This southwestern annual has disjunct 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 east, it is considered probably adventive, sometimes appearing 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).