Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in 2 types of forests located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout 2 consecutive years. During the 3rd year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds' nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling's features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition.
Context Mediterranean landscapes are undergoing severe transformations (land-use change and homogenization) that threatens biodiversity and the services these ecosystems provide. These effects can differ amongst biodiversity facets (plants vs. birds, taxonomic vs. functional) and ecosystem functions (e.g., seed dispersal, forest regeneration, pest control), although these are still poorly understood in Mediterranean landscapes. Objectives Our study aims at understanding how Mediterranean landscape characteristics and land use (tree croplands, shrublands and pine, oak and mixed forest) affect the diversity of birds and plants, and how these changes in biodiversity could affect ecosystem functioning. Methods In 2020–2021, we sampled 49 (5 × 5 m) plots in South-eastern Spain and from five different land uses: tree croplands, shrublands, and pine, oak and mixed forests. We measured land use, habitat diversity and size, together with birds and plant diversity. We assessed both direct and indirect (via bird and plant diversity) effects of landscape characteristics on 6 different ecosystem functions related to forest regeneration, predation, herbivory or aboveground biomass, which imply interactions between birds, plants and their environment. Results Plant communities responded mainly to local features (land use), whereas birds did so to habitat size and landscape diversity (within 500 m radius). Seed and caterpillar predation were more affected by bird’s diversity, whereas regeneration capacity of woody species was driven by both plants and birds. Land use was amongst the most important drivers of all measured functions, with generally higher functioning levels in oak and mixed forests than in the rest of land uses. Conclusions Our results emphasize the complementary information obtained when considering multiple biodiversity facets in studying the consequences of landscape transformation. We also show that these multiple biodiversity changes can be as important as those of land-use or landscape characteristics for ecosystem functioning.
Soil biota influences nutrient cycling and climate regulation and represents an important fraction of global biodiversity, yet we know very little about how this soil biota responds to habitat fragmentation and degradation of habitat quality. We studied the response of different soil trophic groups (microbes and soil fauna), and their trophic structure, to changes in their habitat derived from forest long‐term management and extensive tree die‐off in a Mediterranean ecosystem. Specifically, we evaluated changes in (i) habitat size, (ii) habitat resource availability and heterogeneity and (iii) habitat connectivity. To do this, we sampled the soil biota of 43 holm oak trees (and five open interspaces) differing in size, quality, heterogeneity, connectivity and the effect of die‐off (healthy or affected). We sorted soil biota by trophic group and related their richness to habitat characteristics. Seven of the 12 trophic groups evaluated increased their species richness with soil organic carbon content, which was the most frequently selected driver of soil biota (both microbial and faunal richness). Habitat connectivity positively affected the richness of larger organisms (fauna) and plant attributes (richness, productivity and specific leaf area) also showed significant but contrasting effects depending on the group evaluated. Due to the idiosyncratic responses of different groups, the entire trophic structure (microbes and fauna) was affected by a more complex set of factors than most trophic groups in isolation, including interactions between habitat size and resource availability or connectivity. A major factor influencing habitat resource availability was the die‐off of the dominant tree species (drastically altering tree productivity). We found weaker and more negative relationships between trophic groups under trees suffering from die‐off than beneath healthy trees, particularly between microbial rather than faunal groups. Synthesis. We provide a comprehensive assessment of the response of key members of the soil food web to habitat fragmentation and tree die‐off (landscape‐level plant–soil interactions), illustrating the major role of soil carbon, habitat connectivity and tree die‐off in driving soil biodiversity and trophic structure.
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