On the sympatric evolution and evolutionary stability of coexistence by relative nonlinearity of competition

If two species exhibit different nonlinear responses to a single shared resource, and if each species modifies the resource dynamics such that this favors its competitor, they may stably coexist. This coexistence mechanism, known as relative nonlinearity of competition, is well understood theoretically, but less is known about its evolutionary properties and its prevalence in real communities. We address this challenge by using adaptive dynamics theory and individual-based simulations to compare community stabilization and evolutionary stability of species that coexist by relative nonlinearity. In our analysis, evolution operates on the species' density-compensation strategies, and we consider a trade-off between population growth rates at high and low resource availability. We confirm previous findings that, irrespective of the particular model of density dependence, there are many combinations of overcompensating and undercompensating density-compensation strategies that allow stable coexistence by relative nonlinearity. However, our analysis also shows that most of these strategy combinations are not evolutionarily stable and will be outcompeted by an intermediate density-compensation strategy. Only very specific trade-offs lead to evolutionarily stable coexistence by relative nonlinearity. As we find no reason why these particular trade-offs should be common in nature, we conclude that the sympatric evolution and evolutionary stability of relative nonlinearity, while possible in principle, seems rather unlikely. We speculate that this may, at least in part, explain why empirical demonstrations of this coexistence mechanism are rare, noting, however, that the difficulty to detect relative nonlinearity in the field [...]Comment: PLOS ONE, in pres

Managing land use and land cover change in the biodiversity context with regard to efficiency, equality and ecological effectiveness

The introduction of conservation-friendly farming measures is an important tool for biodiversity conservation. Recently, a debate has started whether this money is spent effectively, i.e. whether it successfully contributes to conserve biodiversity in agricultural landscapes. Several types of criticism have been raised that are adequately responded by environmental policies leading to spatially and temporally heterogeneous habitats. However existing policies for species conservation are still designed to support one conservation measure only by paying an equal amount of compensation to all land-users carrying out the corresponding measure. Regarding ecological findings we firstly point out in which cases environmental policies have to be differentiated in space and time. Secondly, we analyse the necessary and sufficient conditions for transfer schemes to exist that are able to introduce a spatio-temporally heterogeneous land use and land cover type. Thirdly, we reveal that strategic considerations of land-owners limit efficiency and fairness considerations of the policy makers when determining the ecologically accurate payment scheme. However ' surprisingly ' if policy makers seek to minimise their budget required for implementing the desired policy goal, this at the same time guarantees that the individual profits of the land-owners (when performing with the desired policy goal) are as equal as feasible. --

Integrating econimic costs into the analysis of flexible conservation management strategies

Flexible conservation management, where measures are selected in each decision period and depending on the current state of the ecological system, are generally perceived as superior to fixed management, where the same measure is applied in each decision period independent of the current state of the system. In past comparisons of fixed and flexible conservation strategies the additional costs that arise only in flexible strategies have usually been ignored. In this paper we present a framework to integrate these 'costs of flexible management' into the evaluation of flexible conservation strategies. Using the example of an endangered butterfly species we demonstrate that the costs of flexible management may reverse the rank order of flexible and fixed conservation strategies, such that fixed strategies may lead to better ecological results than flexible ones for the same financial budget. --conservation,ecological-economic model,extinction,flexible management

An agglomeration payment for cost-effective biodiversity conservation in spatially structured landscapes

Compensation schemes in which land owners receive payments for voluntarily managing their land in a biodiversity-enhancing manner have become one of the most important instruments for biodiversity conservation worldwide. One key challenge when designing such schemes is to account for the spatial arrangement of habitats bearing in mind that for given total habitat area connected habitats are ecologically more valuable than isolated habitats. To integrate the spatial dimension in compensation schemes and based on the idea of an agglomeration bonus we consider a scheme in which land-owners only receive payments if managed patches are arranged in a specific spatial configuration. We compare the cost-effectiveness of agglomeration payments with spatially homogeneous payments on a conceptual level and for a real world case and find that efficiency gains of agglomeration payments are positive or zero but never negative. In the real world case, agglomeration payments lead to cost-savings of up to 70% compared to spatially homogeneous payments. --agglomeration bonus,biodiversity conservation,cost-effectiveness,ecologicaleconomic modelling,metapopulation,spatial heterogeneity

A model-based approach for designing cost-effective compensation payments for conservation of endangered species in real landscapes

An approach is present which integrates an economic and an ecological model for designing cost-effective compensation payments for conservation of endangered species in real landscapes. The approach is used to develop a cost-effective compensation payment scheme for conservation of an endangered butterfly species (Maculinea teleius) protected by the EU Habitats Directive in the region of Landau, Germany. The economic model determines the costs of relevant conservation measures mowing meadows at different times and frequencies - and the ecological model quantifies the effects of these mowing regimes on the butterfly population. By comparing the ecological effects of different mowing regimes, the cost-effective regime and the corresponding payments are determined as a function of the conservation budget. The results of the case study are used to analyse the effect of metapopulation dynamics on the cost-effectiveness of compensation payment schemes, to evaluate an existing scheme in the region of Landau and to draw conclusions for the institutional design of payment schemes. --Conservation,biodiversity,metapopulation,cost-effectiveness,ecological-economic modelling

Disappearing refuges in time and space: how environmental change threatens species coexistence

Understanding the impacts of environmental changes on species survival is a major challenge in ecological research, especially when shifting from single- to multispecies foci. Here, we apply a spatially explicit two-species simulation model to analyze the effects of geographic range shifting and habitat isolation on different coexistence mechanisms. The model explicitly considers dispersal, local competition, and growth on a single resource. Results highlight that both range shifting and habitat isolation severely impact coexistence. However, the strength of these impacts depends on the underlying coexistence mechanisms. Neutrally coexisting species are particularly sensitive to habitat isolation, while stabilized coexistence through overcompensatory density regulation is much more sensitive to range shifting. We conclude that, at the community level, the response to environmental change sensitively depends on the underlying coexistence mechanisms. This suggests that predictions and management recommendations should consider differences between neutral versus stabilized community structures whenever possibl

A systematic approach for assessing spatially and temporally differentiated opportunity costs of biodiversity conservation measures in grasslands

Biodiversity loss in Europe is caused to a large extent by agricultural intensification. To halt this loss and to support species and habitat types in agricultural areas, agri-environment schemes have been introduced in Europe to compensate farmers for (costly) conservation measures. Currently, agri-environment schemes for grassland in general consider only a few conservation measures with fixed dates and a payment for average opportunity costs, e.g. for later mowing. A systematic approach that calculates farmers` opportunity costs in relation to the timing of grassland use is still lacking. We fill this gap by developing a systematic agri-economic cost assessment approach. Our approach is general enough to be applicable on a large spatial scale but can still sensitively differentiate among different timings. Moreover it is straightforward and time-saving enough to be suitable for implementation in regional scale optimisation procedures. We demonstrate this by applying the systematic cost assessment in the decision support software DSS-Ecopay using the example of grassland species and habitats conservation in the German federal state of Saxony

Resilience trinity: safeguarding ecosystem functioning and services across three different time horizons and decision contexts

Ensuring ecosystem resilience is an intuitive approach to safeguard the functioning of ecosystems and hence the future provisioning of ecosystem services (ES). However, resilience is a multi-faceted concept that is difficult to operationalize. Focusing on resilience mechanisms, such as diversity, network architectures or adaptive capacity, has recently been suggested as means to operationalize resilience. Still, the focus on mechanisms is not specific enough. We suggest a conceptual framework, resilience trinity, to facilitate management based on resilience mechanisms in three distinctive decision contexts and time-horizons: i) reactive, when there is an imminent threat to ES resilience and a high pressure to act, ii) adjustive, when the threat is known in general but there is still time to adapt management, and iii) provident, when time horizons are very long and the nature of the threats is uncertain, leading to a low willingness to act. Resilience has different interpretations and implications at these different time horizons, which also prevail in different disciplines. Social ecology, ecology, and engineering are often implicitly focussing on provident, adjustive, or reactive resilience, respectively, but these different notions and of resilience and their corresponding social, ecological, and economic trade-offs need to be reconciled. Otherwise, we keep risking unintended consequences of reactive actions, or shying away from provident action because of uncertainties that cannot be reduced. The suggested trinity of time horizons and their decision contexts could help ensuring that longer-term management actions are not missed while urgent threats to ES are given priority

Honey bee colony performance affected by crop diversity and farmland structure: a modeling framework

This is the final version. Available on open access from Wiley via the DOI in this recordForage availability has been suggested as one driver of the observed decline in honey bees. However, little is known about the effects of its spatiotemporal variation on colony success. We present a modeling framework for assessing honey bee colony viability in cropping systems. Based on two real farmland structures, we developed a landscape generator to design cropping systems varying in crop species identity, diversity, and relative abundance. The landscape scenarios generated were evaluated using the existing honey bee colony model BEEHAVE, which links foraging to in-hive dynamics. We thereby explored how different cropping systems determine spatiotemporal forage availability and, in turn, honey bee colony viability (e.g., time to extinction, TTE) and resilience (indicated by, e.g., brood mortality). To assess overall colony viability, we developed metrics, PH and PP, which quantified how much nectar and pollen provided by a cropping system per year was converted into a colony's adult worker population. Both crop species identity and diversity determined the temporal continuity in nectar and pollen supply and thus colony viability. Overall farmland structure and relative crop abundance were less important, but details mattered. For monocultures and for four-crop species systems composed of cereals, oilseed rape, maize, and sunflower, PH and PP were below the viability threshold. Such cropping systems showed frequent, badly timed, and prolonged forage gaps leading to detrimental cascading effects on life stages and in-hive work force, which critically reduced colony resilience. Four-crop systems composed of rye-grass–dandelion pasture, trefoil–grass pasture, sunflower, and phacelia ensured continuous nectar and pollen supply resulting in TTE > 5 yr, and PH (269.5 kg) and PP (108 kg) being above viability thresholds for 5 yr. Overall, trefoil–grass pasture, oilseed rape, buckwheat, and phacelia improved the temporal continuity in forage supply and colony's viability. Our results are hypothetical as they are obtained from simplified landscape settings, but they nevertheless match empirical observations, in particular the viability threshold. Our framework can be used to assess the effects of cropping systems on honey bee viability and to develop land-use strategies that help maintain pollination services by avoiding prolonged and badly timed forage gaps.German Academic Exchange ServiceHelmholtz Interdisciplinary GRADuate School for Environmental ResearchBiotechnology and Biological Sciences Research Council (BBSRC

Conservatives and Gamblers: Interpreting plant functional response to water stress in terms of a single indicator

Water availability has a decisive impact on plant growth, survival and distribution. Climate change is expected to alter both the amount and variability of precipitation. To predict and understand plant responses to water stress, efficient and robust mechanisms for describing their functional responses to water availability are needed. However, most ecohydrological processes and models which take into account these responses are inherently complex, difficult to understand and require large amounts of data. We develop a novel straightforward approach and hypothesize that: (1) Plants exhibit two archetypical response patterns under water stress, one typical to slow-growing plants and one typical to fast-growing ones, with most plants being situated between these two. (2) Differences within and between these functional types can be adequately described by a single parameter - the threshold of relative soil water content - at which plants reduce their transpiration in response to water stress. This indicator is straightforward and relies on data which is relatively easy to measure. Its effect has been previously described and it is already used in several models to simulate the effect of water stress on plants. In our approach, we combine this indicator with a description of reactions patterns. This combination provides a general and efficient way of classifying plant responses and allows the assessment of the impact of water stress on a wide variety of plants. Due to its simplicity, our approach offers the opportunity to include water relations of plants in a larger set of models and descriptions than it is possible with more complex ecohydrological descriptions. It also can be used to explain biodiversity in fluctuating environments