Data and the script for the research paper "Within-host ‘infraecology’: asymmetric competition between two co-infecting eye parasites"

The abstract of the research paper is presented below. Here, I will briefly describe the data. Fish were infected either with two parasitic species simultaneously or with each of these species separately. The numbers of infecting agents (per species) were similar in joint and separate exposure treatments. Parasites were localized in either in the lens or vitreous humor of fish. Potential interaction between parasites occupying similar ecological niches was studied.There are three data files. One of them contains data about infection intensities in each treatment accompanied by data about the hosts (size, etc.) and experimental design (e.g., repetitions). The last two files contain data about the sizes of parasites. Variables (column names) are described in a separate file. Finally, there is a file with code written in R, which was used for the data analysis. Just download the data files, set the working directory where these files were downloaded, and enjoy!ABSTRACTParasites within the host body can occupy similar ecological niches and, therefore, compete for resources. Similarly to macroecological environments, within-host habitats often provide unequal access to resources and are naturally asymmetric from the point of view of different parasitic species. For instance, one parasite can live closer to the source of nutrients than another and ‘intercept’ resources, thereby inhibiting the growth of a ‘downstream’ competitor. The eyes of vertebrates are an example of such asymmetric habitats since lenses have priority access to nutrients over the vitreous humor. However, parasitic interactions in asymmetric environments have never been purposefully tested before. We simultaneously infected fish(Salvelinus malma)with lens- and vitreous-dwelling trematodes (Diplostomum pseudospathaceum and Tylodelphys clavata, respectively) to compare infection success and growth of these parasites in the presence/absence of a competitor. We found evidence of competitive interactions between parasites during the infection and growth within hosts. Both parasites decreased the infection success of the competitor to roughly similar extent (symmetric competition). Importantly, in accordance with our initial hypothesis, competition between the parasites during the growth phase was asymmetric. In the presence of lens-dwelling. pseudospathaceum living closer to the nutrient source, vitreous-dwelling T. clavata grew slower. In contrast, T. clavata, the ‘downstream’ parasite, did not influence the growth of the D. pseudospathaceum. Our results show how within-host interspecific interactions and habitat spatial heterogeneity affect the infection success of parasites and the size structure of their infracommunities. We also emphasize that such ‘infraecological’ considerations should be considered when studying infection dynamics and virulence in multi-species parasitic communities.