Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Opstaan voor de biodiversiteit: ‘Kleine stapjes zijn niet genoeg, er is systeemverandering nodig
Turnhout, E. - \ 2019
biodiversity - extinction - species richness - nature management - sustainability
Terug naar de oertijd : herintroductie van de Atlantische steur in de Rijn
Brevé, Niels ; Laak, Gerard de; Houben, Bram ; Reiniers, Karsten ; Zonneveld, Gijs van; Blom, Esther ; Breukelaar, André ; Winter, Hendrik V. ; Vis, Hendry - \ 2015
Visionair : het vakblad van sportvisserij Nederland 10 (2015)38. - ISSN 1569-7533 - p. 4 - 7.
herintroductie van soorten - steuren - bedreigde soorten - uitsterven - rijn - wildbeheer - wildbescherming - reintroduction of species - sturgeons - endangered species - extinction - river rhine - wildlife management - wildlife conservation
De Atlantische steur (Acipenser sturio) behoort tot een ruim 200 miljoen jaar oude diergroep. Deze kraakbeenvissen overleefden de dinosauriërs. Echter, tussen 1920 en 1990 verdween de steur door toedoen van de mens uit vrijwel alle grote rivieren van West-Europa. Het is een geweldige uitdaging om deze oervis met beenplaten en vier snorharen voor uitsterven te behoeden
Zweven boven de afgrond : gieren in Afrika ernstig bedreigd
Nijland, Rik ; Buij, R. - \ 2015
WageningenWorld (2015)4. - ISSN 2210-7908 - p. 22 - 25.
accipitridae - bedreigde soorten - uitsterven - afrika - ziekten - pathogenen - dierecologie - accipitridae - endangered species - extinction - africa - diseases - pathogens - animal ecology
Ze worden opgegeten, vergiftigd door boeren en stropers en verwerkt in traditionele medicijnen. Afrikaanse gieren zijn daardoor in vijftig jaar met 80 procent achteruitgegaan. Als de gieren het laten afweten, worden rottende karkassen mogelijk verspreidingshaarden van ziekten die gevaarlijk zijn voor mens en dier.
International cooperation for biodiversity conservation : an economic analysis
Alvarado Quesada, I. - \ 2015
Wageningen University. Promotor(en): Ekko van Ierland, co-promotor(en): Hans-Peter Weikard. - Wageningen : Wageningen University - ISBN 9789462576124 - 151
biodiversiteit - natuurbescherming - uitsterven - biodiversity - nature conservation - extinction

Biodiversity decline poses significant threats to current and future generations. Although species extinction has been a natural process since the formation of Earth, recent rates of extinction are estimated to be from 100 to 1000 times larger when compared to fossil records. Almost all of the Earth’s ecosystems have been dramatically transformed and some of them are being pushed towards critical thresholds that could risk overall livelihoods and wellbeing of human population. Implications of severe biodiversity loss include irreversible alterations of ecosystem services, vulnerability to natural disasters, human health risks, threats to food and energy security, depletion of natural resources and damage to social relations.

There is an urgent need to study and develop efficient conservation instruments that decision makers can implement to halt the ongoing rate of biodiversity loss. However, this is a complex task due to i) the multidimensional nature of biodiversity conservation in terms of the different levels of biological organisation, and also to ii) the diverse geographical scales of concern at stake (from local to global). The objective of this thesis is to examine the functioning and effectiveness of different economic instruments for biodiversity conservation at diverse scales. In order to achieve this objective, different methodological approaches such as market theory, contract theory, and game theory are implemented.

In Chapter 2, I develop an assessment of economic characteristics for biodiversity markets to work efficiently. I first introduce a set of general conditions to guarantee market efficiency. These conditions are derived from market and contract theory. In the light of these conditions, I analyse the efficiency of five selected market schemes for biodiversity conservation that have been implemented in different countries. An assessment of the upscaling potential of the existing markets reveals that obstacles such as the lack of a standardised unit of measurement for biodiversity and the difficulty to ensure long-term conservation make it difficult to scale up any of the selected mechanisms as they are currently performing. I argue that the creation of a global credit registry for biodiversity would facilitate measurement, reporting and verification (MRV) of biodiversity credits to support market-based mechanisms.

In Chapter 3, I present a game-theoretic model for an international environmental agreement (IEA) for biodiversity conservation. I first introduce three key characteristics that differentiate the case of biodiversity conservation from the conventional emission abatement model: the existence of a natural upper bound of conservation per country, the importance of local benefits, and the subadditivity of the global conservation function. Then, I consider asymmetries in benefits and costs of biodiversity conservation, and separately, in the natural upper bound of conservation per country. Results show that there is scope to achieve a higher degree of cooperation in a potential IEA for biodiversity conservation when subadditivity in the global conservation function is considered. Furthermore, the inclusion of an optimal transfer rule allows not only for larger stable coalitions and higher potential gains of cooperation and conservation, but also for a different composition of coalition structures (in term of country types).

In Chapter 4, I analyse the inclusion of an explicit spatial structure in the modelling of an IEA for conservation. I assess the role of distance and location between countries on coalition formation and overall coalition stability. First, to explain cooperation among neighbouring countries I make use of a specific setting: a circular spatial structure. Furthermore, I employ a notion of distance between countries in terms of their ecosystem dissimilarity: two countries are closer the more species they have in common. I argue that, for the purpose of exploring the stability of conservation agreements, geographical distance may be less important than the dissimilarity of the sets of species that two countries host. Results show that the maximum size of a stable coalition in the model with a spatial structure is of two members. These results are robust with respect to the different spatial patterns assessed within the circular structure. I conclude that the stable coalition with the best global payoff is obtained when stable coalitions are composed of two countries with the smallest possible distance between them. Also, the study shows evidence of a ‘remoteness effect’. Highest payoffs in a stable biodiversity agreement are attained when member countries are the closest to each other, but also to the rest of the countries in the spatial structure.

In Chapter 5, the model for an IEA for conservation with an embedded spatial structure is applied to a case study on regional conservation of the non-breeding habitat of the Golden-winged warbler (Vermivora chrysoptera). I study the incentives of countries to join an agreement for the protection of wintering habitats by calibrating the game theoretical model with empirical data. Also, I include a spatial setting that best describes specific aspects of the migratory behaviour of the species. Results show that when there is a positive willingness to pay of US households to improve the chance of survival of the population of the Golden-winged Warbler, and when allowing for the implementation of a transfer scheme, there is scope for a stable conservation agreement between the United States and the Latin American countries with wintering habitat of the bird species (i.e. full cooperation). For all scenarios of our study, the United States transfers part of its payoff to the Latin American countries to incentivise conservation and stabilise the coalition.

This thesis has shown the importance of taking into account asymmetries between countries – both in their biodiversity endowments as well as in benefits and costs of conservation activities – in the design and application on economic instruments for biodiversity conservation. Furthermore, the implementation of transfer schemes as instruments to incentivise conservation have the potential to contribute to effective biodiversity management.

Profit fluctuations signal eroding resilience of natural resources
Richter, A.P. ; Dakos, V. - \ 2015
Ecological Economics 117 (2015). - ISSN 0921-8009 - p. 12 - 21.
social-ecological systems - early-warning signals - regime shifts - fisheries management - ecosystem services - tipping point - slowing-down - fish stocks - extinction - indicators
A common pattern of environmental crises is a vicious cycle between environmental degradation and socio-economic disturbances. Here we show that while such feedbacks may give rise to critical transitions in social-ecological systems, at the same time they can offer novel o0pportunities for anticipating them. We model a community that has joint access to the harvest grounds of a resource that is prone to collapse. Individuals are tempted to overexploit the resource, while a cooperative harvesting norm spreads through the community via interprersonal relations. Both social and ecological collapses can be induced by environmental or socio-economic driving forces. Regardless of the type and cause of collapse we find that upcoming transitions may be detected using simple socio-economic response variables, such as individual profits. Our findings suggest that such alternative sources of information can be used to detect upcoming critical transitions in social-ecological systems. However, we also find that robust detection of critical transitions may be confounded by recovery attempts undertaken by resource users in the vicinity of an upcoming collapse, which may be falsely interpreted as a stabilization of the social-ecological system.
Spatial sorting and range shifts: consequences for evolutionary potential and genetic signature of a dispersal trait
Cobben, M.M.P. ; Verboom, J. ; Opdam, P.F.M. ; Hoekstra, R.F. ; Jochem, R. ; Smulders, M.J.M. - \ 2015
Journal of Theoretical Biology 373 (2015). - ISSN 0022-5193 - p. 92 - 99.
woodpecker dendrocopos-medius - climate-change - wave-front - expanding population - local adaptation - metapopulation - diversity - expansion - edge - extinction
Species are shifting their ranges under climate change, with genetic and evolutionary consequences. As a result, the spatial distribution of genetic diversity in a species’ range can show a signature of range expansion. This genetic signature takes time to decay after the range stops expanding and it is important to take that lag time into account when interpreting contemporary spatial patterns of genetic diversity. In addition, the return to spatial equilibrium on an ecologically relevant timescale will depend on migration of genetic diversity across the species’ range. However, during a range shift alleles may go extinct at the retracting range margin due to spatial sorting. Here we studied the spatial pattern of genotypes that differ in dispersal rate across the species range before, during and after a range shift, assessed the effect of range retraction on this pattern, and quantified the duration of the ephemeral genetic signature of range expansion for this trait. We performed simulation experiments with an individual-based metapopulation model under several contemporary climate change scenarios. The results show an increase of the number of individuals with high dispersal rate. If the temperature increased long enough the allele coding for low dispersal rate would go extinct. The duration of the genetic signature of range expansion after stabilisation of the species’ distribution lasted up to 1200 generations after a temperature increase for 60 years at the contemporary rate. This depended on the total displacement of the climate optimum, as the product of the rate of temperature increase and its duration. So genetic data collected in the field do not necessarily reflect current selection pressures but can be affected by historic changes in species distribution, long after the establishment of the current species’ range. Return to equilibrium patterns may be hampered by loss of evolutionary potential during range shift.
Inbreeding depression and purging in a haplodiplois: gender-related effects
Tien, N.S.H. ; Sabelis, M.W. ; Egas, M. - \ 2015
Heredity 114 (2015). - ISSN 0018-067X - p. 327 - 332.
x-linked genes - female fecundity - load - populations - selection - genetics - mite - extinction
Compared with diploid species, haplodiploids suffer less inbreeding depression because male haploidy imposes purifying selection on recessive deleterious alleles. However, alleles of genes only expressed in the diploid females are protected in heterozygous individuals. This leads to the prediction that haplodiploids suffer more from inbreeding effects on life-history traits controlled by genes with female-limited expression. To test this, we used a wild population of the haplodiploid mite Tetranychus urticae. First, negative effects of inbreeding were investigated by comparing maturation rate, juvenile survival, oviposition rate and longevity between lines created by three generations of either outbreeding or mother-son inbreeding. Second, purging through inbreeding was investigated by comparing the intensity of inbreeding depression between outbred families with known inbreeding/outbreeding mating histories. Negative effects of inbreeding and evidence for purging were found for the female trait oviposition rate, but not for juvenile survival and longevity. Both male and female maturation rate were negatively affected by inbreeding, most likely due to maternal effects because inbred offspring of outbred mothers was not affected. These results support the hypothesis that, in haplodiploids inbreeding effects and genetic variation due to deleterious recessive alleles may depend on gender.
Data from: Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages
Caughlin, T.T. ; Ferguson, J.M. ; Lichstein, J.W. ; Zuidema, Pieter ; Bunyavejchewin, S. ; Levey, D.J. - \ 2014
University of Florida
tropical forests - Anthropocene - fruit production - neighborhood model - seed addition experment - Saccopetalum - extinction - germination - tree demography - seedling demography - tree population - seedlings - neighborhood - tropical forest dynamics - negative density dependence - Miliusa - Annonaceae - seed dispersal - spatial model - Frugivory - Miliusa horsfieldii - overhunting
Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.
Island life shapes the physiology and life history of eastern bluebirds (Sialia sialis)
Matson, K.D. ; Mauck, R.A. ; Lynn, S.E. ; Tieleman, B.I. - \ 2014
Physiological and Biochemical Zoology 87 (2014)1. - ISSN 1522-2152 - p. 172 - 182.
body-size - immune-response - birds - populations - conservation - biodiversity - haptoglobin - extinction - trends - growth
Abstract Island organisms face a range of extrinsic threats to their characteristically small populations. Certain biological differences between island and continental organisms have the potential to exacerbate these threats. Understanding how island birds differ from their continental relatives may provide insight into population viability and serve as a predictive tool for conservation efforts. We compared an eastern bluebird population in Ohio with a threatened population in Bermuda in terms of the birds' development, morphology, immunology, and reproduction. These comparisons revealed that island nestlings had shorter wings and island adults had longer wings than their continental analogs. Island nestlings also had shorter tarsi than continental nestlings at day 8 posthatch, but this difference was absent at day 15 and in adults. Adults weighed less in Bermuda than in Ohio, and both nestlings and adults in Bermuda exhibited higher levels of two immunological indexes (concentrations of an acute-phase protein and titers of nonspecific antibodies). Clutch sizes and hatch rates did not differ between the island and continental populations; however, as the breeding season progressed, brood sizes declined in Bermuda, whereas no such decline occurred in Ohio. Despite these differences and differences in nestling development, island and continental parents fed their nestlings at equal rates. Overall, our results suggest that the Bermuda phenotype may be adjusted to certain aspects of the island environment but not to others. Efforts to conserve the bluebirds of Bermuda may be improved by focusing on the intraseasonal patterns in nestling mortality and, more generally, the survival probabilities of different age classes.
Approaches to defining a planetary boundary for biodiversity
Mace, G.M. ; Reyers, B. ; Alkemade, R. ; Biggs, R. ; Stuart Chapin, F. ; Cornell, S.E. ; Diaz, S. - \ 2014
Global environmental change : human and policy dimensions 28 (2014). - ISSN 0959-3780 - p. 289 - 297.
plant functional traits - global biodiversity - ecosystem services - phylogenetic diversity - tree mortality - tipping points - conservation - extinction - time - biosphere
The idea that there is an identifiable set of boundaries, beyond which anthropogenic change will put the Earth system outside a safe operating space for humanity, is attracting interest in the scientific community and gaining support in the environmental policy world. Rockstrom et al. (2009) identify nine such boundaries and highlight biodiversity loss as being the single boundary where current rates of extinction put the Earth system furthest outside the safe operating space. Here we review the evidence to support a boundary based on extinction rates and identify weaknesses with this metric and its bearing on humanity's needs. While changes to biodiversity are of undisputed importance, we show that both extinction rate and species richness are weak metrics for this purpose, and they do not scale well from local to regional or global levels. We develop alternative approaches to determine biodiversity loss boundaries and extend our analysis to consider large-scale responses in the Earth system that could affect its suitability for complex human societies which in turn are mediated by the biosphere. We suggest three facets of biodiversity on which a boundary could be based: the genetic library of life; functional type diversity; and biome condition and extent. For each of these we explore the science needed to indicate how it might be measured and how changes would affect human societies. In addition to these three facets, we show how biodiversity's role in supporting a safe operating space for humanity may lie primarily in its interactions with other boundaries, suggesting an immediate area of focus for scientists and policymakers.
Within and between population variation in inbreeding depression in the locally threatened perennial Scabiosa columbaria
Angeloni, F. ; Vergeer, P. ; Wagemaker, C.A.M. ; Ouborg, N.J. - \ 2014
Conservation Genetics 15 (2014)2. - ISSN 1566-0621 - p. 331 - 342.
among-family variation - false discovery rate - self-fertilization - life-history - genetic differentiation - grassland plant - mating systems - size - extinction - conservation
Inbreeding depression plays a central role within the conservation genetics paradigm. Until now inbreeding depression is incorporated into models of population viability as a mean value (e.g. number of lethal equivalents) for all traits in a population. In this study of the locally threatened perennial plant species Scabiosa columbaria we investigated both the mean and the variance among families of inbreeding depression in eight life history traits for five natural populations varying in size from 300 to more than 120,000 individuals. Significant inbreeding depression was found in all populations and all traits. The mean inbreeding depression value per trait was never correlated to population size. Within each population, highly significant variation in inbreeding depression between families (VIFLID) was found. Per trait, families with inbreeding depression next to families with outbreeding depression were often found within the same population. Inbreeding depression at the family level was in many cases not correlated among traits and independent of correlations between traits themselves. VIFLID was negatively correlated with population size: in two traits these correlations were significant. The results underline that inbreeding depression is a complex, highly dynamic phenomenon. Models of viability should incorporate inbreeding depression distributions, with a trait specific mean and variance. Moreover, models of metapopulation dynamics should incorporate genotype quality as factor in colonization success.
When to declare successful eradication of an invasive predator?
Rout, T.M. ; Kirkwood, R.J. ; Sutherland, D.R. ; Murphy, S. ; McCarthy, M. - \ 2014
Animal Conservation 17 (2014)2. - ISSN 1367-9430 - p. 125 - 132.
feral cat eradication - fox vulpes-vulpes - phillip-island - population - extinction - california - penguins - victoria
Imperfect detection methods make it difficult to tell whether an invasive species has been successfully eradicated. However, management cannot continue indefinitely when individuals are no longer detected – at some point, efforts must be reduced or ceased entirely. The risks of mistakenly inferring that an eradication attempt has been successful can be high: the species can bounce back and even expand its range, causing environmental and economic damage, and rendering the initial eradication campaign redundant. This decision problem, balancing the risks of declaring eradication prematurely with the costs of continued management, is currently being contemplated by managers of the fox eradication programme on Phillip Island, in Victoria, Australia. We used a Bayesian catch-effort model to analyse data on the number of foxes removed and sighted using different methods. We estimate that there were 11 foxes remaining on Phillip Island as of end of June 2012. Baiting was the most effective method for removing foxes per person-hour invested, and spotlighting was the most effective method for sighting foxes without removal. We then projected forward into the future, assuming management effort continues at current levels, but no further foxes are detected (removed or sighted). Under this scenario, the mean estimate for the number of foxes remaining drops below a single fox after three years with no detections, and the probability that eradication has been successful is 0.69. This is the optimal time to declare eradication, given our estimated cost of declaring eradication prematurely. This framework indicates the minimum number of years for which management of foxes on the island must continue and allows decision makers to assess the trade-offs involved in any decision to declare eradication.
Toward better application of minimum area requirements in conservation planning
Pe’er, G. ; Tsianou, M.A. ; Franz, K.W. ; Matsinos, Y.G. ; Mazaris, A.D. ; Storch, D. ; Kopsova, L. ; Verboom, J. ; Baguette, M. ; Stevens, V.M. ; Henle, K. - \ 2014
Biological Conservation 170 (2014). - ISSN 0006-3207 - p. 92 - 102.
population viability analysis - home-range size - land-use change - body-size - extinction - mammals - birds - fragmentation - biodiversity - management
The Minimum Area Requirements (MAR) of species is a concept that explicitly addresses area and therefore can be highly relevant for conservation planning and policy. This study compiled a comprehensive database of MAR estimates from the literature, covering 216 terrestrial animal species from 80 studies. We obtained estimates from (a) Population Viability Analyses (PVAs) which explored a range of area-related scenarios, (b) PVAs that provided a fixed value – either MAR or the minimum viable population size (MVP) alongside other area-relevant information, and (c) empirical studies of occupancy patterns in islands or isolated habitat patches across area. We assessed the explanatory power of life-history traits (body mass, feeding guild, generation length and offspring size), environmental variables (average precipitation and temperature), research approach and phylogenetic group on MAR estimates. PVAs exploring area showed strong correlation between MAR and body mass. One to two additional variables further improved the predictive power. PVA reporting fixed MAR, and occupancy-based studies, were better explained by the combination of feeding guild, climatic variables and additional life history traits. Phylogeny had a consistent but usually small contribution to the predictive power of models. Our work demonstrates that estimating the MAR across species and taxa is achievable but requires cautious interpretation. We further suggest that occupancy patterns are likely sensitive to transient dynamics and are therefore risky to use for estimating MAR. PVA-based evaluations enable considering time horizon and extinction probability, two aspects that are critical for future implementation of the MAR concept into policy and management.
Species living in hars environments have low clade rank and are localized on former Laurasian continents: a case study of Willemia (Collembola)
Prinzing, A. ; Haese, C.A. D'; Pavoine, S. ; Ponge, J.F. - \ 2014
Journal of Biogeography 41 (2014)2. - ISSN 0305-0270 - p. 353 - 365.
general-purpose genotype - niche conservatism - phylogenetic perspective - desiccation tolerance - evolutionary dynamics - cretaceous collembola - drought acclimation - diversity gradient - biological traits - extinction
Aim Certain species have few living relatives (i.e. they occupy low clade ranks) and hence they possess high conservation value and scientific interest as unique representatives of ancient lineages. However, we do not know whether particular environments favour the maintenance of low clade ranks or whether the distribution of environments across the globe affects the global distribution of clade ranks and, hence, evolutionary uniqueness. In this study, we tested whether and how harsh environments decrease the clade ranks of the species that inhabit them. Location: Global. Methods We described the phylogeny of the collembolan genus Willemia by a parsimonious method based on 52 morphological characters and estimated the species’ use of harsh environments (polar, high mountain, desert, polluted, waterlogged, saline and acidic) from 248 publications. Results: We found that the use of different types of harsh environments is maintained among close relatives and has similar phylogenetic signals (except for the use of salinity). The use of harsh environments might therefore affect the diversification of lineages. Correcting for the phylogenetic non-independence of species, we found that species using harsh environments have comparatively low clade ranks. We also found that species using harsh environments occur almost exclusively on former Laurasian continents and that, as a statistical consequence, Laurasian species tend to have lower clade ranks. Main conclusions: We suggest that harsh environments maintain low-claderank species by decreasing, simultaneoulsy or successively, extinction and speciation, which may eventually explain the major variation in clade rank across the globe. Keywords Abiotic stress, diversification, habitat, Laurasia, niche conservatism, phylogenetic reconstruction, phylogenetic GLS analysis, phylogenetic principal components, root-skewness test, springtails.
The estimation of species richness of Dutch bryophytes between 1900 and 2011. Documentation of VBA-procedures based on the Frescalo program
Bijlsma, R.J. - \ 2013
KNNV (BLWG-rapport 15) - 44
mossen - bryophyta - bedreigde soorten - uitsterven - flora - nederland - mosses - endangered species - extinction - netherlands
In 2011 the Ministery of Economic Affairs, Agriculture and Innovation asked the BLWG to update the Dutch Red List of bryophytes. The Red List is derived from distribution data recorded between 1900 and 2011 on a quadrant basis (5 x 5 km squares). The Dutch recording grid for distribution data consists of 1476 quadrants. The proper estimation of species richness for different time periods requires a method to correct for recording bias. We used the method and Frescalo program published recently by Hill (2012). This BLWG-report documents the implementation of the Frescalo program in Visual Basic for Applications (MS Access 2010) including modules for input/output and describes the corresponding database structure. Additional analyses evaluate parameter settings. The Frescalo program estimates species richness by evaluating local frequencies in neighbourhoods of each quadrant. The VBA-version determines neighbourhoods by considering physical distance and abiotic similarity (features of soil, ground water and geomorphology). Model output mainly depends on 1) the size of the neighbourhood used to estimate local species frequencies; 2) the proportion of local benchmark species used to estimate sampling intensity; 3) the expected mean neighbourhood frequency (assumed to be independent of species richness). Frescalo output is used to calculate the expected number of quadrants per species for each decade between 1900 and 2011.
Genetic incompatibility drives mate choice in a parasitic wasp
Thiel, A. ; Weeda, A.C. ; Boer, J.G. de; Hoffmeister, T.S. - \ 2013
Frontiers in Zoology 10 (2013). - ISSN 1742-9994 - 6 p.
complementary sex determination - field crickets - selection - mhc - preferences - hymenoptera - quality - extinction - increases - humans
Introduction: Allelic incompatibility between individuals of the same species should select for mate choice based on the genetic make-up of both partners at loci that influence offspring fitness. As a consequence, mate choice may be an important driver of allelic diversity. A complementary sex determination (CSD) system is responsible for intraspecific allelic incompatibility in many species of ants, bees, and wasps. CSD may thus favour disassortative mating and in this, resembles the MHC of the vertebrate immune system, or the self-incompatibility (SI) system of higher plants. Results: Here we show that in the monogamous parasitic wasp Bracon brevicornis (Wesmael), females are able to reject partners with incompatible alleles. Forcing females to accept initially rejected partners resulted in sex ratio distortion and partial infertility of offspring. Conclusions: CSD-disassortative mating occurred independent of kin recognition and inbreeding avoidance in our experiment. The fitness consequences of mate choice are directly observable, not influenced by environmental effects, and more severe than in comparable systems (SI or MHC), on individuals as well as at the population level. Our results thus demonstrate the strong potential of female mate choice for maintaining high offspring fitness in this species.
Contagious cooperation, temptation and ecosystem collapse
Richter, A.P. ; Soest, D. van; Grasman, J. - \ 2013
Journal of Environmental Economics and Management 66 (2013)1. - ISSN 0095-0696 - p. 141 - 158.
resource use - punishment - management - dynamics - evolution - economics - model - extinction - fisheries - systems
Real world observations suggest that social norms of cooperation can be effective in overcoming social dilemmas such as the joint management of a common pool resource—but also that they can be subject to slow erosion and sudden collapse. We show that these patterns of erosion and collapse emerge endogenously in a model of a closed community harvesting a renewable natural resource in which individual agents face the temptation to overexploit the resource, while a cooperative harvesting norm spreads through the community via interpersonal relations. We analyze under what circumstances small changes in key parameters (including the size of the community, and the rate of technological progress) trigger catastrophic transitions from relatively high levels of cooperation to widespread norm violation—causing the social–ecological system to collapse.
Early warning signals also precede non-catastrophic transitions
Kefi, S. ; Dakos, V. ; Scheffer, M. ; Nes, E.H. van; Rietkerk, M. - \ 2013
Oikos 122 (2013)5. - ISSN 0030-1299 - p. 641 - 648.
regime shifts - catastrophic shifts - climate-change - slowing-down - ecosystems - thresholds - extinction - time - population - indicator
Synthesis The quickly expanding literature on early warning signals for critical transitions in ecosystems suggests that critical slowing down is a key phenomenon to measure the distance to a tipping point in ecosystems. Such work is broadly misinterpreted as showing that slowing down is specific to tipping points. In this contribution, we show why this is not the case. Early warning signals based on critical slowing down indicate a broader class of situations where a system becomes increasingly sensitive to perturbations. Ecosystem responses to external changes can surprise us by their abruptness and irreversibility. Models have helped identifying indicators of impending catastrophic shifts, referred to as 'generic early warning signals'. These indicators are linked to a phenomenon known as 'critical slowing down' which describes the fact that the recovery rate of a system after a perturbation decreases when the system approaches a bifurcation - such as the classical fold bifurcation associated to catastrophic shifts. However, contrary to what has sometimes been suggested in the literature, a decrease in recovery rate cannot be considered as specific to approaching catastrophic shifts. Here, we analyze the behavior of early warning signals based on critical slowing down in systems approaching a range of catastrophic and non-catastrophic situations. Our results show that slowing down generally happens in situations where a system is becoming increasingly sensitive to external perturbations, independently of whether the impeding change is catastrophic or not. These results highlight that indicators specific to catastrophic shifts are still lacking. More importantly, they also imply that in systems where we have no reason to expect catastrophic transitions, slowing down may still be used in a more general sense as a warning signal for a potential decrease in stability
Differences in the climatic debts of birds and butterflies at a continental scale
Devictor, V. ; Swaay, C. van; Brereton, T. ; Brotons, L. ; Chamberlain, D. ; Heliölä, J. ; Herrando, S. ; Julliard, R. ; Kuussaari, M. ; Lindström, A. ; Reif, J. ; Roy, D.B. ; Schweiger, O. ; Settele, J. ; Stefanescu, C. ; Strien, A. van; Turnhout, C. van; Vermouzek, Z. ; Wallis de Vries, M.F. ; Wynhoff, I. ; Jiguet, F. - \ 2012
Nature Climate Change 2 (2012). - ISSN 1758-678X - p. 121 - 124.
evolutionary responses - global change - extinction - adaptation
Climate changes have profound effects on the distribution of numerous plant and animal species(1-3). However, whether and how different taxonomic groups are able to track climate changes at large spatial scales is still unclear. Here, we measure and compare the climatic debt accumulated by bird and butterfly communities at a European scale over two decades (1990-2008). We quantified the yearly change in community composition in response to climate change for 9,490 bird and 2,130 butterfly communities distributed across Europe(4). We show that changes in community composition are rapid but different between birds and butterflies and equivalent to a 37 and 114 km northward shift in bird and butterfly communities, respectively. We further found that, during the same period, the northward shift in temperature in Europe was even faster, so that the climatic debts of birds and butterflies correspond to a 212 and 135 km lag behind climate. Our results indicate both that birds and butterflies do not keep up with temperature increase and the accumulation of different climatic debts for these groups at national and continental scales.
Robustness of variance and autocorrelation as indicators of critical slowing down
Dakos, V. ; Nes, E.H. van; Odorico, P. D'; Scheffer, M. - \ 2012
Ecology 93 (2012)2. - ISSN 0012-9658 - p. 264 - 271.
early-warning signals - regime shifts - critical transitions - catastrophic shifts - leading indicators - ecosystems - environments - thresholds - extinction - systems
Ecosystems close to a critical threshold lose resilience, in the sense that perturbations can more easily push them into an alternative state. Recently, it has been proposed that such loss of resilience may be detected from elevated autocorrelation and variance in the fluctuations of the state of an ecosystem due to critical slowing down; the underlying generic phenomenon that occurs at critical thresholds. Here we explore the robustness of autocorrelation and variance as indicators of imminent critical transitions. We show both analytically and in simulations that variance may sometimes decrease close to a transition. This can happen when environmental factors fluctuate stochastically and the ecosystem becomes less sensitive to these factors near the threshold, or when critical slowing down reduces the ecosystem's capacity to follow high-frequency fluctuations in the environment. In addition, when available data is limited, variance can be systematically underestimated due to the prevalence of low frequencies close to a transition. By contrast, autocorrelation always increases toward critical transitions in our analyses. To exemplify this point, we provide cases of rising autocorrelation and increasing or decreasing variance in time series prior to past climate transitions.
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