Quaternionic hyperbolic Kleinian groups with commutative trace skew-fields

Let $\mathrm{\Gamma }$ be a nonelementary discrete subgroup of $\mathrm{S}\mathrm{p}(n,1)$. We show that if the trace skew-field of $\mathrm{\Gamma }$ is commutative, then $\mathrm{\Gamma }$ stabilizes a copy of complex hyperbolic subspace of quaternionic hyperbolic $n$-space.