The first Psyllid for Iceland: Trioza anthrisci Burckhardt, 1986, and an update of the Icelandic Auchenorrhyncha fauna: (Insecta: Hemiptera)

The Icelandic fauna of Auchenorrhyncha and Psylloidea was assessed at 14 locations in the south, west and north of the country in August 2013. In total, 1,556 individuals belonging to six species were recorded: Javesella pellucida, Ribautiana ulmi, Edwardsiana rosae, Cicadula quadrinotata, Macrosteles laevis and Jassargus pseudocellaris. Edwardsiana rosae and R. ulmi have only been found in Reykjavík, while the other species are all widespread and common on Iceland. Two further species known to occur on Iceland were not recorded: Evacanthus interruptus and Philaenus spumarius, which both have very restricted distributions. Additionally, with the finding of Trioza anthrisci Burckhardt (Hemiptera: Triozidae) the first psyllid species was recorded from Iceland. One female was found near the airport of the northern town of Akureyri. Some of this species’ main host plants (Angelica sylvestris and the introduced Anthriscus sylvestris) are widespread in the coastal lowlands, but might not have been adequately sampled during earlier investigations. Because only one individual was found, and because of its proximity to an airport, the native status of the species for Iceland remains to be determined, but is not unlikely given its northern occurrence in Scandinavia

Of dwarves and giants:How large herbivores shape arthropod communities on salt marshes

Om plantensoortenrijkdom te behouden worden op kwelders (buitendijkse graslanden die regelmatig overstromen met zeewater) en veel andere typen natuurgebieden steeds vaker grote grazers, zoals koeien of paarden, ingezet. Hierbij krijgen insecten en andere ongewervelden echter weinig aandacht. Dit proefschrift beschrijft hoe gemeenschappen van ongewervelden reageren op beweiding, met aandacht voor verschillen tussen soorten grazers, beweidingsdichtheden en rotatiebeheer (jaarlijkse wisseling tussen beweide en onbeweide jaren). Plantensoortenrijkdom neemt vaak toe wanneer grote grazers worden ingezet. Dit komt grotendeels omdat deze dieren, door hoge planten op te eten, zorgen dat meer licht de bodem breikt, en lagere planten een kans krijgen. Uit mijn onderzoek blijkt echter dat soortenrijkdom van ongewervelden vaak afneemt in aanwezigheid van grote grazers. Op kwelders zijn de meeste soorten insecten en andere ongewervelden afhankelijk van hoge vegetatie als voedselbron of als bescherming tegen overstromingen, terwijl een minderheid aan soorten korte vegetatie prefereert. Als de vegetatie wordt opgegeten door grote grazers zullen de bestaansmogelijkheden voor de meeste soorten dus afnemen of verdwijnen. Beweidingsdichtheid blijkt voor soortenrijkdom van ongewervelden de belangrijkste bepalende factor te zijn. Dit bepaalt hoe veel vegetatie wordt opgegeten, en dus welke mogelijkheden er voor ongewervelden bestaan. Welke soort grazer wordt ingezet lijkt hier een ondergeschikte rol te spelen. De beste kans om soortenrijkdom van ongewervelden op kwelders en andere typen graslanden te waarborgen ligt in het creeëren van heterogeniteit. Dit kan bereikt worden door verschillend beheerde terreinen naast elkaar te behouden, te beweiden met lage dichtheden of met rotatiebeheer

Effects of large herbivores on grassland arthropod diversity

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio-temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top-down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity

Rewilding with large herbivores:Positive direct and delayed effects of carrion on plant and arthropod communities

Carrion of large animals is an extremely nutrient rich, ephemeral resource that is essential for many species, but is scarce in the anthropogenic Western-European landscape due to legislative restrictions. Rewilding, a novel conservation strategy that aims at restoring natural processes with minimal human intervention, is increasing in popularity and could lead to increased carrion availability in the landscape. It is therefore important to understand the effects of carrion on biodiversity. We investigated the direct and delayed (five months) effects of red deer (Cervus elaphus) carcasses on plants and arthropods in the Oostvaardersplassen, the Netherlands, one of the oldest rewilding sites in Europe. Specifically, we tested whether carrion has a positive direct effect on the abundances and diversity of various arthropod functional groups, as well as a delayed effect on the vegetation and arthropods through the increased nutrient availability. During the active decomposition stage in spring, we, not surprisingly, observed higher abundances of carrion associated species (scavengers and their specialized predators) at the carrion sites than at control sites without carrion, but no higher abundances of predators or detritivores. In late summer, after near-complete decomposition, plant biomass was five times higher, and nutritional plant quality (C:N ratio) was higher at the carrion sites than at the control sites. Arthropod abundance and diversity were also manifold higher, owing to higher numbers of herbivorous and predatory species. Regression analysis showed that abundances of herbivores and detritivores were positively related to plant biomass, and predator abundances were positively related to abundances of herbivores and detritivores, suggesting bottom-up effects propagating through the food chain. Our results show that even in a naturally nutrient-rich ecosystem like the Oostvaardersplassen, carrion can have strong positive effects on local plant biomass and nutritional quality and arthropod abundances, lasting the whole growing season. We found evidence that these effects were first directly caused by the presence of carrion, and later by the enhanced nutrient availability in the soil. This highlights the importance of the indirect pathways by which carrion can structure arthropod communities

Revisiting global trends in freshwater insect biodiversity: A reply

Abstract Jähnig et al. make some useful points regarding the conclusions that can be drawn from our meta‐analysis; however, some issues require clarification. First, we never suggested that there was a globally increasing trend of freshwater insect abundances, but only spoke of an average increasing trend in the available data. We also did not suggest that freshwater quality has improved globally, but rather that documented improvements in water quality can explain at least some of the trends we observed. Second, as we acknowledged, our data are not a representative set of freshwater ecosystems around the world, but they are what is currently accessible. Third, there is indeed no doubt that changes in abundance or biomass need not correlate with changes in other aspects of biodiversity, such as species richness or functional composition. Our analysis was specifically focused on trends in community abundance/biomass because it has been the subject of recent study and speculation, and is a widely available metric in long‐term studies. To better understand the recent changes in freshwater insect assemblages, we encourage freshwater ecologists to further open their troves of data from countless long‐term monitoring schemes so that larger and more comprehensive syntheses can be undertaken