Environmental Science & Technology
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Item MOSQUITOES AND VEGETATION ACROSS SOCIOECONOMIC GRADIENTS(2024) Rothman, Sarah; Leisnham, Paul T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The biomass and composition of local vegetation is a key resource for juvenile mosquitoes, affecting a suite of life history traits including survival, development rate, and body size. In cities across the United States, both plant and mosquito communities vary with socioeconomics. Vegetation is typically more abundant and biodiverse in high-income neighborhoods, whereas mosquitoes are often more numerous and more likely to vector diseases in low-income neighborhoods. While prior work has examined the effects of plant resources on mosquitoes, my dissertation evaluates how these communities interact across a socioeconomically diverse urban landscape. Chapter 1 is a scoping review of current knowledge of the individual relationships between mosquitoes, plants, and socioeconomics in cities. In Chapter 2, I describe fine-scale vegetation surveys on socioeconomically diverse residential properties in Baltimore, MD and Washington, D.C. that revealed less canopy cover, more vines, and more non-native plant species on lower-income blocks. In Chapter 3, I used leaves from the most frequently observed canopy species on low- and high-income blocks, and species common to both, as detrital resource bases in competition trials between two dominant urban mosquitoes, Aedes albopictus and Culex pipiens. Population performance for both species was greater when reared with characteristically low-income than characteristically high-income detritus, suggesting that socioeconomically diverse plant communities are an important factor in shaping urban mosquito communities. Overall, population performances were greatest when mosquitoes were reared in the regionally representative detritus, and I used this detritus base in Chapter 4 to evaluate the effects of varying temperatures. Aedes albopictus population performance was optimized at higher mean temperatures characteristic of low-income blocks, while C. pipiens performance was best at lower mean temperatures characteristic of high-income blocks. Population performance was often lower, however, when temperatures fluctuated around a high or low mean than when the temperature was stable, suggesting that laboratory studies may need to mimic field conditions to obtain applicable results. My research provides a deeper understanding of the mechanisms behind previously observed relationships, and may help guide management and policy strategies to address environmental injustices and public health threats.Item The Role of Tire Leachate in Condition-Specific Competition and the Persistence of a Resident Mosquito from a Competitively Superior Invader(MDPI, 2022-10-22) Villena, Oswaldo C.; Sullivan, Joseph H.; Landa, Edward R.; Yarwood, Stephanie A.; Torrents, Alba; Zhang, Aijun; Leisnham, Paul T.(1) Background: Condition-specific competition, when the outcome of competition varies with abiotic conditions, can facilitate species coexistence in spatially or temporally variable environments. Discarded vehicle tires degrade to leach contaminants into collected rainwater that provide habitats for competing mosquito species. We tested the hypothesis that more highly degraded tires that contain greater tire leachate alters interspecific mosquito competition to produce a condition-specific advantage for the resident, Culex pipiens, by altering the outcome of competition with the competitively superior invasive Aedes albopictus. (2) Methods: In a competition trial, varying densities of newly hatched Ae. albopictus and Cx. pipiens larvae were added to tires that had been exposed to three different ultraviolet (UV)-B conditions that mimicked full-sun, shade, or no UV-B conditions in the field. We also measured Cx. pipiens and Ae. albopictus oviposition preference among four treatments with varying tire leachate (high and low) and resources (high and low) amounts to determine if adult gravid females avoided habitats with higher tire leachate. (3) Results: We found stronger competitive effects of Cx. pipiens on the population performance and survival of Ae. albopictus in tires exposed to shade and full-sun conditions that had higher concentrations of contaminants. Further, zinc concentration was higher in emergent adults of Ae. albopictus than Cx. pipiens. Oviposition by these species was similar between tire leachate treatments but not by resource amount. (4) Conclusions: These results suggest that degraded tires with higher tire leachate may promote condition-specific competition by reducing the competitive advantage of invasive Ae. albopictus over resident Cx. pipiens and, combined with Cx. pipiens’ preferential oviposition in higher resource sites, contribute to the persistence of the resident species.Item The Role of Tire Leachate in Condition-specific Competition and the Persistence of a Resident Mosquito from a Competitively Superior Invader(MDPI, 2022-10-22) Villena, Oswaldo C.; Sullivan, Joseph H.; Landa, Edward R.; Yarwood, Stephanie A.; Torrents, Alba; Zhang, Aijun; Leisnham, Paul T.(1) Background: Condition-specific competition, when the outcome of competition varies with abiotic conditions, can facilitate species coexistence in spatially or temporally variable environments. Discarded vehicle tires degrade to leach contaminants into collected rainwater that provide habitats for competing mosquito species. We tested the hypothesis that more highly degraded tires that contain greater tire leachate alters interspecific mosquito competition to produce a conditionspecific advantage for the resident, Culex pipiens, by altering the outcome of competition with the competitively superior invasive Aedes albopictus. (2) Methods: In a competition trial, varying densities of newly hatched Ae. albopictus and Cx. pipiens larvae were added to tires that had been exposed to three different ultraviolet (UV)-B conditions that mimicked full-sun, shade, or no UV-B conditions in the field. We also measured Cx. pipiens and Ae. albopictus oviposition preference among four treatments with varying tire leachate (high and low) and resources (high and low) amounts to determine if adult gravid females avoided habitats with higher tire leachate. (3) Results: We found stronger competitive effects of Cx. pipiens on the population performance and survival of Ae. albopictus in tires exposed to shade and full-sun conditions that had higher concentrations of contaminants. Further, zinc concentration was higher in emergent adults of Ae. albopictus than Cx. pipiens. Oviposition by these species was similar between tire leachate treatments but not by resource amount. (4) Conclusions: These results suggest that degraded tires with higher tire leachate may promote condition-specific competition by reducing the competitive advantage of invasive Ae. albopictus over resident Cx. pipiens and, combined with Cx. pipiens’ preferential oviposition in higher resource sites, contribute to the persistence of the resident species.Item FIELD TESTING THE ATTRACTANCY AND TOXICITY OF THE PRO-FRAGRANCE COMPOUND, OKOUMAL, TO GRAVID AEDES MOSQUITOES AND THEIR OFFSPRING LARVAE(2020) Babu, Maya; Leisnham, Paul T.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mosquitoes are among the most prominent and medically important insects in the world, causing substantial public health concerns in many regions. Aedes spp. mosquitoes are arguably the most important invasive species in the United States and worldwide. Oviposition traps are typically baited with plant infusions that release a suite of volatile compounds that attract gravid female mosquitoes, but plant infusions require weekly maintenance and are difficult to standardize. The overall goal of my thesis was to evaluate the efficacy of Okoumal, a pro-fragrance compound, at attracting ovipositing gravid adult Aedes mosquitoes and act as a toxin to their larvae offspring using field and laboratory trials. My results indicate that although Okoumal is toxic to Aedes larvae, there is little evidence of it being an attractant to oviposition gravid female Ae. albopictus casting doubt of its use as a bait in mosquito surveillance and control.Item Spatio-temporal mechanisms of urban mosquito coexistence in Baltimore, MD(2019) Saunders, Megan Elizabeth Maria; Leisnham, Paul T.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding the interactions governing species distributions and community structure are of fundamental ecological importance. Mosquitoes that utilize container habitats at their larval stage usually engage in strong competition and competitive exclusion is expected; however, numerous container-utilizing mosquito species co-occur in the same individual container habitats and regionally coexist. I investigated spatial and temporal mechanisms governing the distributions and abundances of the competitively superior invasive Aedes albopictus and resident Culex spp. mosquitoes in four neighborhoods with varying socioeconomic status in Baltimore, Maryland. Specifically, I investigated if the findings from both field surveys and field and laboratory experiments were consistent with four spatial and temporal hypotheses for species coexistence that act at different scales: spatial partitioning among neighborhoods and blocks, seasonal condition-specific competition, aggregation among individual container habitats, and priority colonization effects within individual containers. I found modest but important evidence for all hypotheses that could each facilitate Culex spp. coexistence with Ae. albopictus. I found clear neighborhood effects, with low SES neighborhoods supporting higher abundances of mosquitoes than high SES neighborhoods overall, but with the highest abundances of Ae. albopictus in low SES neighborhoods and Culex spp. being more variable among neighborhoods. Culex spp. abundances were higher in the early summer compared to mid-summer peaks in abundance for Ae. albopictus. Laboratory competition trials showed increased aggregation of Ae. albopictus had a slight positive effect on Culex spp. population performance, and aggregation conditions sufficient for coexistence among experimentally placed ovitraps and negative associations of Aedes and Culex genera in resident containers in the field. Lastly, I found that priority colonization of a container leads to stronger population performance for both species, and that resource availability seems to affect Culex spp. more than competition. The results of my dissertation have revealed the role of several ecological mechanisms that may facilitate the regional coexistence of Culex spp. with Ae. albopictus and is among the first bodies of work to do so. Due to their roles in the transmission of human pathogens, future examination of other spatial and temporal mechanisms of coexistence between Ae. albopictus and resident Culex spp. is warranted.Item THE EFFECTIVENESS OF RESIDENT- BASED MOSQUITO CONTROL THROUGH CHANGES IN KNOWLEDGE AND BEHAVIOR ALONG A SOCIOECONOMIC GRADIENT(2014) Bodner, Danielle Elizabeth; Leisnham, Paul T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Controlling mosquito abundances in urban landscapes requires management of water-holding containers by residents. We tested the hypothesis that print materials reduce human exposure to mosquitoes through improved resident knowledge and behaviors across urban landscapes. Households that varied in socio-economic status were administered knowledge, attitude, and practice (KAP) surveys in 2010 and 2012, and had their yards surveyed for container habitats in 2010, 2011, and 2012. Half of the households received education materials in 2011 and 2012. During the summer of 2013, larval and adult abundances were measured across four socioeconomically-diverse neighborhoods in Baltimore, MD. Our education intervention was insufficient to motivate residents to reduce containers. Source reduction was predicted by improvements in knowledge and education intervention. Overall adult abundances were heterogeneous across neighborhoods, and adult Aedes albopictus abundances were predicted by the infested container index. Future research needs to examine socio-ecological processes that may differentially affect immature vs. adult habitats.Item Linking socioeconomic factors to mosquito control in residential Washington, D.C.(2011) Dowling, Zara; Leisnham, Paul T; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urban larval mosquito control strategies include elimination of aboveground water-holding containers by private residents (`source reduction') and larviciding of belowground storm drains and utility manholes. Effective source reduction is dependent on public education campaigns that identify key sources of mosquitoes, target at-risk neighborhoods, and create an informed and motivated citizenry. I conducted 242 yard surveys for mosquito larval habitats paired with Knowledge, Attitude, and Practice (KAP) questionnaires administered to residents in six socioeconomically-diverse neighborhoods in the greater Washington, D.C. metropolitan area, and sampled 201 belowground habitats adjacent to these households. In chapter 2, I analyze associations between resident socioeconomic status, knowledge, attitudes, practices and mosquito indices. In chapter 3, I examine variations in larval habitat quality, quantity and type across neighborhoods of differing socioeconomic status. In chapter 4, I compare larval populations in aboveground and belowground habitats. The implications for educational literature and mosquito management are discussed.