Jewish populations in Yemen and Ethiopia have distinct histories

From the abstract of the article Mitochondrial DNA reveals distinct evolutionary histories for Jewish populations in Yemen and Ethiopia by Amy L. Non, Ali Al-Meeri, et. al., published in the January 2011 issue of the American Journal of Physical Anthropology:

A high frequency of sub-Saharan African L haplogroups was found in both Jewish populations, indicating a significant African maternal contribution unlike other Jewish Diaspora populations. However, no identical haplotypes were shared between the Yemenite and Ethiopian Jewish populations, suggesting very little gene flow between the populations and potentially distinct maternal population histories...Specifically, Yemenite Jewish mitochondrial diversity reflects potential descent from ancient Israeli exiles and shared African and Middle Eastern ancestry with little evidence for large-scale conversion of local Yemeni. In contrast, the Ethiopian Jewish population appears to be a subset of the larger Ethiopian population suggesting descent primarily through conversion of local women.