ORCID Profile
0000-0002-2747-3102
Current Organisation
University of Georgia
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Publisher: Wiley
Date: 19-02-2010
DOI: 10.1111/J.1461-0248.2009.01428.X
Abstract: More erse communities of consumers typically use more resources, which often is attributed to resource partitioning. However, experimentally demonstrating this role of resource partitioning in erse communities has been difficult. We used an experimental response-surface design, varying intra- and interspecific consumer densities, to compare patterns of resource exploitation between simple and erse communities of aphid predators. With increasing density, each single consumer species rapidly plateaued in its ability to extract more resources. This suggests intraspecific competition for a subset of the resource pool, a hallmark of resource partitioning. In contrast, more erse-predator communities achieved greater overall resource depletion. By statistically fitting mechanistic models to the data, we demonstrated that resource partitioning rather than facilitation provides the better explanation for the observed differences in resource use between simple and erse communities. This model-fitting approach also allowed us to quantify overlap in resource use by different consumer species.
Publisher: Wiley
Date: 24-08-2020
Publisher: Springer Science and Business Media LLC
Date: 07-2010
DOI: 10.1038/NATURE09183
Abstract: Human activity can degrade ecosystem function by reducing species number (richness) and by skewing the relative abundance of species (evenness). Conservation efforts often focus on restoring or maintaining species number, reflecting the well-known impacts of richness on many ecological processes. In contrast, the ecological effects of disrupted evenness have received far less attention, and developing strategies for restoring evenness remains a conceptual challenge. In farmlands, agricultural pest-management practices often lead to altered food web structure and communities dominated by a few common species, which together contribute to pest outbreaks. Here we show that organic farming methods mitigate this ecological damage by promoting evenness among natural enemies. In field enclosures, very even communities of predator and pathogen biological control agents, typical of organic farms, exerted the strongest pest control and yielded the largest plants. In contrast, pest densities were high and plant biomass was low when enemy evenness was disrupted, as is typical under conventional management. Our results were independent of the numerically dominant predator or pathogen species, and so resulted from evenness itself. Moreover, evenness effects among natural enemy groups were independent and complementary. Our results strengthen the argument that rejuvenation of ecosystem function requires restoration of species evenness, rather than just richness. Organic farming potentially offers a means of returning functional evenness to ecosystems.
Publisher: Wiley
Date: 20-04-2012
Publisher: Wiley
Date: 20-04-2012
Publisher: Elsevier BV
Date: 11-2014
Publisher: Wiley
Date: 10-05-2017
DOI: 10.1111/GCB.13714
Abstract: Agricultural intensification is a leading cause of global bio ersity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant ersification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect bio ersity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant ersification on abundance, local ersity (communities within fields), and regional ersity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in-field plant ersity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in-field plant ersification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant ersification promote erse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving erse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.
Publisher: The Royal Society
Date: 24-01-2018
Abstract: At local scales, native species can resist invasion by feeding on and competing with would-be invasive species. However, this relationship tends to break down or reverse at larger scales. Here, we consider the role of native species as indirect facilitators of invasion and their potential role in this ersity-driven ‘invasion paradox’. We coin the term ‘native turncoats’ to describe native facilitators of non-native species and identify eight ways they may indirectly facilitate species invasion. Some are commonly documented, while others, such as indirect interactions within competitive communities, are largely undocumented in an invasion context. Therefore, we use models to evaluate the likelihood that these competitive interactions influence invasions. We find that native turncoat effects increase with the number of resources and native species. Furthermore, our findings suggest the existence, abundance and effectiveness of native turncoats in a community could greatly influence invasion success at large scales.
Publisher: Wiley
Date: 02-12-2019
DOI: 10.1002/EAP.2031
Publisher: Wiley
Date: 20-04-2012
Publisher: Wiley
Date: 09-2012
DOI: 10.1890/12-0188.1
Abstract: Greater resource use by erse communities might result from species occupying complementary niches. Demonstrating niche complementarity among species is challenging, however, due to the difficulty in relating differences between species in particular traits to their use of complementary resources. Here, we overcame this obstacle by exploiting plastic foraging behavior in a community of predatory insects common on Brassica oleracea plants in Washington, USA. These predators complemented one another by partitioning foraging space, with some species foraging primarily along leaf edges and others at leaf centers. We hypothesized that emergent bio ersity effects would occur when predators partitioned foraging space on leaves, but not when spatial complementarity was d ened. Indeed, on intact leaves, edge- and center-foraging predators combined to kill more prey than any single predator species could by itself. These emergent ersity effects, however, disappeared on plants damaged by the caterpillar Plutella xylostella. Caterpillar chew-holes brought edge habitats to the center of leaves, so that all predator species could attack aphids anywhere on plants. With spatial niche differences diminished, there were no benefits of predator ersity the most voracious single predator species killed the most aphids. Thus, caterpillar herbivory determined whether multi-predator-species effects reflected complementarity or species' in idual impacts. Our study provides direct evidence for a causative relationship between niche differentiation and increased resource consumption by erse communities, as revealed by ecological engineers that homogenize the foraging environment.
Publisher: Wiley
Date: 10-02-2022
DOI: 10.1002/EAP.2523
Abstract: Recent foodborne illness outbreaks have heightened pressures on growers to deter wildlife from farms, jeopardizing conservation efforts. However, it remains unclear which species, particularly birds, pose the greatest risk to food safety. Using ,000 pathogen tests and 1565 bird surveys covering 139 bird species from across the western United States, we examined the importance of 11 traits in mediating wild bird risk to food safety. We tested whether traits associated with pathogen exposure (e.g., habitat associations, movement, and foraging strategy) and pace‐of‐life (clutch size and generation length) mediated foodborne pathogen prevalence and proclivities to enter farm fields and defecate on crops. C ylobacter spp. were the most prevalent enteric pathogen (8.0%), while Salmonella and Shiga‐toxin producing Escherichia coli (STEC) were rare (0.46% and 0.22% prevalence, respectively). We found that several traits related to pathogen exposure predicted pathogen prevalence. Specifically, C ylobacter and STEC‐associated virulence genes were more often detected in species associated with cattle feedlots and bird feeders, respectively. C ylobacter was also more prevalent in species that consumed plants and had longer generation lengths. We found that species associated with feedlots were more likely to enter fields and defecate on crops. Our results indicated that canopy‐foraging insectivores were less likely to deposit foodborne pathogens on crops, suggesting growers may be able to promote pest‐eating birds and birds of conservation concern (e.g., via nest boxes) without necessarily compromising food safety. As such, promoting insectivorous birds may represent a win‐win‐win for bird conservation, crop production, and food safety. Collectively, our results suggest that separating crop production from livestock farming may be the best way to lower food safety risks from birds. More broadly, our trait‐based framework suggests a path forward for co‐managing wildlife conservation and food safety risks in farmlands by providing a strategy for holistically evaluating the food safety risks of wild animals, including under‐studied species.
Publisher: Wiley
Date: 09-2012
DOI: 10.1890/12-0110.1
Abstract: Healthy ecosystems include many species (high richness) with similar abundances (high evenness). Thus, both aspects of bio ersity are worthy of conservation. Simultaneously conserving richness and evenness might be difficult, however, if, for ex le, the restoration of previously absent species to low densities brings a cost in reduced evenness. Using meta-analysis, we searched for benefits to bio ersity following adoption of two common land-management schemes: the implementation of organic practices by farmers and of controlled burning by natural-land managers. We used rarefaction to eliminate s ling bias in all of our estimates of richness and evenness. Both conservation practices significantly increased evenness and overall abundance across taxonomic classifications (arthropods, birds, non-bird vertebrates, plants, soil organisms). Evenness and richness varied independently, leading to no richness-evenness correlation and no significant overall change in richness. Demonstrating the importance of rarefaction, analyses of raw data that did not receive rarefaction indicated misleadingly strong benefits of organic agriculture and burning for richness while underestimating true gains in evenness. Both organic farming and burning favored species that were not numerically dominant, re-balancing communities as uncommon species gained in iduals. Our results support the assertion that richness and evenness capture separate facets of bio ersity, each needing in idual attention during conservation.
Publisher: Wiley
Date: 02-2012
DOI: 10.1890/11-0399.1
Abstract: Resource consumption often increases with greater consumer bio ersity. This could result either from complementarity among consumers or the inclusion of particular key species, and it is often difficult to differentiate between these two mechanisms. We exploited a simple plant mutation (reduced production of surface waxes) to alter foraging within a community of aphid predators, and thus perhaps shift the nature of resulting predator ersity effects. We found that greater predator species richness dramatically increased prey suppression and plant biomass only on mutant, reduced-wax pea plants (Pisum sativum). On pea plants from a sister line with wild type, waxier plant surfaces, predator species richness did not influence predators' impacts on herbivores or plants. Thus, a change in plant surface structure acted to turn on, or off, the cascading effects of predator ersity. Greater predator richness encouraged higher densities of true predators but did not lead to greater reproduction by a parasitoid, Aphidius ervi fecundity of each natural enemy species was similar for the two plant types. Behavioral observations indicated that although A. ervi was less likely to forage within species-rich predator communities, low-wax plants mitigated this interference by encouraging generally greater A. ervi foraging and thus high rates of aphid dislodgement (aphids dropped from plants to escape A. ervi, but not the other predators). Thus, only species-rich, low-wax plants simultaneously encouraged strong species-specific effects of A. ervi, and strong complementarity among the other predator species. In summary, our study provides evidence that ersity effects in predator assemblages are sensitive to habitat characteristics. Further, we show that a simple plant morphological trait, controlled by a single gene mutation, can dramatically alter the cascading effects of predator species richness on herbivores and plants.
No related grants have been discovered for William Snyder.