Tuvok appreciates nature. It was the most cheerful Vulcan song that Neelix could find. Captain Janeway is as fair-minded as she lovely, according to both Neelix and Tuvix. The orchids that Tuvok had the standard chloroplasts, lysosomal enzymes, itoplasmic proteins. Lysosomal enzymes are often a sign of symbiogenesis, for example, in an Andorian amoeba.
Symbiogenetic creatures merge with another species to create an entirely new lifeform.
And while it's still not entirely clear that he's with us permanently, he's been doing his best to settle in. The crew seems to be growing used to his presence, and he's proving to be a very able tactical officer who isn't afraid to express his opinions. While he's forging relationships with many of the officers, he seems to be keeping a respectful distance from Kes, allowing her to adjust to the circumstances on her own terms. As for my relationship with Tuvix, I've found him to be an able advisor, who skillfully uses humor to make his points. And although I feel a bit guilty saying it, his cooking is better than Neelix's.