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All pairwise differences in average bird predation among urban tree habitats from Steel-Dwass multiple comparisons test for A) summer 2017 and B) spring 2018. Bars sharing a letter are not significantly different (P < 0.05)
Source publication
Predation by natural enemies is important for regulating herbivore abundance and herbivory. Theory predicts that complex habitats support more natural enemies, which exert top-down control over arthropods and therefore can reduce herbivory. However, it is unclear if theory developed in other more natural systems similarly apply to predation by vert...
Citations
... Arthropods are experiencing global declines, which can disrupt energy transfer in food webs and affect ecosystem services (Hallmann et al., 2017;Lister & Garcia, 2018;Sánchez-Bayo & Wyckhuys, 2019). Arthropods are a particularly important food resources for birds, providing calcium and amino acids, and arthropods in urban forests are often crucial to bird success in urban environments (Long & Frank, 2020;Nagy & Holmes, 2005;Seress et al., 2018). The phenology of strict herbivores like caterpillars, the larval form of butterflies and moths in the order Lepidoptera, are reliant on particular plant communities (Koricheva & Hayes, 2018). ...
... These results suggest urban forests invaded by nonnative plants can support some arthropod populations which in turn provide food resources for other wildlife, including birds, that depend on calcium and amino acid-rich foods to feed their young Long & Frank, 2020;Nagy & Holmes, 2005;Parsons et al., 2020). ...
Aim
Ecological theory and empirical evidence indicate that greater structural complexity and diversity in plant communities increases arthropod abundance and diversity. Nonnative plants are typically associated with low arthropod abundance and diversity due to lack of evolutionary history. However, nonnative plants increase the structural complexity of forests, as is common in urban forests. Therefore, urban forests are ideal ecosystems to determine whether structural complexity associated with nonnative plants will increase abundance and diversity of arthropods, as predicted by complexity literature, or whether structural complexity associated with nonnative plants will be depauperate of arthropods, as predicted by nonnative plant literature.
Location
We sampled 24 urban temperate deciduous and mixed forests in two cites, Raleigh, North Carolina and Newark, Delaware, in the eastern United States.
Methods
We quantified ground cover vegetation and shrub layer vegetation in each forest and created structural complexity metrics to represent total, nonnative and native understory vegetation structural complexity. We vacuum sampled arthropods from vegetation and quantified the abundance, biomass, richness and diversity of spiders and non‐spider arthropods.
Results
Nonnative plants increase understory vegetation complexity in urban forests. In Raleigh and Newark, we found support for the hypotheses that dense vegetation will increase arthropod abundance and biomass, and against the hypothesis that nonnative vegetation will decrease arthropods. Urban forest arthropod abundance and biomass, but not diversity, increased with greater nonnative and native structural complexity.
Main Conclusions
Invaded urban forests may provide adequate food in the form of arthropod biomass to transfer energy to the next trophic level, but likely fail to provide ecological services and functions offered by diverse species, like forest specialists. Urban land managers should survey urban forests for nonnative and native plant communities and prioritize replacing dense nonnative plants with native species when allocating vegetation maintenance resources.
... Forest remnants in the city are scattered and surrounded by high buildings, resulting in extreme cases of forest fragmentation (Dobbs, Nitschke, & Kendal, 2017). These forests become "green islands" in a matrix of urban land uses, helping to maintain biodiversity and ecosystem services (Canedoli, Manenti, & Padoa-Schioppa, 2018;Long & Frank, 2020). Reforestation is one of the direct approaches to support the maintenance of ecological functions and services of urban forests (Williams et al., 2009;Aronson et al., 2016). ...
Urban forests are highly fragmented in mega-cites, acting as islands in terms of preserving species diversity. To maintain the ecological services of urban forests, management measures such as reforestation have been implemented, which might have a long-term effect on biodiversity. To understand how fragmentation and reforestation affect the natural regeneration of urban forests, we investigated the relationship between forest area, isolation and seed dispersal mode and the diversity and composition of woody species at the tree, seedling, and sapling stages in 28 secondary forests of the mega-city of Wuhan, China. We found that the alpha diversity of woody species was positively correlated with forest area, while their beta diversity was negatively correlated with forest area. The beta diversity of nonanimal-dispersed species significantly correlated with isolation. Animal-dispersed plants had consistently a higher alpha diversity from trees to seedlings and saplings, while their beta diversity was lower than nonanimal-dispersed plants at the seedling and sapling stage. The community composition of woody plants in urban forests was largely congruent among the three life stages. However, only the communities of animal-dispersed plants were consistent across life stages in small or highly-isolated forest patches. The results show that the woody plant diversity of urban forests is largely similar to that expected by island theory. Animal-dispersed trees are more likely to regenerate successfully due to a more diverse set of species used in reforestation and their higher tolerance to urban forest fragmentation. More management measures for nonanimal-dispersed species, such as enriching and repeating reforestation, will be required to maintain their high biodiversity in urban forests.
... This method has been successfully used to estimate predation pressure on caterpillars (Ferrante et al. 2014, Howe et al. 2009, Loiselle & Farji-Brener 2002, Richards & Coley 2007, Tvardikova & Novotny 2012. The majority of these studies were carried out in wooded areas with a different level of succession, whereas only a few studies have evaluated predation pressure in urban and suburban environments (Eötvös et al. 2018, Ferrante et al. 2014, Kozlov et al. 2017, Long & Frank 2020, Roels et al. 2018. Although it has been suggested that generalist predators are similarly attracted by chemical cues of artificial and real caterpillars (Ferrante et al. 2017b, Richards & Coley 2007, this method does not measure actual predation rates . ...
Growing urban expansion can alter ecological processes within trophic networks. Predation on herbivores is known to vary with the size of the area covered by vegetation, successional stage, altitude and predator community structure; however there are gaps in understanding how this occurs in urban and suburban environments. The purpose of this study was to determine whether predation pressure on artificial models of caterpillars varied with the degree of urbanisation and type of substrate. Artificial caterpillars were placed on two types of substrates (leaf vs . stem) in two areas of the city (urban vs . suburban). Total predation was measured as the number of models with evidence of attack by predators, with the predation rate estimated on a weekly basis. Predation was affected by the degree of urbanisation, being higher in urban ( x̄ = 9.88%; SD = 4.09%, n = 8) than suburban areas ( x̄ = 5.75%, SD = 4.21%, n = 8). Attack marks were observed in 23.8% ( n = 125) of artificial caterpillars. The weekly predation rate on leaves ( x̄ = 9.63%, SD = 5.95%, n = 8) was higher than that on stems ( x̄ = 6%, SD = 4.2%, n = 8). These results suggest that the incidence of predation might vary with the degree of urbanisation and by the type of substrate on which prey organisms are found.
... In some respects, this pattern may match demand for such services, with a higher need for litter removal in population-dense areas. However, invertebrate pest outbreaks often occur in urban areas and isolated green spaces within a high impervious surface context may be more vulnerable to such outbreaks (Long & Frank, 2020). Furthermore, despite particularly high demand for cultural ecosystem services in areas with more impervious surface cover (Goodness et al., 2016;Valente-Neto et al., 2021), they are likely most scarce there due to the absence of colorful species. ...
Land use intensification in urban areas can have profound effects on biological communities that provide valuable ecosystem services to urban residents. We used a response-and-effect functional trait approach to determine how bird species’ responses to local and landscape-scale habitat of urban green spaces affects the supply of cultural and regulating ecosystem services. We sampled bird communities and habitat variables in urban green spaces that varied in local- and landscape-scale habitat composition and compiled a dataset of species’ response and effect traits related to nesting, foraging, diet, and visual and acoustic aesthetic appeal. Overall, the landscape-scale context of a green space had a stronger influence on species’ abundances than local- scale habitat. Landscape-scale impervious surface surrounding our study sites interacted with response traits related to nesting in human-built structures, clutch size, wing length, canopy foraging, and consumption of seeds and invertebrates to drive bird species’ abundances. Because correlations between response and effect traits can influence the effect traits available to provide ecosystem services at a site, we explored the correlation of these three response traits to a suite of effect traits. We determined that the response traits were correlated with several effect traits related to diet and regulating services but correlated with few of the plumage and acoustic traits that produce cultural services. Finally, we found that effect traits associated with cultural and regulating ecosystem services varied strongly along the landscape-scale gradient of urbanization. Sites with high impervious surface cover are expected to have low levels of invertebrate pest control and visual appeal but high levels of acoustic appeal, diet evenness (generalism), and granivory. Overall, our study highlights the key role of landscape-scale habitat in driving bird-mediated ecosystem services and underscores the importance of regional urban planning to create healthy and livable cities.
... It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted January 20, 2023. ; https://doi.org/10.1101/2023.01.19.524212 doi: bioRxiv preprint proved to be a good predictor of biodiversity, including acoustic diversity, likely due to the complex 170 architecture of trees and diversity of resources and trophic interactions between trees, insect 171 herbivores and their natural enemies (Barbaro et al., 2022;Long & Frank, 2020 Here, we addressed the LBIH through the lens of predation by simultaneously characterizing changes 194 in insectivorous bird community diversity, bird predation, and the biodiversity-function relationship 195 while controlling for local factors throughout the European distribution range of the pedunculate oak 196 (Quercus robur L., 1753), a major forest tree species. Specifically, we predict the following (Fig. 1): (i) 197 bird diversity (including bird acoustic diversity, insectivorous bird species richness and functional 198 diversity) and predation rates increase toward lower latitudes; (ii) bird predation rates increase with 199 bird acoustic activity, species richness and greater functional diversity of insectivorous birds; (iii) bird 200 diversity, acoustic activity and bird predation rates increase with increasing forest cover at both local 201 (neighborhood) and larger spatial scales; (iv) large-scale variability in bird predation rates is primarily 202 driven by local changes in the diversity and activity of birds. ...
According to the Latitudinal Biotic Interaction Hypothesis (LBIH), the general increase in biodiversity towards lower latitudes can be partially explained by an increase in the intensity of biotic interactions. While LBIH received some support for plant-herbivores interactions, much less is known about how higher trophic levels may contribute to shape biotic interactions across latitudinal gradients. We hypothesized that the diversity of insectivorous birds increases towards lower latitude, leading to higher predation rates on insect herbivores.
We deployed plasticine caterpillars in 138 oak trees in 47 sites along a 19 degree 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; and (ii) infer both taxonomic and functional diversity of insectivorous birds from recordings.
The functional diversity of insectivorous birds increased towards lower latitude. Bird predation increased with latitude, forest cover and bird acoustic diversity but decreased with mean annual temperature and functional richness of insectivorous birds. Contrary to our predictions, latitudinal clines in bird predation attempts were not directly mediated by changes in insectivorous bird diversity or acoustic diversity, but latitude and habitat still had independent effects on predation attempts.
Our study does not fully support the predictions of the LBIH of more biotic interactions southwards and advocates for better accounting for activity and abundance of insectivorous birds when studying the large-scale variation in insect-tree interactions.
... The stability of this clay product was proven under summer temperatures (Roels et al. 2018). The green-colored clay models effectively captured predatory interactions, and as a result, the impressions were visible on the clay surface (Low et al. 2014, Sam et al. 2015, Roels et al. 2018, Long and Frank 2020, Khan and Joseph 2021a. A 30 × 4 mm (length × diameter) model, simulating the late instar caterpillar pest, such as fifth instar of S. frugiperda larva, was prepared by rolling the clay on a smooth wooden surface using a piece of a 10 cm × 5 cm clear acrylic sheet (Khan and Joseph 2021a). ...
Arthropod predators are abundant in turfgrass systems, and they play an important role in managing pests. Understanding the vertical distribution of predation is critical to developing cultural strategies that enhance and conserve predatory services. However, little is known on how the predation is vertically distributed within the turfgrass canopy. Thus, the objective of this study was to determine the vertical distribution of predation within the turfgrass canopy. Clay models were used to emulate the general appearance of Noctuidae caterpillars, to estimate the predatory activity. The choice and no-choice experiments were conducted by placing clay models at 2.54, 5.08, and 7.62 cm from the thatch surface and denoted as lower, intermediate, and upper levels, respectively, within turfgrass canopy. The predator-mediated impressions, paired mark, scratch, deep cut mark, deep distortion, prick, dent, stacked surface impression, scooped mark, granulation, and U-shaped mark, were identified on clay models. The incidence and severity of impressions were significantly greater on clay models placed at the lower canopy level than on those placed at the intermediate and upper canopy levels in the choice and no-choice experiments (P < 0.05). Thus, predators are more likely to find their prey at the soil level. This information can be used to refine management strategies, such as mowing height and insecticide use for effectively managing soil-borne and foliar-feeding arthropod pests and beneficial arthropods.
... In built-up areas, habitats for animals are very scarce. Tree crowns can attract birds, insects, and other animals to settle or forage [42,43], thus facilitating the colonization of animal-dispersed plants. In our study, the species richness and proportion of animal-dispersed plants were significantly higher in the habitats with tree cover than in those without tree cover. ...
A large number of trees have been planted in built-up areas to improve the urban environment, but the effects of tree cover on spontaneous understory herbs are not yet well understood. This study surveyed spontaneous herbs in two kinds of habitats (habitats with and without tree cover) in the built-up area of the small city Junlian in Sichuan Province, China. A total of 222 species of spontaneous herbaceous plants in 180 genera of 71 families were recorded, including a vulnerable species and six species endemic to China. Although the overall species richness values were similar in the two kinds of habitat, the average species richness per quadrat of all plants, perennials, plants with the dwarf growth form, and animal-dispersed plants was significantly higher in the habitats with tree cover than in those without tree cover. The overall species association was significantly positive in the habitats with tree cover (VR = 1.51, p < 0.05) and neural (VR = 0.86) in the habitats without tree cover. Among the top 25 frequently recorded species in each kind of habitat, the species association of plants with the same trait combination type differed greatly in the two kinds of habitats. For the species association between annuals, only 13.33% of species pairs were significantly associated in the habitats with tree cover, while 22.22% of the species pairs were significantly negatively associated in the habitats without tree cover. For the species association between plants with tall growth forms, the proportion of significant positive associations in the habitats with tree cover was approximately twice than in the habitats without tree cover. For the species association between plants with the dwarf growth form, the proportion of negative associations in the habitats without tree cover was approximately twice that in the habitats with tree cover. Species with the same dispersal mode generally had a very low proportion of negative interspecific associations or a high proportion of positive interspecific associations in habitats unfavorable to their establishment. Our findings suggest that tree cover can improve the species richness of the spontaneous herbaceous species beneath them and profoundly influence interspecific coexistence relationships in a built-up area.
... Land cover diversity in the surrounding landscape may further provide complementary habitats and alternative prey for natural enemies, especially the generalist ones, which in turn would promote pest topdown regulation. Still, how the spatial pattern of urban trees influences the relative importance of bottom-up and top-down forces controlling pest dynamics remains an understudied question (Long & Frank, 2020). ...
Urban tree isolation affects the abundance of pests and their enemies. • Urban tree isolation affects the top-down regulation of pests by their enemies. • Monospecific Eucalyptus patches had more herbivore insects than isolated trees. • Pest parasitism rate was 30-fold greater in urban forest patches than isolated trees. • Pest-predator-parasitoid abundance interdependence differed by tree arrangement. A R T I C L E I N F O Keywords: Anthocoris nemoralis Glycaspis brimblecombei Psyllaephagus bliteus Urban forest Top-down regulation Resource concentration A B S T R A C T The proximity to transportation hubs and the large movement of goods and people in cities make trees especially prone to invasive insect pests. Urban tree arrangements, in isolated tree sites or in forest patches, may alter their susceptibility to insect herbivory. Surprisingly little is known about how urban tree spatial arrangements influence pest abundance and top-down regulation by natural enemies. We sampled the abundance of an invasive pest of Eucalyptus, the psyllid Glycaspis brimblecombei, and of two of its natural enemies, the specialist exotic parasitoid Psyllaephagus bliteus and the generalist native predator Anthocoris nemoralis over two years. We measured insect abundances in isolated trees versus monospecific planted forest patches in 17 pairs of sites, each within a Portuguese city. The abundance of the exotic pest was threefold higher in forest patches than in isolated trees. The parasitism rate was ~ 30 times higher in forest patches (11.5 %) than in isolated trees (0.4 %). The interdependence among insect species abundances also differed between spatial arrangements. In isolated trees, predator and parasitoid abundances depended markedly on prey abundance. In forest patches, we found a marked dependence of the predator on the composition of the surrounding landscape. Our study adds empirical data indicating that urban tree isolation matters for pest abundance and regulation by its enemies. In similar systems, avoiding dense monospecific patches of exotic trees and increasing the compositional heterogeneity of the landscape are promising paths to maintain the sustainability of urban trees and their environmental and societal benefits.
... We found a significant negative correlation between predator attack rate and insect herbivory measured later in the season. This finding suggests a potential relationship between herbivory and predation in urban environments (Faeth et al., 2005; but see Long & Frank, 2020). However, we refrain from concluding that predation was the main driver of insect herbivory for several reasons. ...
Insect herbivory is an important component of forest ecosystems functioning and can affect tree growth and survival. Tree diversity is known to influence insect herbivory in natural forest, with most studies reporting a decrease in herbivory with increasing tree diversity. Urban ecosystems, on the other hand, differ in many ways from the forest ecosystem and the drivers of insect herbivory in cities are still debated. We monitored 48 urban trees from five species – three native and two exotic – in three parks of Montreal (Canada) for leaf insect herbivory and predator activity on artificial larvae, and linked herbivory with both predation and tree diversity in the vicinity of focal trees. Leaf insect herbivory decreased with increasing tree diversity and with increasing predator attack rate. Our findings indicate that tree diversity is a key determinant of multitrophic interactions between trees, herbivores and predators in urban environments and that managing tree diversity could contribute to pest control in cities.
... Therefore, the number of studies examining how urban landscapes and urbanization processes (defined here as reduced vegetation cover and increasing proportion of impervious surfaces) affect arthropods has increased considerably in recent decades (Dale and Frank, 2018;Fenoglio et al., 2020). However, observations report inconsistent (positive, negative or neutral) effects of urbanization on the abundances of herbivores (Bergerot et al., 2010;Dale and Frank, 2014;Herrmann et al., 2012;Korányi et al., 2021;Liu et al., 2016;Long and Science of the Total Environment 834 (2022) 155396 Frank, 2020) and their natural enemies (Alaruikka et al., 2002;Burks and Philpott, 2017;Dale and Frank, 2014;Rocha and Fellowes, 2020;Tamburini et al., 2016;Zolotarev and Belskaya, 2015). ...
... First, feeding guild of arthropods provides important information about ecological traits related to resource-acquisition, behavior and life-cycle (Raupp et al., 2010) and thus might influence their response to urbanization [e.g. positive effects on sap-feeders (Dale and Frank, 2014;Korányi et al., 2021), adverse effects on chewing folivores (Long and Frank, 2020;Moreira et al., 2019), and inconsistent effects on leaf miners (Denys and Schmidt, 1998;Dobrosavljević et al., 2020;Moreira et al., 2019)]. Second, arthropods from different taxonomic and functional groups have distinct sensitivities to the altered abiotic conditions of urban environments (e.g. ...
Biological control is a major ecosystem service provided by pest natural enemies, even in densely populated areas where the use of pesticides poses severe risks to human and environmental health. However, the impact of urbanization on this service and the abundance patterns of relevant functional groups of arthropods (herbivores, predators, and parasitoids) remain contested. Here, we synthesize current evidence through three hierarchical meta-analyses and show that advancing urbanization leads to outbreaks of sap-feeding insects, declining numbers of predators with low dispersal abilities, and weakened overall biological pest control delivered by arthropods. Our results suggest that sedentary predators may have the potential to effectively regulate sap-feeders, that are one of the most important pests in urban environments. A well-connected network of structurally diverse and rich green spaces with less intensive management practices is needed to promote natural plant protection in urban landscapes and sustainable cities.
