PATTERNS OF SPECIATION AND LIMITS TO PHYLOGENETIC RESOLUTION

The practice of phylogenetic systematics frequently includes the assum ption that cladogenesis occurs by a series of bifurcations. Consequent ly, a phylogenetic tree that includes one or more polytomous nodes is generally viewed as unresolved. However, while some polytomies surely represent a failure of resolution, others may be real or the best reso lution that can be achieved. Therefore, polytomies should be considere d as phylogenetic hypotheses in the same way as bifurcating topologies .