Influence of urbanisation and plants on the diversity and abundance of aphids and their ladybird and hoverfly predators in domestic gardens

Rocha, Elise Amador; Souza, Estevão N.F.; Bleakley, Lewis A.D.; Burley, Christopher; Mott, Jade L.; Rue-Glutting, Gloria; Fellowes, Mark D. E.

doi:10.14411/eje.2018.013

Cited by 24 publications

(23 citation statements)

References 63 publications

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“…Predatory ants found on PA colonies and mutualistic ants found on BB colonies were positively associated with the proportion of roads and buildings in the habitat, respectively. The presence of mutualistic ant-aphid interactions was positively associated with more plant diverse sites; aphid diversity in urban gardens is associated with plant diversity and abundance 16 . Urbanised areas may serve as habitat and corridors for dry-adapted and heat tolerant species such as ants 39,40 , and such habitats select for opportunistic, highly competitive ant species 41,42 .…”

Section: Discussionmentioning

confidence: 95%

Urbanisation alters ecological interactions: Ant mutualists increase and specialist insect predators decrease on an urban gradient

Rocha

Fellowes

2020

Sci Rep

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The modification of habitats in urban areas is thought to alter patterns of species interactions, by filtering specialist species and those at higher trophic levels. However, empirical studies addressing these hypotheses remain limited in scope and number. This work investigates (1) how main urban land uses affect predator-prey and mutualistic interactions, and (2) how specialist and generalist predators respond to size and availability of urban green spaces. In a large town in the UK, experimental colonies of ant-attended Black bean aphid Aphis fabae and non-ant-attended Pea aphid Acyrthosiphon pisum were monitored over two years. Ants were more frequently found in highly urbanised sites; however mutualistic ants were also more often encountered when the habitat was more plant diverse. Aphids were not affected by urban land uses, but A. fabae numbers were positively related to the presence of mutualists, and so indirectly affected by urbanisation. Predators were the only group negatively affected by increased urbanisation, and specialist species were positively related to increased proportion of urban green areas within the habitats. While this work supports the hypothesis that specialist predators are negatively affected by urbanisation, we also show that a fundamental ecological interaction, mutualism, is affected by urbanisation. Urbanisation is one of the defining environmental trends of recent times, almost completely modifying natural environments and significantly reducing local biodiversity 1,2. Nevertheless, in most urban areas some native vegetation remains alongside introduced species within the urban matrix, mostly in parks and suburban gardens 3 , and their presence promotes biodiversity and provides ecosystem services (e.g. pollination, nutrient cycling). Urban areas can therefore be of value for biodiversity and conservation 4. However, we have little understanding of how urbanisation modifies the patterns of species interactions. At a simple level, urbanisation replaces natural systems with smaller sealed and impermeable areas, resulting in the reduction and fragmentation of habitat 5. Beyond that, urbanisation changes key factors including local climate, nutrient availability, and disturbance levels 6. Such factors change host plant quality, availability and accessibility (bottom-up factors), alter the abundance and diversity of natural enemies (top-down factors), and may modify the occurrence or intensity of mutualisms and competition (lateral factors) 7,8. All such changes may alter how species interact, changing how ecological communities are structured in urban environments 9. Interactions between arthropod predators and their prey are particularly predisposed to being disrupted by urbanisation 8,10 , with specialist predators in particular likely to present a higher degree of sensitivity to the environmental disturbances that arises from habitat alteration 10-12. It is not only consumptive interactions that may be affected by urbanisation. It is likely that mutualisms will also be affected ...

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Section: Discussionmentioning

confidence: 95%

Urbanisation alters ecological interactions: Ant mutualists increase and specialist insect predators decrease on an urban gradient

Rocha

Fellowes

2020

Sci Rep

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“…Several studies focused on conservation biological control have demonstrated a positive effect of floral diversity on insect natural enemies and predation or parasitism of nearby herbivores [ 9 , 57 , 58 , 59 ]. Dale et al [ 9 ] found that diverse wildflower plantings on golf courses increased both natural enemy abundance and their associated predation of fall armyworm caterpillars up to 18 m away compared to less diverse wildflower plantings and areas with no floral resources.…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, Blaauw and Isaacs [ 24 ] showed that as the size of wildflower patches increased, natural enemy density almost doubled, and diversity increased with plot size and wildflower presence compared to mown grass areas. Additionally, Rocha et al [ 57 ] found that urban gardens with higher floral richness had greater hoverfly and ladybeetle abundance than less florally rich gardens. Although we did not detect a consistent effect of plant diversity on natural enemies, we did on our last survey date, which supports previous findings.…”

Section: Discussionmentioning

confidence: 99%

Mixed-Species Gardens Increase Monarch Oviposition without Increasing Top-Down Predation

Nestle

Daniels

Dale

2020

Insects

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Monarch butterfly populations have declined by over 80% in the last 20 years. Conservation efforts focus on the creation of milkweed habitats to mitigate this decline. Previous research has found monarchs lay more eggs per milkweed stem in urban gardens than natural habitats and recent work identified specific garden designs that make urban gardens more attractive to monarchs. Increasing plant diversity can reduce specialist insect herbivore colonization via bottom-up (e.g., plant) and top-down (e.g., predation) regulatory factors. Although this is beneficial for pest management efforts, it contradicts conservation efforts. In this study, we explored if adding multiple flowering species to garden-sized milkweed plantings affected monarch oviposition or top-down regulation of larvae. We compared monarch egg abundance, natural enemy abundance and richness, and biological control of monarch larvae in milkweed monocultures and milkweed mixed with four additional wildflower species. We found that monarchs laid 22% more eggs on sentinel milkweed plants in mixed-species plots with no effect of plant diversity on monarch survival. We also found higher natural enemy richness, wasp, and predatory bug abundance in the mixed-species plots and this did not translate to higher biological control rates. Our results provide more evidence that plant selection and habitat design are important for monarch conservation.

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“…Our findings align with those from central Chile, where urbanization intensity was a negative driver of aphidophagous native abundance, native richness, and coccinellid body size within parks across a rural to urban landscape gradient (Grez et al., 2019). Likewise, increased impervious surface was negatively associated with lady beetle species richness within urban gardens in Berkshire, England (Rocha et al., 2018), and native and alien lady beetle abundance within vacant lots in Cleveland, Ohio (Parker et al., 2020). In contrast to aphidophagous species, Buckeye Lady Beetle Blitz volunteers found positive relationships between the density of the built environment and the abundance of coccidophagous and fungivorous lady beetles within their gardens.…”

Section: Discussionmentioning

confidence: 99%

Community science data suggests that urbanization and forest habitat loss threaten aphidophagous native lady beetles

Gardiner

Perry

Riley

et al. 2021

Ecology and Evolution

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Influence of urbanisation and plants on the diversity and abundance of aphids and their ladybird and hoverfly predators in domestic gardens

Cited by 24 publications

References 63 publications

Urbanisation alters ecological interactions: Ant mutualists increase and specialist insect predators decrease on an urban gradient

Urbanisation alters ecological interactions: Ant mutualists increase and specialist insect predators decrease on an urban gradient

Mixed-Species Gardens Increase Monarch Oviposition without Increasing Top-Down Predation

Community science data suggests that urbanization and forest habitat loss threaten aphidophagous native lady beetles

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