Figure 4

Structure in the parasite community and its relationship to toll-like receptor (TLR)-mediated responses. A) Limited structuring of the parasite community. Principal components analysis (PCA) of infection variables showed a first component (PC1^P) accounting for 20% of total variation. Large PC1^Ppositive coefficients (shown alongside individual infection variables) occurred for Heligmosomoides polygyrus, Calodium hepaticum and Polyplax serrata, indicating a pattern of positive covariation between these species. At the same time, a moderate negative coefficient for Eimeria spp. faecal oocyst count indicated a possible contrasting trend in coccidial oocyst shedding. Coefficients for Brachylaemus recurvum, Skjrabinotaenia lobata, Syphacia stroma, Ixodes trianguliceps and laelapid mites were small, indicating a lack of influence on PC1^P. B) Strong association between infection status and toll-like receptor (TLR)-mediated responsiveness. When PC1^Pscores were used to represent a major aspect of variation in the parasite community and PC1^Iscores from a PCA of log-transformed TLR-mediated responses (see Figure 2) were used to represent overall innate immune responsiveness, there was a strong confounder-adjusted relationship between the two variables (general linear mixed model, P < 0.001). Plot shows the scatter of individual observations with a least square regression line for reference.