DOI: 10.5061/dryad.wh70rxwnm
title: Individual fish infection data from metapopulation epidemics used to calculate resistance, tolerance and competence

description: Host competence, defined as the likelihood that a host will transmit
 infection, may be affected by an individual’s resistance to infection and
 its ability to withstand damage caused by infection (tolerance). Host
 competence may therefore be one of the most important factors to impact
 host-parasite dynamics, yet the relationships among resistance, tolerance,
 and competence are poorly understood.  The objective of the
 present study was to determine whether individual host resistance (ability
 to resist or minimize infection) and/or tolerance (ability to withstand or
 minimize reduction in fitness due to infection) contributed to the
 competence (ability to spread infection) of hosts using guppies infected
 with the ectoparasite, Gyrodactylus turnbulli. This
 individual-fish level analysis used data collected from a previous
 metapopulation experiment that had tracked host-parasite dynamics at the
 metapopulation scale using individually marked guppies that were moved
 among experimental tanks within replicate metapopulations. Fish
 tolerance was measured as the residual from a fish’s expected survival
 post-infection for a given parasite burden. Fish resistance was measured
 as the peak parasite load ( - log-transformed). Host competence was
 measured as the incidence (number of new infections over two days after
 the arrival of a fish to a tank) weighted by the density of available
 uninfected fish in the tank. In contrast to the assumption of a trade-off
 between resistance and tolerance, individual fish tolerance and resistance
 were both negatively associated with competence. Connectivity (the number
 of fish with which an individual came into contact) was not associated
 with competence.  Our results indicate that resistance and
 tolerance are both important to disease spread. These findings highlight
 the importance of understanding how individual defence against parasites
 may contribute to its competence as a host, and therefore impact
 metapopulation-level dynamics.
description: Fish were weight, measured, marked and assembled into
 metapopulations consisting of 4 tanks each of 8 fish. Parasites were then
 introduced to the metapopulations either by infecting one fish in each
 tank with 2 parasites, or by infection four fish in one tank with two
 parasites. Infections on each individual were then monitored every two
 days either for 120 days or until no parasites were found in the whole
 metapopualtion for two consecutive counting days. Additionally, every 10
 days one fish from each tank was haphazardly selected and moved to the
 next tank in the metapopulation in a unidirectional looped manner
 (A-&gt;B-&gt;C-&gt;D-&gt;A). The raw data recorded for
 each fish (uploaded here) were initial weight and length, location within
 the metapopulation for each 10-day interval and parasite load every two
 days. These raw data were then used to calculate our
 variables of interest. Resistance to parasites was calculated as the
 fish's maximum parasite burden (-log-transformed). Tolerance to
 parasites was calculated as the residual from a fitted exponential decay
 curve of survival post-infection and maximum parasite load. Competence of
 an individual fish was measured as the number of uninfected fish in a tank
 that became infected two days after that fish was introduced to that tank,
 multiplied by the density of uninfected fish in the tank and excluding
 cases where all fish in the tank were already infected or the migrating
 fish was uninfected to account for opportunity. For infected fish that
 moved to tanks with uninfected fish more than once, an average of this
 competence was used.