Coinfection of host populations alters pathogen prevalence, host mortality, and pathogen evolution. Because pathogens compete for limiting resources, whether multiple pathogens can coexist in a host population can depend on their within-host interactions which, in turn, can depend on the order in which pathogens infect hosts (within-host priority effects). However, the consequences of within-host priority effects for pathogen coexistence have not been tested. Using laboratory studies with a coinfected zooplankton system, we found that pathogens had increased fitness in coinfected hosts when they were the second pathogen to infect a host, compared to when they were the first pathogen to infect a host. With these results, we parameterized a pathogen coexistence model with priority effects, finding that pathogen coexistence (1) decreased when priority effects increased the fitness of the first pathogen to arrive in coinfected hosts, and (2) increased when priority effects increased the fitness of the second pathogen to arrive in coinfected hosts. We also identified the natural conditions under which we expect within-host priority effects to foster coexistence in our system. These outcomes were the result of positive or negative frequency dependence created by feedback loops between pathogen prevalence and infection order in coinfected hosts. This suggests that priority effects can systematically alter conditions for pathogen coexistence in host populations, thereby changing pathogen community structure and potentially altering host mortality and pathogen evolution via emergent processes.
Dose x Exposure timing experiment for Metschnikowia infection
This file contains experimental results underlying figures B6 and B7. NAs in the Spores column are a results of hosts dying too early for mature spores to develop, thus not allowing us to assay infection success.
MetschSporeDoseFeedback_dryad.csv
Dose x Exposure timing experiment for Pasteuria infection
This file contains experimental results underlying figures B6 and B7. NAs in the Spores column are a results of hosts dying too early for mature spores to develop, thus not allowing us to assay infection success.
PastSporeDoseFeedback_dryad.csv
Figure 6 code and script
This R code contains the simulations to create the data underlying Figure 6. It also contains the code to create figure 6, minus some modifications made in other programs.
Pathogen_coex_fig6_script.R
metschnikowia, pateuria, within host priority effects data
This data is from our experiment where we measured within host priority effects in daphnia coinfected with Pasteuria and Metschnikowia. The columns have the following meanings. "Treatment"= Treatment number, aligning to Table 1 in the main text. "treatnameM" and "treatnameP" indicate what the treatment was from the view of a focal parasite (e.g., the 1st arrival in coinfection treatment for Pasteuria would be the 2nd arrival in coinfection treatment for metschnikowia). "Replicate" = replicate. "Parasite" indicates whether a row contains Metschnikowia and host fitness data (1) or Pasteuria data (2). "Count1-4" indicates individual spore counts (4 per replicate). "average" indicates average spore count per replicate. "indowrk" indicates whether metschnikowia or pasteuria inoculations were successful. ""treatwork" indicates whether all inoculations for a replicate were successful. "co" indicates whether a replicate belonged to a coinfection treatment. "stillalive" indicates whether the host was still alive at the end of the experiment. "contaminated" indicates whether a replicate was infected by pathogens it was not exposed to. "Pasteuria" indicates whether the treatment was not exposed to pasteuria (0), singly exposed to pasteuria (1), or exposed to both pathogens (2). "exposed" indicates whether the replicate was exposed to any pathogens. "dissolved" indicates whether the host had partially dissolved after death before we could collect it. "dayslife" indicated days post exposure the host lived. "totbab" indicates total offspring a host had over its lifetime. "lastrepro" Indicates final day of reproduction for the host. The remaining columns indicate the number of offspring found whenever we checked hosts.
metsch_past_PE_coinf_dryad.csv
Code for Figure 4
This R script runs the simulation to create the data underlying figures 4 and 5. It also creates figure 4, minus some modifications made in other programs.
fig_4_script_Amnat.R
Analytic coexistence analysis
This code runs the simulation to create the data underlying figure B8.
invasionanalyticalamnat.R
National Science Foundation, Award: DEB-1601353, DEB-1655626, DEB-1305836, DEB-1748729
