At least 40 spoken languages form the large tupi family in its subfamilies tupi-Guarani, Mawe, Aweti, Arikem, Juruna, Monde, tupari, Munduruku, ramarama and Purubora, providing a wealth of data for linguistic studies about variation – variation explained by genetic relations (common origin, ultimately from the presumed language ‘proto-tupi’) or by contact relations with other indigenous or non-indigenous languages. the interest in indigenous languages has increased in recent years, evinced by the publication of a growing number of descriptive, historical-comparative and other studies. Most studies published in this volume originate from a linguistic symposium organized by Wolf dietrich and sebastian drude at the 54th international Congress of Americanists in Vienna, in 2012. the symposium was dedicated to “Historical variation and variation by contact among the tupian languages”. those studies that deal with problems of linguistic genealogy, genetics, language change, and syntactic typology across several tupi languages or a single tupi language are published in this special “dossier”. the first six papers deal with problems of the whole tupi family or at least one of its sub-families. three of them investigate evolutionary topics; three are cross-linguistic synchronic studies. Eduardo dos santos and colleagues from the area of human genetics, in their paper “origins and demographic dynamics of tupi expansion: a genetic tale”, use recent genetic data in order to show that the Madeira-Guapore region may indeed be considered to be the tupi homeland. Ancient tupi expansion within the Madeira-Guapore region and dispersion to other south American areas seems to be related to patrilocal practices. this outcome allows for new interpretations of archaeological and linguistic data, for instance the dispersion of female associated technologies like ceramics and terminologies related to ceramics. Ana Vilacy Galucio and colleagues from the tupi Comparative Project, in their paper “on the genetic relationship and degree of relatedness with the tupi linguistic family”, present the first lexicostatistical and phylogenetic attempt of the genetic classification of most languages of the tupi family, including four languages of the tupi-Guarani branch. Based on all relevant previous studies of particular branches of the family, and applying lexicostatistics to a semantically based word list,, the article demonstrates that the two major branches of the state of rondonia, Monde and tupari, have high percentages of shared cognates. this supports the results of the first article of this volume. the paper by sergio Meira and sebastian drude gives an overview of their reconstruction of the segmental phonology of Proto-Maweti-Guarani, the hypothetical proto-language from which modern Mawe, Aweti, and the