Our Views on Contemporary Taxonomy

 

Work in Progress

 

When Carl Linnaeus (Carl von Linné) wrote his Systema Naturae in 1735, he introduced the three kingdoms of nature, according to classes, orders, genera and species, laying a foundation for biological nomenclature and a hierarchically organized biological classification.

A genus is a taxonomic rank used in the biological classification which comes above species, but below family. The standards for genus classification are not strictly defined, but genera usually groups together descendants of an ancestral taxon which exhibit ecological, morphological and evolutionarily similarities.

A species is the basic unit of biological classification, and is often defined as a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The presence of locally adaptive traits may further subdivide species into intraspecific taxa such as subspecies.

However, it should be remembered that both concepts are artificial, and Nature is not an assembly line manufacturing genera and species under unvarying criteria, and placing evolutionary restrictions within either category. Genera and species are more or less man-made groupings, with man-defined boundaries, which were designed for our convenience in understanding and classifying the natural world.

Although we are interested in evolutionary biology, we would argue for a need of a STABLE biological classification notwithstanding phylogenetic groupings.

Taxonomy is an ever-changing and controversial field of biology. Recent reshuffles in the avian tree of life grouped falcons and parrots, flamingoes and pigeons. Are these groups of birds REALLY related?

People, including some biologists, are no longer able to track this onslaught of changes in animal systematics, seemingly designed to confuse the general public, conservationists, fellow biologists, and government workers alike. A late friend of ours, a prominent herpetologist with 50 years of experience, once admitted that he was sometimes at loss, trying to meet naming standards for once familiar species. Keeping and updating biological databases, which is always a challenge, has become a daunting task because of the ongoing taxonomic frenzy, creating duplicates, which may deceive a person unfamiliar with a certain group of organisms.

Naturalists may be discouraged as well. In the mid-1960s, most ornithological authorities recognized ca. 7,200 bird species, but at the beginning of the 21st century this number rose to over 10,000 species. Although some new remarkable birds have been discovered recently, the vast majority of this increase came from taxonomic splits. Even though some birders are enthusiastic about adding newly-split species to their life-lists, others may find it frustrating, because species are being split at a rate which does not permit keeping up with these new taxonomic changes.

In some cases the boundaries between newly outlined species are so vague, that geographic distribution may be the only clew to a species’ identity, although our knowledge of distribution of some species is far from perfect. Perhaps, positive identification of certain species will soon be impossible without tissue collecting and genetic testing, making many observations an educated guess.

Although every genetically and morphologically distinct biological population merits protection, I would argue that conservation status does not require elevation of such population to the level of species. It is more likely that continuous splitting of species may affect conservation efforts, when species with questioned taxonomic status could slip though loopholes in legislation, international conventions and conservation plans.

Species-describing authorities often fail to identify any distinctive diagnostic features, presenting identical organisms as different species. A good example is the Lynx Edition’s Handbook of the Mammals of the World, where identical or nearly-identical paintings illustrate “different species” of antelopes and primates. Another problem with splitting is the uncertainty as to which “new species” biological information collected over years should be assigned to.

Some species, or subspecies, may be altogether “lost” through such taxonomic changes. The Black Rat Snake (Elaphe obsoleta), a distinct and strikingly coloured colubrid from eastern North America, is a classic example. In the early 2000s Elaphe obsoleta was split into three clades, corresponding to populations west of the Mississippi River, east of the Mississippi and west of the Appalachian Mountains, and east of the Appalachians. These clades were later elevated to full species, i.e., Elaphe obsoleta (western), E. spiloides (central), and E. alleghaniensis (eastern). However, much "taxonomic uncertainty" remained for a very large area of E. obsoleta range in eastern North America, and the precise distributions of E. alleghaniensis and E. spiloides in the Appalachians was questioned. It is also unclear whether these three new species differ morphologically and could be easily identified in the field.

Additionally, the snakes of genus Elaphe occurring in the New World were moved to the resurrected genus Pantherophis in 2002. Although Pantheropis is not recognized by Integrated Taxonomic Information System (ITIS), many databases quickly replaced Elaphe with Pantherophis, thus making the species in question Pantherophis obsoletus. Its common name also changed to the “Western Rat Snake” or “Western ratsnake, which was now attributed to the populations west of the Mississippi, and no longer applicable to the black rat snakes found around the lower Great Lakes. However, some conservation databases disagree on which parts of the former E. obsoleta range should be included in the newly-defined obsoleta (or obsoletus), and which are attributed to spilodes. Thus, the lower Great Lakes populations are assigned to either P. spiloides (central ratsnake), P. alleghaniensis (eastern ratsnake) or P. obsoletus (western? ratsnake). To make the matter more confusing, some authorities have scrapped obsoleta altogether, as an invalid taxon, effectively making the obsoleta obsolete!

If one searches for the Black Rat Snake or Elaphe obsoleta in conservation databases nowadays, the query may return no results, or point out to a different species; as if this distinct serpent has disappeared off the face of the Earth altogether.

The ranid frogs of North America, such as Leopard, Pickerel and Green frogs, are another good example of hasty changes in organisms’ classification. These Nearctic frogs, traditionally placed in the mostly Eurasian genus Rana, were moved to Lithobates in 2005, from conclusions of a study based on limited species and gene sampling. This separation was based on an argument, that Rana was polyphyletic, although in 2016 another group of researchers proved that the group is in fact monophyletic. I agree with the latter statement, but expect that these ranid frogs will be tossed back and forth between these genera, before the issue is settled.

I suspect that a similar controversy will occur in at least some American toads formerly included in the genus Bufo, and which exhibit little morphological differences from their Eurasian cousins.

I can only wonder how many similar changes occurred in taxonomy of less known organisms.

The taxonomists of old, and of not so distant past, draw their, perhaps subjective, conclusions from morphological (e.g. skeletal) features or behavioural traits. These features could have been questioned by examining the very same specimens or similar study skins or skulls, which could be seen and touched.

However, nowadays many splits (or lumps) are based on minute differences in mitochondrial DNA, RNA, codes of certain genes, or composition of chemicals between the organisms, and the conclusions are based on mathematical models. Are these new species mere lineages originating from slightly different individuals of the same species, like differences we are seeing in contemporary humans, for example? Yet, no one is proposing splitting Homo sapiens sapiens into several species … 

Most of these genetic and molecular studies could be performed only by specialized labs with expensive equipment, and some experiments probably could not be replicated with a different brand of equipment, or if the original samples are lacking, or the tissues were subjected to contamination. Besides, the criteria used for mapping boundaries between species are not uniform, and vary between classes of animals or plants, and between kingdoms.

Another issue, as I see it, is the software used in these analyses. It appears that at least some models cannot handle too many samples, and often phytogenic trees, distances between genes and reading of biological clocks are read from a relatively small number of specimens. Such phylogenies may differ, depending on a taxon used as a control. Otherwise it would “Voilà! Here is your phylogenetic tree”.

The worst of all, some of these major changes in taxonomy may be based upon a single published paper, endorsed by 1-2 reviewers, and without any further deliberation. Such papers may disregard taxonomic, conservation and social consequences. Clearly no one would publish a paper suggesting that, let’s say, American Robin has no or little genetic variability. However, if we were to propose that there are northern, southern, eastern and western robins (or fifty species of African Elephant), which differ significantly in cytochrome b or nuclear rhodopsin, but indistinguishable otherwise, such paper could be published; addiing further confusion and creating unnecessary difficulties for the robin or the elephant identification and conservation.

The situation almost calls for having two parallel taxonomic systems or dual taxonomy. One used in a day to day understanding, cataloguing and conservation of the natural world, and another for the use in evolutionary biology; at least until such times when a consensus is reached and drastic renaming and taxonomic changes are no longer expected.

My point is that species and populations evolve at different rates and a single feature such as difference in a gene, a song or tail lengths does not make an organism from a certain location a different species; just the fact that such organism, or a population, inhabits a geomorphologically, climatically or structurally different location may account for these differences, but does not warrant specific recognition.

To make the long story short, I would like to state the following: in Wild Nature Images we will use traditional taxonomy, sometimes agreeing with, but often rejecting novel, unusual, and unsustainable taxonomic changes and groupings. However, we will try to provide historic and contemporary synonymy, whenever possible.

Michael Patrikeev

Wild Nature Images

 

Please note that this blog is a work in progress.

 

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