What is the theme in Close Range: Wyoming Stories by Annie Proulx?

Infidelity appears in many of the stories in this collection. In The Lonely Coast, the narrator's husband is caught with the fifteen year old temporary ranch hand. In this same story, a woman sees her lover touching another woman in a sexual manner, causing her to shoot him at the end of the story. In Pair a Spurs, the main character's wife is caught in bed with her husband's best friend. Infidelity also appears in The Mud Below and The Governors of Wyoming, as well as Brokeback Mountain. In each story the infidelity had a different impact on the characters and the plot, but each is an important theme to those particular stories.