Homomorphisms into mapping class groups. An addendum

This is an addendum to arXiv: 0810.5376. We show, using our methods and an auxiliary result of Bestvina-Bromberg-Fujiwara, that a finitely generated group with infinitely many pairwise non-conjugate homomorphisms to a mapping class group virtually acts non-trivially on an $R$-tree, and, if it is finitely presented, it virtually acts non-trivially on a simplicial tree