How accurate are probability-based estimates of wetland extent? Results of a California validation study

Estimates of wetland and stream extent and distribution form the basis for state and federal monitoring and management programs and guide policy development decisions. The current default approach, comprehensive mapping, provides the most complete information on extent and distribution but is prohibitively expensive across large geographic areas. In contrast, probabilistic mapping produces statistical estimates of extent and distribution at a fraction of the cost of comprehensive mapping. This study provides a direct comparison to address how well probability-based estimates of wetland extent approximate results from comprehensive mapping, and the degree to which inter-mapper variability contributes to overall error in probability-based estimates. Two regions of California were selected based on existence of recent, comprehensive wetland and stream maps. Probabilistic sample plot locations were selected by generalized random tessellation stratified sampling and sample plot maps were produced from the same source imagery as the comprehensive maps. Sample maps were compared for inter-mapper variability, plot-by-plot differences between sample and comprehensive maps, and differences between sample estimates and comprehensive totals. On a plot-by-plot basis differences in mapped wetland area between comprehensive maps and probabilistic sample maps approached 50 % in either the positive or negative direction, leading to uncertainty in directly comparing maps derived from these two approaches. With application of standardized protocols and rigorous quality control measures, we were able to achieve a 97 % overall accuracy rate between independent mapping teams applying the probabilistic mapping approach. Our results suggest caution when comparing comprehensive and sample based wetland extent estimates and highlight the importance of mapper intercalibration.     

How much does a spotted hyaena eat? Perspective from the Namib Desert

The amount of food consumed by a clan of spotted hyaenas in the Namib desert was determined gravimetrically for 19 nights and the amount consumed by each individual was calculated according to its feeding time budget. At large, fleshy ungulate carcasses, each adult clan member ate about 8.7kg nightly, except for the bottom-ranking male, who obtained only half that amount per night. Skin and bone remains were consumed at a slower rate of 2kg/hyaena/night. Medium-sized ungulates were devoured rapidly so that each hyaena obtained more during such feeding nights than at large carcasses. Over a 29 day period, a hyaena clan consumed five cacasses at a rate of 4.0kg/hyaena/day, which compared well with previous estimates of average daily consumption in large social carnivores studied elsewhere. Annually, sixteen Namib hyaenas ate some 4.8% of the ungulate bio-mass, removing, in terms of numbers 14.3% of the gemsbok and 2.2% of the mountain zebra. This depletion did not appear to limit these populations.     

Dermacentor reticulatus – a tick on its way from glacial refugia to a panmictic Eurasian population

The ornate dog tick (Dermacentor reticulatus) shows a recently expanding geographic distribution. Knowledge on its intraspecific variability, population structure, rate of genetic diversity and divergence, including its evolution and geographic distribution, is crucial to understand its dispersal capacity. All such information would help to evaluate the potential risk of future spread of associated pathogens of medical and veterinary concern. A set of 865 D. reticulatus ticks was collected from 65 localities across 21 countries, from Portugal in the west to Kazakhstan and southern Russia in the east. Cluster analyses of 16 microsatellite loci were combined with nuclear (ITS2, 18S) and mitochondrial (12S, 16S, COI) sequence data to uncover the ticks’ population structures and geographical patterns. Approximate Bayesian computation was applied to model evolutionary relationships among the found clusters. Low variability and a weak phylogenetic signal showing an east–west cline were detected both for mitochondrial and nuclear sequence markers. Microsatellite analyses revealed three genetic clusters, where the eastern and western cluster gradient was supplemented by a third, northern cluster. Alternative scenarios could explain such a tripartite population structure by independent formation of clusters in separate refugia, limited gene flow connected with isolation by distance causing a “bipolar pattern”, and the northern cluster deriving from admixture between the eastern and western populations. The best supported demographic scenario of this tick species indicates that the northern cluster derived from admixture between the eastern and western populations 441 (median) to 224 (mode) generations ago, suggesting a possible link with the end of the Little Ice Age in Europe.     

How predacious are predators? A study on Ocypus similis,a rove beetle of cereal fields

It is attempted determine the diet breadth and to quantify the predator pressure by Ocypus similis (F.) (Coleoptera: Staphylinidae), a dominant species of the rove beetle fauna in a winter wheat field. Laboratory and field experiments were conducted to determine the range of prey taxa and the consumption of a whole predator generation (including larvae) during its activity in the field. In laboratory experiments, adults and larvae of O. similis fed on a variety of prey except spiders and larvae of soldier beetles (Cantharidae), but they preferred millipedes as food (Diplopoda: Julidae, Polydesmidae). This preference could also be observed in the field. Although the predator population reached its maximum density in April, highest predator pressure occurred in June because of high consumption rates during the second larval stage. Adult beetles and the individuals of the second larval stage contributed both about 1/3 to total population consumption. Predation by adult beetles was mainly restricted to early spring and summer while larval consumption was highest from April to July. The staphylinids reduced the population density of diplopods by 7–35%. Because millipedes are an important part of the decomposer community, predator activity may lead to a decrease of decomposition rates.     

How important are trophic state,macrophyte and fish population effects on cladoceran community? A study in Lake Erhai

Environmental controls on cladoceran community structure in lake ecosystems are complex and may involve many environmental parameters including trophic state and fish populations. In Lake Erhai, a plateau lake located in southwest China, it was hypothesized that a combination of lake eutrophication and planktivorous fish introduction would increase the abundance of cladoceran, while also decreasing cladoceran size. To test this hypothesis, we examined temporal changes in cladoceran microfossils in the sediments of Lake Erhai over the past century. The influence of changing macrophyte coverage within the littoral region of the lake was also considered. Results demonstrated that cladoceran abundance (measured as flux of cladoceran fossils in the sediments) increased markedly accompanying eutrophication of the lake. In addition, there was a shift in the dominant cladoceran species from those species that prefer oligotrophic conditions to those that prefer mesotrophic and eutrophic conditions. A reduction in the ephippium length of Daphnia spp. was observed and attributed to the introduction of the planktivorous fish Neosalanx taihuensis. Our findings indicated that eutrophication and fish introduction were the main controls affecting cladoceran community structure during the recent decades, and predation by planktivorous fish had an important impact on Daphnia body size.     

How threatened are alpine environments? a cross taxonomic study

Cold-adapted ecosystems are often considered to be stable, species poor, and well protected. However, such ecosystems have been identified as being especially sensitive to threats from global warming. Despite this, recent studies have found low proportions of Red Listed species in these systems. In this study we explored the number of alpine species (dependent on alpine habitats for their survival) and their Red List status in Sweden. We determined the proportion of Red Listed species and explored discrepancies among different groups of organisms in terms of the proportion of Red Listed species and the criteria used for Red Listing. We found a total of 389 alpine species in twelve analyzed species groups. The overall proportion of Red Listed species was 29%, with 15% regarded as threatened. There were substantial differences among taxonomic groups with respect to the proportion of Red Listed species. Among mammals 75% of the species are Red Listed, along with 63% of butterflies and 50% of birds. In addition the single alpine dragonfly species and all three alpine stinging wasp species are also Red Listed. Although beetles, bumblebees and grasshoppers are represented by a total of 17 alpine species, none are Red Listed. In contrast to previous studies, our results show that the proportion of Red Listed species is high in alpine environments, indicating that ecosystems found above the tree line are indeed threatened. No species in Sweden have been Red Listed on the basis of the IUCN criterion E (unfavorable quantitative analysis), this is surprising since entire cold-adapted ecosystems are likely to disappear in the future. We highlight the need for a better and more coordinated application of the IUCN criteria, as well as a more stringent strategy to assess the extinction risks for alpine species, thus maintaining reliable Red Lists.     

How many founders,how large a population?

The number of population founders and the size of the population are two important variables in determining how much gene diversity can be retained in a population. A model is developed to determine the most cost‐effective balance of those two variables, based on comparing the marginal costs of increasing the number of founders vs. increasing the population size. Marginal costs, in this case, are the costs of increasing the number of founders or the population size by one animal. For a goal of retaining 90% gene diversity for 10–15 generations (approximately 100 years), the current recommendation of 20 effective founders is very close to the least‐cost solution when the ratio of the marginal costs is equal to one. However, when the ratio is greater or less than one that number can change considerably. Zoo Biol 29:638–646, 2010. © 2010 Wiley‐Liss, Inc.     

How accurate are population models? Lessons from landscape‐scale tests in a fragmented system

There is a growing debate about the ability of Population Viability Analysis (PVA) to predict the risk of extinction. Previously, the debate has focused largely on models where spatial variation and species movement are ignored. We present a synthesis of the key results for an array of different species for which detailed tests of the accuracy of PVA models were completed. These models included spatial variation in habitat quality and the movement of individuals across a landscape. The models were good approximations for some species, but poor for others. Predictive ability was limited by complex processes typically overlooked in spatial population models, these being interactions between landscape structure and life history attributes. Accuracy of models could not be determined a priori, although model tests indicated how they might be improved. Importantly, model predictions were poor for some species that are among the best‐studied vertebrates in Australia. This indicated that although the availability of good life history data is a key part of PVA other factors also influence model accuracy. We were also able to draw broad conclusions about the sorts of populations and life history characteristics where model predictions are likely to be less accurate. Predictions of extinction risk are often essential for real‐world population management. Therefore, we believe that although PVA has been shown to be less than perfect, it remains a useful tool particularly in the absence of alternative approaches. Hence, tests of PVA models should be motivated by the cycle of testing and improvement.     

Effect of guanabenz on the peristaltic reflex and on the spontaneous rhythmic movements of the ileum isolated from the rabbit: do the alpha-2-adrenoreceptors constitute a homogenous population?

The inhibitory effect of the predominantly alpha-2 adrenoceptor agonist, guanabenz, on the peristaltic reflex and on the pendular movements of the rabbit isolated ileum was investigated. Guanabenz depressed or abolished the peristaltic reflex as well as the pendular movements. These effects were concentration-dependent. Guanabenz is much more potent inhibiting the peristaltic reflex (IC50 1 X 10(-7) M) than the pendular movements (IC50 1 X 10(-5) M). The choline ester, acetylcholine restored the peristaltic reflex and the anticholinesterase, eserine, restored the pendular movements previously abolished by guanabenz. During the blockade of the peristaltic reflex produced by guanabenz, the pendular movements were virtually not changed. It is therefore reasonable to suppose that the inhibitory effect of guanabenz reflects the different properties of alpha-2 adrenoceptors associated with cholinergic nerve terminals within the myenteric plexus and the longitudinal smooth muscle subserving the peristaltic reflex and the pendular movements.     

Mechanistic studies on DNA photolyase, II. Is the blue enzyme isolated from Escherichia coli a mutant?

The contrasting properties of the DNA photolyases isolated from Escherichia coli, and from Saccharomyces cerevisiae suggested the possibility that the E. coli enzyme may have suffered mutagenesis as a consequence of the extensive use of ultraviolet irradiation/photoreactivation as a selection technique during the cloning. We have therefore recloned this gene using a UV-independent protocol and confirmed the original sequence.     

Is the SF-36 a valid measure of change in population health? Results from the Whitehall II Study.

OBJECTIVE: To measure within-person change in scores on the short form general health survey (SF-36) by age, sex, employment grade, and disease status. DESIGN: Longitudinal study with a mean of 36 months (range 23-59 months) follow up, with screening examination and questionnaire to detect physical and psychiatric morbidity. SETTING: 20 civil service departments originally located in London. PARTICIPANTS: 5070 male and 2197 female office based civil servants aged 39-63 years. MAIN OUTCOME MEASURES: Change in the eight scales of the SF-36 (adjusted for baseline score and length of follow up) and effect sizes (adjusted change standard deviation of differences). RESULTS: Within-person declines (worsening health) with age were greater than estimated by cross sectional data alone. General mental health showed greater declines among younger participants (P for linear trend < 0.001). Employment grade was inversely related to change; lower grades had greater deteriorations than higher grades (P < 0.001 for each scale in men; P < 0.05 for each scale in women except general health perceptions and role limitations due to physical problems). The greatest declines were seen among participants with disease at baseline, with the effects of physical and psychiatric morbidity being additive. Effect sizes ranged from 0.20 to 0.65 in participants with both physical and psychiatric morbidity. CONCLUSIONS: Health functioning, as measured by the SF-36, changed in hypothesised directions with age, employment grade, and disease status. These changes occurred within a short follow up period, in an occupational, high functioning cohort which has not been the subject of intervention, suggesting that the SF-36 is sensitive to changes in health in general populations.     

How many species of Hipposideros have occurred on Madagascar since the Late Pleistocene?

Populations of the Malagasy Hipposideros commersoni (family Hipposideridae) are threatened by deforestation and hunting. Maximum likelihood and Bayesian analysis of 148 cytochrome b sequences found this species to be paraphyletic and composed of three well‐supported monophyletic clades. Clades B and C form a monophyletic lineage that can be referred to H. commersoni; these two clades are separated by 6% sequence variation. Clade A represents a distinct evolutionary lineage separate (9–11% average sequence divergence) from H. commersoni (clades B and C) and is named herein as a new species, H ipposideros cryptovalorona sp. nov. In the phylogeny presented herein, this species is strongly associated with the outgroup taxa Hipposideros gigas and Hipposideros vittatus, both restricted to Africa. External, cranial and dental measurements taken from the same individuals used in the molecular study indicate no clear distinction in morphology amongst these three clades; this includes noseleaf structure and craniodental characteristics. Principal component analyses showed limited separation of the three clades. Comparison to a Quaternary fossil species from north‐west Madagascar, Hipposideros besaoka, found little morphological overlap between any of the three clades and this extinct species. Hence, at least three species of Hipposideros have occurred on Madagascar since the Late Pleistocene, two extant (H. commersoni s.s. and H. cryptovalorona sp. nov.) and one extinct (H. besaoka). © 2015 The Linnean Society of London     

Does a heavy fruit crop reduce the tree ring increment? Results from a 12-year study in a subalpine zone

Life history theory posits that an increased investment in reproduction should result in decreased vegetative investment. Switching resources from growth to reproduction are also expected in species experiencing selection pressure for high variation of seed crops. In this study, we tested whether the reproductive effort of trees, measured as the number of fruits produced, is related to their radial growth increment. We examined a population of Sorbus aucuparia, a fleshy-fruited tree species with highly variable interannual individual fruit production growing in the subalpine zone and under strong selection pressure from pre-dispersal seed predators. We used 12-year data to test the relationship between fruit crop and radial growth increments in current, previous and subsequent years, and found no trade-off between growth and reproduction. For almost all trees, there was no correlation between fruit crop and radial growth increment in the same year or next year. Only a few trees showed a positive correlation between fruit crop and previous-year growth. In the statistics, we took advantage of the high variability of individual fruit crops in high production years. In four heavy crop years, we compared the radial growth increments of trees with heavy crops with those of trees with low fruit crops. Current and next-year radial growth did not differ between trees with low and high fruit crops. In all those years, however, trees having heavy fruit crops had higher previous-year growth increments. We suggest that the harsh subalpine weather conditions account for the lack of a trade-off between growth and reproduction in the studied population.     

How important are seabirds in the diet of black rats on islands with a superpredator?

This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats.     

Does malnutrition in utero determine diabetes and coronary heart disease in adulthood? Results from the Leningrad siege study,a cross sectional study.

OBJECTIVE: To investigate the relation between decreased maternal food intake and risk factors for coronary heart disease in adult life. DESIGN: Cross sectional study. SUBJECTS: 169 subjects exposed to malnutrition in utero (intrauterine group) during the siege of Leningrad (now St Petersburg) in 1941-4; 192 subjects born in Leningrad just before rationing began, before the siege (infant group); and 188 subjects born concurrently with the first two groups but outside the area of the siege (unexposed group). SETTING: Ott Institute of Obstetrics and Gynaecology, St Petersburg. MAIN OUTCOME MEASURES: Development of risk factors for coronary heart disease and diabetes mellitus-obesity, blood pressure, glucose tolerance, insulin concentrations, lipids, albumin excretion rate, and clotting factors. RESULTS: There was no difference between the subjects exposed to starvation in utero and those starved during infant life in: (a) glucose tolerance (mean fasting glucose: intrauterine group 5.2 (95% confidence interval 5.1 to 5.3), infant group 5.3 (5.1 to 5.5), P = 0.94; mean 2 hour glucose: intrauterine group 6.1 (5.8 to 6.4), infant group 6.0 (5.7 to 6.3), P = 0.99); (b) insulin concentration; (c) blood pressure; (d) lipid concentration; or (e) coagulation factors. Concentrations of von Willebrand factor were raised in the intrauterine group (156.5 (79.1 to 309.5)) compared with the infant group (127.6 (63.9 to 254.8); P < 0.001), and female subjects in the intrauterine group had a stronger interaction between obesity and both systolic (P = 0.01) and diastolic (P = 0.04) blood pressure than in the infant group. Short adult stature was associated with raised concentrations of glucose and insulin 2 hours after a glucose load-independently of siege exposure. Subjects in the unexposed group had non-systematic differences in subscapular to triceps skinfold ratio, diastolic blood pressure, and clotting factors compared with the exposed groups. CONCLUSIONS: Intrauterine malnutrition was not associated with glucose intolerance, dyslipidaemia, hypertension, or cardiovascular disease in adulthood. Subjects exposed to malnutrition showed evidence of endothelial dysfunction and a stronger influence of obesity on blood pressure.     

How to lift a model for individual behaviour to the population level?

The quick answer to the title question is: by bookkeeping; introduce as p(opulation)-state a measure telling how the individuals are distributed over their common i(ndividual)-state space, and track how the various i-processes change this measure. Unfortunately, this answer leads to a mathematical theory that is technically complicated as well as immature. Alternatively, one may describe a population in terms of the history of the population birth rate together with the history of any environmental variables affecting i-state changes, reproduction and survival. Thus, a population model leads to delay equations. This delay formulation corresponds to a restriction of the p-dynamics to a forward invariant attracting set, so that no information is lost that is relevant for long-term dynamics. For such equations there exists a well-developed theory. In particular, numerical bifurcation tools work essentially the same as for ordinary differential equations. However, the available tools still need considerable adaptation before they can be practically applied to the dynamic energy budget (DEB) model. For the time being we recommend simplifying the i-dynamics before embarking on a systematic mathematical exploration of the associated p-behaviour. The long-term aim is to extend the tools, with the DEB model as a relevant goal post.