Tread carefully to avoid a doesn't play well with others impression.

I was in a somewhat similar situation (PhD supervisor in a different area), although I had plenty of contacts in my own area. In my applications, I never explicitly brought this up, but did claim that I was rather independent in setting and pursuing my research goals. The evidence I brought up was here's some single author paper and here's a bunch of papers coauthored with all sorts of different people. I left it to the letter from my supervisor to say anything more, because he is in a much better position to put this positively.

Tread carefully to avoid a doesn't play well with others impression.

I was in a somewhat similar situation (Ph.D. supervisor in a different area), although I had plenty of contacts in my own area. In my applications, I never explicitly brought this up but did claim that I was rather independent in setting and pursuing my research goals. The evidence I brought up was here's some single-author paper and here's a bunch of papers coauthored with all sorts of different people. I left it to the letter from my supervisor to say anything more because he is in a much better position to put this positively.