Relevance of Comet Assay and Phosphorylated-Hsp90α in Cancer Patients' Peripheral Blood Leukocytes as Tools to Assess Cisplatin-based Chemotherapy Clinical Response and Disease Outcome.

Cisplatin (cPt) is a commonly used treatment for solid tumors. The main target of its cytotoxicity is the DNA molecule, which makes the DNA damage response (DDR) crucial for cPt-based chemotherapy. Therefore, it is essential to identify biomarkers that can accurately predict the individual clinical response and prognosis. Our goal was to assess the usefulness of alkaline comet assay and immunocytochemical staining of phosphorylated Hsp90α (p-Hsp90α), γH2AX, and 53BP1 as predictive/prognostic markers. Pre-chemotherapy peripheral blood leukocytes were exposed to cPt in vitro and collected at 0, 24 (T24), and 48 (T48) hr post-drug removal. Healthy subjects were also included. Baseline DNA damage was elevated in cancer patients (variability between individuals was observed). After cPt, patients showed increased γH2AX foci/nucleus (T24 and T48). Both in healthy persons and patients, the nuclear p-Hsp90α and N/C (nuclear/cytoplasmic) ratio augmented (T24), decreasing at T48. Favorable clinical response was associated with high DNA damage and p-Hsp90α N/C ratio following cPt. For the first time, p-Hsp90α significance as a predictive marker is highlighted. Post-cPt-DNA damage was associated with longer disease-free survival and overall survival. Our findings indicate that comet assay and p-Hsp90α (a marker of DDR) would be promising prognostic/predictive tools in cP-treated cancer patients.

Amidinoquinoxaline N-oxides: synthesis and activity against anaerobic bacteria.

We present herein an in-depth study on the activity of amidinoquinoxaline N-oxides 1 against Gram-positive and Gram-negative anaerobic bacteria. Based on 5-phenyl-2,3-dihydropyrimidoquinoxaline N-oxide 1a, the selected structural variations included in our study comprise the substituents α- to the N-oxide function, the benzofused ring, substitution and quaternization of the amidine moiety, and the amidine ring size. Compounds 1 showed good to excellent antianaerobic activity, evaluated as the corresponding CIM50 and CIM90 values, and an antimicrobial spectrum similar to metronidazole. Six out of 13 compounds 1 had CIM90 values significantly lower than the reference drug. Among them, imidazoline derivatives 1i-l were the most active structures. Such compounds were synthesized by base-promoted ring closure of the corresponding amidines. The N-oxides under study showed no significant cytotoxicity against RAW 264.7 cells, with high selectivity indexes. Their calculated ADME properties indicate that the compounds are potentially good oral drug candidates. The antianaerobic activity correlated satisfactorily with the electron affinity of the compounds, suggesting that they may undergo bioreductive activation before exerting their antibacterial activity.

Control of allergic rhinitis in four latin american countries: Rinola study.

Background: Allergic rhinitis (AR) affects up to 40% of the general population, there are large-scale multicenter studies that have described its characteristics and few studies have focused on studying patients with AR in Latin America (LA). Methodology: A cross-sectional, descriptive, multicenter study was carried out in four LA countries (Colombia, Argentina, Cuba and Peru). Patients diagnosed with AR between November 2017 and June 2020 were included. Sociodemographic and clinical data, sensitization profile and current treatment were collected in the Electronic Data Collection (BDClinic). Patients also filled out this questionnaires: Rhinitis Control Assessment Test (RCAT), Reflexive Total Nasal Symptom Score (rTNSS), Modified ARIA Criteria for AR Severity (mARIA) and ESPRINT-15. Risk of bias was examined by applying the STROBE checklist. Results: The study included 412 patients. Median age was 25 years (15-39). Two hundred and twenty four (54.3%) were women. Nasal obstruction was present in 303 (73.5%). Three hundred and thirty four (81%) had a persistent AR. One hundred and twenty one (31.3%) had associated asthma. The most frequently positive skin tests were: Dermatophagoides pteronyssinus in 365 (88.6%) and Dermatophagoides farinae in 331 (81.3%). Four hundred and eleven patients (99%) reported that AR affected their quality of life. The median score of ESPRINT-15 was 1.87 (0.93-2.93), The mean values of RCAT and rTNSS were 19.01 (±4.59) and 5.4 (±2.97) respectively. Two hundred and fifty (60%) were receiving only oral antihistamines. Physicians decided to start nasal corticosteroids in 296 (71.8%). Only seventy patients (16.9%) were receiving immunotherapy. Conclusion: These findings confirm that most of patients with AR in LA have a persistent disease with a negative impact on quality of life. Dust mites are the main sensitizers. These findings will allow to know the true impact of AR and can lead to a better disease management.

DNA Damage Repair Proteins, HSP27, and Phosphorylated-HSP90α as Predictive/Prognostic Biomarkers of Platinum-based Cancer Chemotherapy: An Exploratory Study.

Platinum analogs are commonly used for cancer treatment. There is increasing interest in finding biomarkers which could predict and overcome resistance, because to date there is no reliable predictive/prognostic marker for these compounds. Here we studied the immunohistochemical expression of proteins involved in DNA damage response and repair (γH2AX, 53BP1, ERCC1, MLH1, and MSH2) in primary tumor tissues from patients treated with platinum-based chemotherapy. Levels and localization of Heat Shock Protein (HSP)27 and phospho-(Thr5/7)-HSP90α (p-HSP90α) were also determined. The implications in clinical response, disease-free survival and overall survival were analyzed. High γH2AX and 53BP1 expressions were associated with poor clinical response. Nuclear p-HSP90α, as well as nuclear absence and low cytoplasmic expression of HSP27 correlated with good response. Patients with high γH2AX and high cytoplasmic HSP27 expressions had shorter overall survival and disease-free survival. MLH1, MSH2, or ERCC1 were not associated with clinical response or survival. We report the potential utility of p-HSP90α, HSP27, γH2AX, and 53BP1 as predictive/prognostic markers for platinum-based chemotherapy. We present the first study that evaluates the predictive and prognostic value of p-HSP90α in primary tumors. Our research opens new possibilities for clinical oncology and shows the usefulness of immunohistochemistry for predicting chemotherapy response and prognosis in cancer.

Phenotypic plasticity masks range-wide genetic differentiation for vegetative but not reproductive traits in a short-lived plant.

Genetic differentiation and phenotypic plasticity jointly shape intraspecific trait variation, but their roles differ among traits. In short-lived plants, reproductive traits may be more genetically determined due to their impact on fitness, whereas vegetative traits may show higher plasticity to buffer short-term perturbations. Combining a multi-treatment greenhouse experiment with observational field data throughout the range of a widespread short-lived herb, Plantago lanceolata, we (1) disentangled genetic and plastic responses of functional traits to a set of environmental drivers and (2) assessed how genetic differentiation and plasticity shape observational trait-environment relationships. Reproductive traits showed distinct genetic differentiation that largely determined observational patterns, but only when correcting traits for differences in biomass. Vegetative traits showed higher plasticity and opposite genetic and plastic responses, masking the genetic component underlying field-observed trait variation. Our study suggests that genetic differentiation may be inferred from observational data only for the traits most closely related to fitness.

Global gene flow releases invasive plants from environmental constraints on genetic diversity.

When plants establish outside their native range, their ability to adapt to the new environment is influenced by both demography and dispersal. However, the relative importance of these two factors is poorly understood. To quantify the influence of demography and dispersal on patterns of genetic diversity underlying adaptation, we used data from a globally distributed demographic research network comprising 35 native and 18 nonnative populations of Plantago lanceolata Species-specific simulation experiments showed that dispersal would dilute demographic influences on genetic diversity at local scales. Populations in the native European range had strong spatial genetic structure associated with geographic distance and precipitation seasonality. In contrast, nonnative populations had weaker spatial genetic structure that was not associated with environmental gradients but with higher within-population genetic diversity. Our findings show that dispersal caused by repeated, long-distance, human-mediated introductions has allowed invasive plant populations to overcome environmental constraints on genetic diversity, even without strong demographic changes. The impact of invasive plants may, therefore, increase with repeated introductions, highlighting the need to constrain future introductions of species even if they already exist in an area.

Mutualistic interactions reshuffle the effects of climate change on plants across the tree of life.

Climatically induced local species extinctions may trigger coextinction cascades, thus driving many more species to extinction than originally predicted by species distribution models. Using seven pollination networks across Europe that include the phylogeny and life history traits of plants, we show a substantial variability across networks in climatically predicted plant extinction-and particularly the subsequent coextinction-rates, with much higher values in Mediterranean than Eurosiberian networks. While geographic location best predicts the probability of a plant species to be driven to extinction by climate change, subsequent coextinctions are best predicted by the local network of interactions. These coextinctions not only increase the total number of plant species being driven to extinction but also add a bias in the way the major taxonomic and functional groups are pruned.

Geographic location, local environment, and individual size mediate the effects of climate warming and neighbors on a benefactor plant.

Predictions of plant responses to global warming frequently ignore biotic interactions and intraspecific variation across geographical ranges. Benefactor species play an important role in plant communities by protecting other taxa from harsh environments, but the combined effects of warming and beneficiary species on their performance have been largely unexamined. We analyzed the joint effects of elevated temperature and neighbor removal on the benefactor plant Silene acaulis, in factorial experiments near its low- and high-latitude range limits in Europe. We recorded growth, probability of reproduction and fruit set during 3 years. The effects of enhanced temperature were positive near the northern limit and negative in the south for some performance measures. This pattern was stronger in the presence of neighbors, possibly due to differential thermal tolerances between S. acaulis and beneficiary species in each location. Neighbors generally had a negative or null impact on S. acaulis, in agreement with previous reviews of overall effects of plant-plant interactions on benefactors. However, small S. acaulis individuals in the north showed higher growth when surrounded by neighbors. Finally, the local habitat within each location influenced some effects of experimental treatments. Overall, we show that plant responses to rising temperatures may strongly depend on their position within the geographic range, and on species interactions. Our results also highlight the need to consider features of the interacting taxa, such as whether they are benefactor species, as well as local-scale environmental variation, to predict the joint effects of global warming and biotic interactions on species and communities.

Evaluación neuropsicológica en niños y adolescentes con fenilcetonuria e hiperfenilalaninemia y su relación con los niveles de fenilalanina plasmática / Neuropsychological assessment among children and adolescents with phenylketonuria and hyperphenylalaninemia and its relationship with plasma phenylalanine levels

Aunque, con tratamiento precoz, los pacientes con fenilcetonuria pueden presentar niveles de inteligencia normales, es importante optimizar el control dietético para mantener niveles de fenilalanina adecuados y poder desarrollar su potencial intelectual sin alteraciones en sus tareas diarias por déficits en las funciones ejecutivas. Se presenta una serie de 26 pacientes, diagnosticados y tratados precozmente, a quienes se realizó una evaluación psicométrica junto con determinaciones de fenilalanina a lo largo de su vida y en el momento de realización de los tests. Se observa una tendencia a la relación inversa entre el cociente intelectual y la fenilalanina concurrente, la mediana de fenilalanina y el cociente fenilalanina/tirosina, así como una tendencia a la relación negativa entre las funciones ejecutivas y los valores de fenilalanina concurrentes y durante la vida.

Although with early treatment phenylketonuria patients may have average intelligence levels, it is important to optimize the nutritional management to maintain adequate phenylalanine levels, so that patients can develop their intellectual potential free of abnormalities in their daily activities due to deficits of cognitive executive functions. This study presents a series of 26 patients, diagnosed and treated early, who underwent a psychometric evaluation together with phenylalanine determinations along their lives, and at the time of doing the tests. A trend is observed towards a reverse relationship between IQ and concurrent phenylalanine concentration, phenylalanine median and phenylalanine/tyrosine ratio. Likewise, a trend towards a negative relationship is observed between executive functions and concurrent phenylalanine values along patients' lives.

Neuropsychological assessment among children and adolescents with phenylketonuria and hyperphenylalaninemia and its relationship with plasma phenylalanine levels. / Evaluación neuropsicológica en niños y adolescentes con fenilcetonuria e hiperfenilalaninemia y su relación con los niveles de fenilalanina plasmática.

Although with early treatment phenylketonuria patients may have average intelligence levels, it is important to optimize the nutritional management to maintain adequate phenylalanine levels, so that patients can develop their intellectal potential free of abnormalities in their daily activities due to deficits of cognitive executive functions. This study presents a series of 26 patients, diagnosed and treated early, who underwent a psychometric evaluation together with phenylalanine determinations along their lives, and at the time of doing the tests. A trend is observed towards a reverse relationship between IQ and concurrent phenylalanine concentration, phenylalanine median and phenylalanine/tyrosine ratio. Likewise, a trend towards a negative relationship is observed between executive functions and concurrent phenylalanine values along patients' lives.

Aunque, con tratamiento precoz, los pacientes con fenilcetonuria pueden presentar niveles de inteligencia normales, es importante optimizar el control dietético para mantener niveles de fenilalanina adecuados y poder desarrollar su potencial intelectual sin alteraciones en sus tareas diarias por déficits en las funciones ejecutivas. Se presenta una serie de 26 pacientes, diagnosticados y tratados precozmente, a quienes se realizó una evaluación psicométrica junto con determinaciones de fenilalanina a lo largo de su vida y en el momento de realización de los tests. Se observa una tendencia a la relación inversa entre el cociente intelectual y la fenilalanina concurrente, la mediana de fenilalanina y el cociente fenilalanina/tirosina, así como una tendencia a la relación negativa entre las funciones ejecutivas y los valores de fenilalanina concurrentes y durante la vida.

Geographic variation in genetic and demographic performance: new insights from an old biogeographical paradigm.

The 'centre-periphery hypothesis' (CPH) is a long-standing postulate in ecology that states that genetic variation and demographic performance of a species decrease from the centre to the edge of its geographic range. This hypothesis is based on an assumed concordance between geographical peripherality and ecological marginality such that environmental conditions become harsher towards the limits of a species range. In this way, the CPH sets the stage for understanding the causes of distribution limits. To date, no study has examined conjointly the consistency of these postulates. In an extensive literature review we discuss the birth and development of the CPH and provide an assessment of the CPH by reviewing 248 empirical studies in the context of three main themes. First, a decrease in species occurrence towards their range limits was observed in 81% of studies, while only 51% demonstrated reduced abundance of individuals. A decline in genetic variation, increased differentiation among populations and higher rates of inbreeding were demonstrated by roughly one in two studies (47, 45 and 48%, respectively). However, demographic rates, size and population performance less often followed CPH expectations (20-30% of studies). We highlight the impact of important methodological, taxonomic, and biogeographical biases on such validation rates. Second, we found that geographic and ecological marginality gradients are not systematically concordant, which casts doubt on the reliability of a main assumption of the CPH. Finally, we attempt to disentangle the relative contribution of geographical, ecological and historical processes on the spatial distribution of genetic and demographic parameters. While ecological marginality gradients explain variation in species' demographic performance better than geographic gradients, contemporary and historical factors may contribute interactively to spatial patterns of genetic variation. We thereby propose a framework that integrates species' ecological niche characteristics together with current and past range structure to investigate spatial patterns of genetic and demographic variation across species ranges.

Adaptation of the Long-Lived Monocarpic Perennial Saxifraga longifolia to High Altitude.

Global change is exerting a major effect on plant communities, altering their potential capacity for adaptation. Here, we aimed at unveiling mechanisms of adaptation to high altitude in an endemic long-lived monocarpic, Saxifraga longifolia, by combining demographic and physiological approaches. Plants from three altitudes (570, 1100, and 2100 m above sea level [a.s.l.]) were investigated in terms of leaf water and pigment contents, and activation of stress defense mechanisms. The influence of plant size on physiological performance and mortality was also investigated. Levels of photoprotective molecules (α-tocopherol, carotenoids, and anthocyanins) increased in response to high altitude (1100 relative to 570 m a.s.l.), which was paralleled by reduced soil and leaf water contents and increased ABA levels. The more demanding effect of high altitude on photoprotection was, however, partly abolished at very high altitudes (2100 m a.s.l.) due to improved soil water contents, with the exception of α-tocopherol accumulation. α-Tocopherol levels increased progressively at increasing altitudes, which paralleled with reductions in lipid peroxidation, thus suggesting plants from the highest altitude effectively withstood high light stress. Furthermore, mortality of juveniles was highest at the intermediate population, suggesting that drought stress was the main environmental driver of mortality of juveniles in this rocky plant species. Population structure and vital rates in the high population evidenced lower recruitment and mortality in juveniles, activation of clonal growth, and absence of plant size-dependent mortality. We conclude that, despite S. longifolia has evolved complex mechanisms of adaptation to altitude at the cellular, whole-plant and population levels, drought events may drive increased mortality in the framework of global change.

Demographic compensation among populations: what is it, how does it arise and what are its implications?

Most species are exposed to significant environmental gradients across their ranges, but vital rates (survival, growth, reproduction and recruitment) need not respond in the same direction to those gradients. Opposing vital rate trends across environments, a phenomenon that has been loosely called 'demographic compensation', may allow species to occupy larger geographical ranges and alter their responses to climate change. Yet the term has never been precisely defined, nor has its existence or strength been assessed for multiple species. Here, we provide a rigorous definition, and use it to develop a strong test for demographic compensation. By applying the test to data from 26 published, multi-population demographic studies of plants, we show that demographic compensation commonly occurs. We also investigate the mechanisms by which this phenomenon arises by assessing which demographic processes and life stages are most often involved. In addition, we quantify the effect of demographic compensation on variation in population growth rates across environmental gradients, a potentially important determinant of the size of a species' geographical range. Finally, we discuss the implications of demographic compensation for the responses of single populations and species' ranges to temporal environmental variation and to ongoing environmental trends, e.g. due to climate change.

Diversity of ageing across the tree of life.

Evolution drives, and is driven by, demography. A genotype moulds its phenotype's age patterns of mortality and fertility in an environment; these two patterns in turn determine the genotype's fitness in that environment. Hence, to understand the evolution of ageing, age patterns of mortality and reproduction need to be compared for species across the tree of life. However, few studies have done so and only for a limited range of taxa. Here we contrast standardized patterns over age for 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it has been predicted that evolution should inevitably lead to increasing mortality and declining fertility with age after maturity, there is great variation among these species, including increasing, constant, decreasing, humped and bowed trajectories for both long- and short-lived species. This diversity challenges theoreticians to develop broader perspectives on the evolution of ageing and empiricists to study the demography of more species.

Variation in stochastic demography between and within central and peripheral regions in a widespread short-lived herb.

Analyzing intraspecific variation in population dynamics in relation to environmental factors is crucial to understand the current and future distributions of plant species. Across ranges, peripheral populations are often expected to show lower and more temporally variable vital rates than central populations, although it remains unclear how much any differences in vital rates actually contribute to differences in population growth rates. Moreover, few demographic studies accounting for environmental stochasticity have been carried out both at continental and regional scales. In this study we calculated stochastic growth rates in five central and six northern peripheral populations of the widespread shortlived herb Plantago coronopus along the Atlantic Coast in Europe. To evaluate at two spatial scales how mean values and variability of vital rates (i.e., fecundity, recruitment, survival, growth, and shrinkage) contributed to the differences in stochastic growth rates, we performed Stochastic Life Table Response Experiment (SLTRE) analyses between and within central and peripheral regions. Additionally, we searched for correlations between vital rate contributions and local environmental conditions. Lower mean values and greater variability for some vital rates in peripheral than in central populations had an overall negative but nonsignificant effect on the stochastic growth rates in the periphery. Different life cycle components accounted for differences in population growth depending on spatial scale, although recruitment was the vital rate with the highest influence both between and within regions. Interestingly, the same pattern of differentiation among populations was found within central and peripheral areas: in both regions, one group of populations displayed positive contributions of growth and shrinkage and negative contributions of recruitment and survival; the opposite pattern was found in the remaining populations. These differences in vital rate contributions among populations within regions were correlated with precipitation regime, whereas at the continental scale, differences in contribution patterns were related to temperature. Altogether, our results show how populations of P. coronopus exhibit life cycle differences that may enable the species to persist in locations with widely varying environmental conditions. This demographic flexibility may help to explain the success of widespread plants across large and heterogeneous ranges.

A novel method to handle the effect of uneven sampling effort in biodiversity databases.

How reliable are results on spatial distribution of biodiversity based on databases? Many studies have evidenced the uncertainty related to this kind of analysis due to sampling effort bias and the need for its quantification. Despite that a number of methods are available for that, little is known about their statistical limitations and discrimination capability, which could seriously constrain their use. We assess for the first time the discrimination capacity of two widely used methods and a proposed new one (FIDEGAM), all based on species accumulation curves, under different scenarios of sampling exhaustiveness using Receiver Operating Characteristic (ROC) analyses. Additionally, we examine to what extent the output of each method represents the sampling completeness in a simulated scenario where the true species richness is known. Finally, we apply FIDEGAM to a real situation and explore the spatial patterns of plant diversity in a National Park. FIDEGAM showed an excellent discrimination capability to distinguish between well and poorly sampled areas regardless of sampling exhaustiveness, whereas the other methods failed. Accordingly, FIDEGAM values were strongly correlated with the true percentage of species detected in a simulated scenario, whereas sampling completeness estimated with other methods showed no relationship due to null discrimination capability. Quantifying sampling effort is necessary to account for the uncertainty in biodiversity analyses, however, not all proposed methods are equally reliable. Our comparative analysis demonstrated that FIDEGAM was the most accurate discriminator method in all scenarios of sampling exhaustiveness, and therefore, it can be efficiently applied to most databases in order to enhance the reliability of biodiversity analyses.

Extreme reproduction and survival of a true cliffhanger: the endangered Plant Borderea chouardii (Dioscoreaceae).

Cliff sides are extreme habitats, often sheltering a rich and unique flora. One example is the dioecious herb Borderea chouardii (Dioscoreaceae), which is a Tertiary, tropical relict, occurring only on two adjacent vertical cliffs in the world. We studied its reproductive biology, which in some aspects is extreme, especially the unusual double mutualistic role of ants as both pollinators and dispersers. We made a 2-year pollination census and four years of seed-dispersal experiments, recording flower visitors and dispersal rates. Fruit and seed set, self-sowing of seeds, seedling recruitment, and fate of seedlings from seeds sowed by different agents were scored over a period of 17 years. The ants Lasius grandis and L. cinereus were the main pollinators, whereas another ant Pheidole pallidula dispersed seeds. Thus ants functioned as double mutualists. Two thirds of all new seedlings came from self-sown seeds, and 1/3 was dispersed by ants, which gathered the seeds with their oil-rich elaiosome. Gravity played a minor role to dispersal. Both ant dispersal and self-sowing resulted in the same survival rate of seedlings. A double mutualism is a risky reproductive strategy, but B. chouardii buffers that by an unusual long-term demographic stability (some individuals exceed 300 years in lifespan) and its presence in a climatically very stable habitat, inaccessible to large herbivores. Such a combination of traits and habitat properties may explain the persistence of this relict species.

Age and sex-related changes in cytokinins, auxins and abscisic acid in a centenarian relict herbaceous perennial.

It is still an unsolved question of fundamental biology if, and how, perennial plants senesce. Here, age- and sex-related changes in phytohormones were tested in Borderea pyrenaica, a small dioecious geophyte relict of the Tertiary with one of the longest lifespan ever recorded for any non-clonal herb (more than 300 years). Biomass allocation, together with levels of cytokinins, auxins and absicisic acid, and other indicators of leaf physiology (chlorophylls, lipid peroxidation and F (v)/F (m) ratio) were measured in juvenile and mature plants, including both males and females of three age classes (up to 50 years, 50-100 years, and over 100 years). Plants maintained intact capacity of their vegetative growth and reproductive potential. Cytokinin levels decreased with age, but only in females. Such sex-related differences, however, were not associated with symptoms of physiological deterioration in leaves, but with an increased reproductive effort in females. It is concluded that B. pyrenaica does not show clear signs of senescence at the organism level. Altered cytokinin levels in females were associated with their reproductive effort, rather than to a degenerative process. The alternate use of five meristematic points in the tuber could explain the extraordinary longevity of this species.

Nonlinear relationships between vital rates and state variables in demographic models.

To accurately estimate population dynamics and viability, structured population models account for among-individual differences in demographic parameters that are related to individual state. In the widely used matrix models, such differences are incorporated in terms of discrete state categories, whereas integral projection models (IPMs) use continuous state variables to avoid artificial classes. In IPMs, and sometimes also in matrix models, parameterization is based on regressions that do not always model nonlinear relationships between demographic parameters and state variables. We stress the importance of testing for nonlinearity and propose using restricted cubic splines in order to allow for a wide variety of relationships in regressions and demographic models. For the plant Borderea pyrenaica, we found that vital rate relationships with size and age were nonlinear and that the parameterization method had large effects on predicted population growth rates, X (linear IPM, 0.95; nonlinear IPMs, 1.00; matrix model, 0.96). Our results suggest that restricted cubic spline models are more reliable than linear or polynomial models. Because even weak nonlinearity in relationships between vital rates and state variables can have large effects on model predictions, we suggest that restricted cubic regression splines should be considered for parameterizing models of population dynamics whenever linearity cannot be assumed.

Living at the edge: local versus positional factors in the long-term population dynamics of an endangered orchid.

Populations at the margin of geographic ranges of distribution have been considered more vulnerable than central ones, but recent reviews have caste doubt on this generalization. We examined the reproductive and demographic performance of a rare Euroasiatic orchid (Cypripedium calceolus) at its southwesterly range limit and compared our findings with those of previous studies of nine central populations at the center of the orchid's range. We sought to test the central-marginal model and to evaluate factors involved in long-term performance of forest Eurosiberian species with peripheral populations in southern European mountains. We characterized (structure, temporal fluctuations, herbivory, reproductive success, and recruitment at different habitats) four Pyrenean populations of C. calceolus of different sizes (5-3500 ramets) and monitored three of them for up to 13 years. Two quantitative stochastic models (count data and matrix models) were used to assess population trends and viability and the effect of herbivory. Contrary to expectations, and despite the negative effect of sporadic events of herbivory, the peripheral populations we studied (except the smallest one) performed similarly or better than populations occurring in central part of the species' range in terms of reproductive success and population growth rates. Landscape changes over the last 50 years suggest that natural reforestation could be involved in the success of this plant at its southern limit. Forest expansion in the mountain regions of southern Europe may provide new opportunities for plants with geographic distributions centered mainly at higher latitudes and give some hope for their recovery in future scenarios dominated by biodiversity loss.