Morels (Morchella spp.) are one of the most highly prized edible mushr
ooms found in the wild of North America. Because environmental conditi
ons can cause members of the genus to vary morphologically, the number
of species has been disputed. Some authors classify the genus into th
ree to five species, while others argue for as many as 50 species. DNA
from lines of Morchella and a closely related genus (Verpa) was isola
ted. The large subunit of the ribosomal DNA repeat was amplified using
the polymerase chain reaction and then digested with restriction enzy
mes. Restriction fragment length polymorphisms were found among the li
nes investigated and used to separate the lines into genotypic classes
. More genetic variation may occur between geographically isolated pop
ulations of the same species than between two putatively distinct spec
ies. The phylogenetic tree developed from restriction data suggests th
at the black morels (M. angusticeps, M. elata, and M. conica) and the
yellow morels (M. esculenta, M. crassipes, and M. deliciosa) are separ
ate taxonomic groups.