Diaz uses his characters to show the destructive nature of the gender relations/roles of the D.R. using his characters. How & what characters?The Brief Wonderous Life of Oscar Wao
In The Brief Wondrous Life of Oscar Wao, the DR is a character unto itself. Like Sauron from The Lord of the Rings, Trujillo uses the land and its resources to spy, seduce, and destroy its inhabitants. Without the ring, Sauron was impotent; so to it is with Trujillo and the DR--as long as he is in power, he will victimize all, (esp. sexually with the women).
The women in the de Leon family are the main characters who are destroyed by the the machismo, the fuku (as you say, the destructive nature of gender relations in the DR). Men treat women as sexual objects.
Beli, Oscar's mother, is the primary victim--as she grew up in the DR and brought the fuku to the U.S. She is a big-breasted larger-than-life personality who is victimized by men in her village. She makes the tragic mistake of falling in love with one of Trujillo's men (the Gangster).
So says Enotes:
Beli, the surviving daughter who would become Oscar’s mother, grew into a dark-skinned, tall, and big-breasted young woman—an object of lust and jealousy in her small Dominican village. Her tia (aunt) La Inca tried her best to raise Beli properly, but Beli was strong-willed and eager for more than her aunt could provide. In her naivety and desire for excitement, Beli falls in love with one of Trujillo’s men, hoping that he (referred to only as Gangster) would cure her boredom. Gangster, unfortunately, is a married man. His wife, even more unfortunately, is Trujillo’s sister. One night, Beli is beaten, many of her bones are broken, and she is left in a cane field to die. She does not die, but she comes close. In order to protect her, her aunt sends her to New Jersey. There, Beli recovers and marries a man who sticks around only long enough to twice impregnate her. She has a daughter, Lola, and a son, Oscar.