5.1.3.3 Classification of Eukaryotes and Problems
of Nomenclatural Codes
The nomenclature (legitimate names of species, genera, and
taxa of lower or higher rank) of eukaryotes is governed by
two codes. For “plants” in the traditional sense of the term, it
is the “International Code of Botanical Nomenclature.” Until
1975, the code of botanical nomenclature also included the
nomenclature of bacteria (in the modern sense of
prokaryotes), causing duplication and confusion with the
“International Code of Bacterial Nomenclature.”
3 For
“animals” in the traditional sense, that is to say, including
“protozoa” (cf. Sect. 5.5.3), it is the “International Code of
Zoological Nomenclature.”
These codes perpetuate an archaic division between
animals and plants. Modern phylogenies show that the separation between what tradition has called “plants” and
“animals” is totally artificial. The term “plant,” after
Linnaeus
4 in the eighteenth century, concerns such heterogeneous (polyphyletic) organisms, which is not even a functional set (photosynthetic organisms). But the most annoying
is that these codes are independent. This means not only that
the rules for determining the legitimate name of a taxon may
be different but that the same genus name can be used by
different codes to designate different taxa.
Although this constitutes an amazing archaism in the
twenty-first century, it is important to be aware of it, not to
run the risk of serious confusion. Thus, Gracilaria is a
Rhodobionta (Archaeplastida) in the botanical code but a
moth (Lepidoptera, winged with little colors, close to moths)
in the zoological code. Rissoella is Rhodobionta in the botanical code but a gastropod mollusk in the zoological code.
Bonamia is a Magnoliophyta (Convolvulaceae) and a unicellular Haplosporidia, Bostrychia is a Rhodobionta and a bird,
Crambe is a Magnoliophyta and a Porifera (common in the
Mediterranean), Chondrilla is also a Magnoliophyta and a
Porifera, and Eisenia is a Phaeophyceae (Stramenopiles) and
an earthworm. Posidonia is a present-day Magnoliophyta
(Viridiplantae) and a fossil mollusk. Turbinaria is a
Phaeophyceae and a Dendrophylliidae
5 coral. Very slight
differences in spelling can have major meaning differences:
Archaeopteryx is a kind of feathered “reptile” considered the
ancestor of birds, while Archaeopteris is a tree fern that lived
370 Ma ago and that could be the closest kin of
Magnoliophytes (Archaeplastida).
In addition, some groups that were traditionally placed on
the border of the plant and animal worlds are claimed by
both codes of botanical and zoological nomenclature. As a
result, some genera and species may have a valid name that
differs depending on the code considered. This is the case in
the Dinobionta (dinoflagellates for zoologists, Dinophyta or
Dinophyceae for botanists), the euglenoids (Euglenophyta or
Euglena
6 ), and Chlorarachniobionta (Chlorarachniophyta,
Chlorarachnida
7 ).
The independence of the nomenclature of prokaryotes,
compared to that of eukaryotes, is logical, given the very
specific concepts that it uses (cf. Chap. 6). However, one can
only wonder at the independence of codes of zoological
and botanical nomenclature. A unified code, based on phylogeny, has been proposed (phylogenetic or PhyloCode), but
it is currently not used, although this may change in the
future. For instance, the code of botanical nomenclature
still continues to claim a portion of the prokaryotic
Cyanophyceae that it calls “blue-green algae” while these
are cyanobacteria for the ICSP. This fact indicates that this
code is doomed to a comprehensive reform in the short term.
5.1.4 Hierarchical Organization of the Living
World and Evolution of Concepts
from Taxonomy to Phylogeny
The taxonomic approach based on back and forth
movements between nomenclature, natural history, evolution, and embryogenesis has been developed over two
centuries for what was then called the “higher organisms”
(in the modern sense of multicellular eukaryotes). The works
of Linnaeus (1753) have provided a formal framework for it.
Those of Lamarck (1809), Darwin (1859), and many others
have provided a historical and evolutionary perspective,
completed in the twentieth century with the data of evolutionary biology (Table 5.1). Regarding the microorganisms,
especially prokaryotes, the available tools have frozen the
3 For prokaryotes, including Cyanobacteria and Planctomycetes, only
the “International Code of Bacterial Nomenclature” should have the
authority. Discussions are underway to harmonize the nomenclature of
Cyanobacteria and Planctomycetes with the “International Code of
Botanical Nomenclature.”
4 The name of Linnaeus is often translated as “Linne ´.” This goes back to
the tradition that was, until the eighteenth century, to change its name
according to the languages and countries. This is also the choice of the
Royal Swedish Museum of Natural History (www2.nrm.se/fbo/hist/
linnaeus/linnaeus.html.se) website that talks about Carl von Linne ´,
which is the French form he chose himself when he was knighted in
1762 by the King of Sweden. However, the name that appears on the
cover of the book Species Plantarum, chosen as the starting point of the
nomenclature, is “Caroli Linnaei” the declined Latin form of Carolus
Linnaeus.
5 The confusion between Turbinaria “plants” and “animals” is all the
more disturbing given that they can coexist in the same coral reef
ecosystem and even live one on the other.
6 For example, Paranema (Dujardin 1841) is a valid name for a colorless Euglena species according to zoologists. For botanists, the valid
name of the same species is Pseudoparanema (Christen 1962) as
Paranema (Don 1825) is a fern and has the priority.
7 Chlorarachniobionta are amoebae equipped with chloroplasts.
114
C.-F. Boudouresque et al.
of Nomenclatural Codes
The nomenclature (legitimate names of species, genera, and
taxa of lower or higher rank) of eukaryotes is governed by
two codes. For “plants” in the traditional sense of the term, it
is the “International Code of Botanical Nomenclature.” Until
1975, the code of botanical nomenclature also included the
nomenclature of bacteria (in the modern sense of
prokaryotes), causing duplication and confusion with the
“International Code of Bacterial Nomenclature.”
3 For
“animals” in the traditional sense, that is to say, including
“protozoa” (cf. Sect. 5.5.3), it is the “International Code of
Zoological Nomenclature.”
These codes perpetuate an archaic division between
animals and plants. Modern phylogenies show that the separation between what tradition has called “plants” and
“animals” is totally artificial. The term “plant,” after
Linnaeus
4 in the eighteenth century, concerns such heterogeneous (polyphyletic) organisms, which is not even a functional set (photosynthetic organisms). But the most annoying
is that these codes are independent. This means not only that
the rules for determining the legitimate name of a taxon may
be different but that the same genus name can be used by
different codes to designate different taxa.
Although this constitutes an amazing archaism in the
twenty-first century, it is important to be aware of it, not to
run the risk of serious confusion. Thus, Gracilaria is a
Rhodobionta (Archaeplastida) in the botanical code but a
moth (Lepidoptera, winged with little colors, close to moths)
in the zoological code. Rissoella is Rhodobionta in the botanical code but a gastropod mollusk in the zoological code.
Bonamia is a Magnoliophyta (Convolvulaceae) and a unicellular Haplosporidia, Bostrychia is a Rhodobionta and a bird,
Crambe is a Magnoliophyta and a Porifera (common in the
Mediterranean), Chondrilla is also a Magnoliophyta and a
Porifera, and Eisenia is a Phaeophyceae (Stramenopiles) and
an earthworm. Posidonia is a present-day Magnoliophyta
(Viridiplantae) and a fossil mollusk. Turbinaria is a
Phaeophyceae and a Dendrophylliidae
5 coral. Very slight
differences in spelling can have major meaning differences:
Archaeopteryx is a kind of feathered “reptile” considered the
ancestor of birds, while Archaeopteris is a tree fern that lived
370 Ma ago and that could be the closest kin of
Magnoliophytes (Archaeplastida).
In addition, some groups that were traditionally placed on
the border of the plant and animal worlds are claimed by
both codes of botanical and zoological nomenclature. As a
result, some genera and species may have a valid name that
differs depending on the code considered. This is the case in
the Dinobionta (dinoflagellates for zoologists, Dinophyta or
Dinophyceae for botanists), the euglenoids (Euglenophyta or
Euglena
6 ), and Chlorarachniobionta (Chlorarachniophyta,
Chlorarachnida
7 ).
The independence of the nomenclature of prokaryotes,
compared to that of eukaryotes, is logical, given the very
specific concepts that it uses (cf. Chap. 6). However, one can
only wonder at the independence of codes of zoological
and botanical nomenclature. A unified code, based on phylogeny, has been proposed (phylogenetic or PhyloCode), but
it is currently not used, although this may change in the
future. For instance, the code of botanical nomenclature
still continues to claim a portion of the prokaryotic
Cyanophyceae that it calls “blue-green algae” while these
are cyanobacteria for the ICSP. This fact indicates that this
code is doomed to a comprehensive reform in the short term.
5.1.4 Hierarchical Organization of the Living
World and Evolution of Concepts
from Taxonomy to Phylogeny
The taxonomic approach based on back and forth
movements between nomenclature, natural history, evolution, and embryogenesis has been developed over two
centuries for what was then called the “higher organisms”
(in the modern sense of multicellular eukaryotes). The works
of Linnaeus (1753) have provided a formal framework for it.
Those of Lamarck (1809), Darwin (1859), and many others
have provided a historical and evolutionary perspective,
completed in the twentieth century with the data of evolutionary biology (Table 5.1). Regarding the microorganisms,
especially prokaryotes, the available tools have frozen the
3 For prokaryotes, including Cyanobacteria and Planctomycetes, only
the “International Code of Bacterial Nomenclature” should have the
authority. Discussions are underway to harmonize the nomenclature of
Cyanobacteria and Planctomycetes with the “International Code of
Botanical Nomenclature.”
4 The name of Linnaeus is often translated as “Linne ´.” This goes back to
the tradition that was, until the eighteenth century, to change its name
according to the languages and countries. This is also the choice of the
Royal Swedish Museum of Natural History (www2.nrm.se/fbo/hist/
linnaeus/linnaeus.html.se) website that talks about Carl von Linne ´,
which is the French form he chose himself when he was knighted in
1762 by the King of Sweden. However, the name that appears on the
cover of the book Species Plantarum, chosen as the starting point of the
nomenclature, is “Caroli Linnaei” the declined Latin form of Carolus
Linnaeus.
5 The confusion between Turbinaria “plants” and “animals” is all the
more disturbing given that they can coexist in the same coral reef
ecosystem and even live one on the other.
6 For example, Paranema (Dujardin 1841) is a valid name for a colorless Euglena species according to zoologists. For botanists, the valid
name of the same species is Pseudoparanema (Christen 1962) as
Paranema (Don 1825) is a fern and has the priority.
7 Chlorarachniobionta are amoebae equipped with chloroplasts.
114
C.-F. Boudouresque et al.