  Let $k$ and $n$ be integers such that $1\leq k \leq n-1$, and let $G$ be a
simple graph of order $n$. The $k$-token graph $F_k(G)$ of $G$ is the graph
whose vertices are the $k$-subsets of $V(G)$, where two vertices are adjacent
in $F_k(G)$ whenever their symmetric difference is an edge of $G$. In this
paper we show that if $G$ is a tree, then the connectivity of $F_k(G)$ is equal
to the minimum degree of $F_k(G)$.
