Structure in parasite component communities in wild rodents: predictability, stability, associations and interactions .... or pure randomness?

J M Behnke

doi:10.1017/s0031182008000334

Abstract

Experimental data establish that interactions exist between species of intestinal helminths during concurrent infections in rodents, the strongest effects being mediated through the host's immune responses. Detecting immune-mediated relationships in wild rodent populations has been fraught with problems and published data do not support a major role for interactions in structuring helminth communities. Helminths in wild rodents show predictable patterns of seasonal, host age-dependent and spatial variation in species richness and in abundance of core species. When these are controlled for, patterns of co-infection compatible with synergistic interactions can be demonstrated. At least one of these, the positive relationship between Heligmosomoides polygyrus and species richness of other helminths has been demonstrated in three totally independent data-sets. Collectively, they explain only a small percentage of the variance/deviance in abundance data and at this level are unlikely to play a major role in structuring helminth communities, although they may be important in the more heavily infected wood mice. Current worm burdens underestimate the possibility that earlier interactions through the immune system have taken place, and therefore interactions may have a greater role to play than is immediately evident from current worm burdens. Longitudinal studies are proposed to resolve this issue.

Highlights

SUMMARYExperimental data establish that interactions exist between species of intestinal helminths during concurrent infections in rodents, the strongest effects being mediated through the host’s immune responses
Organisms in wild, natural ecosystems live in communities, where they interact with the environment around them and with other organisms (Tokeshi, 1999)
Experimental data establish firmly that interactions exist between intestinal helminths of rodents, and that the strongest effects are mediated through the immune responses of the hosts, but detecting these relationships in naturally occurring wild rodent communities has been fraught with problems (Haukisalmi and Henttonen, 1993 ; Behnke et al 2005) and published data do not support a major role for such interactions in structuring helminth communities in wild rodents (Kisielewska, 1970 a, b, c ; Montgomery and Montgomery, 1990 ; Haukisalmi and Henttonen, 1993 ; Poulin, 2001, Behnke et al 2001)

Summary

SUMMARY

Experimental data establish that interactions exist between species of intestinal helminths during concurrent infections in rodents, the strongest effects being mediated through the host’s immune responses. Helminths in wild rodents show predictable patterns of seasonal, host age-dependent and spatial variation in species richness and in abundance of core species When these are controlled for, patterns of co-infection compatible with synergistic interactions can be demonstrated. At least one of these, the positive relationship between Heligmosomoides polygyrus and species richness of other helminths has been demonstrated in three totally independent data-sets. They explain only a small percentage of the variance/deviance in abundance data and at this level are unlikely to play a major role in structuring helminth communities, they may be important in the more heavily infected wood mice.

INTRODUCTION

Findings

CONCLUSIONS