A new book, Marine Parasitology, edited by Klaus Rohde (my father), has just been published by CSIRO Press here in Australia. The book is a compilation of contributions from 75 scientists around the world, including a section authored by Klaus Rohde and myself, entitled "The ecological niches of parasites".
In this section we discuss host specificity indices (HSI's). Parasites, obviously, live off a host. Some parasite species may restrict themselves to one or a few host species, while others may be less selective and parasitise off a far larger number of host species. HSI's quantify how selective a parasite is to host species. As with measures introduced in virtually every scientific field, there are countless competing/complementary measures, with different advantages and disadvantages, and HSI is no exception. Of particular interest to readers within my own field is the Shannon-Wiener measure for host specificity. This measure is exactly equivalent to the Shannon entropy, which anyone from computer science, physics, information theory or telecommunications will be very familiar with. Once again, as is often the case in science, we see things being used very effectively in completely unintended ways. Who would've thought that marine parasites would have entropy?
The book can be purchased from CSIRO Publishing.