Got me, Tim.
The grain will give the wood away faster than the color. Palm wood has parallel fibers in it, like bamboo, randomly dispersed in the wood matrix. It looks very different from dicot wood. Just looking at the coloring, I'd say that all three are from dicot woods.
As for the origin of the double-spike, I don't know either. I'm pretty comfortable saying it's not coconut, pandanus, or breadfruit wood. It might be from Casuarina equisetifolia (she-oak/ironwood), Terminalia wood, or something else (
if you want to do your own research).
Most of the atoll woods seem to be lighter in color than those weapons, but then again, I don't know what they're making them out of in the Massim region either.
Best,
F