Taxonomic Diversity: The Shifting Baseline of Biogeography
23
conclude that we shall require several dozen Linnaean binomials to describe the Atlantic
population structure. And I shall need to revise my opinion, noted earlier, concerning
the number of species that coexist in today’s oceans.
It has even been suggested that all existing species designations that are not based
on DNA analysis should be relegated to a category to be called the LITU or the “least
inclusive taxonomic unit,” to emphasize our present lack of understanding of their lines
of descent. Such suggestions, it seems to me, come from a cloud-cuckoo-land inhabited by
those who choose to ignore the practical uses for which a classification of the living world
is required. It is very regrettable that the phylogenetic taxonomists did not accept earlier
suggestions that the basic units identifiable by their technique should become “clades”
or “syngens,” named according to a new code. That way, we could have had the best of
both worlds, by accommodating the trickle of new cladistic information into the general
body of our existing taxonomy of the living world. Of course, for microbiota—archaea,
bacteria, cyanobacteria, and prochlorophytes—a taxonomy that mingles numbered or
named clades with Linnaean genera and species has proved essential where cell form is
of little or no assistance in classification. I see no reason why the same approach should
not have been taken with macrobiota.
Whichever way the current fashion for “phylogenetic taxonomy” goes, we ought now
to be aware that two very different categories of “species” are already accommodated
within the existing taxonomy of both macroinvertebrates and vertebrates. Fortunately for
biological oceanographers, the problem is not yet acute and I am still very comfortable
with the use of trinomials to designate the individual, geographically isolated populations
of marine organisms discussed in works that I shall cite as we go along.
This discussion of taxonomic diversity may be a suitable point to introduce a brief
polemic concerning another new concept, that of “biodiversity.” The changes wrought
by us in natural ecosystems have started to capture public attention, and this process
has fed back into science in a manner that is not entirely without problems. To bring
complex issues to the general public requires the reduction of complexity to simplicity,
and the generation of shorthand expressions to stand for complex and improperly understood phenomena. The newly minted term biodiversity with its derivative phrase “loss
of biodiversity” has become a mantra for much of what presently ails the biosphere. It
is also used in some scientific writing as a marketing ploy, as in “Biodiversity of North
Atlantic and North Sea calanoid copepods,” the title of a paper published recently that
contains nothing that might not have been published under the more correct, but less
arresting, title “Diversity of ” This novel usage merits some attention here, because
biotic diversity is an aspect of ecological geography that will concern us in later chapters.
In fact, the omnipresence only 10 years later of a term so “loosely introduced” in 1988
attracted the critical attention (as you might expect it to have done) of the late Ramón
Margalef (1997). He commented that he was “not altogether happy with the success of
biodiversity” and its confusion with the more usual term and supposed that if it has any
specific meaning, it must be the “total specific, taxonomic or genetic richness contained
in nature or in any local or taxonomic part of it.” This, he suggested, is very different from
the classical use of diversity to mean the processes of change and succession, analyzed by
reference to the actual numbers of individuals, species and of their relative biomasses, so
he suggested that we may have to rename the older concept ecodiversity. Thus, biodiversity
would concern the repository of genotypes—as Margalef put it “the actual richness of
nature’s dictionary”—and would complement the concept of diversity as the study of
ecosystems that are evolving in response to external conditions. Ecodiversity, on the other
hand, is in continual flux: an active algal bloom pushes the index down as a small number
of algal taxa comes to dominate the whole spectrum present in a water body. In one of
his inimitable evocations, he suggested that there is a reservoir of ecodiversity in the sea
near the lower boundary of the photic zone, and adjacent to the nutricline, comparable
23
conclude that we shall require several dozen Linnaean binomials to describe the Atlantic
population structure. And I shall need to revise my opinion, noted earlier, concerning
the number of species that coexist in today’s oceans.
It has even been suggested that all existing species designations that are not based
on DNA analysis should be relegated to a category to be called the LITU or the “least
inclusive taxonomic unit,” to emphasize our present lack of understanding of their lines
of descent. Such suggestions, it seems to me, come from a cloud-cuckoo-land inhabited by
those who choose to ignore the practical uses for which a classification of the living world
is required. It is very regrettable that the phylogenetic taxonomists did not accept earlier
suggestions that the basic units identifiable by their technique should become “clades”
or “syngens,” named according to a new code. That way, we could have had the best of
both worlds, by accommodating the trickle of new cladistic information into the general
body of our existing taxonomy of the living world. Of course, for microbiota—archaea,
bacteria, cyanobacteria, and prochlorophytes—a taxonomy that mingles numbered or
named clades with Linnaean genera and species has proved essential where cell form is
of little or no assistance in classification. I see no reason why the same approach should
not have been taken with macrobiota.
Whichever way the current fashion for “phylogenetic taxonomy” goes, we ought now
to be aware that two very different categories of “species” are already accommodated
within the existing taxonomy of both macroinvertebrates and vertebrates. Fortunately for
biological oceanographers, the problem is not yet acute and I am still very comfortable
with the use of trinomials to designate the individual, geographically isolated populations
of marine organisms discussed in works that I shall cite as we go along.
This discussion of taxonomic diversity may be a suitable point to introduce a brief
polemic concerning another new concept, that of “biodiversity.” The changes wrought
by us in natural ecosystems have started to capture public attention, and this process
has fed back into science in a manner that is not entirely without problems. To bring
complex issues to the general public requires the reduction of complexity to simplicity,
and the generation of shorthand expressions to stand for complex and improperly understood phenomena. The newly minted term biodiversity with its derivative phrase “loss
of biodiversity” has become a mantra for much of what presently ails the biosphere. It
is also used in some scientific writing as a marketing ploy, as in “Biodiversity of North
Atlantic and North Sea calanoid copepods,” the title of a paper published recently that
contains nothing that might not have been published under the more correct, but less
arresting, title “Diversity of ” This novel usage merits some attention here, because
biotic diversity is an aspect of ecological geography that will concern us in later chapters.
In fact, the omnipresence only 10 years later of a term so “loosely introduced” in 1988
attracted the critical attention (as you might expect it to have done) of the late Ramón
Margalef (1997). He commented that he was “not altogether happy with the success of
biodiversity” and its confusion with the more usual term and supposed that if it has any
specific meaning, it must be the “total specific, taxonomic or genetic richness contained
in nature or in any local or taxonomic part of it.” This, he suggested, is very different from
the classical use of diversity to mean the processes of change and succession, analyzed by
reference to the actual numbers of individuals, species and of their relative biomasses, so
he suggested that we may have to rename the older concept ecodiversity. Thus, biodiversity
would concern the repository of genotypes—as Margalef put it “the actual richness of
nature’s dictionary”—and would complement the concept of diversity as the study of
ecosystems that are evolving in response to external conditions. Ecodiversity, on the other
hand, is in continual flux: an active algal bloom pushes the index down as a small number
of algal taxa comes to dominate the whole spectrum present in a water body. In one of
his inimitable evocations, he suggested that there is a reservoir of ecodiversity in the sea
near the lower boundary of the photic zone, and adjacent to the nutricline, comparable