This is a guest post by my PhD student Miguel Ángel Collado. My last post on preferring a preference indexes was not satisfactory to us, so we have better options now. Read Miguel Ángel solution below.
We are working on the ecological value of various habitats or sites. In addition to different classical biodiversity indexes, we want to know if we have some sites that are not specially diverse, but they have some ecologically important species attached to them, we could measure this through preference analyses, using null models to compare with our data.
We can define “preference” for an species if the presence of this species on a given site is bigger than expected by random. A way to know this is comparing to null models and establishing an upper threshold for preference, and a lower one for avoidance, this way we would know whether some species of interest have affinity for some sites or just use them as expected.
To see an example of this