Biology subjects

Crowder, D. W.

Publications and source records attributed to Crowder, D. W..

8 recordsLinked to original sources

bioRxiv2024

Niche-Based Priority Effects Predict Microbe Resistance to Erwinia amylovora in Pear Nectar

Fire blight is a devastating disease affecting pome fruit trees that is caused by Erwinia amylovora and leads to substantial annual losses worldwide. While antibiotic-based management approaches like streptomycin can be effective, there are concerns over evolved resistance of the pathogen and non-target effects on beneficial microbes and insects. Using microbial biological control agents (mBCAs) to combat fire blight has promise, but variable performance necessitates the discovery of more effective solutions. Here we used a niche-based predictive framework to assess the strength of priority effects exerted by prospective mBCAs, and the mechanisms behind growth suppression in floral nectar. Through in vitro and in vivo assays, we show that antagonist impacts on nectar pH and sucrose concentration were the primary predictors of priority effects. Surprisingly, overlap in amino acid use, and the degree of phylogenetic relatedness between mBCA and Erwinia did not significantly predict pathogen suppression in vitro, suggesting that competition for limited shared resources played a lesser role than alterations in the chemical environment created by the initial colonizing species. We also failed to detect an association between our measures of in vitro and in vivo Erwinia suppression, suggesting other mechanisms may dictate mBCA establishment and efficacy in flowers, including priming of host defenses.

plant biology↗

bioRxiv2023

Identifying drivers of sewage-associated pollutants in pollinators across urban landscapes

Human sewage can introduce pollutants into food webs and threaten ecosystem integrity. Among the many sewage-associated pollutants, pharmaceuticals and personal care products (PPCPs) are useful indicators of sewage in ecosystems and can also cause potent ecological consequences even at minute concentrations (e.g., ng/L). Despite increased study over the past three decades, PPCPs in terrestrial systems have been less studied than those in aquatic ecosystems. To evaluate PPCP prevalence and drivers in a terrestrial ecosystem, we analyzed managed and native bees collected from agroecosystems in Washington State (USA) for PPCPs. Caffeine, paraxanthine, cotinine, and acetaminophen were detected in all three evaluated taxa (Bombus vosnesenskii, Agapostemon texanus, and Apis mellifera), with B. vosnesenskii and A. texanus having a higher probability of PPCP detection relative to A. mellifera. The probability for PPCP presence in all three taxa increased in landscapes with more human development or greater plant abundance, with significant but negative interactions among these factors. These results suggest that human activity, availability of resources, and species-specific traits affect the introduction and mobilization of PPCPs in terrestrial ecosystems. Consequently, monitoring PPCPs and their ecological responses in terrestrial ecosystems creates opportunities to synthesize consequences of sewage pollution across terrestrial and aquatic ecosystems and organism types.

ecology↗

bioRxiv2022

Using agent-based models to predict pollen deposition in a dioecious crop

Pollination involves complex interactions between plants and pollinators, and variation in plant or pollinator biology can lead to variability in pollination services that are difficult to predict. Models that effectively predict pollination services could enhance the ability to conserve plant-pollinator mutualisms in natural systems and increase crop yields in managed systems. However, while most pollination models have focused either on effects of plant or pollination biology, few models have integrated plant-pollinator interactions. Moreover, crop management causes variation in plant-pollinator interactions and pollination services, but management is rarely considered in pollination models. Here we used extensive datasets for kiwifruit (Actinidia chinensis var. deliciosa) to develop an agent-based model to track insect-provided pollination services with variation in crop cultivars, pollinator traits, and orchard layouts. This allowed us to predict pollination outcomes in a dioecious crop under a range of management scenarios. Our sensitivity analysis indicated that flower density and the proportion of female flowers are the most important factors in successful pollination, both of which growers control via cultivar selection and cultural management practices. Our analysis also indicated that economically viable pollination services and crop yields are attained with [~]60% female flowers and a peak foraging activity of 6 to 8 bees per 1,000 open flowers with diminishing returns for additional pollinators. The quality of pollination service varied across simulated orchard layouts, highlighting the potential use of this model as a framework to screen novel orchard configurations. More broadly, linking complex plant and pollinator interactions in pollination models can help identify factors that may improve crop yields and provide a framework for identifying factors important to pollination in natural ecosystems. HIGHLIGHTS- We develop a model using extensive empirical datasets to predict pollen deposition based on the interactions between flowers and pollinators in a dioecious crop system - We conducted a thorough sensitivity analysis, and analysis of the effect of stochastic variance between model runs, which can be used to inform future design of stochastic agent-based models - Our model effectively predicted the outcomes of varying management regimes of orchard layouts and pollinator introductions on pollination in a dioecious crop - Our model can be extended for other functionally dioecious crops or plant communities where managers want to understand how their decisions impact pollination

ecology↗

bioRxiv2021

Factors affecting virus prevalence in honey bees in the Pacific-Northwest, USA

Global efforts to assess honey bee health show viruses are major stressors that undermine colony performance. Identifying factors that affect virus incidence, such as management practices and landscape context, could aid in slowing virus transmission. Here we surveyed viruses in honey bees from 86 sites in the Pacific Northwest, USA, and tested effects of regional bee density, movement associated with commercial pollination, julian date, and hive management on virus prevalence. We also explored patterns of virus co-occurrence and spatial autocorrelation to identify whether local transmission was a primary driver of pathogen distribution. Our surveys found widespread prevalence of Deformed wing virus (DWV), Sacbrood virus (SBV), and Black queen cell virus (BQCV). BQCV and SBV were most prolific in commercial apiaries, while Chronic bee paralysis virus (CPBV) was more common in hobbyist apiaries than commercial apiaries. DWV was most common in urban landscapes and was best predicted by mite prevalence and julian date, while the incidence of both SBV and BQCV were best predicted by regional apiary density. We did not find evidence of additional spatial autocorrelation for any viruses, although high co-occurrence suggests parallel transmission patterns. Our results support the importance of mite management in slowing virus spread and suggest that greater bee density increases transmission. Our study provides support that viruses are widespread in honey bees and connects known mechanisms of virus transmission to the distribution of pathogens observed across the Pacific Northwest. HighlightsThree viruses were widespread in honey bee populations across the Pacific Northwest, USA Black queen cell and Sacbrood viruses were most common in high density hives Deformed wing virus was most common in hives that had high mite loads The presence of many viruses in bees suggests parallel or synergistic transmission

ecology↗

bioRxiv2021

Recent Urban Development Reduces Bee Abundance and Diversity

Wild bee communities persist in cities despite major disruption of nesting and food resources by urban development. Bee diversity and abundance is key for urban agriculture and maintenance of plant diversity, and assessing what aspects of cities enhance bee populations will promote our capacity to retain and provision bee habitat. Here, we assessed how variation in land cover and neighborhood development history affected bee communities in the midwestern US urban landscape of Madison, Wisconsin. We sampled bee communities across 38 sites with relatively high (> 55%) or low (< 30%) levels of impervious surface, and assessed effects of land use and neighborhood development history on bee abundance and species richness. We show abundance and richness of bees was lower in recently developed neighborhoods, with particularly strong negative effects on soil nesting bees. Soil nesting bees and bee community richness decreased as cover of impervious surface increased, but above ground nesting bees were minimally impacted. Bee community similarity varied spatially and based on dissimilar local land cover, only for soil nesting bees, and the overall bee community. Impervious surface limited bee abundance and diversity, but new neighborhoods were associated with greater negative effects. We suggest that enhancing the structural diversity of new neighborhoods in urban ecosystems may imitate the structural benefits of older neighborhoods for bee populations.

ecology↗

bioRxiv2021

Plant responses to multiple antagonists are mediated by order of attack and phytohormone crosstalk

Plants are often attacked by multiple antagonists, and traits of the attacking organisms, and their order of arrival onto hosts, may affect plant defenses. However, few studies have assessed how multiple antagonists, and varying attack order, affect plant defense or nutrition. To address this, we assessed defensive and nutritional responses of Pisum sativum plants after attack by a vector herbivore (Acrythosiphon pisum), a non-vector herbivore (Sitona lineatus), and a pathogen (Pea enation mosaic virus, PEMV). We show PEMV-infectious A. pisum induced several pathogen-specific plant defense signals, but these defenses were inhibited when S. lineatus was present in peas infected with PEMV. In contrast, feeding by S. lineatus induced anti-herbivore defense signals, but these defenses were enhanced by PEMV. Sitona lineatus also increased abundance of plant amino acids, but only when they attacked after PEMV-infectious A. pisum. Our results suggest that diverse communities of biotic antagonists alter defense and nutritional traits of plants through complex pathways that depend on the identity of attackers and their order of arrival onto hosts. Moreover, we show interactions among a group of biotic stressors can vary along a spectrum from antagonism to enhancement/synergism based on the identity and order of attackers, and these interactions are mediated by a multitude of phytohormone pathways.

ecology↗

bioRxiv2020

Ecological dynamics of the almond floral microbiome in relation to crop management and pollination

O_LICrop tissues harbor microbiomes that can affect host health and yield. However, processes driving microbiome assembly, and resulting effects on ecosystem services, remain poorly understood. This is particularly true of flowering crops that rely on pollinators for yield. C_LIO_LIWe assessed effects of orchard management tactics and landscape context on the flower microbiome in almond, Prunus dulcis. Fourteen orchards (5 conventional, 4 organic, 5 habitat augmentation) were sampled at two bloom stages to characterize bacterial and fungal communities associated with floral tissues. The surveys were complemented by in vitro experiments to assess effects of arrival order and fungicides on nectar microbial communities, and effects of fungicides and microbes on honey bee foraging. Finally, a field trial was conducted to test effects of fungicides and microbes on pollination. C_LIO_LIAs bloom progressed, bacterial and fungal abundance and diversity increased, across all floral tissue types and management strategies. The magnitude by which microbial abundance and diversity were affected varied, with host proximity to apiaries and orchard management having notable effects on bacteria and fungi, respectively. C_LIO_LIExperiments showed immigration history and fungicides affected the composition of nectar microbial communities, but only fungicides affected pollinator foraging through reduced nectar removal. Neither treatment affected pollination services. C_LIO_LISynthesis and applications. Our results shed light on routes through which management practices can shape microbiota associated with flowers of a pollinator-dependent crop. With growing appreciation for the role of floral-associated microbes in affecting biotic interactions at the floral interface, understanding such drivers can potentially inform microbial-derived ecosystem services in agricultural landscapes, including pollination and biocontrol. C_LI

ecology↗

bioRxiv2019

Evidence of adaptive host and vector manipulation by plant viruses revealed through combined meta-analysis and modeling approaches.

A growing number of studies indicate that plant viruses enhance their own transmission by modifying host phenotypes and vector behavior, leading to the hypothesis that such effects are manipulations resulting from virus adaptations. However, few studies have linked putative manipulations with virus components, and the true frequency and magnitude of host and vector manipulation across virus taxa remains unknown. To address this knowledge gap, we performed a meta-analysis to quantify convergence in virus effects on hosts and vectors across taxonomic groups that share transmission mechanism traits, and thereby stand to benefit from similar sequences of vector behavior. We then combined meta-analysis outputs with an epidemiological model to assess consequences of manipulation for virus spread. Overall, transmission mechanism traits strongly predicted the magnitude and nature of virus effects on vector preferences and performance. Models parameterized with meta-analysis data demonstrate that manipulation effects enhance virus spread, and that viruses with long acquisition times and retention durations are under strong selection pressure to manipulate transmission. By combining meta-analysis with epidemiological modeling, our results confirm that host and vector manipulation are important aspects of plant virus ecology and evolution while emphasizing the need to incorporate more pathosystems and transmission mechanism traits in future studies.

ecology↗