The spatial distribution and fecundity of sympatric species of Diplostomum (Digenea) in single and mixed species infections in the intestine of the ring-billed gull ( Larus delawarensis )

Interactions between parasite species may influence their distribution and abundance within communities. Experimental single species infections of Diplostomum spp. in the gut of the definitive host, ringed-billed gulls ( Larus delawarensis Ord, 1815), were compared to mixed species infections to explore interactions among parasites. Three species of Diplostomum (Digenea), designated as Diplostomum sp. 1, Diplostomum sp. 4 and Diplostomum baeri Dubois, 1937 were examined for intestinal distribution and fecundity in single and mixed infections. In single species infections, most specimens of Diplostomum sp. 1 and D. baeri were recovered from the mid-region of the intestine, whereas Diplostomum sp. 4 were mainly present in the anterior region. Significant spatial displacement was observed only for D. baeri when Diplostomum sp. 1 was also present. Intensity was directly correlated to the number of occupied intestinal segments, and the...