea is less assured as the result of our survey.

Journal ArticleDOI
TL;DR: The visible polymorphism of the spittlebug, Philaenus spumarius, has been investigated in the vicinity of a smokeless fuel factory in the Cynon Valley of south Wales and it is suggested that this relationship is due to the selective effects of the local air pollution from the factory.
Abstract: The visible polymorphism of the spittlebug, Philaenus spumarius, has been investigated in the vicinity of a smokeless fuel factory in the Cynon Valley of south Wales. The factory is a significant source of local particulate air pollution. A striking relationship exists between the combined frequencies of the eight dark (melanic) morphs and proximity to the factory. Maximum melanic phenotype frequencies of over 95“, occur in both sexes immediately adjacent to it and decline to levels normal for south Wales 1.5–6 km away, depending on direction. This relationship is largely confined to sites within the valley; samples from adjacent localities outside it have melanic frequencies within normal limits for the south Wales area. Maximum melanic phenotype frequencies in the Cynon Valley are far higher than any known from elsewhere in the species range in Europe, Asia and North America. No consistent difference is apparent in total melanic frequency between males and females at any of the sites in this study. However, marked differences exist between the sexes in the relative contributions of the eight melanic phenotypes to the overall association with the factory. For females the industrial melanism is entirely attributable to the group flanicollis + gibbus + leucocephalus (mainly leucocephalus) whereas in males both this group and the group quadnmaculatus + albomaculatus + leucopthalmus contribute to the relationship. It is suggested that this relationship is due to the selective effects of the local air pollution from the factory. The exact nature of the selection involved is as yet uncertain; it would appear to be strong since the local adaptation involved has developed in a maximum of 40 generations since the factory was opened. Finally, comparison is made with two other insects, a ladybird and a moth, in which high frequencies of melanic forms are also associated with this pollution source.

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TL;DR: It is suggested that the presence of patrolling males is related to the higher nest density of the one population, and the fact that patrolling males tend to be relatively large is possibly related to flight energetics or simply to the ability of large males to seize females, which are usually larger than males, in mid-air.
Abstract: A study of the mating behaviour of males of the beewolf Philanthus zebratus revealed that in one population males display variability in mating tactics and that this variability is related to male body size. There was a tendency for large males to patrol the airspace above the nesting area while smaller males were territorial adjacent to it. The mean sizes of the two groups of males were significantly different, although the size ranges of the two groups overlapped. Only 2.5% of the males were observed to undertake both mating tactics, at different times. Observations are presented on daily and seasonal activity patterns and on the relative location of nests, territories, and patrolling males. A second population, with lower nest density, was observed for several days, revealing only territorial males. It is suggested that the presence of patrolling males is related to the higher nest density of the one population. The fact that patrolling males tend to be relatively large is possibly related to flight energetics or simply to the ability of large males to seize females, which are usually larger than males, in mid-air.