Aim
Climate is a major driver of large‐scale variability in biodiversity, as a likely result of more intense biotic interactions under warmer conditions. This idea fuelled decades of research on ...plant‐herbivore interactions, but much less is known about higher‐level trophic interactions. We addressed this research gap by characterizing both bird diversity and avian predation along a climatic gradient at the European scale.
Location
Europe.
Taxon
Insectivorous birds and pedunculate oaks.
Methods
We deployed plasticine caterpillars in 138 oak trees in 47 sites along a 19° latitudinal gradient in Europe to quantify bird insectivory through predation attempts. In addition, we used passive acoustic monitoring to (i) characterize the acoustic diversity of surrounding soundscapes; (ii) approximate bird abundance and activity through passive acoustic recordings; and (iii) infer both taxonomic and functional diversity of insectivorous birds from recordings.
Results
The functional diversity of insectivorous birds increased with warmer climates. Bird predation increased with forest cover and bird acoustic activity but decreased with mean annual temperature and functional richness of insectivorous birds. Contrary to our predictions, climatic clines in bird predation attempts were not directly mediated by changes in insectivorous bird diversity or acoustic activity, but climate and habitat still had independent effects on predation attempts.
Main Conclusions
Our study supports the hypothesis of an increase in the diversity of insectivorous birds towards warmer climates but refutes the idea that an increase in diversity would lead to more predation and advocates for better accounting for activity and abundance of insectivorous birds when studying the large‐scale variation in insect‐tree interactions.
Résumé
Objectif
Le climat est l'un des principaux facteur structurant de la variabilité à grande échelle de la biodiversité, possiblement en raison d'interactions biotiques plus intenses dans des conditions de température plus élevées. Cette idée a alimenté des décennies de recherche sur les interactions plantes‐herbivores, mais on en sait beaucoup moins sur les interactions impliquant les niveaux trophiques supérieurs. Nous avons comblé cette lacune en caractérisant à la fois la diversité des oiseaux et leur activité de prédation le long d'un gradient climatique à l'échelle européenne.
Localisation
Europe.
Taxon
Oiseaux insectivores et chênes pédonculés.
Méthodes
Nous avons déployé des leurres en pâte à modeler mimant des chenilles sur 138 chênes dans 47 sites le long d'un gradient latitudinal de 19° en Europe pour quantifier l'insectivorie avienne par le biais de tentatives de prédation. De plus, nous avons utilisé la surveillance acoustique passive pour (i) caractériser la diversité acoustique des paysages sonores environnants; (ii) estimer l'abondance et l'activité des oiseaux à travers des enregistrements acoustiques passifs et (iii) déduire à la fois la diversité taxonomique et fonctionnelle des oiseaux insectivores à partir des enregistrements.
Résultats
Nous avons montré une augmentation de la diversité fonctionnelle des oiseaux insectivores avec la température moyenne. La prédation avienne augmentait avec la couverture forestière et l'activité acoustique des oiseaux, mais diminuait avec la température annuelle moyenne et la richesse fonctionnelle des oiseaux insectivores. Contrairement à nos prédictions, la variation de la diversité des oiseaux n'était pas le lien mécaniste entre le climat et la variation des tentatives de prédation sur les leurres, laquelle était directement influencée par le climat et la couverture forestière.
Conclusions Principales
Notre étude confirme l'hypothèse d'une augmentation de la diversité des oiseaux insectivores vers des climats plus chauds, mais ne corrobore pas l'idée qu'une augmentation de la diversité conduirait à davantage de predation. Elle plaide en faveur d'une meilleure prise en compte de l'activité et de l'abondance des oiseaux insectivores lors de l'étude de la variation à grande échelle des interactions entre insectes et arbres.
Many laboratory and field studies have been conducted on rice field spiders in China. There are 375 species, 108 genera, and 22 families of rice field spiders distributed within the major rice ...growing areas and 17 dominant species. The biological and ecological characteristics of 17 rice field spider species have been reported in detail.The biology and ecology of these species show significant differences among regions, farmland habitats, and agricultural practices. Future research should focus on rice field habitat diversity, enhancing the insecticide resistance of dominant spider populations, implementing large-scale breeding of spiders and augmentative release, breeding more leaf dominant species, conducting biosafety assessment of spiders in transgenic crops.
Since the fall armyworm (FAW) Spodoptera frugiperda invaded China, it has coexisted in maize fields with the native cotton bollworm (CBW) Helicoverpa armigera, but the population dynamics and ...competitive mechanisms between the two pests are not well understood. We evaluated interspecific competition between FAW and CBW by analyzing their bidirectional predation in the laboratory, survival rates when their larvae co-infested the same maize plant, and the population dynamics of both in the same maize field. In the predation tests, FAW and CBW larvae preyed on each other. However, the theoretical maximum predation of sixth-instar FAW larvae preying on first–second-instar CBW larvae was 71.4 and 32.3 individuals, respectively, while that of CBW was 38.5 and 28.6 individuals. The field co-infestation trials showed that the older larvae had a higher survival rate when the two pests co-infested the same maize plants, but young larval survival was higher for FAW than CBW. In the maize field from 2019 to 2021 in southern Yunnan, FAW populations were significantly higher than those of CBW. Our findings suggested that FAW larvae had a predation advantage over CBW, which might be an important reason for its dominance in Chinese maize fields. This result provides a scientific basis for developing a monitoring technology and for the integrated management of pests in invaded habitats of FAW.
Field insect population survey indicated that the principal natural predation enemies of cotton bollworm (Helicoverpa armigera Hubner) were Eringonidium graminicola Sundevall, Adonia variegata Goeze, ...Nabis sinoferus Hsiao. The results from experiments showed that the amount of prey consumed of these principal natural enemies increased when the density of prey rised, and decreased when the density of natural enemies increased. The predation function response fitted Holling's predation response equation II, and could be fit with the Disk Equation.
