Phylogenetic trees are representations of evolutionary relationships amongst species. Interviews of instructors and students have revealed that novice biologists have difficulty understanding phylogenetics. Moreover, misinterpretations of phylogenetics are common among college-level students. In this paper we present Phylo-Genie, a tabletop interface for fostering collaborative learning of phylogenetics. We conducted an experimental study with 56 participants, comparing students' conceptual learning and engagement using Phylo-Genie as: 1) a multi-touch tabletop interface and 2) a pen and paper activity. Our findings show that the tabletop implementation fosters collaborative learning by engaging users in the activity. We also shed light on the way in which our design principles facilitated engagement and collaborative learning in a tabletop environment.