Predicting origins of passerines migrating through Canadian migration monitoring stations using stable-hydrogen isotope analyses of feathers: a new tool for bird conservation

The Canadian Migration Monitoring Network (CMMN) consists of standardized observation and migration count stations located largely along Canada’s southern border. A major purpose of CMMN is to detect population trends of migratory passerines that breed primarily in the boreal forest and are otherwise poorly monitored by the North American Breeding Bird Survey (BBS). A primary limitation of this approach to monitoring is that it is currently not clear which geographic regions of the boreal forest are represented by the trends generated for each bird species at each station or group of stations. Such information on “catchment areas” for CMMN will greatly enhance their value in contributing to understanding causes of population trends, as well as facilitating joint trend analysis for stations with similar catchments. It is now well established that naturally occurring concentrations of deuterium in feathers grown in North America can provide information on their approximate geographic origins, especially latitude. We used stable hydrogen isotope analyses of feathers (δ²Hf) from 15 species intercepted at 22 CMMN stations to assign approximate origins to populations moving through stations or groups of stations. We further constrained the potential catchment areas using prior information on potential longitudinal origins based upon bird migration trajectories predicted from band recovery data and known breeding distributions. We detected several cases of differences in catchment area of species passing through sites, and between seasons within species. We discuss the importance of our findings, and future directions for using this approach to assist conservation of migratory birds at continental scales.

Comparison of subcellular partitioning, distribution, and internal speciation of Cu between Cu-tolerant and naive populations of Dendrodrilus rubidus Savigny

When considering contaminated site ecology and ecological risk assessment a key question is whether organisms that appear unaffected by accumulation of contaminants are tolerant or resistant to those contaminants. A population of Dendrodrilus rubidus Savigny earthworms from the Coniston Copper Mines, an area of former Cu mining, exhibit increased tolerance and accumulation of Cu relative to a nearby non-Cu exposed population. Distribution of total Cu between different body parts (posterior, anterior, body wall) of the two populations was determined after a 14 day exposure to 250 mg Cu kg(-1) in Cu-amended soil. Cu concentrations were greater in Coniston earthworms but relative proportions of Cu in different body parts were the same between populations. Cu speciation was determined using extended X-ray absorption fine structure spectroscopy (EXAFS). Cu was coordinated to 0 atoms in the exposure soil but to S atoms in the earthworms. There was no difference in this speciation between the different earthworm populations. In another experiment earthworms were exposed to a range of Cu concentrations (200-700 mg Cu kg(-1)). Subcellular partitioning of accumulated Cu was determined. Coniston earthworms accumulated more Cu but relative proportions of Cu in the different fractions (cytosol > granular > tissue fragments, cell membranes, and intact cells) were the same between populations. Results suggest that Coniston D. rubidus are able to survive in the Cu-rich Coniston Copper Mines soil through enlargement of the same Cu storage reservoirs that exist in a nearby non-Cu exposed population.

Young caregivers in the context of the HIV/AIDS pandemic in sub-Saharan Africa

Against a background of rising adult mortality and morbidity in the context of the HIV/AIDS pandemic in sub-Saharan Africa, this paper provides both quantitative and qualitative evidence for the existence of a largely neglected group of young people with increased responsibility for caregiving. Using questionnaire surveys, focus groups, storyboards and in-depth interviews in three studies across Southern and Eastern Africa some young people in Lesotho, Tanzania and Zimbabwe are found to devote considerable time and energy to caring for sick members of their households. Examination of the tasks carried out by these youngsters finds them to be burdened beyond usual familial and societal expectations of children's 'normal' contributions to the reproduction of households via domestic chores and suchlike. It is concluded that these young people can be described as 'young carers'. The three studies are presented to illuminate different sociospatial aspects of caregiving by young people. First, using qualitative data from Lesotho the range of caring tasks young caregivers; perform for care recipients - usually a grandmother, parent, or sibling - is identified. Second, the impact caregiving responsibilities have on children's primary school attendance is examined using survey data from Tanzania. Third, the wider negative and positive impacts of caregiving including loss of friends and gaining of emotional maturity for young carers and their households is explored with in-depth individual interviews from Zimbabwe. Finally, suggestions are made for further research to deepen understanding of the geographies of caring within the context of the population geographies of the HIV/AIDS pandemic in sub-Saharan Africa and beyond. Copyright (c) 2006 John Wiley & Sons, Ltd.

Phylogeographic analysis of the chloroplast DNA variation in wild common bean (Phaseolus vulgaris L.) in the Americas

The wild common bean (Phaseolus vulgaris) is widely but discontinuously distributed from northern Mexico to northern Argentina on both sides of the Isthmus of Panama. Little is known on how the species has reached its current disjunct distribution. In this research, chloroplast DNA polymorphisms in seven non-coding regions were used to study the history of migration of wild P. vulgaris between Mesoamerica and South America. A penalized likelihood analysis was applied to previously published Leguminosae ITS data to estimate divergence times between P. vulgaris and its sister taxa from Mesoamerica, and divergence times of populations within P. vulgaris. Fourteen chloroplast haplotypes were identified by PCR-RFLP and their geographical associations were studied by means of a Nested Clade Analysis and Mantel Tests. The results suggest that the haplotypes are not randomly distributed but occupy discrete parts of the geographic range of the species. The current distribution of haplotypes may be explained by isolation by distance and by at least two migration events between Mesoamerica and South America: one from Mesoamerica to South America and another one from northern South America to Mesoamerica. Age estimates place the divergence of P. vulgaris from its sister taxa from Mesoamerica at or before 1.3 Ma, and divergence of populations from Ecuador-northern Peru at or before 0.6 Ma. As these ages are taken as minimum divergence times, the influence of past events, such as the closure of the Isthmus of Panama and the final uplift of the Andes, on the migration history and population structure of this species cannot be disregarded.

Biodiversity of Collembola in urban soils and the use of Folsomia candida to assess soil 'quality'

The effects of metal contamination on natural populations of Collembola in soils from five sites in the Wolverhampton area ( West Midlands, England) were examined. Analysis revealed that metal concentrations were elevated above background levels at all sites. One location in particular (Ladymoor, a former smelting site) was highly contaminated with Cd, Cu, Pb and Zn at more than 20 times background levels. Biodiversity indices ( Shannon - Weiner, Simpson index, Margalef index, alpha index, species richness, Shaneven ( evenness) and Berger - Parker dominance) were calculated. Of these indices, estimates of species richness and evenness were most effective at highlighting the differences between the Collembola communities. Indeed, the highest number of species were found at the most contaminated site, although the Collembola population also had a comparatively low evenness value, with just two species dominating. The number of individuals per species were allocated into geometric classes and plotted against the cumulative number of species as a percentage. At Ladymoor, there were more geometric classes, and the slope of the line was shallower than at the other four sites. This characteristic is a feature of polluted sites, where a few species are dominant and most species are rare. The Ladymoor soil also had a dominance of Isotomurus palustris, and was the only site in which Ceratophysella denticulata was found. Previous studies have shown that these two species are often found in sites subject to high metal contamination. Survival and reproduction of the "standard'' test springtail, Folsomia candida (Willem), were determined in a 4 week exposure test to soils from all five sites. Mortality was significantly increased in adults and reproduction significantly lower in the Ladymoor soil in comparison to the other four sites. This study has shown that severe metal contamination can be related to the population structure of Collembola in the field, and performance of F. candida ( in soils from such sites) in the laboratory.

Reproductive conflict delays the recovery of an endangered social species

Evolutionary theory predicts that individuals, in order to increase their relative fitness, can evolve behaviours that are detrimental for the group or population. This mismatch is particularly visible in social organisms. Despite its potential to affect the population dynamics of social animals, this principle has not yet been applied to real-life conservation. Social group structure has been argued to stabilize population dynamics due to the buffering effects of nonreproducing subordinates. However, competition for breeding positions in such species can also interfere with the reproduction of breeding pairs. Seychelles magpie robins, Copsychus sechellarum, live in social groups where subordinate individuals do not breed. Analysis of long-term individual-based data and short-term behavioural observations show that subordinates increase the territorial takeover frequency of established breeders. Such takeovers delay offspring production and decrease territory productivity. Individual-based simulations of the Seychelles magpie robin population parameterized with the long-term data show that this process has significantly postponed the recovery of the species from the Critically Endangered status. Social conflict thus can extend the period of high extinction risk, which we show to have population consequences that should be taken into account in management programmes. This is the first quantitative assessment of the effects of social conflict on conservation.

Aggregation of parasitism risk in an aphid-parasitoid system: Effects of plant patch size and aphid density

Few studies have linked density dependence of parasitism and the tritrophic environment within which a parasitoid forages. In the non-crop plant-aphid, Centaurea nigra-Uroleucon jaceae system, mixed patterns of density-dependent parasitism by the parasitoids Aphidius funebris and Trioxys centaureae were observed in a survey of a natural population. Breakdown of density-dependent parasitism revealed that density dependence was inverse in smaller colonies but direct in large colonies (>20 aphids), suggesting there is a threshold effect in parasitoid response to aphid density. The CV2 of searching parasitoids was estimated from parasitism data using a hierarchical generalized linear model, and CV2>1 for A. funebris between plant patches, while for T. centaureae CV2>1 within plant patches. In both cases, density independent heterogeneity was more important than density-dependent heterogeneity in parasitism. Parasitism by T. centaureae increased with increasing plant patch size. Manipulation of aphid colony size and plant patch size revealed that parasitism by A. funebris was directly density dependent at the range of colony sizes tested (50-200 initial aphids), and had a strong positive relationship with plant patch size. The effects of plant patch size detected for both species indicate that the tritrophic environment provides a source of host density independent heterogeneity in parasitism, and can modify density-dependent responses. (c) 2007 Gessellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.

Predation of Bradysia sp (Diptera: Sciaridae), Liriomyza trifolii (Diptera: Agromyzidae) and Bemisia tabaci (Hemiptera: Aleyrodidae) by Coenosia attenuata (Diptera: Muscidae) in greenhouse crops

We studied the predation behaviour of the "hunter fly" (Coenosia attenuata Stein) in the laboratory and greenhouse. In the laboratory, which was conducted at 25 degrees C at 60-80% RH, with a 16L : 8D photoperiod, we examined the functional response of this species to three different pests, namely the sciarid fly (Bradysia sp.), the tobacco whitefly (Bemisia tabaci) and the leaf miner Liriomyza trifolii. In the greenhouse, we studied the population dynamics of the predator and its prey on pepper and water melon crops grown in southern Spain. Adult hunter flies were found to exhibit a type I functional response to adult sciarid flies and whiteflies, but a type II response to adult leaf miners. The type II response was a result of the greater difficulty in capturing and handling leaf miners compared to the other two species. The dynamics of the predator-prey interaction in the greenhouse revealed that the predator specializes mainly on adult sciarids and that the presence of the other prey can be supplemental, but is never essential for survival of the predator; this, however, is crop-dependent. The results oil the dynamics of the predator-prey systems were obtained through a known population dynamics model with modifications.

The importance of temperature and moisture to the egg-laying behaviour of a pest slug, Deroceras reticulatum

Oviposition behaviour is important when modelling the population dynamics of many invertebrates. The numbers of eggs laid are frequently used to describe fecundity, but this measure may differ significantly from realised fecundity. Oviposition has been shown to be important when describing the dynamics of slug populations, which are important agricultural pests. The numbers of eggs laid by Deroceras reticulatum and their viability were measured across a range of 16 temperature (4, 10, 15 and 23 degrees C) by moisture (33%, 42%, 53% and 58% by dry soil weight) experimental combinations. A fitted quadratic response surface model was used to estimate how D. reticulatum adjusted its egg laying to the surrounding temperature and moisture conditions, with most eggs being laid at a combination of 53% soil moisture and 18 degrees C. The number and proportion of viable eggs also covaried with temperature and moisture, suggesting that D. reticulatum may alter their investment in reproduction to maximise their fitness. We have shown that the number of viable eggs differs from the total number of eggs laid by D. reticulatum. Changes in egg viability with temperature and moisture may also be seen in other species and should be considered when modelling populations of egg-laying invertebrates.

Biodiversity of Collembola in urban soils and the use of Folsomia candida to assess soil 'quality'

The effects of metal contamination on natural populations of Collembola in soils from five sites in the Wolverhampton area ( West Midlands, England) were examined. Analysis revealed that metal concentrations were elevated above background levels at all sites. One location in particular (Ladymoor, a former smelting site) was highly contaminated with Cd, Cu, Pb and Zn at more than 20 times background levels. Biodiversity indices ( Shannon - Weiner, Simpson index, Margalef index, alpha index, species richness, Shaneven ( evenness) and Berger - Parker dominance) were calculated. Of these indices, estimates of species richness and evenness were most effective at highlighting the differences between the Collembola communities. Indeed, the highest number of species were found at the most contaminated site, although the Collembola population also had a comparatively low evenness value, with just two species dominating. The number of individuals per species were allocated into geometric classes and plotted against the cumulative number of species as a percentage. At Ladymoor, there were more geometric classes, and the slope of the line was shallower than at the other four sites. This characteristic is a feature of polluted sites, where a few species are dominant and most species are rare. The Ladymoor soil also had a dominance of Isotomurus palustris, and was the only site in which Ceratophysella denticulata was found. Previous studies have shown that these two species are often found in sites subject to high metal contamination. Survival and reproduction of the "standard'' test springtail, Folsomia candida (Willem), were determined in a 4 week exposure test to soils from all five sites. Mortality was significantly increased in adults and reproduction significantly lower in the Ladymoor soil in comparison to the other four sites. This study has shown that severe metal contamination can be related to the population structure of Collembola in the field, and performance of F. candida ( in soils from such sites) in the laboratory.

Conserving marginal populations of the foodplant (Impatiens noli-tangere) of an endangered moth (Eustroma reticulatum) in a changing climate

Impatiens noli-tangere is scarce in the UK and probably only native to the Lake District and Wales. It is the sole food plant for the endangered moth Eustroma reticulattum. Significant annual fluctuations in the size of I. noli-tangere populations endanger the continued presence of E. reticulatum in the UK. In this study, variation in population size was monitored across native populations of L noli-tangere in the English Lake District and Wales. In 1998, there was a crash in the population size of all metapopulations in the Lake District but not of those found in Wales. A molecular survey of the genetic affinities of samples in 1999 from both regions and a reference population from Switzerland was performed using AFLP and ISSR analyses. The consensus UPGMA dendrogram and a PCO scatter plot revealed clear differentiation between the populations of L noli-tangere in Wales and those in the Lake District. Most of the genetic variation in the UK (H-T= 0.064) was partitioned between (G(ST) = 0.455) rather than within (H-S = 0.034) regions, inferring little gene flow occurs between regions. There was similar bias towards differentiation between metapopulations in Wales, again consistent with low levels of interpopulation gene flow. This contrasts with far lower levels of differentiation in the Lake District which suggests modest rates of gene flow may occur between populations. It is concluded that in the event of local extinction of sites or populations, reintroductions should be restricted to samples collected from the same region. We then surveyed climatic variables to identify those most likely to cause local extinctions. Climatic correlates of population size were sought from two Lake District metapopulations situated close to a meteorological station. A combination of three climatic variables common to both sites explained 81-84% of the variation in plant number between 1990 and 2001. Projected trends for these climatic variables were used in a Monte Carlo simulation which suggested an increased risk of I. noli-tangere population crashes by 2050 at Coniston Water. but not at Derwentwater. Implications of these findings for practical conservation strategies are explored. (C) 2003 Elsevier Ltd. All rights reserved.

Dynamics and foraging behaviour of adult hornet robberflies, Asilus crabroniformis: implications for conservation strategy

Mark resighting studies of the hornet robberfly, Asilus crabroniformis, were carried out during the flight seasons of 1999 and 2000 on agricultural land on the Chilterns in Oxfordshire, UK. Six patches of land were identified which contained characteristics thought to be attractive to hornet robberflies. One hundred and twenty eight adults were marked in 1999 and 257 in 2000. Marking was carried out on one of the patches, but resighting observations were collected from all six sites. The daily population sizes were estimated using the Jolly-Seber method. The daily population size peaked between 50 and 72 from 23 August until 13 September in 2000. This was very similar to the peak population size of between 50 and 74 estimated for 1999. Adults were found to be capable of living for nearly 5 weeks. The maximum linear distance from the point of marking that any individual moved across the study site was 625 m, but some individuals moved over 400 m in a single day. Unsuitable habitat (suburban gardens and a main road) did not present a barrier to dispersal. Males were more likely than females to loiter in sites peripheral to the breeding site, whilst females seemed to be more tied to the breeding site. Most adults were caught from dung piles, but insects avoided fresh dung and preferred instead dung that was well into the process of drying out. A variety of insect species were taken as prey, including many beetles and flies. The findings of the study are discussed in relation to the management of the landscape to enhance the long-term prospects of the hornet robberfly in the UK, and to achieve the UK Biodiversity Action Plan target for this species.

Modulation of anti-pathogenic activity in canine-derived Lactobacillus species by carbohydrate growth substrate

Aims: To investigate the effect of various carbon sources on the production of extracellular antagonistic compounds against two Escherichia coli strains and Salmonella enterica serotype Typhimurium by three canine-derived lactobacilli strains. Methods and Materials: Cell-free preparations, pH neutralized, were used in antibiotic disc experiments as an initial screening. The bacteria/carbohydrate combinations that showed inhibition of the growth of those pathogens, were further investigated in batch co-culture experiments. The cell-free supernatants of the cultures, that decreased the population number of the pathogens in the co-culture experiments to log CFU ml(-1) less than or equal to 4, were tested for inhibition of the pathogens in pure cultures at neutral and acidic pH. Conclusions: The results showed that the substrate seems to affect the production of antimicrobial compounds and this effect could not just be ascribed to the ability of the bacteria to grow in the various carbon sources. L. mucosae, L. acidophilus and L. reuteri, when grown in sugar mixtures consisting of alpha-glucosides (Degree of Polymerization (DP) 1-4) could produce antimicrobial compounds active against all three pathogens in vitro. This effect could not be attributed to a single ingredient of those sugar mixtures and was synergistic. This inhibition had a dose-response characteristic and was more active at acidic pH. Significance and Impact of the Study: Knowledge of the effect that the carbon source has on the production of antimicrobial compounds by gut-associated lactobacilli allows the rational design of prebiotic/probiotic combinations to combat gastrointestinal pathogens.

Pseudogene rescue: an adaptive mechanism of codon reassignment

Alterations to the genetic code – codon reassignments – have occurred many times in life’s history, despite the fact that genomes are coadapted to their genetic codes and therefore alterations are likely to be maladaptive. A potential mechanism for adaptive codon reassignment, which could trigger either a temporary period of codon ambiguity or a permanent genetic code change, is the reactivation of a pseudogene by a nonsense suppressor mutant transfer RNA. I examine the population genetics of each stage of this process and find that pseudogene rescue is plausible and also readily explains some features of extant variability in genetic codes.

Resource availability and the persistence of seed-eating bird populations in agricultural landscapes – a mechanistic modelling approach

1. Reductions in resource availability, associated with land-use change and agricultural intensification in the UK and Europe, have been linked with the widespread decline of many farmland bird species over recent decades. However, the underlying ecological processes which link resource availability and population trends are poorly understood. 2. We construct a spatial depletion model to investigate the relationship between the population persistence of granivorous birds within the agricultural landscape and the temporal dynamics of stubble field availability, an important source of winter food for many of those species. 3. The model is capable of accurately predicting the distribution of a given number of finches and buntings amongst patches of different stubble types in an agricultural landscape over the course of a winter and assessing the relative value of different landscapes in terms of resource availability. 4. Sensitivity analyses showed that the model is relatively robust to estimates of energetic requirements, search efficiency and handling time but that daily seed survival estimates have a strong influence on model fit. Understanding resource dynamics in agricultural landscapes is highlighted as a key area for further research. 5. There was a positive relationship between the predicted number of bird days supported by a landscape over-winter and the breeding population trend for yellowhammer Emberiza citrinella, a species for which survival has been identified as the primary driver of population dynamics, but not for linnet Carduelis cannabina, a species for which productivity has been identified as the primary driver of population dynamics. 6. Synthesis and applications. We believe this model can be used to guide the effective delivery of over-winter food resources under agri-environment schemes and to assess the impacts on granivorous birds of changing resource availability associated with novel changes in land use. This could be very important in the future as farming adapts to an increasingly dynamic trading environment, in which demands for increased agricultural production must be reconciled with objectives for environmental protection, including biodiversity conservation.