mtDNA history of the Cayapa Amerinds of Ecuador: Detection of additional founding lineages for the native American populations

mtDNA variation in the Cayapa, an Ecuadorian Amerindian tribe belonging to the Chibcha-Paezan linguistic branch, was analyzed by use of hypervariable control regions I and II along with two linked regions undergoing insertion /deletion mutations. Three major maternal lineage clusters fit into the A, B, and C founding groups first described by Schurr and colleagues in 1990, whereas a fourth lineage, apparently unique to the Cayapa, has ambiguous af finity to known clusters. The time of divergence from a common maternal anc estor of the four lineage groups is of sufficient age that it indicates an origin in Asia and supports the hypothesis that the degree of variability c arried by the Asian ancestral populations into the New World was rather hig h. Spatial autocorrelation analysis points out (a) statistically significan t nonrandom distributions of the founding lineages in the Americas, because of north-south population movements that have occurred since the first Asi an migrants spread through Beringia into the Americas, and (b) an unusual p attern associated with the D lineage cluster. The values of haplotype and n ucleotide diversity that are displayed by the Cayapa appear to differ from those observed in other Chibchan populations but match those calculated for South American groups belonging to various linguistic stocks. These data, together with the results of phylogenetic analysis performed with the Ameri nds of Central and South America, highlight the difficulty in the identific ation of clear coevolutionary patterns between linguistic and genetic relat ionships in particular human populations.