Big Four ad agency Publicis is now buying in to Latin American digital advertising, acquiring Sao Paulo-based Tribal to add to its Digitas online ad group. Digitas CEO Laura Lang said Tribal is “fundamental” to expanding in the growing region. Publicis bought Digitas back in 2006 and has grafted on various international digital acquisitions in the UK, India, Singapore, China and its native France, so this will be a foothold across the Atlantic. Tribal, which has 100 staff, counts Philips and Microsoft (NSDQ: MSFT) amongst its clients. Publicis is resisting the urge to rename Tribal “Digitas LatAm”; the agency will retain its name as well as its CEO Pierre Mantovani and creative director Renato Fabri. In Brazil, the ad market grew 25.1 percent in 2007, up from 2006’s 19.4 percent, outstripping the economy, according to ZenithOptimedia, which expects 15.4 percent growth this year while other international markets’ growth slows down.