Macrophyte community structure and species occurrence in relation to environmental determinants in the ephemeral aquatic habitats of Gavdos, Greece

The aims of this study were to explore the environmental factors that determine the distribution of plant communities in temporary rock pools and provide a quantitative analysis of vegetation-environment relationships for five study sites on the island of Gavdos, southwest of Crete, Greece. Data from 99 rock pools were collected and analysed using Two-Way Indicator Species Analysis (TWINSPAN), Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) to identify the principal communities and environmental gradients that are linked to community distribution. A total of 46 species belonging to 21 families were recorded within the study area. The dominant families were Labiatae, Gramineae and Compositae while therophytes and chamaephytes were the most frequent life forms. The samples were classified into six community types using TWINSPAN, which were also corroborated by CCA analysis. The principal gradients for vegetation distribution, identified by CCA, were associated with water storage and water retention ability, as expressed by pool perimeter and water depth. Generalised Additive Models (GAMs) were employed to identify responses of four dominant rock pool species to water depth. The resulting species response curves showed niche differentiation in the cases of Callitriche pulchra and Tillaea vaillantii and revealed competition between Zannichellia pedunculata and Chara vulgaris. The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities. Generalised Additive Models are a powerful tool in investigating species response curves to environmental gradients. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in Mediterranean ephemeral pools.

Identifying important endemic areas using ecoregions: birds and mammals in the Indo-Pacific

Concentrations of large numbers of endemic species have been singled out in prioritization exercises as significant areas for global biodiversity conservation. This paper describes bird and mammal endemicity in Indo-Pacific ecoregions. An ecoregion is a relatively large unit of land or water that contains a distinct assemblage of natural communities. We prioritize 133 ecoregions according to their levels of endemicity, and explain how variables such as biome type, whether the ecoregion is on an island or continental mass, montane or non-montane, correlate with the proportion of the total species assemblage that are endemic. Following an exploratory principal components analysis we classify all ecoregions according to the relationship between numbers of endemics and overall species richness. Endemicity is negatively correlated with species richness. We show that plotting the logit transformation of the endemicity of birds and mammals against log of species richness is a more effective and useful way of identifying important ecoregions than simply ordering ecoregions by the proportion of endemic species, or any other single measure. The plot, divided into 16 regions corresponding to the quartiles of the two variables, was used to identify ecoregions of high conservation value. These are the ecoregions with the highest endemicity and lowest species richness. Further analysis shows that island and montane ecoregions, regardless of their biome type, are by far the most important for endemic species.

Reproduction recovery of the crustacean Daphnia magna after chronic exposure to ibuprofen

In mammals, the pharmaceutical ibuprofen (IB), a non-steroidal anti-inflammatory drug, primarily functions by reversibly inhibiting the cyclooxygenase (COX) pathway in the synthesis of eicosanoids (e.g. prostaglandins). Previous studies suggest that IB may act in a similar manner to interrupt production of eicosanoids reducing reproduction in the model crustacean Daphnia magna. On this basis withdrawal of IB should lead to the recovery of D. magna reproduction. Here we test whether the effect of IB is reversible in D. magna, as it is in mammals, by observing reproduction recovery following chronic exposure. D. magna (5-days old) were exposed to a range of IB concentrations (0, 20, 40 and 80 mg l(-1)) for 10 days followed by a 10 day recovery period in uncontaminated water. During the exposure period, individuals exposed to higher concentrations produced significantly fewer offspring. Thereafter, IB-stressed individuals produced offspring faster during recovery, having similar average population growth rates (PGR) (1.15-1.28) to controls by the end of the test. It appears that maternal daphnids are susceptible to IB during egg maturation. This is the first recorded recovery of reproduction in aquatic invertebrates that suffered reproductive inhibition during chronic exposure to a chemical stressor. Our results suggest a possible theory behind the compensatory fecundity that we referred to as 'catch-up reproduction'.

Determination of mitochondrial genetic diversity in mammals

Mitochondrial DNA (mtDNA) is one of the most Popular population genetic markers. Its relevance as an indicator Of Population size and history has recently been questioned by several large-scale studies in animals reporting evidence for recurrent adaptive evolution, at least in invertebrates. Here we focus on mammals, a more restricted taxonomic group for which the issue of mtDNA near neutrality is crucial. By analyzing the distribution of mtDNA diversity across species and relating 4 to allozyme diversity, life-history traits, and taxonomy, we show that (i) mtDNA in mammals (toes not reject the nearly neutral model; (ii) mtDNA diversity, however, is unrelated to any of the 14 life-history and ecological variables that we analyzed, including body mass, geographic range, and The World Conservation Union (IUCN) categorization; (iii) mtDNA diversity is highly variable between mammalian orders and families; (iv) this taxonomic effect is most likely explained by variations of mutation rate between lineages. These results are indicative of a strong stochasticity of effective population size in mammalian species. They Suggest that, even in the absence of selection, mtDNA genetic diversity is essentially unpredictable, knowing species biology, and probably uncorrelated to species abundance.

Urban mammals: what does the future hold? An analysis of the factors affecting patterns of use of residential gardens in Great Britain

1Urban areas are predicted to grow significantly in the foreseeable future because of increasing human population growth. Predicting the impact of urban development and expansion on mammal populations is of considerable interest due to possible effects on biodiversity and human-wildlife conflict. 2The British government has recently announced a substantial housing programme to meet the demands of its growing population and changing socio-economic profile. This is likely to result in the construction of high-density, low-cost housing with small residential gardens. To assess the potential effects of this programme, we analysed the factors affecting the current pattern of use of residential gardens by a range of mammal species using a questionnaire distributed in wildlife and gardening magazines and via The Mammal Society. 3Twenty-two species/species groups were recorded. However, the pattern of garden use by individual species was limited, with only six species/species groups (bats, red fox Vulpes vulpes, grey squirrel Sciurus carolinensis, hedgehog Erinaceus europaeus, mice, voles) recorded as frequent visitors to > 20% of gardens in the survey. 4There was a high degree of association between the variables recorded in the study, such that it was difficult to quantify the effects of individual variables. However, all species/species groups appeared to be negatively affected by the increased fragmentation and reduced proximity of natural and semi-natural habitats, decreasing garden size and garden structure, but to differing degrees. Patterns of garden use were most clearly affected by house location (city, town, village, rural), with garden use declining with increasing urbanization for the majority of species/species groups, except red foxes and grey squirrels. Increasing urbanization is likely to be related to a wide range of interrelated factors, any or all of which may affect a range of mammal species. 5Overall, the probable effects of the planned housing development programme in Britain are not likely to be beneficial to mammal populations, although the pattern of use examined in this study may represent patterns of habitat selection by species rather than differences in distribution or abundance. Consequently, additional data are required on the factors affecting the density of species within urban environments.

Chronic toxicity of ibuprofen to Daphnia magna: Effects on life history traits and population dynamics

The non-steroidal anti-inflammatory drug (NSAID) ibuprofen (IB) is a widely used pharmaceutical that can be found in several freshwater ecosystems. Acute toxicity studies with Daphnia magna suggest that the 48 h EC50 (immobilisation) is 10-100 mg IB l(-1). However, there are currently no chronic IB toxicity dataon arthropod populations, and the aquatic life impacts of such analgesic drugs are still undefined. We performed a 14-day exposure of D. magna to IB as a model compound (concentration range: 0, 20, 40 and 80 mg IB l(-1)) measuring chronic effects on life history traits and population performance. Population growth rate was significantly reduced at all IB concentrations, although survival was only affected at 80 mg IB l(-1). Reproduction, however, was affected at lower concentrations of IB (14-day EC50 of 13.4 mg IB l(-1)), and was completely inhibited at the highest test concentration. The results from this study indicate that the long-term crustacean population consequences of a chronic IB exposure at environmentally realistic concentrations (ng l(-1) to mu g l(-1)) would most likely be of minor importance. We discuss our results in relation to recent genomic studies, which suggest that the potential mechanism of toxicity in Daphnia is similar to the mode of action in mammals, where IB inhibits eicosanoid biosynthesis. (C) 2007 Elsevier Ireland Ltd. All rights reserved.

A simple and rapid method for preserving RNA of aquatic invertebrates for ecotoxicogenomics

Here we describe a novel, inexpensive and simple method for preserving RNA that reduces handling stress in aquatic invertebrates following ecotoxicogenomic experimentation. The application of the method is based on transcriptomic experiments conducted on Daphnia magna, but may easily be applied on a range of other aquatic organisms of a particular size with e.g. amphipod Gammarus pulex representing an upper size limit. We explain in detail how to apply this new method, named the "Cylindrical Sieve (CS) system", and highlight its advantages and disadvantages.

On the stability of populations of mammals, birds, fish and insects

A key concern for conservation biologists is whether populations of plants and animals are likely to fluctuate widely in number or remain relatively stable around some steady-state value. In our study of 634 populations of mammals, birds, fish and insects, we find that most can be expected to remain stable despite year to year fluctuations caused by environmental factors. Mean return rates were generally around one but were higher in insects (1.09 +/- 0.02 SE) and declined with body size in mammals. In general, this is good news for conservation, as stable populations are less likely to go extinct. However, the lower return rates of the large mammals may make them more vulnerable to extinction. Our estimates of return rates were generally well below the threshold for chaos, which makes it unlikely that chaotic dynamics occur in natural populations - one of ecology's key unanswered questions.

Response to comment on "On the regulation of populations of mammals, birds, fish, and insects"

Our conclusions are unaffected by removal of the time series identified by Peacock and Garshelis as harvest data. The relationship between a population's growth rate and its size is generally concave in mammals, irrespective of their body sizes. However, our data set includes quality data for only five mammals larger than 20 kilograms, so strong conclusions cannot be made about these animals.

Response to comments on "On the regulation of populations of mammals, birds, fish, and insects"

The technical comments by Getz and Lloyd-Smith, Ross, and Doncaster focus on specific aspects of our analysis and estimation and do not demonstrate any results opposing our key conclusion-that, contrary to what was previously believed, the relation between a population's growth rate (pgr) and its density is generally concave.

Population-level assessment of risks of pesticides to birds and mammals in the UK

It is generally acknowledged that population-level assessments provide,I better measure of response to toxicants than assessments of individual-level effects. population-level assessments generally require the use of models to integrate potentially complex data about the effects of toxicants on life-history traits, and to provide a relevant measure of ecological impact. Building on excellent earlier reviews we here briefly outline the modelling options in population-level risk assessment. Modelling is used to calculate population endpoints from available data, which is often about Individual life histories, the ways that individuals interact with each other, the environment and other species, and the ways individuals are affected by pesticides. As population endpoints, we recommend the use of population abundance, population growth rate, and the chance of population persistence. We recommend two types of model: simple life-history models distinguishing two life-history stages, juveniles and adults; and spatially-explicit individual-based landscape models. Life-history models are very quick to set up and run, and they provide a great deal or insight. At the other extreme, individual-based landscape models provide the greatest verisimilitude, albeit at the cost of greatly increased complexity. We conclude with a discussion of the cations of the severe problems of parameterising models.

On the regulation of populations of mammals, birds, fish, and insects

A key unresolved question in population ecology concerns the relationship between a population's size and its growth rate. We estimated this relationship for 1780 time series of mammals, birds, fish, and insects. We found that rates of population growth are high at low population densities but, contrary to previous predictions, decline rapidly with increasing population size and then flatten out, for all four taxa. This produces a strongly concave relationship between a population's growth rate and its size. These findings have fundamental implications for our understanding of animals' lives, suggesting in particular that many animals in these taxa will be found living at densities above the carrying capacity of their environments.

Bergmann's rule and body size in mammals

Aim: To describe the geographical pattern of mean body size of the non-volant mammals of the Nearctic and Neotropics and evaluate the influence of five environmental variables that are likely to affect body size gradients. Location: The Western Hemisphere. Methods: We calculated mean body size (average log mass) values in 110 × 110 km cells covering the continental Nearctic and Neotropics. We also generated cell averages for mean annual temperature, range in elevation, their interaction, actual evapotranspiration, and the global vegetation index and its coefficient of variation. Associations between mean body size and environmental variables were tested with simple correlations and ordinary least squares multiple regression, complemented with spatial autocorrelation analyses and split-line regression. We evaluated the relative support for each multiple-regression model using AIC. Results: Mean body size increases to the north in the Nearctic and is negatively correlated with temperature. In contrast, across the Neotropics mammals are largest in the tropical and subtropical lowlands and smaller in the Andes, generating a positive correlation with temperature. Finally, body size and temperature are nonlinearly related in both regions, and split-line linear regression found temperature thresholds marking clear shifts in these relationships (Nearctic 10.9 °C; Neotropics 12.6 °C). The increase in body sizes with decreasing temperature is strongest in the northern Nearctic, whereas a decrease in body size in mountains dominates the body size gradients in the warmer parts of both regions. Main conclusions: We confirm previous work finding strong broad-scale Bergmann trends in cold macroclimates but not in warmer areas. For the latter regions (i.e. the southern Nearctic and the Neotropics), our analyses also suggest that both local and broad-scale patterns of mammal body size variation are influenced in part by the strong mesoscale climatic gradients existing in mountainous areas. A likely explanation is that reduced habitat sizes in mountains limit the presence of larger-sized mammals.

Incorporation of in situ and biomarker assays in higher-tier assessment of the aquatic toxicity of insecticides

This study was designed to test the feasibility of integrating in situ, single species exposures and biomarker analysis into microcosm studies. Experimental ponds were dosed with pirimiphos methyl (PM) and lindane. C. riparius fourth instar larvae were deployed for 48 h on nine separate occasions during the study period before and after treatment. Surviving larvae were analysed for acetylcholinesterase activity (AChE). Survival and biomarker data were compared to chironomid assemblage analysis by monitoring insects emerging from the microcosms. Survival of chironomids within the in situ systems commenced on day + 16 after treatment with 31.6% and 53.3% survival in the lindane and PM treated ponds, respectively. In contrast, the first emergence from the microcosms occurred on days + 27, in respect to lindane, and + 59 for the PM treated ponds. Thus the in situ bioassay was able to demonstrate gradual reduction in toxicity within the sediment before this was evident from macroinvertebrate monitoring. Significant ACNE inhibition was only detected on exposure to PM. Levels decreased from 75% on day + 16 to 26% by day +29. The biomarker analysis confirmed that, by the end of the study, the insecticide was no longer exerting an effect. We discuss how the use of in situ bioassays could also aid comparison of microcosm studies by adding a standardized dimension. (C) 2003 Elsevier Ltd. All rights reserved.

A naked ape would have fewer parasites

Unusually among the mammals, humans lack an outer layer of protective fur or hair. We propose the hypothesis that humans evolved hairlessness to reduce parasite loads, especially ectoparasites that may carry disease. We suggest that hairlessness is maintained by these naturally selected benefits and by sexual selection operating on both sexes. Hairlessness is made possible in humans owing to their unique abilities to regulate their environment via fire, shelter and clothing. Clothes and shelters allow a more flexible response to the external environment than a permanent layer of fur and can be changed or cleaned if infested with parasites. Naked mole-rats, another hairless and non-aquatic mammal species, also inhabit environments in which ectoparasite transmission is expected to be high, but in which temperatures are closely regulated. Our hypothesis explains features of human hairlessness-such as the marked sex difference in body hair, and its retention in the pubic regions-that are not explained by other theories.