An official website of the United States government
Abstract Biodiversity has been linked to reduced disease transmission through the dilution effect process. Traditional ecological measures of biological diversity, such as species richness, are most commonly used to test for the dilution effect. However, such metrics of species diversity do not consider the evolutionary relationship between species, which has important implications for host immune processes and disease transmission. Phylogenetic diversity incorporates the evolutionary relationships of a wildlife community. Host reservoir competency is partly determined by their capacity to mount effective immune responses, which may be phylogenetically determined. As a result, phylogenetic diversity may be a better metric to evaluate the relationship between host diversity and disease transmission, given that closely related species may have more similar pathogen competencies than distantly related ones. Few studies have examined the relationship between phylogenetic diversity and disease transmission, particularly in vector‐borne transmission systems. This study seeks to quantify phylogenetic diversity in the western United States Lyme disease system, where the causal agentBorrelia burgdorferiis vectored by the western black‐legged tick,Ixodes pacificus.We empirically measured mammalian diversity and tick data over seven years. We collected data on ticks, host community, and infection prevalence withBorrelia burgdorferiand constructed generalized linear mixed‐effect models to evaluate the utility of phylogenetic diversity in predicting the prevalence of a tick‐borne pathogen. We found that phylogenetic diversity metrics improved our disease prediction models. Predictions of the overall density and infection prevalence of ticks were improved by the addition of phylogenetic metrics, whereas the density of infected nymphs was solely predicted by a phylogenetic metric over traditional species diversity or richness. Our study found that phylogenetic diversity improves statistical predictions of the Lyme disease pathogen and entomological risk in the western United States and may be informative in other contexts and systems as well.
more »
« less
Idiosyncratic spatial scaling of biodiversity–disease relationships
High host biodiversity is hypothesized to dilute the risk of vector‐borne diseases if many host species are ‘dead ends' that cannot effectively transmit the disease and low‐diversity areas tend to be dominated by competent host species. However, many studies on biodiversity–disease relationships characterize host biodiversity at single, local spatial scales, which complicates efforts to forecast disease risk if associations between host biodiversity and disease change with spatial scale. Here, our objective is to evaluate the spatial scaling of relationships between host biodiversity andBorrelia(the bacterial taxon which causes Lyme disease) infection prevalence in small mammals. We compared the associations between infection prevalence and small mammal host diversity for local communities (individual plots) and metacommunities (multiple plots aggregated within a landscape) sampled by the National Ecological Observatory Network (NEON), an emerging continental‐scale environmental monitoring program with a hierarchical sampling design. We applied a multispecies, spatially‐stratified capture–recapture model to a trapping dataset to estimate five small mammal biodiversity metrics, which we used to predict infection status for a subset of trapped individuals. We found that relationships betweenBorreliainfection prevalence and biodiversity did indeed vary when biodiversity was quantified at different spatial scales but that these scaling behaviors were idiosyncratic among the five biodiversity metrics. For example, species richness of local communities showed a negative (dilution) effect on infection prevalence, while species richness of the small mammal metacommunity showed a positive (amplification) effect on infection prevalence. Our modeling approach can inform future analyses as data from similar monitoring programs accumulate and become increasingly available through time. Our results indicate that a focus on single spatial scales when assessing the influence of biodiversity on disease risk provides an incomplete picture of the complexity of disease dynamics in ecosystems.
more »
« less
- Award ID(s):
- 1954406
- PAR ID:
- 10595939
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecography
- Volume:
- 2025
- Issue:
- 5
- ISSN:
- 0906-7590
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Anthropogenic land use change has led to considerable biodiversity loss, affecting ecosystem functions with unresolved consequences for zoonotic disease transmission. Functional diversity is understudied but potentially important for understanding the role of biodiversity because many zoonotic disease systems are maintained by species with different roles in disease transmission. Here, we explore how functional groups and pathogen genetic diversity influence transmission and human disease risk within the Lyme disease system. Our field and molecular ecology study examined ticks and vertebrates across a fragmented landscape and evaluated several metrics of disease risk. For predicting vector and infected vector density, rodent host richness had a positive effect and was most important, but vector infection prevalence was best predicted by rodent and predator richness together, reflecting how indirect effects may alter tick–host interactions and disease risk. These results indicate that examining species richness generally may obscure important interactions driven by richness within functional groups. Pathogen genotype richness was best predicted by overall vertebrate richness, providing support for the multiple niche polymorphism hypothesis. Our study offers an important perspective on the relationship between biodiversity and disease risk, suggesting that richness within functional groups may offer more nuanced insight into pathogen transmission dynamics than overall biodiversity.more » « less
-
Abstract The dilution effect hypothesis posits that increasing biodiversity reduces infectious disease transmission. Here, we propose that habitat quality might modulate this negative biodiversity–disease relationship. Habitat may influence pathogen prevalence directly by affecting host traits like nutrition and immune response (we coined the term “habitat–disease relationship” to describe this phenomenon) or indirectly by changing host biodiversity (biodiversity–disease relationship). We used a path model to test the relative strength of links between habitat, biodiversity, and pathogen prevalence in a pollinator–virus system. High‐quality habitat metrics were directly associated with viral prevalence, providing evidence for a habitat–disease relationship. However, the strength and direction of specific habitat effects on viral prevalence varied based on the characteristics of the habitat, host, and pathogen. In general, more natural area and richness of land‐cover types were directly associated with increased viral prevalence, whereas greater floral density was associated with reduced viral prevalence. More natural habitat was also indirectly associated with reduced prevalence of two key viruses (black queen cell virus and deformed wing virus) via increased pollinator species richness, providing evidence for a habitat‐mediated dilution effect on viral prevalence. Biodiversity–disease relationships varied across viruses, with the prevalence of sacbrood virus not being associated with any habitat quality or pollinator community metrics. Across all viruses and hosts, habitat–disease and biodiversity–disease paths had effects of similar magnitude on viral prevalence. Therefore, habitat quality is a key driver of variation in pathogen prevalence among communities via both direct habitat–disease and indirect biodiversity–disease pathways, though the specific patterns varied among different viruses and host species. Critically, habitat–disease relationships could either contribute to or obscure dilution effects in natural systems depending on the relative strength and direction of the habitat–disease and biodiversity–disease pathways in that host–pathogen system. Therefore, habitat may be an important driver in the complex interactions between hosts and pathogens.more » « less
-
Globally, zoonotic vector-borne diseases are on the rise and understanding their complex transmission cycles is pertinent to mitigating disease risk. In North America, Lyme disease is the most commonly reported vector-borne disease and is caused by transmission of Borrelia burgdorferi sensu lato (s.l.) from Ixodes spp. ticks to a diverse group of vertebrate hosts. Small mammal reservoir hosts are primarily responsible for maintenance of B. burgdorferi s.l. across the United States. Never- theless, birds can also be parasitized by ticks and are capable of infection with B. burgdorferi s.l. but their role in B. burgdorferi s.l. transmission dynamics is understudied. Birds could be important in both the maintenance and spread of B. burgdorferi s.l. and ticks because of their high mobility and shared habitat with important mammalian reservoir hosts. This study aims to better understand the role of avian hosts in tick-borne zoonotic disease transmission cycles in the western United States. We surveyed birds, mammals, and ticks at nine sites in northern California for B. burgdorferi s.l. infection and collected data on other metrics of host community composition such as abundance and diversity of birds, small mammals, lizards, predators, and ticks. We found 22.8% of birds infected with B. burgdorferi s.l. and that the likelihood of avian B. burgdorferi s.l. infection was significantly associated with local host community composition and pathogen prevalence in California. Addition- ally, we found an average tick burden of 0.22 ticks per bird across all species. Predator and lizard abundances were significant predictors of avian tick infestation. These results indicate that birds are relevant hosts in the local B. burgdorferi s.l. transmission cycle in the western United States and quantifying their role in the spread and maintenance of Lyme disease requires further research.more » « less
-
Context Land use change and deforestation drive both biodiversity loss and zoonotic disease transmission in tropical countrysides. For mosquito communities that can include disease vectors, forest loss has been linked to reduced biodiversity and increased vector presence. The spatial scales at which land use and tree cover shape mosquito communities present a knowledge gap relevant to both biodiversity and public health. Objectives We investigated the responses of mosquito species richness and Aedes albopictus disease vector presence to land use and to tree cover surrounding survey sites at different spatial scales. We also investigated species compositional turnover across land uses and along environmental gradients. Methods We paired a field survey of mosquito communities in agricultural, residential, and forested lands in rural southern Costa Rica with remotely sensed tree cover data. We compared mosquito richness and vector presence responses to tree cover measured across scales from 30 to 1000 m, and across land uses. We analyzed mosquito community compositional turnover between land uses and along environmental gradients of tree cover, temperature, elevation, and geographic distance. Results Tree cover was both positively correlated with mosquito species richness and negatively correlated with the presence of the common invasive dengue vector Ae. albopictus at small spatial scales of 90–250 m. Land use predicted community composition and Ae. albopictus presence. Conclusions The results suggest that local tree cover preservation and expansion can support mosquito species richness and reduce disease vector presence. The identified spatial range at which tree cover shapes mosquito communities can inform the development of land management practices to protect both ecosystem and public health.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/ecog.07541
