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Publisher: Expert Reviews (formerly Future Drugs Ltd)   (Total: 16 journals)

Expert Review of Anticancer Therapy     Full-text available via subscription   (SJR: 1.044, h-index: 37)
Expert Review of Cardiovascular Therapy     Full-text available via subscription   (Followers: 3, SJR: 0.507, h-index: 27)
Expert Review of Clinical Pharmacology     Full-text available via subscription   (Followers: 3, SJR: 0.303, h-index: 9)
Expert Review of Dermatology     Full-text available via subscription   (Followers: 10, SJR: 0.274, h-index: 9)
Expert Review of Endocrinology & Metabolism     Full-text available via subscription   (Followers: 3, SJR: 0.277, h-index: 9)
Expert Review of Gastroenterology and Hepatology     Full-text available via subscription   (Followers: 3, SJR: 0.772, h-index: 16)
Expert Review of Hematology     Full-text available via subscription   (SJR: 0.692, h-index: 10)
Expert Review of Medical Devices     Full-text available via subscription   (Followers: 4, SJR: 0.483, h-index: 30)
Expert Review of Molecular Diagnostics     Full-text available via subscription   (Followers: 2, SJR: 0.985, h-index: 44)
Expert Review of Neurotherapeutics     Full-text available via subscription   (Followers: 1, SJR: 0.956, h-index: 33)
Expert Review of Obstetrics & Gynecology     Full-text available via subscription   (Followers: 6, SJR: 0.226, h-index: 7)
Expert Review of Ophthalmology     Full-text available via subscription   (Followers: 3, SJR: 0.229, h-index: 7)
Expert Review of Pharmacoeconomics & Outcomes Research     Full-text available via subscription   (Followers: 5, SJR: 0.519, h-index: 21)
Expert Review of Proteomics     Full-text available via subscription   (Followers: 2, SJR: 0.948, h-index: 33)
Expert Review of Respiratory Medicine     Full-text available via subscription   (Followers: 1, SJR: 0.545, h-index: 12)
Expert Review of Vaccines     Full-text available via subscription   (Followers: 2, SJR: 1.087, h-index: 42)
Journal Cover Expert Review of Clinical Pharmacology
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     ISSN (Print) 1751-2433
     Published by Expert Reviews (formerly Future Drugs Ltd) Homepage  [16 journals]   [SJR: 0.303]   [H-I: 9]
  • Ontogenetic niche shifts matter in community ecology: a review and future
    • Abstract: Abstract Almost all organisms on Earth exhibit ontogenetic niche shifts, which causes great phenotypic variation among individuals and is thus considered to critically mediate community structure and dynamics. In contrast, community ecology has traditionally assumed that species are composed of identical individuals with invariant traits and ignored the potentially important ecological roles of ontogenetic niche shifts. To bridge the gap, here I briefly review ecologically relevant examples which show that basic insights of species-based community theories can be revised by including the ontogenetic perspective. Specifically, I focus on the most representative animals in the study of ontogenetic niche shifts, i.e., fish, insects, and amphibians. Notably, their ontogenetic niche shifts create novel views of community structure: (1) ontogenetic diet shifts of predatory fish couple pelagic and benthic food webs in aquatic systems, (2) ontogenetic shifts in interaction types of pollinating insects couple herbivory and pollination networks in terrestrial systems, and (3) ontogenetic habitat shifts of amphibians and aquatic insects couple aquatic and terrestrial metacommunities at interface areas. Dynamic models of such stage-structured communities suggest that their ontogenetic niche shifts may affect the community resilience and disturbance responses. Exploring more complex systems (e.g., where many species undergo ontogenetic niche shifts several times or continuously) is a future direction, for which describing body size relationships between interacting organisms would be a promising approach. I conclude that both theoretical and empirical advances are needed to facilitate the ontogenetic perspective for better understanding mechanisms underlying biodiversity and ecosystem functioning which are increasingly threatened by anthropogenic disturbance.
      PubDate: 2014-07-19
  • Impact of human disturbance, density, and environmental conditions on the
           survival probabilities of pipistrelle bat (       class="a-plus-plus">Pipistrellus pipistrellus)
    • Abstract: Abstract Natural and anthropogenic disturbances can strongly impact population dynamics of species and are often responsible for zoonotic emerging infectious diseases. However, long-term studies on the demographic consequences of human disturbances are unusual. We used 6 years (1995–2000) of mark-recapture data to investigate how climatic conditions, human disturbance and density affect sex- and age-specific apparent survival probabilities of the pipistrelle bat (Pipistrellus pipistrellus, Schreber 1774) in a maternity colony. Our study demonstrated that density played an important role in population dynamics of pipistrelle bat and that its effect differed with respect to age and sex. Notably, human disturbance caused a strong decline of adult female survival, suggesting that perturbations have important consequences in bat-colony dynamics. Juvenile female survival was negatively influenced by density, being considerably lower in high densities. In contrast, juvenile and adult males were apparently not affected as they had constant survival probabilities. Although climatic factors can markedly affect population dynamics of temperate insectivorous bats, in this study, the weather conditions did not influence the survival rates of pipistrelle bats. We provide the first report that demonstrates the density-dependent effect on bat survival. That is especially relevant to better understanding of the bat-population dynamics and to evaluate the consequences of human disturbance and their potential changes in the maternity colony structure.
      PubDate: 2014-07-01
  • Phylogeography and genetic structure of disjunct        class="a-plus-plus">Salix arbutifolia populations
           in Japan
    • Abstract: Abstract Disjunct geographic distributions of boreal plant species at the southern edges of their ranges are expected to result in low genetic diversity and high genetic differentiation in the disjunct populations. This prediction was tested in a riparian willow, Salix arbutifolia, distributed in the northeastern Eurasian continent and the Sakhalin, Hokkaido, and Honshu Islands, using chloroplast DNA haplotypes and nuclear microsatellite genotypes. Hokkaido and Honshu populations shared a chloroplast haplotype identical to a closely related species, S. cardiophylla. This haplotype was divergent from haplotypes in the Eurasian continent (Primorsky) and the Sakhalin Island. In the nuclear microsatellites, most Hokkaido populations were genetically closer to Primorsky populations than to Sakhalin populations in spite of the geographical vicinity between Sakhalin and Hokkaido. The unexpected genetic divergence between Sakhalin and Hokkaido implies a complicated history of migration and colonization. The most peripheral populations in Honshu had the lowest genetic diversity and were most differentiated from the others. Thus, low genetic diversity and high genetic differentiation at the range periphery suggest substantial effects of genetic drift on genetic structure in the disjunct populations of Salix arbutifolia at the southern edge of its range.
      PubDate: 2014-07-01
  • Scale and system dependencies of indirect effects of large herbivores on
           phytophagous insects: a meta-analysis
    • Abstract: Abstract An increasing number of studies are being conducted to examine the density- or trait-mediated indirect effects of large herbivores on phytophagous insects. However, these effects are highly context dependent and no general trends have been made clear. We conducted a meta-analysis focusing on three factors capable of affecting detection of the indirect effects of large herbivores on phytophagous insects: type of response variable, experimental scale, and characteristics of study organisms. Overall, large herbivores exerted a negative effect on insects, a trend that was prominent in studies using insect abundance as a response variable. No particular trends were observed in studies using herbivory rate as a variable, and these studies often focused on plant trait-mediated effects more than density-mediated ones. Experimental scale affected the strength of indirect effects: within-year or individual tree level experiments did not follow any trends, whereas 1–10 year experiments or 0–10 ha scale experiments show a negative impact on insects. Characteristics of large herbivores and growth forms of transmitter plants also contributed to variations in the observed effect size; negative effects were reported in livestock-grassland ecosystems and neutral effects in tree-dominated systems. There was a close association between response variable, experimental scale, and characteristics of study organisms, and these effects jointly contributed to the apparent trends. To predict the impacts of large herbivores at ecosystem level, it is necessary to eliminate these biases arising from study design and to evaluate the effect on insect densities at large spatial and temporal scales.
      PubDate: 2014-07-01
  • Sustainability of exploited ecologically interdependent species
    • Abstract: Abstract This paper examines the application of maximum sustainable yield (MSY) policy in ecosystem and indicates when the ecosystem based fisheries management approach is required for conservation purpose. To describe the possible impacts of applying global MSY policy in an ecosystem, we have considered both specialist and generalist prey–predator models with different fishing efforts. It is found that harvesting both prey and predator species in specialist prey–predator systems, to achieve global maximum sustainable total yield (MSTY) under independent efforts, will cause the extinction of the predator species. In contrast, the global MSTY may exist in a generalist prey–predator system. If global MSTY does not exist, then it is due to the extinction of predator species. Hence, the prey species never goes to extinction under independent efforts and this scenario is quite different from the one found under combined harvesting effort.
      PubDate: 2014-07-01
  • Two-year cyclicity in recruitment of a fish population is driven by an
           inter-stage effect
    • Abstract: Abstract A 25-year time series for a vendace (Coregonus albula (L.)) population was analysed with mathematical models to reveal the factors that regulate its recruitment. The fitted recruitment model was an age-structured model incorporating the compensatory effects of the spawning population and the abundance of the previous year class. Wind forcing index was also added as an example of an external source of recruitment variability. The auto-correlation analysis revealed a tendency for 2-year generation cyclicity in recruitment. The compensatory effects of both spawning biomass and previous year class abundance on recruitment had to be incorporated into the model to remove cyclicity from residuals. Wind forcing during the larval and early juvenile periods negatively affected recruitment. Re-estimating the parameters of the Cushing recruitment function and the effect of previous year-class from simulated data revealed that the time series structure and measurement errors induce strong biases in parameters exaggerating the density independent population growth rate parameter and the amount of compensation. The negative effect of previous year class was also exaggerated but less severely. Simulations with the artificially perturbed deterministic model skeleton revealed a tendency for cyclicity in recruitment. The model typically generated dampening oscillations, but the dynamics appeared as limit cycles when assuming high mortality, a low level of compensation by spawning biomass and a considerable negative effect of the previous year-class. No single ultimate mechanism for inter-stage effects causing cyclicity can be presently designated despite the rather extensive studies on vendace population dynamics. Several of the suggested mechanisms may be operating in concert.
      PubDate: 2014-07-01
  • Habitat and microsite influence demography of two herbs in intact and
           degraded scrub
    • Abstract: Abstract Identifying environmental factors associated with vital rate variation is critical to predict population consequences of environmental perturbation. We used matrix models to explore effects of habitat and microsite on demography of two widespread herbs, Chamaecrista fasciculata (partridge pea) and Balduina angustifolia (yellow buttons). We evaluated models simulating population dynamics in common microsites (shrub, litter, bare sand) within two habitats (intact, degraded Florida scrub) using data on experimental populations initiated by sowing seeds, and natural seed production. Models included four stages (seed bank, small vegetative, large vegetative, reproductive) and three vital rates (survival, growth, fecundity), summarized in sixteen transitions. We conducted life table response experiments to assess contributions of each habitat and microsite to population growth rates. We found that (1) C. fasciculata had greatest population growth in degraded habitat and litter microsites, (2) B. angustifolia had similar population growth between habitats and greatest in bare sand microsites, (3) advancing growth transitions of C. fasciculata had greatest elasticity on population growth in degraded habitat, shrub, and litter, as did seed survival in intact habitat and bare sand, (4) seed survival and advancing growth transitions of B. angustifolia had greatest elasticity on population growth in both habitats, as did seed survival in shrub and litter, and advancing growth in bare sand. Greater population growth of C. fasciculata in degraded scrub is probably explained by release from belowground competition; B. angustifolia may be most affected by competition with shrubs. Microsites in intact scrub were not ecologically equivalent to those in degraded scrub emphasizing that intact scrub is ecologically complex and critical to preserve.
      PubDate: 2014-07-01
  • Evidence for density-dependent habitat occupancy at varying scales in an
           expanding bird population
    • Abstract: Abstract Understanding factors shaping the spatial distribution of animals is crucial for the conservation and management of wildlife species. However, few studies have investigated density-dependent habitat selection in wild populations in non-equilibrium conditions and at varying spatial scales. Here, we investigated density-dependent habitat selection at varying spatial scales in an increasing white stork Ciconia ciconia population using a long term data set in western France. During a 16-year study period, the breeding population density increased from 0.66 nests per 100 km2 to 6.6 nests per 100 km2. At the beginning of the colonisation of the area settlement probability of storks was mainly positively affected by grasslands located near wetlands. Areas with intensive or moderately intensive agriculture were extremely unlikely to be occupied by breeding birds. However, selection for the initially preferred habitats faded as stork density increased although the proportions of habitat types remained unchanged. At the same time selection for initially less favoured habitats had increased. Moreover, we found that the spatial scale of selection for each foraging habitat variable was consistent over time. Our results suggest that snapshot analyses of resource selection in populations at high density may be misleading for population conservation or management. In contrast, a longitudinal approach to resource selection can be a valuable tool for understanding resource limitation.
      PubDate: 2014-07-01
  • Comparison of occupancy modeling and radiotelemetry to estimate ungulate
           population dynamics
    • Abstract: Abstract Radiotelemetry and unmarked occupancy modeling have been used to estimate animal population growth, but have not been compared for ungulates. We compared white-tailed deer (Odocoileus virginianus) population growth estimates from radiomarked individuals and occupancy modeling of unmarked individuals and evaluated advantages and disadvantages of each method. Estimates of population growth were obtained using remote camera (N = 54/year) detection/non-detection occupancy surveys of unmarked deer and from survival and recruitment data of radiomarked adult females (N = 87) and neonate fawns (N = 127) in a predominantly forested region of the Upper Peninsula of Michigan, USA, 2009–2011. We hypothesized that occupancy models and radiotelemetry data would have similar population growth trends because both methods sampled the same temporally closed population. Percent changes in camera trap data generally reflected finite population growth (λ) of radiomarked deer which increased (λ = 1.10 ± 0.01) from 2009 to 2010, but decreased (λ = 0.87 ± 0.02) from 2010 to 2011. Also, unmarked adult female abundance and fawn:adult female ratios generally reflected trends in radiomarked deer survival and recruitment. Royle–Nichols occupancy model abundance estimates had wide confidence intervals, which may preclude using this method from accurately estimating deer population growth. Radiotelemetry provided more precise population growth estimates, while allowing collection of vital rates and location data. However, the Royle–Nichols occupancy model may be preferred to radiotelemetry because it reflected yearly variation in population growth with reduced labor and no invasive marking. Researchers should consider the objectives and logistics of their study when choosing a specific method.
      PubDate: 2014-07-01
  • Estimating the abundance of rare and elusive carnivores from
           photographic-sampling data when the population size is very small
    • Abstract: Abstract Conservation and management agencies require accurate and precise estimates of abundance when considering the status of a species and the need for directed actions. Due to the proliferation of remote sampling cameras, there has been an increase in capture–recapture studies that estimate the abundance of rare and/or elusive species using closed capture–recapture estimators (C–R). However, data from these studies often do not meet necessary statistical assumptions. Common attributes of these data are (1) infrequent detections, (2) a small number of individuals detected, (3) long survey durations, and (4) variability in detection among individuals. We believe there is a need for guidance when analyzing this type of sparse data. We highlight statistical limitations of closed C–R estimators when data are sparse and suggest an alternative approach over the conventional use of the Jackknife estimator. Our approach aims to maximize the probability individuals are detected at least once over the entire sampling period, thus making the modeling of variability in the detection process irrelevant, estimating abundance accurately and precisely. We use simulations to demonstrate when using the unconditional-likelihood M 0 (constant detection probability) closed C–R estimator with profile-likelihood confidence intervals provides reliable results even when detection varies by individual. If each individual in the population is detected on average of at least 2.5 times, abundance estimates are accurate and precise. When studies sample the same species at multiple areas or at the same area over time, we suggest sharing detection information across datasets to increase precision when estimating abundance. The approach suggested here should be useful for monitoring small populations of species that are difficult to detect.
      PubDate: 2014-07-01
  • Covariation between mean vole density and variability drives the numerical
           response of storks to vole prey
    • Abstract: Abstract Hušek et al. (Popul Ecol 55:363–375, 2013) showed that the numerical response of storks to vole prey was stronger in regions where variability in vole density was higher. This finding is, at first sight, in contradiction with the predictions of life-history theory in stochastic environments. Since the stork productivity-vole density relationship is concave, theory predicts a negative association between the temporal variability in vole density and stork productivity. Here, we illustrate this negative effect of vole variability on stork productivity with a simple mathematical model relating expected stork productivity to vole dynamics. When comparing model simulations to the observed mean density and variability of thirteen Czech and Polish vole populations, we find that the observed positive effect of vole variability on stork numerical response is most likely due to an unusual positive correlation between mean and variability of vole density.
      PubDate: 2014-07-01
  • Loss of nesting sites is not a primary factor limiting northern Chimney
           Swift populations
    • Abstract: Abstract Aerially-foraging insectivorous bird populations have been declining for several decades in North America and habitat loss is hypothesized as a leading cause for the declines. Chimney Swifts (Chaetura pelagica) are a model species to test this hypothesis because nest site use and availability is easily assessed. To determine if nest site availability is a limiting factor for Chimney Swifts, we established a volunteer-based survey to inventory and describe chimneys (n = 928) that were used or unused by swifts. A logistic regression model showed that swifts preferred chimneys with a greater length exposed above the roofline and greater inside area, which were not associated with residential buildings. The average chimney used by swifts extended 2.86 m above the roofline with an internal area of 10,079 cm2. The regression model represents the range of nest-site conditions that swifts will tolerate; this was used to build a linear discriminant function (ldf) that had an I-index of 82 % (measure of prediction success). We applied the ldf coefficients to predict chimney occupancy in three southern Ontario communities. Of 366 open chimneys, the ldf classified 139 as suitable but only 24.4 % were occupied by swifts. Given that >75 % of suitable sites were unoccupied, swifts are likely not experiencing competition from habitat saturation. Our results suggest that Chimney Swift populations, and likely other aerially-foraging insectivorous birds, are limited primarily by other processes not measured in this study, such as changes in prey.
      PubDate: 2014-07-01
  • Little tern breeding success in artificial and natural habitats: modelling
           population growth under uncertain vital rates
    • Abstract: Abstract As a consequence of habitat loss, breeding in man-made habitats has become increasingly common for many coastal breeding bird species. While artificial sites provide valuable substitutes, they may also be more attractive, and importantly, differ in quality from natural sites. Therefore, information on habitat specific breeding success and their potential for supporting stable populations are needed. We compared little tern (Sternula albifrons) breeding success (nest and hatching success) between natural habitat (sandy beaches) and artificial port habitat at Bothnian Bay, Finland from 2006 to 2011. We further reviewed published estimates on pre-fledging and adult survival for little terns and least terns (Sternula antillarum), and used these ranges to estimate plausible parameter spaces for population growth rates given our estimates of breeding success. Nest success was among the highest reported for little terns in the artificial habitat (82 %) while being lower in the natural habitat (58 %). This difference may have resulted from differences in colony sizes and levels of disturbance. Hatching success did not differ significantly, but the percentage of successful nests containing unhatched eggs was twice as high in the natural habitat. The parameter spaces for population growth rates indicated that the artificial habitat has good potential to sustain stable populations (66 % positive growth rate) while for the natural habitat this potential was lower (37 % positive growth rate). While our results suggest that artificial habitats can be very productive breeding sites for habitat deprived tern populations, management should concentrate on improving both habitats with emphasis on natural sites.
      PubDate: 2014-06-11
  • Patterns of spatio-temporal variation in the survival rates of a
           viviparous lizard: the interacting effects of sex, reproductive
           trade-offs, aridity, and human-induced disturbance
    • Abstract: Abstract Examination of the spatial and temporal variation in survival rates provides insight on how the action of natural selection varies among populations of single species. In this study, we used mark-recapture data from seven populations of the viviparous lizard Sceloporus grammicus in Central Mexico and a multi-model inference framework to examine interpopulation variation in the survival of adult males and females. We aimed to analyze the potential effects of aridity, human-induced disturbance, and reproductive costs on the survival rates of these lizards. For females in particular, we also searched for a negative relationship between litter size (adjusted for female size) and female survival. Our results demonstrate seasonal changes in survival for males and females. In three out of our seven study sites female survival decreased during the birthing season. In contrast, male survival did not appear to decrease during the mating season. We found an interaction between site-specific aridity and reproductive season affecting female survival. A decrease in female survival during the birthing season was observed in relatively arid sites. In one of these arid sites we found a negative effect of size-adjusted litter size on female survival: females producing more offspring than those expected for their size were more likely to die. This result represents evidence of a physiological trade-off for gravid females occurring in at least one of the studied populations. Interpopulation variation in the degree of human-induced disturbance could not explain the observed patterns of spatial variation in survival rates. Our results demonstrate wide variation in sex-specific survival patterns of this viviparous lizard and provide evidence that negative associations between reproduction and survival are highly dependent on the local environmental conditions.
      PubDate: 2014-06-06
  • Can livestock carrion availability influence diet of wintering red
           kites' Implications of sanitary policies in ecosystem services and
    • Abstract: Abstract The diet of wintering red kites Milvus milvus over the last decade in central Spain was recorded to evaluate the influence of sanitary policies on carcasses use. The results show major differences in diet composition of red kites wintering in areas with and without availability of livestock carcasses. In the area without livestock carcasses (north-western Madrid province), red kites fed on a similarly large proportion of wild lagomorphs across the study period. In the area with livestock farming (Segovia province), red kites exploited carcasses from different livestock schemes (stabled livestock—primarily swine—versus free-ranging ruminants) depending on changing sanitary regulations as consequence of the Bovine Spongiform Encephalopathy or ‘mad cow’ crisis initiated in 2001. During the period of restrictive sanitary legislation (after the ‘mad cow’ crisis) that greatly limited the use of animal by-products from ruminants as food for avian scavengers, kites mostly predated on common voles and scavenged on swine carcasses. After the implementation of the less restrictive regulations (since 2011; regulations CE1069/2009, CE142/2011) that again permitted the abandonment of extensive livestock remains in the countryside and in feeding stations, the proportion of ruminants in the kites’ diet increased while the proportion of swine carrion decreased. Carcass dumps acted as temporally and spatially predictable sources of abundant food from stabled livestock before and even just after the mad-cow crisis, but become relatively unpredictable foraging places afterwards due to the generalized carrion destruction in authorized plants, primarily of swine considered as non-risk for the transmission of the bovine encephalopathy. This illustrates the deep and sometimes unexpected consequences that sanitary policies can impose on the composition and availability of food resources for scavenger wildlife. Much effort is still required to reconcile sanitary and environmental policies in order to ensure the conservation of avian scavengers and the provision of ecosystem services.
      PubDate: 2014-05-27
  • Plant species diversity and forage quality as affected by pasture
           management and simulated cattle activities
    • Abstract: Abstract Grazed pastures have been historically used in Japan for animal production with little concern to biodiversity. However, pasturing has significant effects on biodiversity and productivity because it produces gaps in the distribution of vegetation due to animal activities. We hypothesized that different grazing activities would have effects on the diversity of plant species and forage quality in different ways and that the sward type would modify these effects. Therefore, we attempted to predict the diversity of plant species and changes in total nutrient content per area at the time since treatment on the basis of simulations of cattle activities in three pastures with different vegetation compositions. We created three ground types (grazed areas, cleared ground, and undisturbed areas) in three pastures (improved, partially improved semi-natural, and semi-natural pasture) and recorded the percentage cover of each plant within the plots. We repeatedly calculated the biodiversity indices from these community data by varying the sampling probabilities for each ground type, which provided us with the expected species diversity indices with the changing proportions of each ground type. Furthermore, we investigated the dry matter and forage qualities. For improved and partially improved semi-natural pasture, our models predicted that plant diversity increased as a saturating function of the proportion of cleared ground and grazed area relative to the undisturbed area, although our models also showed exponential curves for the semi-natural pasture. Forage samples from cleared ground plots and semi-natural pasture had the lowest forage quality among all pastures. Based on the predicted effects of cattle pasturing on the plant species biodiversity and forage quality, it may be more beneficial to maintain a small proportion of cleared ground in the improved pasture during intensive grazing.
      PubDate: 2014-05-20
  • Demographic effects of warming, elevated soil nitrogen and thinning on the
           colonization of a perennial plant
    • Abstract: Abstract Global change is causing significant modifications to native plant communities. These effects can be direct through changes in productivity, or indirect through the spread of invading species. Identifying vital traits important for individual species’ response to environmental variation could be useful for making predictions about how entire communities may respond to global change. I studied the effects of factors associated with global change on the demography of an experimentally introduced species, Pityopsis aspera. In a Florida old-field, I investigated how warming, increased soil nitrogen and thinning of the extant plant community affected survival, growth and reproduction of P. aspera using a life table response experiment. The estimated population growth rate (λ) of P. aspera was reduced by nitrogen addition, as a result of decreased fecundity. However, λ increased in response to the warming treatment, as a result of increased fecundity. In the presence of thinning, both warming and nitrogen served to increase λ as a result of an increase in the growth of young individuals. This experiment illustrates how different vital rates contribute to the population level responses of an experimentally introduced plant to warming, and nitrogen deposition. Results also show how these demographic responses may occur via indirect effects through established species. This work highlights the importance of studying interactions among temperature, soil nitrogen and demography across the entire life cycle in order to capture the complex and, often, non-additive relationships mediating global change effects.
      PubDate: 2014-05-18
  • Genetic effects of living in a highly polluted environment: the case of
           the silverside Basilichthys
    (Jenyns) (Teleostei: atherinopsidae) in the
           Maipo River basin, central Chile
    • Abstract: Abstract Freshwater systems are one of the environments most impacted by human activity, with pollution being a highly important factor. In Chile, several rivers exhibit varied levels of pollution, one of which is the Maipo River basin where the city of Santiago is located. The silverside Basilichthys microlepidotus (Jenyns) is an endemic fish species that inhabits this basin, thus we hypothesized that pollution has affected gene diversity and migration in populations of B. microlepidotus from the Maipo River basin. The aim of this study was to identify the population structure of B. microlepidotus in this basin and to determine if the populations of the silverside inhabiting polluted sites present differences in gene diversity and gene flow compared to populations inhabiting non-polluted areas. Using the variability of eight microsatellites, five populations of silverside were detected; three inhabiting non-polluted sites and two inhabiting polluted sites. From this, it was inferred that B. microlepidotus has been able to tolerate pollution in the Maipo River basin. No differences in gene diversity or migration were detected between polluted and non-polluted sites but comparison with historical estimation revealed an increase in the current migration rate when all the data from the basin were compared. A reduction in current effective population size was also observed when compared to historical values, and this is probably due to river degradation. Despite the disappearance of other fish species recorded at this basin, our results suggest that B. microepidotus is tolerant to pollution, thus indicating that native species respond differently to this environmental factor.
      PubDate: 2014-05-17
  • Iwao’s patchiness regression through the origin: biological
           importance and efficiency of sampling applications
    • Abstract: Abstract Iwao’s mean crowding-mean density relation can be treated both as a linear function describing the biological characteristics of a species at a population level, or a regression model fitted to empirical data (Iwao’s patchiness regression). In this latter form its parameters are commonly used to construct sampling plans for insect pests, which are characteristically patchily distributed or overdispersed. It is shown in this paper that modifying both the linear function and statistical model to force the intercept or lower functional limit through the origin results in more intuitive biological interpretation of parameters and better sampling economy. Firstly, forcing the function through the origin has the effect of ensuring that zero crowding occurs when zero individuals occupy a patch. Secondly, it ensures that negative values of the intercept, which do not yield an intuitive biological interpretation, will not arise. It is shown analytically that sequential sampling plans based on regression through the origin should be more efficient compared to plans based on conventional regression. For two overdispersed data sets, through-origin based plans collected a significantly lower sample size during validation than plans based on conventional regression, but the improvement in sampling efficiency was not large enough to be of practical benefit. No difference in sample size was observed when through-origin and conventional regression based plans were validated using underdispersed data. A field researcher wishing to adopt a through-origin form of Iwao’s regression for the biological reasons outlined above can therefore be confident that their sampling strategies will not be affected by doing so.
      PubDate: 2014-04-01
  • Parameter estimation for reaction-diffusion models of biological invasions
    • Abstract: Abstract In this note, we discuss parameter estimation for population models based on partial differential equations (PDEs). Parametric estimation is first considered in the perspective of inverse problems (i.e., when the observation of the solution of a PDE is exactly observed or noise-free). Then, adopting the point of view of statistics, we turn to parametric estimation for PDEs using more realistic noisy measurements. The approach that we describe uses mechanistic-statistical models which combine (1) a PDE-based submodel describing the dynamic under study and (2) a stochastic submodel describing the observation process. This Note is expected to contribute to bridge the gap between modelers using PDEs and population ecologists collecting and analyzing spatio-temporal data.
      PubDate: 2014-04-01
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