Urban green spaces such as gardens often consist of native and exotic plant species, which provide pollen and nectar for flower-visiting insects. Although some exotic plants are readily visited by ...pollinators, it is unknown if and at which time of the season exotic garden plants may supplement or substitute for flower resources provided by native plants. To investigate if seasonal changes in flower availability from native vs. exotic plants affect flower visits, diversity and particularly plant–pollinator interaction networks, we studied flower-visiting insects over a whole growing season in 20 urban residential gardens in Germany. Over the course of the season, visits to native plants decreased, the proportion of flower visits to exotics increased, and flower-visitor species richness decreased. Yet, the decline in flower-visitor richness over the season was slowed in gardens with a relatively higher proportion of flowering exotic plants. This compensation was more positively linked to the proportion of exotic plant species than to the proportion of exotic flower cover. Plant–pollinator interaction networks were moderately specialized. Interactions were more complex in high summer, but interaction diversity, linkage density, and specialisation were not influenced by the proportion of exotic species. Thus, later in the season when few native plants flowered, exotic garden plants partly substituted for native flower resources without apparent influence on plant–pollinator network structure. Late-flowering garden plants support pollinator diversity in cities. If appropriately managed, and risk of naturalisation is minimized, late-flowering exotic plants may provide floral resources to support native pollinators when native plants are scarce.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Forest ecosystems are an integral component of the global carbon cycle as they take up and release large amounts of C over short time periods (C flux) or accumulate it over longer time periods (C ...stock). However, there remains uncertainty about whether and in which direction C fluxes and in particular C stocks may differ between forests of high versus low species richness. Based on a comprehensive dataset derived from field-based measurements, we tested the effect of species richness (3-20 tree species) and stand age (22-116 years) on six compartments of above- and below-ground C stocks and four components of C fluxes in subtropical forests in southeast China. Across forest stands, total C stock was 149 ± 12 Mg ha
with richness explaining 28.5% and age explaining 29.4% of variation in this measure. Species-rich stands had higher C stocks and fluxes than stands with low richness; and, in addition, old stands had higher C stocks than young ones. Overall, for each additional tree species, the total C stock increased by 6.4%. Our results provide comprehensive evidence for diversity-mediated above- and below-ground C sequestration in species-rich subtropical forests in southeast China. Therefore, afforestation policies in this region and elsewhere should consider a change from the current focus on monocultures to multi-species plantations to increase C fixation and thus slow increasing atmospheric CO
concentrations and global warming.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Human-induced biodiversity change impairs ecosystem functions crucial to human well-being. However, the consequences of this change for ecosystem multifunctionality are poorly understood beyond ...effects of plant species loss, particularly in regions with high biodiversity across trophic levels. Here we adopt a multitrophic perspective to analyze how biodiversity affects multifunctionality in biodiverse subtropical forests. We consider 22 independent measurements of nine ecosystem functions central to energy and nutrient flow across trophic levels. We find that individual functions and multifunctionality are more strongly affected by the diversity of heterotrophs promoting decomposition and nutrient cycling, and by plant functional-trait diversity and composition, than by tree species richness. Moreover, cascading effects of higher trophic-level diversity on functions originating from lower trophic-level processes highlight that multitrophic biodiversity is key to understanding drivers of multifunctionality. A broader perspective on biodiversity-multifunctionality relationships is crucial for sustainable ecosystem management in light of non-random species loss and intensified biotic disturbances under future environmental change.
Humans modify ecosystems and biodiversity worldwide, with negative consequences for ecosystem functioning. Promoting plant diversity is increasingly suggested as a mitigation strategy. However, our ...mechanistic understanding of how plant diversity affects the diversity of heterotrophic consumer communities remains limited. Here, we disentangle the relative importance of key components of plant diversity as drivers of herbivore, predator, and parasitoid species richness in experimental forests and grasslands. We find that plant species richness effects on consumer species richness are consistently positive and mediated by elevated structural and functional diversity of the plant communities. The importance of these diversity components differs across trophic levels and ecosystems, cautioning against ignoring the fundamental ecological complexity of biodiversity effects. Importantly, plant diversity effects on higher trophic-level species richness are in many cases mediated by modifications of consumer abundances. In light of recently reported drastic declines in insect abundances, our study identifies important pathways connecting plant diversity and consumer diversity across ecosystems.
Unravelling the relationships between insect population dynamics and habitat properties is often complex. Established theoretical concepts, which predict an influence of available resources on sex ...determination, have often not been tested with quantitative field data. Cavity-nesting Hymenoptera are suitable to assess the influence of habitat properties on reproductive parameters, as haplodiploidy enables direct responses to local conditions. We hypothesize that with increasing resource availability, the population sex ratio (share of females per site), sex allocation preference per individual offspring (the probability of producing either a male or a female offspring per brood cell) and resource allocation per individual offspring will be favouring towards females. We sampled offspring of Osmia cornuta, Osmia caerulescens and Trypoxylon figulus and their resource provisions using trap nests on 30 study sites in an agricultural landscape in southwest Germany, from March to August 2020. The potential influence of resource availability, landscape variables, temperature, seasonal progression, and nesting opportunities on sex and resource provisions was tested. Population sex ratio was not related to habitat properties. Sex allocation preference in the three species, however, depended on several variables including cavity size and seasonal progression, with pronounced differences amongst species. Individual resource provisioning mainly differed between sexes, as male larvae received less provisions than female larvae. As there was no influence of resource availability, we conclude that the sex ratio of established populations was balanced at the selected study sites by available resources in the landscape. At the individual scale, sex and resource allocation were influenced in species-specific ways. As such, sex determination and resource allocation are essential life history properties of sexually reproducing organisms.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aenictus is the most species-rich genus of army ants in the subfamily Dorylinae and one of the most species rich ant genera in China and the world. In this paper, a new species of the Aenictus ...ceylonicus group, Aenictus hoelldobleri sp. n. , is described and illustrated based on the worker caste. The new species occurs in the subtropical forests of south-east China and is morphologically most similar to Aenictus henanensis Li & Wang, 2005 and Aenictus wudangshanensis Wang, 2006. Aenictus hoelldobleri sp. n. can be distinguished from both species by the shape of the subpetiolar process. The new species also resembles Aenictus lifuiae Terayama 1984 and Aenictus thailandianus Terayama & Kubota, 1993 but clearly differs in various features of the cuticular sculpture. A key to the Chinese species of the Aenictus ceylonicus group based on the worker caste is provided, which may help to reassess and clarify the taxonomic status of the abundant Chinese records of the true Aenictus ceylonicus (Mayr, 1866), a species which almost certainly does not occur in China. Several new locality records are given, among them the first record of Aenictus watanasiti Jaitrong & Yamane, 2013 from China. Keywords: Army ants, Dorylinae, Gutianshan National Nature Reserve, species descriptions, subtropical forest, taxonomy
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Species and processes in ecosystems are part of multi-trophic interaction networks. Plants represent the lowest trophic level in terrestrial ecosystems, and experiments have shown a stabilizing ...effect of plant diversity on higher trophic levels. Such evidence has been mainly collected in experimental grasslands. Forests are structurally more complex than grasslands and support the majority of the global biodiversity, but studies on multi-trophic interaction networks are missing in experimental tree diversity gradients. In a forest diversity experiment in southeast China, we examined how tree diversity affects the structure of trophobiotic networks. Trophobioses are tri-trophic interactions between plants, sap-sucking Hemiptera and honeydew-collecting ants that can be subdivided into a largely mutualistic Hemiptera–ant and an antagonistic plant– Hemiptera network. We inspected almost 7000 trees in 146 plots ranging from monocultures to 16 tree species mixtures and found 194 trophobioses consisting of 15 tree, 33 Hemiptera and 18 ant species. We found that tree diversity increased the proportion of trees harboring trophobioses. Consistent with the prediction that mutualistic and antagonistic networks respond differently to changing environments, we found that the generality index of the mutualistic Hemiptera–ant but not the antagonistic plant–Hemiptera network increased with tree diversity. High generality, maintained by high tree diversity, might correspond to higher functional stability. Hence, our results indicate that tree diversity could increase via bottom–up processes the robustness of ant–Hemiptera associations against changing environmental conditions. In turn, the plant–Hemiptera network was highly complementary, suggesting that host-specific Hemiptera species may be vulnerable to co-extinction if their host plants disappear. Based on our results, we provide possible future research directions to further disentangle the bottom–up effect of tree diversity on the structure of trophobiotic networks.
Synthesis
It is now widely accepted that plant diversity promotes ecosystem functionality and stability. However, it is still largely unknown how plant diversity affects interactions between trophic levels and if different interaction types are affected differently. Using a tri-trophic study system consisting of plants, sap-sucking Hemiptera, and ants we provide evidence that increasing local plant diversity stabilizes the mutualistic Hemiptera–ant but not the antagonistic plant–Hemiptera networks. Our results suggest that bottom–up effects of plant diversity on trophic interactions might generally depend on the type of interaction (mutualistic versus antagonistic) considered.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Tree diversity in forests is an important driver of ecological processes including herbivory. Empirical evidence suggests both negative and positive effects of tree diversity on herbivory, which can ...be, respectively, attributed to associational resistance or associational susceptibility. Tree diversity experiments allow testing for associational effects, but evidence regarding which pattern predominates is mixed. Furthermore, it is unknown if herbivory on tree species of native vs. exotic origin is influenced by changing tree diversity in a similar way, or if exotic tree species escape natural enemies, resulting in lower damage that is unrelated to tree diversity. To address these questions, we established a young tree diversity experiment in temperate southwestern Germany that uses high planting density (49 trees per plot; plot size 13 m2). The species pool consists of six congeneric species pairs of European and North American origin (12 species in total) planted in monocultures and mixtures (1, 2, 4, 6 species). We assessed leaf damage by leaf-chewing insects on more than 5,000 saplings of six broadleaved tree species. Plot-level tree species richness increased leaf damage, which more than doubled from monocultures to six-species mixtures, strongly supporting associational susceptibility. However, leaf damage among congeneric native and exotic species pairs was similar. There were marked differences in patterns of leaf damage across tree genera, and only the genera likely having a predominately generalist herbivore community showed associational susceptibility, irrespective of the geographical origin of a tree species. In conclusion, an increase in tree species richness in young temperate forests may result in associational susceptibility to feeding by generalist herbivores.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A new species of army ant from the Aenictus wroughtonii group is described and illustrated based on the worker caste. Aenictus gutianshanensis Staab, sp. n. is known form a single colony collected in ...the subtropical mixed evergreen broad-leaved forest of the Gutianshan National Nature Reserve, South-East China. The new species is probably most closely related to A. vieti Jaitrong & Yamane, 2010 known from North Vietnam and Taiwan. It is suggested that the abundant records of A. camposi Wheeler & Chapman, 1925 from East and South-East China should be reevaluated, as they are probably A. gutianshanensis or A. vieti and not A. camposi, which is distributed in Sundaland, the Philippines, and the southernmost part of continental South-East Asia.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Automated cameras (including camera traps) are an established observation tool, allowing, for example the identification of behaviours and monitoring without harming organisms. However, limitations ...including imperfect detection, insufficient data storage and power supply restrict the use of camera traps, making inexpensive and customizable solutions desirable. We describe a camera system and evaluation toolset based on Raspberry Pi computers and YOLOv5 that can overcome those shortcomings with its modular properties. We facilitate the set‐up and modification for researchers via detailed step‐by‐step guides.
A customized camera system prototype was constructed to monitor fast‐moving organisms on a continuous schedule. For testing and benchmarking, we recorded mason bees (Osmia cornuta) approaching nesting aids on 20 sites. To efficiently process the extensive video material, we developed an evaluation toolset utilizing the convolutional neural network YOLOv5 to detect bees in the videos.
In the field test, the camera system performed reliably for more than a week (2 h per day) under varying weather conditions. YOLOv5 detected and classified bees with only 775 original training images. Overall detection reliability varied depending on camera perspective, site and weather conditions, but a high average detection precision (78%) was achieved, which was confirmed by a human observer (80% of algorithm‐based detections confirmed).
The customized camera system mitigates several disadvantages of commercial camera traps by using interchangeable components and incorporates all major requirements a researcher has for working in the field including moderate costs, easy assembly and an external energy source. We provide detailed user guides to bridge the gap between ecology, computer science and engineering.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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