Early Māori adapted the tropically based east Polynesian culture in line with the challenges associated with a larger and more diverse environment, eventually developing their own distinctive culture. Social organisation was largely communal with families (''whānau''), subtribes (''hapū'') and tribes (''iwi'') ruled by a chief (''rangatira''), whose position was subject to the community's approval. The British and Irish immigrants brought aspects of their own culture to New Zealand and also influenced Māori culture, particularly with the introduction of Christianity. However, Māori still regard their allegiance to tribal groups as a vital part of their identity, and Māori kinship roles resemble those of other Polynesian peoples. More recently, American, Australian, Asian and other European cultures have exerted influence on New Zealand. Non-Māori Polynesian cultures are also apparent, with Pasifika, the world's largest Polynesian festival, now an annual event in Auckland.