Taxacom: Neotypification and common usage

[kotatsu at fripost.org]

Dear colleagues,

I'm looking at a case where a parasite species was described about 180 
years ago (1842) from what may be a mixture of species (amount unknown), 
of which only a single syntype specimen remains. Unfortunately, this 
syntype specimen appears to not be the same species as has been reported 
from this host in the intervening 180 years. The original description is 
largely useless even to get to the genus level, and the original 
illustration is poor, but shows at least one potentially important 
character (setae in a certain area) which are absent in the illustration 
*and* in the remaining specimen, but present in the species that 
normally parasitizes this host. Two authors in the 1960?1970s 
redescribed the species poorly, and this redescription is of a different 
species than the syntype specimen, which they did not examine.

In 2020, two sets of authors discussed this species (one set in reaction 
to the other), and reached different conclusions:

Set 1 -- the syntype specimen (which they erroneously call the 
'holotype') is conspecific with the illustration and not contradicted by 
the original description. Therefore, the name of this species can follow 
the specimen, which thus is assumed to be from an unknown host. The 
species of parasite that is normally found on this host thus needs a new 
name, which they provide, including a description and illustration and a 
review of the previous reports. They have visited many of the museums 
where previously reported specimens are stored, and invariably these are 
the same as the new species, and not the same as the syntype specimen. 
No further specimens conspecific with the syntype specimen have been 
found, but the group is very poorly known so this is not a surprise. 
These authors do not redescribe or illustrate the syntype specimen, and 
appear to have made no efforts trying to compare this specimen with 
other specimens in the same collection from the same collector 180 years 
ago. The question of mix-up of specimens is thus open.

Set 2 -- it cannot be established beyond reasonable doubt that the 
syntype specimen is actually part of the original set of specimens seen 
by the author in 1842, and much of his collection is lost. The 
collection has changed hands at least once since 1842, it is unknown who 
slide-mounted the specimens, and at least two earlier authors contradict 
each other concerning which specimens were included in the original 
purchase. It is therefore possible that the rest of the original type 
series included the species normally found on this host, and that the 
syntype specimen is either a mix-up, a contamination, or some other form 
of error. All other reports of parasites in this genus from this host 
have used the 1842 name, and for the purposes of stability, we should 
continue to use this name and treat the new name established by Set 1 as 
a subjective junior synonym. To this end, Set 2 erects a neotype and 
four neoparatypes, which correspond to the parasite species normally 
found on this host, as well as the one illustrated and described as a 
new species by Set 1. Set 2 keeps the door open to applying to the 
Commission for an official ruling if this neotypification meets 
well-founded resistance.

In the ~180 years between the original description and the revision, 
there appear to be about 25?30 publications that use the old name for 
this species. However, all except two of these are either just 
inclusions in lists of members of a given genus, with no further 
information added, or regional faunal lists where identity of the 
specimens has been assumed based on host associations. Until 2020, there 
has been no way to identify the original species either from 
descriptions or illustrations, and as Set 1 also do not describe the 
syntype specimen, this is still true.

Without going into which set of authors is correct (although I'd value 
input on this as well), I'm wondering about the process of setting aside 
type specimens that are suddenly found not to represent the common 
understanding of the species name. Where, if anywhere, is the limit for 
"common usage" the stability of which could be threatened if the names 
are changed? I've seen various case reports and opinions in the 
Bulletin, where often authors will list a number of publications within 
a certain framework to show that the name is in use, but is there any 
official standard for this?

Further, if there is an accepted official standard, is this affected by 
the circumstances of usage? Apart from faunal lists where identity is 
assumed based on host associations, there is no information of any kind 
attached to this name between 1842 and the present. The 2020 authors 
also do not attach any new information beyond that the syntype is not 
conspecific with the species normally found on the host.

It would seem to me that this kind of usage would "count" towards any 
kind of standard for the number of publications a name needs to appear 
in to be commonly accepted. Is just listing a name without making any 
effort to establish whether you're applying the name to the correct 
taxon sufficient to assert that the name is in common, universal usage? 
Seems to me this would be rewarding laziness.

I'd value any input on this.

Cheers,
Daniel


-- 
Dr. Daniel R. Gustafsson, Research Assistant Professor
Institute of Zoology Guangdong Academy of Sciences, Guangzhou, China.

Ask me about chewing lice!