Taxacom: On species diagnoses and DNA-based descriptions in taxonomic practice

[Stephen Thorpe]

 Thomas,Details aside, the broad answer to your questions involves the fact that taxonomists and related scientists all have slightly different ideas and different vested interests. The challenge for the ICZN is to try to accommodate everyone and alienate no one, even though the different ideas and vested interests are conflicting! Those who want to name new species based purely on DNA tend to be people without much knowledge or talent for identifying species morphologically and also tend to be people whose job requires them to push through a big workload quickly, in a profit making funding context. Spending a long time painstakingly trying to do morphological analyses runs counter to that. They just want to grind a specimen up, shove it through a machine and instantly get an answer. Others, like myself, take great delight in learning how to identify species morphologically.Cheers, Stephen
    On Saturday, 26 August 2023 at 01:16:59 pm NZST, Thomas McCabe via Taxacom <taxacom at lists.ku.edu> wrote:  
 
 Hello. I am a physician biologist with an interest in biological taxonomy
and the discussions at Taxacom. May I add a comment and questions about the
journal article referenced by Thomas Pape ("Tightening the requirements for
species diagnoses would help integrate DNA-based descriptions in taxonomic
practice", *PLoS* Biol 21(8): e3002251)? The authors of this paper go
beyond nomenclature to advocate for taxonomic species diagnoses that are
both contrastive and state-specific. The authors also attend to the
interesting possibility and problems of defining species solely with
genome-wide DNA sequences.

Regarding defining species, I request thoughts on two questions, the first
skeptical, the second leading.

First, a question about using a genome-wide DNA sequence as sole diagnosis
for a taxonomic species. Suppose technology advances so that a description
of the complete sequence of all the nucleic acid macromolecules making up
the genetic complement of each potential specimen supposedly representing a
newly-discovered taxonomic species is attainable. Then, if each living
being has a unique genetic complement (at least one single nucleotide
polymorphism or indel making one of its DNA sequences unique among those of
other living beings), what will prevent a seeker of cryptic species from
using every specimen as a type for a separate taxonomic species?

Second, and related to the first question, if each natural species is a
lineage-segment, why is each taxonomic species diagnosis drawn from one or
more unrelated specimens instead of from a directly observed
lineage-segment of specimens? That is, cannot biological taxonomy be an
experimental, as well as a descriptive, science?

Respectfully,

Thomas McCabe, M.D., M.P.H.

Independent Scholar
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