Early phylogenetic analyses supported the hypothesis that the genus comprises only a few species with considerable phenotypic variation. Subsequent multigenic DNA studies, however, have revealed more than a dozen genealogically distinct species in North America and at least as many in Europe. DNA studies revealed three discrete clades, or genetic groups, consisting of the white morels (Morchella rufobrunnea and Morchella anatolica), the yellow morels (Morchella esculenta and others), and the black morels (Morchella elata and others). The fire-associated species Morchella tomentosa, commonly known as the gray morel, is distinct for its fine hairs on the cap ridges and unique sclerotia-like underground structures, and may also deserve its own clade based on DNA evidence. Within the yellow and black clades, there are dozens of distinct species, most endemic to individual continents or regions. This species-rich view is supported by studies in Western Europe, Turkey, Cyprus, Israel, China, Patagonia and the Himalayas.