Multiple Geographic Origins of Commensalism and Complex Dispersal History of Black Rats
(A). Global distribution of lineages I and II, showing inferred direction of movement of lineage I rats into the Middle East and from there, independently to Madagascar and Europe (and thence globally, as ship-borne emigrants). Note that lineage II is represented in South Africa and western USA. (B) Semi-schematic diagram showing the inferred natural ranges of each of lineages I–VI of the RrC, including the inferred ‘Sundaic’ sublineages of Lineage IV (hatched), which is fully congruent with the range of Lineage VI. Points of particular interest include: 1) extensive range overlap between lineages II and V (R. sakeratensis) in Thailand and central to southern Laos; 2) extensive range overlap between Lineages IV and VI (R. tiomanicus) on the Sundaic islands; 3) abutting or narrowly overlapping ranges of Lineages II and IV in central to southern Laos and Thailand; and 4) lack of evidence for natural range overlap among Lineages I–III prior to the onset of widespread habitat disruption and human-mediated dispersal. It is not clear whether the natural range of Lineage II included Taiwan or whether the natural range of lineage I included Sri Lanka. (C). Distribution in Asia of lineages I,II and IV showing inferred directions of prehistoric movement for each of lineage. Regional movement of Lineages II and IV has resulted in a broad zone of geographic overlap that includes Indonesia and the Philippines.