CONFOUND IT! The taxonomy of plants mistaken for Cistanthe arenaria (Cham.) Carolin ex Hershk. (MONTIACEAE, Cistantheae sect. Rosulatae Hershk.)

Cistanthe arenaria (Cham.) Carolin ex Hershk. is a species of Montiaceae distributed from Chile’s Maule to Araucanía Regions. But the name historically and currently has been applied also to readily distinct species distributed from the Libertador Bernardo O’Higgins to Coquimbo Regions: C. chamissoi (Barnéoud) Carolin ex Hershk., C. trigona (Bertero ex Colla) Carolin ex Hershk, C. vicina(Phil.) Carolin ex Hershk., and C. subverticillata (Phil.), ined. (≡ Calandrinia subverticillata Phil.). The source of this confusion traces to two 1833 works by Hooker & Arnott and Lindley. Here, the taxonomy and diagnostic characteristics of these species are clarified.