Morchella, the true morels, is a genus of edible sac fungi closely related to anatomically simpler cup fungi in the order Pezizales (division Ascomycota). These distinctive fungi have a honeycomb appearance due to the network of ridges with pits composing their caps. Morels are prized by gourmet cooks, particularly in Catalan and French cuisine, but can be toxic if consumed raw or undercooked. Due to difficulties in cultivation, commercial harvesting of wild morels has become a multimillion-dollar industry in the temperate Northern Hemisphere, in particular North America, Turkey, China, the Himalayas, India, and Pakistan where these highly prized fungi are found in abundance.
Typified by Morchella esculenta in 1794, the genus has been the source of considerable taxonomical controversy throughout the years, mostly with regard to the number of species involved, with some mycologists recognising as few as three species and others over thirty. Current molecular phylogenetics suggest there might be over seventy species of Morchella worldwide, most of them exhibiting high continental endemism and provincialism.
The genus is currently the focus of extensive phylogenetic, biogeographical, taxonomical and nomenclatural studies, and several new species have been described from Australia, Canada, Cyprus, Israel, Spain, and Turkey.
When gathering morels for the table, care must be taken to distinguish them from the poisonous "false morels", a term loosely applied to describe Gyromitra esculenta, Verpa bohemica, and other morel lookalikes. Although false morels are sometimes eaten without ill effect, they can cause severe gastrointestinal upset, loss of muscular coordination (including cardiac muscle), or even death.[2][3] Incidents of poisoning usually occur when they are eaten in large quantities, inadequately cooked, or over several days in a row. False morels contain gyromitrin, an organic carcinogenic poison, hydrolyzed in the body into monomethylhydrazine (MMH).[4] Gyromitra esculenta in particular, has been reported to be responsible for up to 23% of mushroom fatalities each year in Poland.[5]
The fruit bodies of Morchella species are highly polymorphic, varying in shape, color, and size. While in many cases they do not exhibit clear-cut distinguishing features microscopically, this has historically contributed to uncertainties in taxonomy.[8][9][10][11] Discriminating between the various taxa described is further hindered by uncertainty over which of these are truly biologically distinct. Remarkably, some authors in the past had suggested that the genus contains as few as 3 to 6 species,[12][13][14][15][16] while others recognised as many as 34.[17][18][19] Efforts to clarify the situation and re-evaluate old classical names (such as Morchella elata and others) in accordance to current phylogenetic data have been challenging, due to vague or ambiguous original descriptions and loss of holotype material.[20][21] In 2012, the simultaneous description of several new taxa from Europe by Clowez[19] and North America by Kuo and colleagues[22] resulted in several synonymities further complicating matters, until a transatlantic study by Richard and colleagues resolved many of these issues in 2014.[20] The genus is currently undergoing extensive re-evaluation with regard to the taxonomic status of several species.