Biodiversity loss underlies the dilution effect of biodiversity

Abstract

The dilution effect predicts increasing biodiversity to reduce the risk of infection, but the generality of this effect remains unresolved. Because biodiversity loss generates predictable changes in host community competence, we hypothesized that biodiversity loss might drive the dilution effect. We tested this hypothesis by reanalyzing four previously published meta-analyses that came to contradictory conclusions regarding generality of the dilution effect. In the context of biodiversity loss, our analyses revealed a unifying pattern: dilution effects were inconsistently observed for natural biodiversity gradients, but were commonly observed for biodiversity gradients generated by disturbances causing losses of native biodiversity. Incorporating biodiversity loss into tests of generality of the dilution effect further indicated that scale-dependency may strengthen the dilution effect only when biodiversity gradients are driven by biodiversity loss. Together, these results help to resolve one of the most contentious issues in disease ecology: the generality of the dilution effect.

Biodiversity loss underlies the dilution effect of biodiversity

“…For example, our reanalysis includes 208 effect sizes from Civitello et al ., 2015, 85 of which are included in at least one additional meta‐analysis, and 123 of which are unique to the Civitello et al ., 2015 dataset. Specific details of which manuscripts and studies were included in which dataset can be found in Table and on Figshare (Halliday, 2020), respectively. The column titled, “Moderators that interact with biodiversity loss” summarises the tests of statistical interactions between biodiversity loss and previously‐hypothesised moderators of the dilution effect.…”

“…Heterogeneity was estimated using restricted maximum likelihood, and separate random intercepts were assigned to the manuscript from which from which effect sizes originated and to parasite species to account for underlying heterogeneity and a lack of independence among effect sizes within a manuscript and across manuscripts that tested the same parasite species. The raw data and an annotated R Markdown script for these analyses are available on Figshare (Halliday, 2020).…”

Cascading effects of sand stabilization on pathogen communities: Connecting global and local processes

“…In disease ecology, disentangling the mechanisms that mediate diversity–disease relationships is a timely endeavour (Halliday & Rohr, 2019; Rohr et al., 2020), and our path analyses, complemented by other correlative and experimental data (Garrido, Halle, et al, 2021; Messika et al., 2017), improved our mechanistic understanding of dilution by resistant hosts and amplification mediated by vectors in natural communities. Other global processes, such as climate change, biodiversity loss, latitude gradients in biotic interactions, and afforestation or deforestation, can affect pathogen occurrence (Dillon & Meentemeyer, 2019; Halliday, Rohr, et al., 2020; Liu et al., 2020), and a causal modelling approach is likely to provide new insights into them as well.…”

Strategies for Managing Marine Disease

“…However, in some cases, loss of biodiversity can lead to a reduction in disease transmission. As such, biodiversity conservation may buffer the spread of EIDs, but with the magnitude and direction of the relationship dependent upon pathogen biology (mode of transmission, host specificity), host composition, spatial scale, and context of the change in biodiversity (Halliday et al 2020(Young et al 2017.…”