If the natural increase of a tribe is not dissipated by disastrous wars, subsidiary groupings tend to develop. In New Zealand, the larger tribes tracing descent from an eponymous ancestor divided as their numerical strength increased into secondary groups tracing descent from ancestors more recent than the common ancestor of the primary group. These secondary Maori groups of subtribes are termed hapu in distinction to the tribe, which is termed iwi. Most of the Mangaian tribes were too small or of too recent an origin to develop subtribes.
The smaller tribes, Te Kama, Kanae, and Tui-kura, had no chance of material increase, as they were constantly defeated in war. The Manaune were of too recent an origin to reach the stage of subdivision. Though the Ngati-Tane were one of the early tribes, the modern Ngati-Tane originated from a single male ancestor at the same recent time as the Manaune. The Ngati-Vara really commenced its growth with Mautara, who was a contemporary of the two single male ancestors of the Manaune and Ngati-Tane. Mautara, however, had a large male family, and the rate of increase of Ngati-Vara in the earlier generations succeeding Mautara was much greater than that of both Ngati-Tane and Manaune. The Ngati-Vara split into factions which did not actually reach the stage of subtribes and thus were not given specific names. They were alluded to merely as the descendants of the younger sons of Mautara who took up arms against the descendants of the older sons. The juniors (teina) fought the seniors (tuakana) through jealousy and wrecked the tribe.
The Tongaiti tribe, powerful in the early period of occupation, evidently budded off two subtribes called Teipe and Teaaki.
The mechanism of the subdivision is not known, but each selected a tribal god after whom the group was named. This involved dedication at the cutting of the navel cord, and the subsequent automatic grouping was assured. Though subtribes by origin, they were regarded as specific groupings to which the tribal term kopu was applied.
The Teipe subtribe seems to have become fairly strong during the early part of Ngauta's rule. Under the chief Maruataiti, they attempted to wrest the temporal supremacy from the parent tribe but were defeated by Ngauta at the battle of Auruia. After this lesson, they were allied with Ngauta and enjoyed prosperity. They again became somewhat arrogant, for after they had insulted Ngauta the Tongaiti crushed them in the battle of Ikuari. Later again they recovered, and their restless spirit caused them to join Ruanae in his struggle against Te Uanuku of the Ngati-Vara. After their defeat at Arira, they ceased to influence the politics of the country and the remnants furnished human sacrifices to Rongo.
The Teaaki subtribe shared the prosperity of the Tongaiti under the rule of Ngauta. After the final defeat of Ngauta by the Ngariki, they attempted to revive the fallen fortunes of the tribe by plotting to kill the leaders of Ngariki. The plot failed and the main families with the chiefs Iro, Tuavira, Akaina, and Pati were expelled from the island. Koroa (12, p. 134) in a lament thus referred to them.
Kua pau Te'a'aki! Teaaki [tribe] is gone, Kua ta'una te matakeinanga o Te-tipi The people of Te-tipi have been consumed [by fire], Poroara io ia Ngariki. Driven away by the Ngariki.
The tribe thus vanished from Mangaia, but as the exiles safely landed on Rarotonga, the Mangaian element in Titikaveka should represent, in part, the expelled Tea-aki. They blended, however, with the local people, assumed a new grouping, and the name Teaaki disappeared.
The Ngariki claim that they were a tribe when Mangaian history opened. The important offices of that period were held by three brothers who formed the high chiefs (nga ariki) of the tribe. Enjoying a long period of early success in war, the tribe increased to the extent of subdivision.
The senior division was named after Paparangi, the son of Rangi. This division is often referred to as Ngariki. It had its own high chief (ariki), the last of whom was Maunganui (26, p. 244). In the distribution of authority, Rongo gave Rangi the drum of peace, and Rangi was the first Temporal Lord of Mangaia. It was probably intended that the temporal rule should descend in the senior line.
The Akatauira division took its name direct from one of the brothers. Rongo gave Te Akatauira the karakia (prayers and ritual). These formed the necessary equipment of the Inland and Shore High Priests of Rongo. As the last Inland High Priest was Te Ao of the Akatauira, it is probable that the more important of the two offices passed in succession in the Akatauira tribe. The tribe also had its own high chief, the last of whom happened to be also the holder of the office of high priest. The Akatauira held the mangaia under Panoko with the assistance of One of the Tongaiti.
The Vaeruarangi took its name from the son of Mokoiro. To Mokoiro, Rongo gave the authority over food. This developed into the office of the official Ruler of Food (te ariki i te tapora kai), which went by succession in the Vaeruarangi tribe. The office, at times, coincided with that of the high chief (ariki) of the tribe, for the names of Namu and Kaoa appear both as official Rulers of Food (12, p. 314) and as leaders of the Vaeruarangi tribe in battle (12, p. 310). The last High Chief and Ruler of Food was Mauri, who was visited by John Williams in 1829 (12, p. 314).
The three divisions of the Ngariki thus developed into distinct tribes which fought against each other for supremacy in spite of the fact that they worshiped the one god Motoro.