Beta-diversity of lepidopteran larval communities in a Japanese temperate forest: effects of phenology and tree species

Gradients in richness and turnover of a forest passerine's diet prior to breeding: A mixed model approach applied to faecal metabarcoding data

Rather little is known about the dietary richness and variation of generalist insectivorous species, including birds, due primarily to difficulties in prey identification. Using faecal metabarcoding, we provide the most comprehensive analysis of a passerine's diet to date, identifying the relative magnitudes of biogeographic, habitat and temporal trends in the richness and turnover in diet of Cyanistes caeruleus (blue tit) along a 39 site and 2° latitudinal transect in Scotland. Faecal samples were collected in 2014-2015 from adult birds roosting in nestboxes prior to nest building. DNA was extracted from 793 samples and we amplified COI and 16S minibarcodes. We identified 432 molecular operational taxonomic units that correspond to putative dietary items. Most dietary items were rare, with Lepidoptera being the most abundant and taxon-rich prey order. Here, we present a statistical approach for estimation of gradients and intersample variation in taxonomic richness and turnover using a generalised linear mixed model. We discuss the merits of this approach over existing tools and present methods for model-based estimation of repeatability, taxon richness and Jaccard indices. We found that dietary richness increases significantly as spring advances, but changes little with elevation, latitude or local tree composition. In comparison, dietary composition exhibits significant turnover along temporal and spatial gradients and among sites. Our study shows the promise of faecal metabarcoding for inferring the macroecology of food webs, but we also highlight the challenge posed by contamination and make recommendations of laboratory and statistical practices to minimise its impact on inference.

Pest consumption in a vineyard system by the lesser horseshoe bat (Rhinolophus hipposideros)

Herbivorous arthropods cause immense damage in crop production annually. Consumption of these pests by insectivorous animals is of significant importance to counteract their adverse effects. Insectivorous bats are considered amongst the most voracious predators of arthropods, some of which are known crop pests. In vineyard-dominated Mediterranean agroecosystems, several crops are damaged by the attack of insect pests. In this study we aimed 1) to explore the diet and pest consumption of the lesser horseshoe bat Rhinolophus hipposideros and 2) analyse whether the composition of pest species in its diet changes throughout the season. We employed a dual-primer DNA metabarcoding analysis of DNA extracted from faeces collected in three bat colonies of a wine region in Southwestern Europe during the whole active period of most pest species. Overall, 395 arthropod prey species belonging to 11 orders were detected; lepidopterans and dipterans were the most diverse orders in terms of species. Altogether, 55 pest species were identified, 25 of which are known to cause significant agricultural damage and 8 are regarded as pests affecting grapevines. The composition of pest species in faeces changed significantly with the season, thus suggesting several periods should be sampled to assess the pest consumption by bats. As a whole, the results imply that R. hipposideros acts as a suppressor of a wide array of agricultural pests in Mediterranean agroecosystems. Therefore, management measures favouring the growth of R. hipposideros populations should be considered.

Effects of Forest Management Practices on Moth Communities in a Japanese Larch (Larix kaempferi (Lamb.) Carrière) Plantation

Biodiversity in forests is strongly affected by forest management practices, such as clearcutting and aggregated retention. Therefore, the assessment of the effects of forest management on biodiversity is a major concern in forest ecology. In the present study, we aimed to characterize the effects of forest management practices, after one year, on the abundance, species richness, community composition, and functional groups of moths in forests. The moths were sampled in four different forest stands: three stands (clearcutting, aggregated retention, and no cutting) in a planted Japanese larch forest and one stand in a natural Mongolian oak forest. The results revealed that the moth communities changed in response to the changes in vegetation after the implementation of forest management practices, and clearcutting increased the abundance and species richness of herbivorous and warm-adapted species. The structure and function of moth communities were affected by the forest management practices such as clearcutting and aggregated retention, which were reflected by a decrease in community indices and change in moth community composition with changes in vegetation.

Evaluating the spatio-temporal factors that structure network parameters of plant-herbivore interactions

Despite the dynamic nature of ecological interactions, most studies on species networks offer static representations of their structure, constraining our understanding of the ecological mechanisms involved in their spatio-temporal stability. This is the first study to evaluate plant-herbivore interaction networks on a small spatio-temporal scale. Specifically, we simultaneously assessed the effect of host plant availability, habitat complexity and seasonality on the structure of plant-herbivore networks in a coastal tropical ecosystem. Our results revealed that changes in the host plant community resulting from seasonality and habitat structure are reflected not only in the herbivore community, but also in the emergent properties (network parameters) of the plant-herbivore interaction network such as connectance, selectiveness and modularity. Habitat conditions and periods that are most stressful favored the presence of less selective and susceptible herbivore species, resulting in increased connectance within networks. In contrast, the high degree of selectivennes (i.e. interaction specialization) and modularity of the networks under less stressful conditions was promoted by the diversification in resource use by herbivores. By analyzing networks at a small spatio-temporal scale we identified the ecological factors structuring this network such as habitat complexity and seasonality. Our research offers new evidence on the role of abiotic and biotic factors in the variation of the properties of species interaction networks.

Four ways towards tropical herbivore megadiversity

Most multicellular species alive are tropical arthropods associated with plants. Hence, the host-specificity of these species, and their diversity at different scales, are keys to understanding the assembly structure of global biodiversity. We present a comprehensive scheme in which tropical herbivore megadiversity can be partitioned into the following components: (A) more host plant species per se, (B) more arthropod species per plant species, (C) higher host specificity of herbivores, or (D) higher species turnover (beta diversity) in the tropics than in the temperate zone. We scrutinize recent studies addressing each component and identify methodological differences among them. We find substantial support for the importance of component A, more tropical host species. A meta-analysis of published results reveals intermediate to high correlations between plant and herbivore diversity, accounting for up to 60% of the variation in insect species richness. Support for other factors is mixed, with studies too scarce and approaches too uneven to allow for quantitative summaries. More research on individual components is unlikely to resolve their relative contribution to overall herbivore diversity. Instead, we call for the adoption of more coherent methods that avoid pitfalls for larger-scale comparisons, for studies assessing different components together rather than singly, and for studies that investigate herbivore beta-diversity (component D) in a more comprehensive perspective.