In a Nexus, can a Dev Team member work on more than one Scrum Team?

If the teams within a Nexus are managing their dependencies, why would a Dev Team member need to?

True but in theory can they?

kind of in the same fold of questioning, does a Scrum Team member have to be full time? I think the answer is no.. 

What would be the effect of having to work in multiple teams? 

Just out of my own curiosity, from where in the organization if this question coming from?

I don't think it's a good idea. A Nexus is 3-9 Scrum teams working on a common product. One of the core Scrum values is "focus". I would make the argument that a person that is working on multiple Scrum teams is not focused on the "work of a Sprint and the goals of the Scrum Team" (a quote directly from the Scrum Guide) and that this is, at best, a not-ideal situation to be in and would make execution of a team's Scrum process more difficult.

I would also disagree with the idea that someone working on two or more Scrum teams is the same as someone working part time. Someone who is working part time can still be focused on the work of a single Sprint and the goals of the Scrum Team. Someone working on two teams is focused on the work of two Sprints and the goals of two Scrum Teams.

I really can't see advantages for the business, the stakeholders, or the teams in having one development team member support multiple Scrum teams. I think that a Product Owner may be able to support 2, maybe 3, Scrum Teams if those teams are supporting a single product. A Scrum Master may be able to support 2, 3, or even 4 teams, depending on the maturity of the organization and teams. But I can't make a case for a Development Team member being on multiple teams.

True but in theory can they?

Unless the Scrum or Nexus Guide rule it out, then it’s possible. These frameworks are only minimally prescriptive, and the rules which do apply are briefly and tightly described.

Hence the art in applying Scrum and Nexus lies not in knowing whether or not something is possible, but rather in determining whether, in a given context, it is likely to prove a good idea.

Thanks Ian Mitchel and others for the clarity. 

That was my thinking, I don't think it is prescribed anywhere in the Scrum or Nexus guides that a Dev Team member has to be full time on a Scrum Team or negates them working on different Scrum Teams in a Nexus.