SAN MIGUEL, Ariz. — The phone calls started almost as soon as President Trump signed his executive order, making official his pledge to build a wall to separate the United States from Mexico.

Verlon M. Jose, vice chairman of the Tohono O’odham Nation, whose reservation extends along 62 miles of the border, heard from people he knew and those he had never heard of. All of them were outraged and offered to throw their bodies, Standing Rock-style, in the way of any construction that would separate the tribe’s people on the north side of the border and the south side, where they live in six villages within the boundaries of the group’s ancestral lands.

“If someone came into your house and built a wall in your living room, tell me, how would you feel about that?” Mr. Jose asked in an interview last week. He spread his arms, as if embracing the ground that stretched before him, a rugged expanse of crackled dirt speckled in saguaros, and said, “This is our home.”