[Taxacom] Describing genera without molecular phyolgies

[JF Mate]

Thanks John. A useful article as I am struggling with the same problems in
my group but from the other side.  I can't comment on snails but my opinion
is that without a phylogenetic framework, molecular or morphological,
taxonomists should be extremely prudent creating supra-specific taxa.

Best

Jason

On Sat, 23 May 2020, 12:52 John Grehan via Taxacom, <
taxacom at mailman.nhm.ku.edu> wrote:

> Since I do that all the time I am in some sympathy with the extracted text
> below of a fairly recent article. Thought it might be of interest to others
> who may not be aware of it.
>
> John Grehan
>
> BARNA PÁLL-GERGELY 2017 Should we describe genera without molecular
> phylogenies? Zootaxa 4232 (4): 593–596
>
> For nearly a decade I have published species descriptions and revisions of
> land snails in peer- reviewed journals. As a systematist, it is often
> requisite to reclassify species into other, sometimes unnamed genera.
> Although in most cases editors and reviewers have not commented on the
> taxonomic changes I have made and the new taxa I described, I sometimes
> received negative critiques when I described new genera unaided by
> molecular phylogenetic support. I feel these critiques have become
> increasingly more frequent, and am convinced that many fellow taxonomists
> share this experience. Addressing this problem is particularly difficult
> due to three reasons. First, it is impossible to support these observations
> with statistical data (i.e. the frequency of similar reviews increasing or
> not); second, the increasing number of published phylogenetic works reveals
> more and more cases of polyphyletic genera, which might suggest that
> morphology-based generic grouping is unreliable, and thus, should be
> avoided; and third, no publications exist suggesting not to describe genera
> using (still) reliable morphological foundations. Subsequently, the
> unsatisfactory review process of taxonomic works is often exacerbated by
> the biases of reviewers and their inobservance of valuable historic
> convention in light of the current wave of molecular phylogenies. Moreover,
> the future value of morphological descriptions for biodiversity assessments
> (i.e. IUCN) is not even addressed. Here, I argue against prohibiting
> descriptions of genera without phylogenetic support, and make suggestions
> how editors and reviewers should handle "phylogeny-free" genus
> descriptions. To illustrate my experience, I quote some text from previous
> reviews and editorial comments that I have received: Editor of a taxonomic
> journal, (07.02.2012). "(...) In particular, I need you to provide much
> more information regarding your decision to erect new genera; as of now you
> provide no rationale, and you must fully defend this approach. I frankly
> would feel much more comfortable if you had corroborating DNA sequence
> analyses to demonstrate that these are not simply subgenera or even simple
> groups within already existing genera -- and you have not even minimally
> done this. There is a strong burden of poof to undertake such splitting,
> and I expect these decisions to be clearly reasoned and proved with
> empirical data. If you cannot do this, then I strongly suggest that you
> place your new taxa into already existing generic entities." Anonymous
> reviewer (02.11.2016). "(...) As for the description of a new subgenus, I
> am strongly opposed to this taxonomic proposal. Taxonomy serves three
> possible purposes: (1) the ego of the author, (2) the human desire to
> classify things, (3) the scientific purpose to conceptualize ideas about
> the evolutionary relationships amongst organisms. The only purpose this new
> subgenus serves is 1. (...) As for purpose 3, attempting to conceptualize
> the evolutionary relationships of species, this decision is even worse.
> Inevitably, you are making a statement about the evolution of this group
> and you imply that one species is the sister group of all other species
> combined based on one character. You have a one in six chance that you are
> right because your treatment is not backed up by any phylogenetic
> analysis." Anonymous reviewer (23.11.2016) "(...) The taxonomic description
> of the new species is also good. However, in the absence of molecular
> sequence data, I consider that there are insufficient grounds for erecting
> a new genus. (...) As taxonomists living in the 21st century we have a
> responsibility to investigate the phylogenetic basis of
> historically-erected genera and sub-genera by the combined study of
> morphological and molecular data. This is often not possible because of
> limited funding, and so the best course when describing species new to
> science is to work with existing generic and sub-generic names and to avoid
> contributing to taxonomic instability by creating new generic level taxa
> purely on the basis of a few shell characters." 594 · Zootaxa 4232 (4) ©
> 2017 Magnolia Press PÁLL-GERGELY In the first case, my proposal to erect
> new pulmonate land snail genera was based on shell and genital anatomical
> characters, whereas in the latter two cases, I attempted to describe new
> (sub)genera based on differences of the breathing tubes, a traditional
> approach used in the respective land snail groups (Kobelt, 1902). In other
> words, 30–200 years ago the scientific community would not have questioned
> the establishment of these new genera based on morphology. Naturally,
> without knowing the background of the above examples, it is not possible to
> form an opinion whether I was right or wrong when I tried to erect new
> genera, although this is not my point here. Instead, I aim to show that the
> preference of existing generic names over erecting new genera is strong.
> Are the reviewers right? Strictly speaking, the reviewers, who disapprove
> and forbid morphology-based genera may be right. "How do I know that they
> are really monophyletic?" We cannot know whether a taxon is monophyletic
> without a proper phylogeny. To investigate this question we have to go back
> to the definition of the genus. If we define a genus as "a group of species
> that are more closely related to one another than they are to any species
> assigned to another genus" (Wood & Collard 1999: 201), then only an
> appropriate phylogeny would provide satisfactory evidence, although a
> hypothesis of monophyly based on morphology should be also acceptable. If
> we define a genus as a group of species defined by apomorphic character
> states, morphology is sufficient. Regardless of generic definitions or
> criteria, which are usually not given in genus descriptions, monophyly of
> genera is, or at least should be assumed (Ebach et al. 2006) (although
> species are not necessarily monophyletic; Schluter & Nagel 1995, Nosil et
> al. 2002). The level of provided supporting evidence should be up to the
> journal's policy and the taxonomists' personal preference. In the vast
> majority of species descriptions, no species criteria are specified. Unlike
> genera, describing species without molecular support appears acceptable.
> Species criteria (e.g. presence of reproductive barriers) are mostly
> assumed rather than tested in species descriptions. On the contrary,
> assuming monophyly is deemed to be insufficient by some members of the
> taxonomic community. The reason for this double standard is puzzling.
> Especially since one might encounter larger difficulties handling synonyms
> of species than those of genera. Reviewers suggesting not to describe
> phylogeny-free genera supposedly aim to minimize the subjectivity of
> taxonomy caused by the never-ending battle of lumpers and splitters. This
> goal is admirable. However, taxonomy is a science, and all new taxa that
> are proposed are hypotheses that can be refuted and falsified (Evenhuis
> 2008). Not always a matter of money Although molecular phylogeny becomes an
> everyday tool for some proportion of professional taxonomists, it is not
> available for many researchers due to the lack of funds. Moreover, in
> Europe, 60 % of new taxa are described by nonprofessionals (Fontaine et al.
> 2012), who have nearly no chance to support their taxonomic decisions with
> molecular phylogeny. However, the lack of funds and limited access to
> molecular laboratories explain only a fragment of cases when molecular
> phylogeny could not be performed. In many cases it is not possible to
> perform phylogenetic analysis due to a number of other reasons. For
> example, the absence of specimens in museum collections potentially
> containing DNA (e.g. empty mollusc shells and wrongly preserved historical
> specimens; see Jaksch et al. 2016); type localities of species described
> centuries ago are not precise enough to allow revisiting the original
> sites; the original sites are destroyed and the targeted species might be
> extinct in the wild; not to mention fossil taxa, which also need to be
> placed in the system obviously without molecular support. Furthermore,
> molecular studies that propose new taxa should also return to morphological
> characters in light of the molecular phylogenetic trees. More repercussions
> than merits Genera, irrespective of the fact that they are "old" or "new",
> are testable hypotheses of monophyletic groups that predict the
> distribution of characters (Platnick 1979; Wheeler 2004). In the absence of
> molecular support, I cannot see a good scientific reason to prefer existing
> genera over new genera. The action of placing a species into a genus
> irrespective of being named or not, is a hypothesis of the species'
> evolutionary history. Describing new, morphologically well-defined genera
> is not "unnecessary splitting", but small steps towards understanding
> evolutionary relationships of organisms. Forcing classification of new
> species into already named genera could have more repercussions than
> merits. It would, for example, result in unnecessarily "dumping" of species
> into well-defined genera, the reduction of diagnostic apomorphic characters
> in morphologically defined groups. Such practice will turn a well-defined
> genus into a wastebasket taxon, which may, for instance, create artificial
> biogeographic "connections" between areas. Taxonomy and systematics faces
> several challenges in the 21st Century, and the naming of new genera
> without phylogeny is certainly not the biggest of these. For instance,
> incorrect identification of specimens used for molecular studies (Nilsson
> et al. 2006; Groenenberg et al. 2011), taxonomic inflation (Isaac et al.
> 2004; Harris & Froufe 2005), and DESCRIBE GENERA WITHOUT MOLECULAR
> PHYLOGENIES? Zootaxa 4232 (4) © 2017 Magnolia Press · 595 the increasing
> gap between phylogeny and classification (Franz 2005) are much more serious
> problems. On one hand, phylogeny provides us with a powerful tool to
> hypothesise evolutionary relationships. On the other hand, since the
> world's biodiversity is largely unknown (some 86% of non-marine eukaryotic
> species are unknown; Mora et al. 2011) and the number of taxonomists is
> decreasing (Bebber et al. 2014; Wheeler 2014), it is not yet the time to
> regulate morphology-based grouping of species. Instead of criticising their
> well-trained, professional expertise (gleaned through years of intense
> study), we should invest more trust in the taxonomic evaluations of the
> decreasing number of taxonomists as well as allow more freedom for
> morphology-based grouping. Especially, given that if someone wants to
> describe something, he/she can find a way to do so in local, small non
> peer-reviewed journals or self-published books. One-sided critiques
> emphasising only the taxonomic value of molecular assessment could well
> result in the weakening trust of taxonomists (mostly the ones not dependent
> on impact factors) in peer-reviewed journals, which is already a major
> problem in today's taxonomy. Morphology is still what makes the organism a
> tangible entity beyond its DNA. Necessary changes in the review process
> What we need, is better editorial practice. To overcome this recent trend,
> I suggest considering the following points: (1) Authors have to justify
> their conclusions clearly with their data. Also, if the reason is other
> than no access to molecular laboratory and funds, they should state the
> reason why molecular phylogeny is not performed. (2) Editors need to
> understand the hypothesis-driven nature of taxonomy, systematics and
> phylogeny, and need to be able to ignore reviewers who do not engage the
> subject. (3) Reviewers should refrain from rejecting the description of new
> genera on the basis of the lack of molecular data. Instead, they should be
> critical of poorly defined genera, no clear gaps in the morphological
> continuum, overlapping character states across genus-group taxa, and genera
> awaiting descriptions based on non-conventional morphological characters.
> (4) Taxonomic journals could state whether they allow, discourage or
> prohibit descriptions of taxa above species level without molecular
> phylogenetic support. On one hand, this would allow the authors to prepare
> to the nature of reviews, and choose journals where the lack of sequence
> data will not result in changing the proposed taxonomic decisions. On the
> other hand, this would create a rather harmful division in how journals
> deal with taxonomic submissions.
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