According to John Sorenson, it is an interesting commentary on Nephite conceptions of the land that the territory on the south described as "wilderness" (Alma 31:3) should be "full of Lamanites." Clearly the essence of "wilderness" lay not in the absence of inhabitants but in something else, apparently the substantial modifications of the landscape that civilization entails. Probably that southern section had been only lightly populated in earlier times but was now being settled seriously. . . .
The Zoramite land of Antionum "bordered upon the wilderness south" (Alma 31:3). While the population settled in the south wilderness were called "Lamanites" by the Nephites, there . . . was apparently an ethnic variety as confirmed by not only Alma's observation that "many of them are our brethren" in the land of Antionum (Alma 31:35), but that eventually "the Nephites [in the land of Jershon] were compelled, alone, to withstand against the Lamanites, who were a compound of Laman and Lemuel, and the sons of Ishmael, and all those who had dissented from the Nephites, who were Amalekites and Zoramites, and the descendants of the priests of Noah." (Alma 43:13). Just previous to this, the Lamanites "came into the land of Antionum" [apparently from the south wilderness] (Alma 43:5). [John L. Sorenson, An Ancient American Setting for the Book of Mormon, pp. 240-242]