Agaricus macrochlamys , a New Species from the (Sub)tropical Cloud Forests of North America and the Caribbean, and Agaricus fiardii , a New Synonym of Agaricus subrufescens .

Agaricus is a genus of fungi in the family Agaricaceae, with several highly priced edible and medicinal species. Here we describe Agaricus macrochlamys , a new species, in A . sect. Arvenses , sympatric and morphologically cryptic with the edible and medicinally cultivated mushroom, A. subrufescens . Phylogenetic analyses showed that A. macrochlamys is closely related to A. subrufescens , and that A. fiardii is a new synonym of A. subrufescens . Despite being morphologically cryptic, A. macrochlamys can be distinguished from A. subrufescens by several ITS and tef1α species-specific markers and a 4-bp insertion in the tef1α sequence. Furthermore, A. subrufescens is a cosmopolitan species, while A. macrochlamys distribution is so far restricted to Mexico, the Dominican Republic, and the United States.