Detecting non-tree-like signal using multiple tree topologies

Abstract

Recent applications of phylogenetic methods to historical linguistics have been criticized for assuming a tree structure in which ancestral languages differentiate and split up into daughter languages, while language evolution is inherently non-tree-like (François 2014; Blench 2015: 32–33). This article attempts to contribute to this debate by discussing the use of the multiple topologies method (Pagel & Meade 2006a) implemented in BayesPhyloge- nies (Pagel & Meade 2004). This method is applied to lexical datasets from four different language families: Austronesian (Gray, Drummond & Green- hill 2009), Sinitic (Ben Hamed & Wang 2006), Indo-European (Bouckaert et al. 2012), and Japonic (Lee & Hasegawa 2011). Evidence for multiple topologies is found in all families except, surprisingly, Austronesian. It is suggested that reticulation may arise from a number of processes, including dialect chain break-up, borrowing (both shortly after language splits and later on), incomplete lineage sorting, and characteristics of lexical datasets. It is shown that the multiple topologies method is a useful tool to study the dynamics of language evolution.