Should an application for a second postdoc position include a reference to PhD supervisor? I'm preparing an application for another postdoc job; the end of my first term is nearing, and it has been 1.5 years since finishing my PhD. My thesis work was mostly done in not-well known research institute in a small country; my current postdoc position is in a significantly better university (world's top 100, strong in my area).

I'm somewhat reluctant to include my former PhD advisor as a reference because our relationship was strained in the last year of my studies.

The first reference I'll have is the PI in my current project. For the second reference, alternative options are:


another professor from my current university / project;
the director of the research institute I did my PhD in;
my former PhD advisor.


Which one would you suggest?
If you're afraid the relationship with your supervisor results in a negative reference for you, I suggest not to include him. However, based on the alternative options you have, you must be sure that they actually know you and are able to provide a reference for you.

Although the director of the institute potentially carries more weight (he's the director, after all), he must know about your work and your work ethic. If you worked closely with another professor in your project, it's more likely he is able to provide a better reference for you, and I would choose the professor over the director in that case.