Lars Dalby

Mammal predator and prey species richness are strongly linked at macroscales

Predator-prey interactions play an important role for species composition and community dynamics at local scales, but their importance in shaping large-scale gradients of species richness remains unexplored. Here, we use global range maps, structural equation models (SEM), and comprehensive databases of dietary preferences and body masses of all terrestrial, non-volant mammals worldwide, to test whether (1) prey bottom-up or predator top-down relationships are important drivers of broad-scale species richness gradients once the environment and human influence have been accounted for, (2) predator-prey richness associations vary among biogeographic regions, and (3) body size influences large-scale covariation between predators and prey. SEMs including only productivity, climate, and human factors explained a high proportion of variance in prey richness (R2=0.56) but considerably less in predator richness (R2=0.13). Adding predator-to-prey or prey-to-predator paths strongly increased the explained variance in both cases (prey R2=0.79, predator R2=0.57), suggesting that predator-prey interactions play an important role in driving global diversity gradients. Prey bottom-up effects prevailed over productivity, climate, and human influence to explain predator richness, whereas productivity and climate were more important than predator top-down effects for explaining prey richness, although predator top-down effects were still significant. Global predator-prey associations were not reproduced in all regions, indicating that distinct paleoclimate and evolutionary histories (Africa and Australia) may alter species interactions across trophic levels. Stronger cross-trophic-level associations were recorded within categories of similar body size (e.g., large prey to large predators) than between them (e.g., large prey to small predators), suggesting that mass-related energetic and physiological constraints influence broad-scale richness links, especially for large-bodied mammals. Overall, our results support the idea that trophic interactions can be important drivers of large-scale species richness gradients in combination with environmental effects.

Establishing macroecological trait datasets: digitalization, extrapolation, and validation of diet preferences in terrestrial mammals worldwide

Ecological trait data are essential for understanding the broad-scale distribution of biodiversity and its response to global change. For animals, diet represents a fundamental aspect of species’ evolutionary adaptations, ecological and functional roles, and trophic interactions. However, the importance of diet for macroevolutionary and macroecological dynamics remains little explored, partly because of the lack of comprehensive trait datasets. We compiled and evaluated a comprehensive global dataset of diet preferences of mammals (“MammalDIET”). Diet information was digitized from two global and cladewide data sources and errors of data entry by multiple data recorders were assessed. We then developed a hierarchical extrapolation procedure to fill-in diet information for species with missing information. Missing data were extrapolated with information from other taxonomic levels (genus, other species within the same genus, or family) and this extrapolation was subsequently validated both internally (with a jack-knife approach applied to the compiled species-level diet data) and externally (using independent species-level diet information from a comprehensive continentwide data source). Finally, we grouped mammal species into trophic levels and dietary guilds, and their species richness as well as their proportion of total richness were mapped at a global scale for those diet categories with good validation results. The success rate of correctly digitizing data was 94%, indicating that the consistency in data entry among multiple recorders was high. Data sources provided species-level diet information for a total of 2033 species (38% of all 5364 terrestrial mammal species, based on the IUCN taxonomy). For the remaining 3331 species, diet information was mostly extrapolated from genus-level diet information (48% of all terrestrial mammal species), and only rarely from other species within the same genus (6%) or from family level (8%). Internal and external validation showed that: (1) extrapolations were most reliable for primary food items; (2) several diet categories (“Animal”, “Mammal”, “Invertebrate”, “Plant”, “Seed”, “Fruit”, and “Leaf”) had high proportions of correctly predicted diet ranks; and (3) the potential of correctly extrapolating specific diet categories varied both within and among clades. Global maps of species richness and proportion showed congruence among trophic levels, but also substantial discrepancies between dietary guilds. MammalDIET provides a comprehensive, unique and freely available dataset on diet preferences for all terrestrial mammals worldwide. It enables broad-scale analyses for specific trophic levels and dietary guilds, and a first assessment of trait conservatism in mammalian diet preferences at a global scale. The digitalization, extrapolation and validation procedures could be transferable to other trait data and taxa.

Interpreting seasonal range shifts in migratory birds: a critical assessment of ‘short-stopping’ and a suggested terminology

AbstractThe term ‘short-stopping’ is increasingly used in ecology to describe spatio-temporal changes in occurrence of migratory species. Spurred by the insight that it has been used in a variety of contexts, we reviewed its use in avian ecology. A literature search yielded 59 papers explicitly treating short-stopping in birds, most of them in peer-reviewed journals. The term was first used in 1967 to describe a northward shift in wintering Canada Geese in North America and has been used with increasing frequency to the present day. Geese dominate the short-stopping literature, which is confined to the northern hemisphere. Short-stopping has been used to describe (1) a shortened autumn migration that results in a wintering distribution closer to breeding areas, (2) a shortened spring migration that results in a breeding distribution closer to wintering areas, and (3) a delay in autumn migration that leads to a perceived reduced abundance in some part of the winter range. We advocate that short-stopping should be used only to describe (1) range shifts that involve shortening of the migratory corridor, and that they are qualified explicitly by season (i.e. breeding/winter) and degree (i.e. full or partial range shift). In other cases of breeding, wintering or entire range shifts where the migratory corridor is elongated or remains the same, we recommend using the term ‘range shift’, qualified by season, geography and orientation (i.e. the direction of the range shift). We also discuss the need for spatially explicit avian count monitoring mechanisms (rather than capture–recapture or hunting bag data) designed specifically to track such changes in distribution in the future.ZusammenfassungDie Deutung jahreszeitlicher Gebietsverschiebungen bei Zugvögeln: eine kritische Beurteilung des Begriffs “short-stopping”und Vorschläge zur Terminologie Der Begriff “short-stopping”wird in der Ökologie zunehmend zur Beschreibung räumlich-zeitlicher Änderungen im Vorkommen ziehender Arten gebraucht. Motiviert von der Erkenntnis, dass diese Bezeichnung in den verschiedensten Zusammenhängen verwendet wird, untersuchten wir deren Gebrauch auf dem Gebiet der Ökologie der Vögel. Eine Literaturrecherche erbrachte 59 Publikationen, die sich explizit mit Zugwegverkürzungen bei Vögeln beschäftigen, die meisten davon in Zeitschriften, die einem Gutachterverfahren unterlagen. Der Begriff wurde zuerst 1967 verwendet, um eine nordwärtige Verschiebung bei überwinternden Kanadagänsen in Nordamerika zu beschreiben und ist mit zunehmender Häufigkeit bis heute in Gebrauch. Gänse dominieren die Literatur zum Thema Zugwegverkürzung, welche zudem auf die Nordhemisphäre beschränkt ist. Mit „short-stopping“wurden beschrieben: (a) ein verkürzter Herbstzug, welcher zu einer näher an den Brutgebieten liegenden Winterverbreitung führt; (b) ein verkürzter Frühjahrszug, der bewirkt, dass die Verbreitung zur Brutzeit näher an die Überwinterungsgebiete rückt; und (c) ein verzögerter Herbstzug, der in einer beobachteten verringerten Häufigkeit in Teilen des Überwinterungsgebietes resultiert. Wir empfehlen, die Bezeichnung „short-stopping”nur auf Gebietsverschiebungen anzuwenden, die durch eine Verkürzung des Zugkorridors zustande kommen und die ausdrücklich durch die Jahreszeit (d. h. Brutzeit/Winter) und ihr Ausmaß (d. h. vollständige oder teilweise Gebietsverschiebung) gekennzeichnet sind. In anderen Fällen der Verschiebung von Brut-, Überwinterungs- oder Gesamtverbreitungsgebieten, bei denen der Zugkorridor länger wird oder sich nicht ändert, empfehlen wir die Verwendung des Begriffs Gebietsverschiebung (“range shift”), mit einer zusätzlichen jahreszeitlichen, geografischen oder richtungsbezeichnenden Angabe (d. h. die Richtung der Gebietsverschiebung). Außerdem diskutieren wir den Bedarf an speziell entwickelten, räumlich genauen Monitoring-Techniken für Vogelbestände (anstelle von Fang-Wiederfang-Daten oder Jagdstatistiken), um solche Veränderungen zukünftig nachvollziehen zu können.

Landscape structure and management alter the outcome of a pesticide ERA: Evaluating impacts of endocrine disruption using the ALMaSS European Brown Hare model

There is a gradual change towards explicitly considering landscapes in regulatory risk assessment. To realise the objective of developing representative scenarios for risk assessment it is necessary to know how detailed a landscape representation is needed to generate a realistic risk assessment, and indeed how to generate such landscapes. This paper evaluates the contribution of landscape and farming components to a model based risk assessment of a fictitious endocrine disruptor on hares. In addition, we present methods and code examples for generation of landscape structures and farming simulation from data collected primarily for EU agricultural subsidy support and GIS map data. Ten different Danish landscapes were generated and the ERA carried out for each landscape using two different assumed toxicities. The results showed negative impacts in all cases, but the extent and form in terms of impacts on abundance or occupancy differed greatly between landscapes. A meta-model was created, predicting impact from landscape and farming characteristics. Scenarios based on all combinations of farming and landscape for five landscapes representing extreme and middle impacts were created. The meta-models developed from the 10 real landscapes failed to predict impacts for these 25 scenarios. Landscape, farming, and the emergent density of hares all influenced the results of the risk assessment considerably. The study indicates that prediction of a reasonable worst case scenario is difficult from structural, farming or population metrics; rather the emergent properties generated from interactions between landscape, management and ecology are needed. Meta-modelling may also fail to predict impacts, even when restricting inputs to combinations of those used to create the model. Future ERA may therefore need to make use of multiple scenarios representing a wide range of conditions to avoid locally unacceptable risks. This approach could now be feasible Europe wide given the landscape generation methods presented.

Current and Potential Threats to Nordic Duck Populations — A Horizon Scanning Exercise

We review the current and future threats to duck populations that breed, stage, moult and/or winter in the Nordic countries. Migratory duck species are sensitive indicators of their changing environment, and their societal value confirms the need to translate signals from changes in their distribution, status and abundance into a better understanding of changes occurring in their wetland environments. We used expert opinion to highlight 25 major areas of anthropogenic change (and touch briefly on potential mitigation measures through nature restoration and reserve management projects) that we consider key issues likely to influence Nordic duck populations now and in the near future to stimulate debate, discussion and further research. We believe such reviews are essential in contributing to development of successful management policy as well as stimulating specific research to support the maintenance of duck species in favourable future conservation status in the face of multiple population pressures and drivers.

Seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios from hunter-based surveys

AbstractDemographic monitoring is vital for tracking and modelling the population dynamics of highly mobile bird populations. However, different types of monitoring can sometimes lead to different outcomes, and understanding the causes of equivocal results is an important step to advance future monitoring schemes. This study found consistent seasonal variation in Eurasian Wigeon Anas penelope sex and age ratios among Danish hunter-based wing surveys, and describes how accounting for this variation might explain reported discrepancies between this and other monitoring methods. Early season flocks were dominated by adult males, and juvenile proportions were highest in November and significantly lower before and after this peak. Nationwide field assessments undertaken in January 2012 showed no significant differences from sex and age ratios in the wing survey data from that particular hunting season (2011/2012), indicating that this survey is a good predictor of Wigeon demography. These results highlight the need to account for consistent temporal variation in such demographic time series when using the results to model population parameters.ZusammenfassungJahreszeitliche Schwankungen in Geschlechterverhältnis und Altersstruktur bei der Eurasischen Pfeifente (Anas penelope) anhand von Erhebungen durch Jäger Für die Nachverfolgung und Modellierung populationsdynamischer Prozesse ist bei hochmobilen Vogelpopulationen ein demographisches Monitoring von entscheidender Bedeutung. Unterschiedliche Arten des Monitorings können jedoch gelegentlich zu unterschiedlichen Resultaten führen, und das Verständnis der Ursachen von mehrdeutigen Ergebnissen ist ein wichtiger Schritt in der Entwicklung zukünftiger Monitoring-Systeme. In den Erhebungen dänischer Jäger fanden sich durchgängig jahreszeitliche Schwankungen im Geschlechterverhältnis und in der Altersstruktur der Eurasischen Pfeifente (Anas penelope); diese Studie beschreibt, wie die Berücksichtigung solcher Unterschiede eventuell die Diskrepanzen zwischen den Ergebnissen aus unterschiedlichen Monitoring-Methoden erklären könnte. Schwärme zu Beginn der Saison wurden von adulten Männchen dominiert, während der Anteil junger Vögel im November am höchsten und vor und nach diesem Spitzenwert signifikant niedriger war. Im Januar 2012 landesweit durchgeführte Freiland-Bewertungen zeigten keine signifikanten Unterschiede im Geschlechterund Altersverhältnis zu den Erhebungen dieser speziellen Jagdsaison (2011/2012), was nahelegt, dass eine solche Erhebung ein guter Prädiktor für demographische Aussagen bei Pfeifenten ist. Diese Ergebnisse unterstreichen die Notwendigkeit, konsistente zeitliche Schwankungen in derartigen demographischen Zeitreihen zu berücksichtigen, wenn die Ergebnisse dazu benutzt werden, Populationsmerkmale zu modellieren.

Using dark diversity and plant characteristics to guide conservation and restoration

Summary 1.Dark diversity is a promising concept for prioritising management efforts as it focuses on species that are present in the regional pool, but locally absent even though environmental requirements are met. Currently, we lack knowledge of what characterises species belonging to the dark diversity more often than others, although this is important knowledge for restoration and conservation actions. 2.We applied the concept to a massive national (Danish) plant diversity database, containing 236,923 records from 15,160 surveys involving 564 species. This enabled the first geographically comprehensive (43,000 km2) assessment of dark diversity, at a spatial resolution relevant for conservation and restoration planning (78 m2) across multiple terrestrial habitats, thereby maximising the practical applications of this concept. The probability for a given plant species to belong to the dark diversity was computed and logistically regressed against variables representing its ecological preferences (e.g. nutrient availability), strategies (competitor, stress tolerant, ruderal), mycorrhizal relationships, establishment capacities (seed mass) and dispersal abilities. 3.Forty-six percent of the species had a high probability (>95%) of being part of dark diversity, whereas for 7% of the species this probability was less than 60%. 4.Typical dark diversity plants tended to depend on mycorrhiza, were mostly adapted to low light and low nutrient levels, had poor dispersal abilities and were ruderals and stress intolerant. 5.Synthesis and applications. Characterising species that are more often absent from suitable sites than others (dark diversity species) has important implications for the planning and management of natural ecosystems. From our study, practitioners gain insight into the factors triggering the absence of individual plant species in a seemingly suitable habitat. We highlight the need to carefully consider mycorrhizal inoculations with a suitable assemblage of fungi to promote the establishment success of dark diversity plants. Additionally, time lags in plant species dispersal and establishment as well as spatial connectivity in fragmented habitats are central to consider in nature management although assisted migration might also aid poor dispersers. Finally, nutrient-poor localities are probably important “islets” allowing nitrophobic dark diversity plant species to thrive within agricultural landscapes that are generally nutrient rich. This article is protected by copyright. All rights reserved.

Dark diversity illuminates the dim side of conservation and restoration

1 Dark diversity is a promising concept for prioritizing management efforts as it focuses on missing species, i.e., species present in the regional pool, but locally absent despite suitable environmental conditions. 2 We applied the concept to a massive national plant diversity database (236,923 records from 15,160 surveys involving 564 species) to provide the first geographically comprehensive assessment of dark diversity across a large area (43,000 km2), at a spatial scale (~75 m2) relevant for conservation and restoration planning and across multiple terrestrial habitats, thus maximising its practical application potential. The likelihood for a given plant species to belong to the dark diversity pool was computed and logistically regressed against its ecological preferences (nutrient availability, pH etc.), strategies (competitor, stress tolerance, ruderal), mycorrhizal dependence and infection percentage, seed mass and maximum dispersal distance. 3 Forty-six percent of the species were absent in >95 % of the suitable sites, whereas 7 % of the species were absent in less than 60 % of sites that were deemed suitable. 4 Species that were more likely to belong to the dark diversity tended to depend on mycorrhiza, were mostly adapted to low light and nutrient levels, had poor dispersal abilities, were ruderals and had a low stress tolerance. Synthesis and applications Our findings have important implications for the planning and management of natural ecosystems requiring detailed knowledge of what triggers the presence/absence of individual plant species in a seemingly suitable habitat. We conclude that practitioners may need to carefully consider mycorrhizal inoculations with a suitable assemblage of fungi for certain plant species to become established. Also assisted migration might be necessary to help poor dispersers although spatial and temporal processes are also important to have in mind. Finally, it is important to vary nutrient loads making room for plant species to colonise both nutrient-poor and nutrient-rich localities.

Vascular plants are strong predictors of multi-taxon species richness

Plants regulate soils and microclimate, provide substrate for heterotrophic taxa, are easy to observe and identify and have a stable taxonomy, which strongly justifies the use of plants as bioindicators in monitoring and conservation. However, insects and fungi make up the vast majority of species. Surprisingly, it remains untested whether plants are strong predictors of total multi-taxon species richness. To answer this question, we collected an extensive data set on species richness of vascular plants, bryophytes, macrofungi, lichens, plant-galling arthropods, gastropods, spiders, carabid beetles, hoverflies and OTU richness from environmental DNA metabarcoding. Plant species richness per se was a moderate predictor of richness of other taxa. Taking an ecospace approach to modelling, the addition of plant-derived bioindicators revealed 1) a consistently positive effect of plant richness on other taxa, 2) prediction of 12-55% of variation in other taxa and 48 % of variation in the total species richness.

Vascular plant species richness and bioindication predict multi‐taxon species richness

Handling Editor: Karen Bacon Abstract 1. Plants regulate soils and microclimate, provide substrate for heterotrophic taxa, are easy to observe and identify and have a stable taxonomy, which strongly justifies their use as indicators in monitoring and conservation. However, there is no consensus as to whether plants are strong predictors of total multi-taxon species richness. In this study, we investigate if general terrestrial species richness can be predicted by vascular plant richness and bioindication. 2. To answer this question, we collected an extensive dataset on species richness of vascular plants, bryophytes, macrofungi, lichens, plant-galling arthropods, gastropods, spiders, carabid beetles, hoverflies, and genetic richness (operational taxonomic units = OTUs) from environmental DNA metabarcoding. We also constructed a Conservation Index based on threatened red list species. Besides using richness of vascular plants for prediction of other taxonomic groups, we also used plant-derived calibration of the abiotic environment (moisture, soil fertility and light conditions) as well as the degree of anthropogenic impact. 3. Bivariate relationships between plant species richness and other species groups showed no consistent pattern. After taking environmental calibration by bioindication into account, we found a consistent, and for most groups significant, positive effect of plant richness. Plant species richness was also important for richness of fungal OTUs, Malaise OTUs and for the Conservation Index. Our multiple regression analyses revealed (a) a consistently positive effect of plant richness on other taxa, (b) prediction of 12%–55% of variation in other taxa and 48% of variation in the total species richness when bioindication and plant richness were used as predictors. 4. Our results justify that vascular plants are strong indicators of total biodiversity across environmental gradients and broad taxonomic realms and therefore a natural first choice for biodiversity monitoring and conservation planning.