This southwestern yellow-flowered terpenoid annual (mostly in Tex., Okl. and Mo.) has disjunct clusters of occurrences in c. Ky. and c. Tenn., where it has been treated in Xanthocephalum (Ch). It is unknown if these eastern populations are relictual from presettlement glades and grasslands, or if they are more recently adventive. In Ky. and Tenn., the species is often associated with grazed or otherwise disturbed sites. Further north and east, it is considered probably adventive, having sometimes appeared as waifs from wool-combing at mills (W). Amphiachyris is closely related to Gutierrrezia (of southwestern states to South America), and sometimes combined (FNA 20); chromosome numbers are remarkably low in both of these genera (usually 2n = 8).