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Conclusions and Suggestions for Future Work

This chapter has shown that niche restriction at the levels of host species,

host population and microhabitats within or on host individuals is

universal among parasites. It has also been shown that, even in hermaph-

roditic parasites, cross-fertilization is important (and obligatory at least

for some species) and that niche segregation is often not the result

of interspecific competition, but of selection to reduce the chances of

190 K. Rohde

Fig. 9.7. (a) Number of species of metazoan ectoparasites on the heads and the

gills per species of marine teleosts (5666 fish of 112 species examined). Note:

maximum number 27 parasite species, but most fish species with fewer than five. If

27 is considered to be the maximum possible, the percentage of empty niches on all

fish species would be 84.1%. (b) Abundance (= mean number of metazoan

ectoparasites of all species per host species). Note: maximum abundance more

than 3000, but most species with fewer than five. (From Rohde, 1998.)