Agaricus

The genus Agaricus L. includes popular species of mushrooms collected or cultivated either for human consumption or for their therapeutic properties. In this genus, traditional circumscription of species remains very difficult because of the homogeneity of its morphological macro- and microcharacters and the existence of species complexes.

In the Tropics, however, Agaricus show more morphological diversity, and tropical species are in many cases very different from the temperate species. In fact, in the temperate areas only species belonging to the subgenus Agaricus have been found, with the exception of some isolated records, as for example A. haematosarcus collected in the Mediterranean island of Sardinia (Italy, Europe) belonging to subgenus Lanagaricus. In fact, before Heinemann’s (1956) studies on the tropical Agaricus species in the Belgian Congo (at present Democratic Republic of the Congo) no subgenera were recognized within the genus Agaricus. Heinemann.’s (1956) studies demonstrated a greater diversity in genus Agaricus by creating two new subgenera containing three new sections each: Subgenus Lanagaricus containing Olivelli, Lanosi and Trisulphurati sections y subgenus Conioagaricus containing sections Intermedii, Pulverotecti and Striati, and the new section Brunneopicti in subgenus Agaricus.

It seems that these infrageneric taxa created by Heinemann are typically tropical because in the last 50 years no species belonging to them have been collected in temperate areas, with some exceptions as the abovementioned.

However, many temperate species have been recorded in tropical areas, although no molecular methods have been applied so far in order to know if the species determined on the basis of morphological characters also match in its molecular characters with the species to which they were assigned.

Even today, Agaricus species are continuously being discovered in tropical areas whose adscription to traditional sections or subsections is problematic and only tentative because while some morphological characters agree well other species belonging to the involved divisional rank other are clearly atypical and according to our first molecular data many times they don’t belong to any previously known subdivisional rank. The recently discovered Agaricus subsaharianus L.A. Parra, Hama & De Kesel from Niger, Burkina Faso and Tanzania is a good example of this.