DOI: 10.5061/dryad.3j9kd51mj
title: Beyond single host, single parasite interactions: quantifying competence for complete multi-host, multi-parasite communities

description: Understanding parasite transmission in communities requires knowledge of
 each species’ capacity to support transmission. This property,
 “competence”, is a critical currency for modeling transmission under
 community change and for testing diversity-disease theory. Despite the
 central role of competence in disease ecology, we lack a clear
 understanding of the factors that generate competence and drive its
 variation. We developed novel conceptual and quantitative approaches to
 systematically quantify competence for a multi-host, multi-parasite
 community. We applied our framework to an extensive dataset: five
 amphibian host species exposed to four parasitic trematode species across
 five ecologically realistic exposure doses. Together, this experimental
 design captured twenty host-parasite interactions while integrating
 important information on variation in parasite exposure. Using
 experimental infection assays, we measured multiple components of the
 infection process and combined them to produce competence estimates for
 each interaction. With directly estimated competence values, we asked
 which components of the infection process best explained variation in
 competence: barrier resistance (the initial fraction of administered
 parasites blocked from infecting a host), internal clearance (the fraction
 of established parasites lost over time) or pre-transmission mortality
 (the probability of host death prior to transmission). We found that
 variation in competence among the twenty interactions was best explained
 by differences in barrier resistance and pre-transmission mortality,
 underscoring the importance of host resistance and parasite pathogenicity
 in shaping competence. We also produced dose-integrated estimates of
 competence that incorporated natural variation in exposure to address
 questions on the basis and extent of variation in competence. We found
 strong signals that host species identity shaped competence variation (as
 opposed to parasite species identity). While variation in infection
 outcomes across hosts, parasites, individuals, and doses was considerable,
 individual heterogeneity was limited compared to among-species
 differences. This finding highlights the robustness of our competence
 estimates and suggests that species-level values may be strong predictors
 for community-level transmission in natural systems. Competence emerges
 from distinct underlying processes and can have strong species-level
 characteristics; thus, this property has great potential for linking
 mechanisms of infection to epidemiological patterns.
description: All methods related to the present data can be found in the
 methods and appendix of Stewart Merrill et al. 2022 Functional
 Ecology.
description: <strong style="font-size:1.1em;font-family:KievitWeb , sans-serif;">competence_data.xlsx </strong>contains the raw experimental data
 for parasites encysting in individually inoculated amphibian hosts. The
 raw data are in the the "data" tab, and the metadata (including
 a guide to the column headers and additional notes) are in the
 "metadata" tab.