Towards nationally harmonized mapping and quantification of ecosystem services.

The EU 2020 Biodiversity Strategy requests EU Member States to map and assess ecosystem services within national territories, and to promote and integrate these values into policy-making. This calls for standardized and harmonized data, indicators, and methods to assess ecosystem services within national boundaries. Current approaches for assessing ecosystem services often oversimplify cross-scale heterogeneity, sacrificing the spatial and thematic detail required to support the needs and expectations of decision-makers at different levels. Hence, nationally harmonized models for mapping and quantifying ecosystem services are needed. This paper presents the Natural Capital Model (NC-Model), a spatially-explicit set of models for quantifying and mapping ecosystem services within the Netherlands. Its aim is to support the integration of ecosystem services within spatial planning and policy-making at the national level, contributing to the fulfilment of national and international environmental policy targets. Models introduce previously unexplored combinations of explanatory variables for modelling ecosystem functions and the socioeconomic benefits they accrue, making use of publicly-available and high-resolution spatial data. To capture spatial and thematic heterogeneity across the urban-rural gradient, the NC-Model comprises a subset of ecosystem service models tailored to the urban environment. To demonstrate the model's application, we expand on six urban ecosystem service models and implement them to quantify and map ecosystem services for Municipality of Amsterdam. High-resolution ecosystem supply and use maps provide detailed spatial information useful for supporting spatial planners and decision-makers who wish to optimize the allocation of natural elements while supporting the needs of citizens. They paint a picture on the interlinkages that exist between natural elements, ecological functions, and socioeconomic well-being in a friendly manner, tailored to various audiences with differing priorities. Their open-access nature enables their customization, supporting the sharing of knowledge and data to endorse ecosystem service modelling efforts by external parties within and outside the Netherlands.

Detection of genetic incompatibilities in non-model systems using simple genetic markers: hybrid breakdown in the haplodiploid spider mite Tetranychus evansi.

When two related species interbreed, their hybrid offspring frequently suffer from reduced fitness. The genetics of hybrid incompatibility are described by the Bateson-Dobzhansky-Muller (BDM) model, where fitness is reduced by epistatic interactions between alleles of heterospecific origin. Unfortunately, most empirical evidence for the BDM model comes from a few well-studied model organisms, restricting our genetic understanding of hybrid incompatibilities to limited taxa. These systems are predominantly diploid and incompatibility is often complete, which complicates the detection of recessive allelic interactions and excludes the possibility to study viable or intermediate stages. Here, we advocate research into non-model organisms with haploid or haplodiploid reproductive systems and incomplete hybrid incompatibility because (1) dominance is absent in haploids and (2) incomplete incompatibility allows comparing affected with unaffected individuals. We describe a novel two-locus statistic specifying the frequency of individuals for which two alleles co-occur. This approach to studying BDM incompatibilities requires genotypic characterization of hybrid individuals, but not genetic mapping or genome sequencing. To illustrate our approach, we investigated genetic causes for hybrid incompatibility between differentiated lineages of the haplodiploid spider mite Tetranychus evansi, and show that strong, but incomplete, hybrid breakdown occurs. In addition, by comparing the genotypes of viable hybrid males and inviable hybrid male eggs for eight microsatellite loci, we show that nuclear and cytonuclear BDM interactions constitute the basis of hybrid incompatibility in this species. Our approach opens up possibilities to study BDM interactions in non-model taxa, and may give further insight into the genetic mechanisms behind hybrid incompatibility.

Mechanisms and ecological consequences of plant defence induction and suppression in herbivore communities.

BACKGROUND: Plants are hotbeds for parasites such as arthropod herbivores, which acquire nutrients and energy from their hosts in order to grow and reproduce. Hence plants are selected to evolve resistance, which in turn selects for herbivores that can cope with this resistance. To preserve their fitness when attacked by herbivores, plants can employ complex strategies that include reallocation of resources and the production of defensive metabolites and structures. Plant defences can be either prefabricated or be produced only upon attack. Those that are ready-made are referred to as constitutive defences. Some constitutive defences are operational at any time while others require activation. Defences produced only when herbivores are present are referred to as induced defences. These can be established via de novo biosynthesis of defensive substances or via modifications of prefabricated substances and consequently these are active only when needed. Inducibility of defence may serve to save energy and to prevent self-intoxication but also implies that there is a delay in these defences becoming operational. Induced defences can be characterized by alterations in plant morphology and molecular chemistry and are associated with a decrease in herbivore performance. These alterations are set in motion by signals generated by herbivores. Finally, a subset of induced metabolites are released into the air as volatiles and function as a beacon for foraging natural enemies searching for prey, and this is referred to as induced indirect defence. SCOPE: The objective of this review is to evaluate (1) which strategies plants have evolved to cope with herbivores and (2) which traits herbivores have evolved that enable them to counter these defences. The primary focus is on the induction and suppression of plant defences and the review outlines how the palette of traits that determine induction/suppression of, and resistance/susceptibility of herbivores to, plant defences can give rise to exploitative competition and facilitation within ecological communities "inhabiting" a plant. CONCLUSIONS: Herbivores have evolved diverse strategies, which are not mutually exclusive, to decrease the negative effects of plant defences in order to maximize the conversion of plant material into offspring. Numerous adaptations have been found in herbivores, enabling them to dismantle or bypass defensive barriers, to avoid tissues with relatively high levels of defensive chemicals or to metabolize these chemicals once ingested. In addition, some herbivores interfere with the onset or completion of induced plant defences, resulting in the plant's resistance being partly or fully suppressed. The ability to suppress induced plant defences appears to occur across plant parasites from different kingdoms, including herbivorous arthropods, and there is remarkable diversity in suppression mechanisms. Suppression may strongly affect the structure of the food web, because the ability to suppress the activation of defences of a communal host may facilitate competitors, whereas the ability of a herbivore to cope with activated plant defences will not. Further characterization of the mechanisms and traits that give rise to suppression of plant defences will enable us to determine their role in shaping direct and indirect interactions in food webs and the extent to which these determine the coexistence and persistence of species.