Jacob 5

Lets track the Nephites throughout the chapter.

Jacob 5:25 And he said unto the servant: Look hither and behold the last. Behold, this have I planted in a good spot of ground; and I have nourished it this long time, and only a part of the tree hath brought forth tame fruit, and the other part of the tree hath brought forth wild fruit; behold, I have nourished this tree like unto the others.
26 And it came to pass that the Lord of the vineyard said unto the servant: Pluck off the branches that have not brought forth good fruit, and cast them into the fire.
27 But behold, the servant said unto him: Let us prune it, and dig about it, and nourish it a little longer, that perhaps it may bring forth good fruit unto thee, that thou canst lay it up against the season. this is the first clear reference to th Nephites. They were planted in the promised land, and only half of them were good.

5:39 And it came to pass that they went down into the nethermost parts of the vineyard. And it came to pass that they beheld that the fruit of the natural branches had become corrupt also; yea, the first and the second and also the last; and they had all become corrupt.
40 And the wild fruit of the last had overcome that part of the tree which brought forth good fruit, even that the branch had withered away and died. and here we are at the beginning of this dispensation, where the Nephites had all perished and the Lamanites had overcome them. He continues to say, 43 And behold this last, whose branch hath withered away, I did plant in a good spot of ground; yea, even that which was choice unto me above all other parts of the land of my vineyard.
44 And thou beheldest that I also cut down that which cumbered this spot of ground, that I might plant this tree in the stead thereof.
45 And thou beheldest that a part thereof brought forth good fruit, and a part thereof brought forth wild fruit; and because I plucked not the branches thereof and cast them into the fire, behold, they have overcome the good branch that it hath withered away., speaking of the Jaredites who were inhabiting the land prior to the Nephites.