In 2009, the botanist Naomi Fraga was hunting a flower without a name near Carson City, Nev. Ms. Fraga saw that the plant was going extinct in real time as its desert valley habitat was bulldozed to make way for Walmarts and housing developments. But in order to seek legal protections for it, she had to give it a name.

The diminutive yellow flower became the Carson Valley monkeyflower or, officially, Erythranthe carsonensis, allowing conservationists to petition the U.S. Fish and Wildlife…