Since its original naming the genus has been changed a few times. Sphaeria is a genus that is not now accepted. It rapidly became a catch-all genus. With such confusion it became easier to put species originally named in Sphaeria into other genera that were well described and well-known. Consequently, Saccardo transferred Berkeley's fungus from Sphaeria to Cordyceps in 1878 and there it happily remained for ca. 130 years.
Why
couldn't it stay in Cordyceps?
As with Sphaeria,
Cordyceps was becoming
unwieldy although it was rapidly recognised as a pathogen of insects,
other invertebrates (especially spiders) and of other fungi. It
became convenient to lump many species into this one genus. A few
attempts were made to sub-divide the genus (notably by Yosio Kobayasi
in Japan from the 1930s to 1980s) but no real effort was made to
break the genus up. One exception was Tom Petch who named several
species to a new genus which he called Ophiocordyceps.
The type species of Cordyceps
produces extremely long thread-like ascospores that break into
typically 128 part-spores[1].
By contrast, the type species of Petch's Ophiocordyceps
had ascospores that were long (although not thread-like) but
significantly did not divide into part-spores on release. They
remained whole. This genus was not widely accepted by contemporaries
of Petch (namely Yosio Kobayasi and Edwin Mains) and faded into
obscurity.
Fast
forward to the present. Importantly, the last 20+ years has seen a
revolution in how we look at taxonomy - whether it be that of a humble bacterium or of a blue whale. Whereas, in the past,
relationships were based on shared characteristics the advent of
molecular phylogenetics has brought a powerful tool to bear upon
taxonomy. Molecular methods can therefore show that there is only a
2% difference between human DNA and our nearest relatives the
chimpanzee and bonobo. Within the human species there is only a 0.1%
difference in the DNA of all humans.
The
same techniques apply to fungi. The type species of Cordyceps
is Cordyceps militaris.
It was the first species named for what is now recognised as
Cordyceps. It
therefore stands as the basis by which all other 'Cordyceps'
must be compared. A major study was published in 2007 (I was one of
the authors) that looked at a wide and representative range of
species that had previously been considered to be Cordyceps
as well as related species of other insect fungi[2].
Our study showed that Cordyceps
fell into four distinct groups that were spread across three
different families. Effectively, three new genera had to be found for
the species that did not group closely with Cordyceps
militaris. Two new genera were
named in the study – Elaphocordyceps
and Metacordyceps. One
group included Cordyceps sinensis
and one of the species that Petch had used to create Ophiocordyceps
– Cordyceps unilateralis.
As a result, Ophiocordyceps
was resurrected and the Chinese Cordyceps
became the Chinese Ophiocordyceps.
By current thinking (but who is to say this will not change in the
future) Petch was right whilst Kobayasi and Mains were wrong.
So,
as noted at the beginning Cordyceps sinensis
is more correctly called Ophiocordyceps sinensis.
It will take time for this name to be used widely although it is
catching on. Even I still refer to Cordyceps sinensis
when talking generally.
References:
[1]
Hywel-Jones, N.L. (2002). Multiples of eight in Cordyceps
ascospores. Mycological Research
106: 2-3.
[2]
Sung,
G-H., Hywel-Jones, N.L. Sung, J-M, Luangsa-ard, J.J., Shrestha, B. &
Spatafora, J.W. (2007). Phylogenetic classification of Cordyceps
and
the clavicipitaceous fungi. Studies
in Mycology 57:
5-59.
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In 1993 Olympics, female chinese athletes won the running competition and broke all kinds of world record. Later their coach informed the reporters that the athletes were adding cordyceps to their routine. Cordyceps is popular among athletes even now.
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