Moving targets: determinants of nutritional preferences and habitat use in an urban ant community

Stahlschmidt, Zachary R.; Johnson, Donald B.

doi:10.1007/s11252-018-0796-0

Cited by 16 publications

(20 citation statements)

References 60 publications

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“…Ants are abundant and important components of terrestrial ecosystems (Underwood & Fisher, 2006), including urban ecosystems (e.g., Menke et al, 2011; Penick, Savage, & Dunn, 2015; Stahlschmidt & Johnson, 2018). They are effective behavioral thermoregulators and, thus, are adapted and sensitive to a wide range of temperatures (Angilletta et al, 2007; Chick, Perez, & Diamond, 2017; Jumbam, Jackson, Terblanche, McGeoch, & Chown, 2008; Lighton & Turner, 2004; Underwood & Fisher, 2006).…”

Section: Methodsmentioning

confidence: 99%

City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community

Johnson

Stahlschmidt

2020

Ecology and Evolution

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Cities are rapidly expanding, and global warming is intensified in urban environments due to the urban heat island effect. Therefore, urban animals may be particularly susceptible to warming associated with ongoing climate change. We used a comparative and manipulative approach to test three related hypotheses about the determinants of heat tolerance or critical thermal maximum (CTmax) in urban ants—specifically, that (a) body size, (b) hydration status, and (c) chosen microenvironments influence CTmax. We further tested a fourth hypothesis that native species are particularly physiologically vulnerable in urban environments. We manipulated water access and determined CTmax for 11 species common to cities in California's Central Valley that exhibit nearly 300‐fold variation in body size. There was a moderate phylogenetic signal influencing CTmax, and inter (but not intra) specific variation in body size influenced CTmax where larger species had higher CTmax. The sensitivity of ants’ CTmax to water availability exhibited species‐specific thresholds where short‐term water limitation (8 hr) reduced CTmax and body water content in some species while longer‐term water limitation (32 hr) was required to reduce these traits in other species. However, CTmax was not related to the temperatures chosen by ants during activity. Further, we found support for our fourth hypothesis because CTmax and estimates of thermal safety margin in native species were more sensitive to water availability relative to non‐native species. In sum, we provide evidence of links between heat tolerance and water availability, which will become critically important in an increasingly warm, dry, and urbanized world that others have shown may be selecting for smaller (not larger) body size.

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Section: Methodsmentioning

confidence: 99%

City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community

Johnson

Stahlschmidt

2020

Ecology and Evolution

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“…The pavement ant is a non‐native generalist that has become one of the most common species in agricultural and urban environments in much of the US (Helms et al., 2019; Zhang et al., 2019). An omnivore, it feeds on a mixed diet of arthropod prey and honeydew (Stahlschmidt & Johnson, 2018) and its diet is likely to vary with available resources (Penick et al., 2015).…”

Section: Methodsmentioning

confidence: 99%

“…Other ants are obligate predators, and many generalist species lie somewhere in between, opportunistically hunting, scavenging and feeding on honeydew (Clay et al., 2017; Gibb et al., 2015; Hölldobler & Wilson, 1990). Generalist ants—for whom fitness is often maximized on a mixed diet of honeydew and insect prey—maintain an optimal nutritional balance by adjusting their foraging preferences or overall food intake (Csata & Dussutour, 2019; Kaspari et al., 2020; Kay, 2004; Krabbe et al., 2019; Stahlschmidt & Johnson, 2018; Wilder et al., 2011). Trophic position in ants can thereby vary within and among species (Hanisch et al., 2019; Pfeiffer et al., 2014; Potapov et al., 2019; Roeder & Kaspari, 2017) and trophic variability helps modulate responses to the environment.…”

Section: Introductionmentioning

confidence: 99%

Bioenergy landscapes drive trophic shifts in generalist ants

Helms

Roeder

Ijelu

et al. 2020

Journal of Animal Ecology

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Changes in trophic niche—the pathways through which an organism obtains energy and nutrients—are a fundamental way in which organisms respond to environmental conditions. But the capacity for species to alter their trophic niches in response to global change, and the ways they do so when able, remain largely unknown. Here we examine food webs in three long‐term and large‐scale experiments to test how resource availability and nutritional requirements interact to determine an organism's trophic niche in the context of one of the largest global trends in land use—the rise in bioenergy production. We use carbon and nitrogen stable isotope analyses to characterize arthropod food webs across three biofuel crops representing a gradient in plant resource richness (corn monocultures, fields dominated by native switchgrass and restored prairie), and to quantify changes in the trophic niche of a widespread generalist ant species across habitats. In doing so, we measure the effects of basal resource richness on food chain length, niche breadth and trophic position. We frame our results in the context of two hypotheses that explain variation in trophic niche—the niche variation hypothesis which emphasizes the importance of resource diversity and ecological opportunity, and the optimal diet hypothesis which emphasizes dietary constraints and the availability of optimal resources. Increasing plant richness lengthened food chains by 10%–20% compared to monocultures. Niche breadths of generalist ants did not vary with resource richness, suggesting they were limited by optimal diet requirements and constraints rather than by ecological opportunity. The ants instead responded to changes in plant richness by shifting their estimated trophic position. In resource‐poor monocultures, the ants were top predators, sharing a trophic position with predatory spiders. In resource‐rich environments, in contrast, the ants were omnivores, relying on a mix of animal prey and plant‐based resources. In addition to highlighting novel ecosystem impacts of alternate bioenergy landscapes, our results suggest that niche breadth and trophic diversification depend more on the presence of optimal resources than on ecological opportunity alone.

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“…Urban and fragmented ecosystems may create complex, patchwork habitats that allow some groups of organisms to partition niches effectively (18). Native ant biodiversity in northern California is strongly linked to urbanization; disturbed, urbanized habitats have lower native ant species richness but support higher levels of invasive ant species.…”

Section: Introductionmentioning

confidence: 99%

Spatial and temporal partitioning and tree preference in California woodland ants

MacArthur-Waltz

Nelson

Lee

et al. 2019

Preprint

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Spatial and temporal partitioning of habitat may facilitate diversity and have important impacts 10 on ant communities. To investigate niche overlap in an ant community in a northern California oak 11 woodland, we observed ant foraging on trees in 4 seasonal surveys, each lasting 2 weeks, in a 9.5-hectare 12 plot over the course of a year. Foraging activity in all 5 observed ant species differed by season, time of 13 day, and/or the genera of trees used. Of the 3 ant species most frequently observed, Camponotus 14 semitestaceus was most active during spring and summer nights, Formica moki was most active during 15 spring and summer days, and Prenolepis imparis was most active during both day and night of fall and 16 winter. All ant species preferred native trees to exotic trees and preferred evergreen trees to deciduous 17 trees. Our results suggest that native evergreen oaks such as Quercus agrifolia, currently threatened by 18 sudden oak death (Phytophthora ramorum), may be important for supporting ant biodiversity. 19 20 Acknowledgements for many hours of field work assistance. We thank Rodolfo 25 Dirzo, Daniel Friedman and Maria Wojakowski for providing advice and assistance with statistical 2 26 analysis. Leander D.L. Anderegg, Talia Borofsky, Kaleda Denton, and Tyler McFadden provided helpful 27 comments on the manuscript. The Stanford Maps and Records Office (340 Bonair Siding, Stanford, CA 28 94305) provided detailed maps of trees on the Stanford grounds that were invaluable for this project. 29 30

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Moving targets: determinants of nutritional preferences and habitat use in an urban ant community

Cited by 16 publications

References 60 publications

City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community

City limits: Heat tolerance is influenced by body size and hydration state in an urban ant community

Bioenergy landscapes drive trophic shifts in generalist ants

Spatial and temporal partitioning and tree preference in California woodland ants

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