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We used extensive atlas and census data to assess trends in the distribution and population levels of birds on lowland farmland in Britain between the late 1960s and early 1990s. Many species of farmland birds have become less widespread or have declined in numbers, or both, but few have become more widespread or have increased. Of the 28 species classified as farmland birds the distributions of 24 contracted between 1970 and 1990. Of the 18 farmland species for which it was possible to assess population change, 15 were less abundant in 1990 than in 1970. Seven of the species were estimated to have undergone population decreases of at least 50%. Farmland species showing the largest population declines tended also to show substantial range contractions. Farmland species underwent an appreciably larger contraction of distribution than species associated with any other habitat. Furthermore, farmland species tended to decrease in abundance, whereas woodland species tended to increase. Population declines among farmland birds became evident in the mid- to late 1970s, a period when several fundamental changes were taking place in British agricultural practices. These included a great reduction in the spring sowing of cereals, a simplification of crop rotations, increased use of chemical pesticides and inorganic fertilizers, and more-intensive grassland management. We suggest that the declines of farmland bird species have been caused or aggravated by this pervasive intensification of agriculture. Existing research on declining farmland birds, however, indicates that there is no single mechanism underlying the population changes. We identify priorities for research, focusing mainly on relationships between bird populations and agricultural practices, but we also recognize a need for a better understanding of the role of predation.

Considerable effort has been spent documenting correlations between dioecy and various ecological and morphological traits for the purpose of testing hypotheses about conditions that favor dioecy. The data analyzed in these studies with few exceptions, come from local floras, within which it was possible to contrast the subsets of dioecious and nondioecious taxa with regard to the traits in question. However, if there is a strong phylogenetic component to the presence or absence of dioecy, regional sampling may result in spurious associations. Here, we report results of a categorical multivariate analysis of the strengths of various associations of dioecy with other traits over all flowering plants. Families were scored for presence of absence of monoecy or dioecy, systematic position, numbers of species and genera, growth forms, modes of and dispersal, geographic distribution, and trophic status. Seven percent of angiosperm genera (959 of 13,500) contain at least some dioecious species, and approximately 6% of angiosperm species (14,620 of 240,000) are dioecious. The most consistent associations in the data set relate the presence of dioecy to monoecy, wind or water pollination, and climbing growth. At both the family and the genus level, insect pollination is under represented among dioecious plants. At the family level, a positive correlation between dioecy and woody growth results primarily from the association between dioecy and climbing growth (whether woody or herbaceous) because neither the tree nor the shrub growth forms alone are consistently correlated with a family's tendency to include dioecious members. Dioecy appears to have evolved most frequently via monoecy, perhaps through divergent adjustments of floral sex ratios between individual plants. Monoecy itself is related to abiotic pollination and climbing growth as revealed by multivariate analysis

The global distribution of 22 potentially harmful organochlorine compounds was investigated in more than 200 tree bark samples from 90 sites worldwide. High concentrations of organochlorines were found not only in some developing countries but also in industrialized countries, which continue to be highly contaminated even though the use of many of these compounds is restricted. The distribution of relatively volatile organochlorine compounds (such as hexachlorobenzene) is dependent on latitude and demonstrates the global distillation effect, whereas less volatile organochlorine compounds (such as endosulfan) are not as effectively distilled and tend to remain in the region of use

In April and May 1979, an unusual anthrax epidemic occurred in Sverdlovsk, Union of Soviet Socialist Republics. Soviet officials attributed it to consumption of contaminated meat. U.S. agencies attributed it to inhalation of spores accidentally released at a military microbiology facility in the city. Epidemiological data show that most victims worked or lived in a narrow zone extending from the military facility to the southern city limit. Farther south, livestock died of anthrax along the zone's extended axis. The zone paralleled the northerly wind that prevailed shortly before the outbreak. It is concluded that the escape of an aerosol of anthrax pathogen at the military facility caused the outbreak

Species distribution patterns within naturally fragmented habitat have been found to often exhibit patterns of pronounced nestedness. Highly predictable extinction sequences are implied by these nested species distribution patterns, thus the patterns are important to both the philosophy and practice of conservation biology. A simple thermodynamic measure of the order and disorder apparent in the nested patterns is described. The metric offers (i) a measure of the uncertainty in species extinction order, (ii) a measure of relative populational stabilities, (iii) a means of identifying minimally sustainable population sizes, and (iv) an estimate of the historical coherence of the species assemblage. Four presumptions govern the development of the metric and its theory: (i) the fragmented habitat was once whole and originally populated by a single common source biota, (ii) the islands were initially uniform in their habitat heterogeneity and type mix, and have remained so throughout their post-fragmentation history, (iii) no significant clinal (latitudinal) gradation exists across the archipelago so as to promote species turnover across the archipelago, and (iv) all species of interest are equally isolated on all islands. The violation of these conditions promotes species distributions which are idiosyncratic to the general extinction order expected in fragmentation archipelagos. While some random variation in extinction order is to be expected, idiosyncratic distributional patterns differ from randomness and are readily segregatable from such noise. A method of identifying idiosyncratic species and sites is described.

The remarkable features of quaking aspen, including its broad geographic and environmental range, life history, asexual reproduction, patterns of sex ratio, genetic variation and growth rate, are discussed.

We describe an extensive metapopulation study on the Glanville fritillary Melitaea cinxia, in a network of 1502 discrete habitat patches, comprising the entire distribution of this butterfly species in Finland. A thorough survey of the easily detected larval groups revealed a local population in 536 patches (dry meadows). We demonstrate that this system satisfies the four necessary conditions for a species to persist in a balance between stochastic local extinctions and recolonizations. Patterns of patch occupancy support several qualitative and quantitative model predictions. With decreasing regional density and average area of habitat patches, the butterfly occurs in a diminishing fraction of suitable habitat. To our knowledge, this is the first conclusive demonstration, based on a comparison of many conspecific metapopulations, of declining habitat occupancy and hence of increasing threat to survival caused by increasing habitat fragmentation.

More than 300 isolates of the Irish potato famine fungus, Phytophthora infestans, collected in 20 countries on five continents, were analyzed for genetic variation at the mating type and two allozyme loci. A subset of more than 200 isolates was also analyzed for DNA \"fingerprint\" variation. A surprising result was that a single clonal lineage dominated most populations worldwide. All of the variation within this lineage appeared to have arisen by mitotic recombination or by mutation. In addition to the most common clonal lineage, a number of different, but apparently closely related, lineages occurred in the United States and Canada. The low levels of gene diversity in the derived populations compared to the presumed ancestral population in central Mexico indicate that P. infestans went through extreme genetic bottlenecks during its dispersal. The genetic data are consistent with the hypothesis that the initial migration of P. infestans in the 1840s was from Mexico to the United States and that only a single genetic individual was transported to Europe and subsequently to the rest of the world. If this hypothesis is correct, then the Irish potato famine was caused by a single clonal genotype of P. infestans.

A review of recent studies published over a 23-year timespan (1990–2012) showed rapidly increasing interest in exploring how environmental contaminants and parasitism might influence each other and (or) interact to affect host health. Those experimental and observational studies fall into three broad categories (comparative studies of the possible influence of each factor on the other, correlative studies between contaminants and parasitism, and studies on relative bioaccumulation of contaminants by parasites versus their hosts). Despite the exponential increase in relevant studies, little attention has been paid to how contaminants and parasitism should co-occur among individuals within host populations and (or) how the nature of co-distributions should be incorporated into study designs and analyses. Null expectations of co-distributions between contaminants and parasitism can be derived from underlying distributions of each factor. Using a subset of studies, we found contaminant distributions showed positive skew in about one third of cases testing for correlations between contaminant concentrations and parasitism among hosts. We show such skew is expected for theoretical reasons. We used this information to guide simulations wherein the oft-cited negative binomial distribution of parasitism (also supported by theory) was combined with both log-normal (skewed) and normal distributions of contaminants to generate expected null co-distributions. Simulations demonstrated an increasingly concave (or L-shaped) co-distribution with increasing contaminant positive skew: proportionately more individuals experience low levels of each factor while few to none experienced high contaminant and high parasite burdens simultaneously. Our results have the following implications: they call into question experimental studies exposing specimens to parasites and pollutants at levels higher than, or even equal to, observed averages, and they provide a framework for exploring how individual-based effects might scale up into effects at the population level. Potential improvements to study designs and (or) statistical tests are offered that recognize the need to understand the underlying distributions of both contaminants and parasitism and the degree to which one can infer host population effects.

Sexual size dimorphism (SSD) typically increases with body size (hyperallometry) in taxa in which males are the larger sex and decreases with body size (hypoallometry) in taxa in which females are larger. We demonstrate the commonality of these trends, both of which indicate greater evolutionary divergence in male size than in female size and strong covariation between the sexes. We postulate that both of these components of allometry evolve in response to sexual selection on male size coupled with genetic correlations for size between males and females, and we argue that this hypothesis can be generalized to taxa in which females are the larger sex. For such taxa, we predict hypoallometry for SSD, sexual selection on male size, and a correlation between the intensity of sexual selection and male size. An analysis of total length in 31 populations of the water strider, Aquarius remigis, demonstrates significant hypoallometry for SSD. Comparisons of mating and single males within 12 populations reveal significant positive univariate or multivariate selection gradients in nine populations and a significant correlation between the intensity of sexual selection and mean male size, when environmentally based variation in mean size among sites is removed. These results provide the first quantitative evidence that allometry for SSD may evolve in response to sexual selection favoring large males, even in taxa in which females are the larger sex.