Taxacom: Barcodes and species

[Stephen Thorpe]

 I suspect that it is complicated. Unless they are perfect clones, no two individuals will have identical sequences. The question is whether there is a minimum genetic difference between any two distinct species. It might depend on where in the genome one looks. It has been said that Geodorcus capito and G. sororum illustrate a nonstandard situation. Morphologically, males are as different as could be (within the same genus). Females only differ in size and there is apparently no known genetic difference beyond individual variation. They are nearby allopatric.
The problem seems to be that different approaches can be taken to nonstandard cases and there is no objective right or wrong answer. Are G. capito and G. sororum just allopatric populations of the same species with morphologically divergent males? Are they genetically indistinguishable distinct species?
Those who criticize descriptive taxonomy as "not real science", simply don't understand that there is no objective truth of the matter in all cases and so the best that we can do is simply to describe the patterns that we see.
Stephen
    On Sunday, 19 May 2024 at 06:08:20 pm NZST, John Grehan via Taxacom <taxacom at lists.ku.edu> wrote:  
 
 As I am pretty ignorant of technical details of species designation and
barcode identity, I would be grateful for any feedback on whether it is
possible for two 'species' to have identical 'barcodes' (never liked that
label with its essentialist connotations).

I have a colleague who has collected some ghost moths from the same date
and location. There are two morphs - for simplicity 'white spot' and
'plain'. Dissections of genitalia also show differences, with the white
spot and plain each showing consistent differences, although only 2
specimens for white spot and 3 for plain. Even with this small sample I am
kind of intrigued that the external difference matches the internal
difference.

The genitalic differences are prominent enough that I would normally view
them as indicative of species difference. Perhaps there is a single
polymorphic species, but correlated external and internal differences were
a bit of a surprise. Any comments or enlightenment would be very welcome.

Cheers, John

-- 
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Nurturing nuance while assailing ambiguity for about 37 years, 1987-2024.