After a long road, that began with a comment, ‘Of course related eucalypts don’t coexist, most of them are distributed allopatrically, and if they do re-mix, they will hybridise anyway’..  followed by many years of field-work, lab work, running models, revisions, more revisions, even more revisions..  we came to the conclusion, that indeed, evolutionary history probably explains why closely related species don’t co-occur.

Ecology is also important. Species in plots tend to have similar trait values (especially specific leaf area). One cool thing about a model-based approach is that we can estimate how much different factors influence co-occurrence and we can detect interactions- e.g. similar species co-occur unless they hybridise. The negative effect of reproductive compatibility was nearly as strong as the positive effect of having similar traits.

See more here