P. Arneberg et al., HOST DENSITIES AS DETERMINANTS OF ABUNDANCE IN PARASITE COMMUNITIES, Proceedings - Royal Society. Biological Sciences, 265(1403), 1998, pp. 1283-1289
Several epidemiological models predict a positive relationship between
host population density and abundance of directly transmitted macropa
rasites. Here, we generalize these, and test the prediction by a compa
rative study. We used data on communities of gastrointestinal strongyl
id nematodes from 19 mammalian species, representing examination of 66
70 individual hosts. We studied both the average abundance of all stro
ngylid nematodes within a host species, and the two components of abun
dance, prevalence and intensity. The effects of host body weight, diet
, fecundity and age at maturity and parasite body size were controlled
for directly, and the phylogenetically independent contrast method wa
s used to control for confounding factors more generally. Host populat
ion density and average parasite abundance were strongly positively co
rrelated within mammalian taxa, and across all species when the effect
s of host body weight were controlled for. Controlling for other varia
bles did not change this. Even when looking at single parasite species
occurring in several host species, abundance was highest in the host
species with the highest population density. Prevalence and intensity
showed similar patterns. These patterns provide the first macroecologi
cal evidence consistent with the prediction that transmission rates de
pend on host population density in natural parasite communities.