Host specificity, parasite community size and the relation between abundance and its variance

We investigated the empirical relationship between mean abundance and its variance, known as Taylor's power law, in fleas parasitic on small mammals. It has been suggested that the exponent of this function, b, represents a true biological character of a species and, dependent on the level of host specificity, varies among species. Other empirical and theoretical studies suggest that exponent b depends on interspecific competition and varies intraspecifically. We tested these hypotheses using data from central and eastern Slovakia. We demonstrate that the slope of Taylor's relationship (a) is repeatable within a flea species, i.e. the slope represents a true species character; (b) increases with an increase of the degree of flea host specificity; and (c) decreases with an increase in flea community size. We discuss our results with the idea that the host can mediate interactions among and within flea species.