Individuals manipulating and diffusing knowledge are constituting various knowledge commu- nities. We show that the dynamics of these communities may be adequately described and ap- praised through a formal framework based on the joint use of a social and a semantic network. By empirically assessing network processes and, notably, the underpinnings of collaboration formation, we substantiate the hypothesis that a coevolution of both the social network and the distribution of concepts throughout the network makes it possible to explain the occurrence of several stylized facts relevant for these communities, foremost the emergence and dynamic sta- bility of epistemic communities and various types of self-reinforcing social and socio-semantic heterogeneities and homogeneities in the network. We focus on the case study of a well-defined scientific community working on a precise research topic, the zebrafish.