Canarium mutabile roseoparvum or the Infrasubspecific Problem
A few years ago, the problem of the subspecies was posed to me in a naturalist but also ethical way. I was working on the definition of a possible form of Strombus mutabilis Swainson, 1821 from French Polynesia. Personal harvests in 2003 and 2009 allowed me to identify a form of almost plain pinkish or salmon flesh color. The opening is distinctly orange with white teeth; the general form is robust with a pronounced suture. The average size is much smaller than the nominal form with values between 17 and 21mm, the observed specimens being adult on conchyliological criteria. The biotope for this particular form is similar in lagoons of Tahaa, Raiatea, Huahine and Moorea: in the small cavities filled with sand of the coral slab close to the reef, in 1 to 3m of water.
I then tried to work on an infraspecific rank more neutral philosophically and better adapted to the field: the morph.
On that purpose, it must be remembered that taxonomy must be at the service of the study of nature, and not the other way around.
What the International Code of Zoological Nomenclature says: ”TITLE IV. OF THE CRITERIA OF AVAILABILITY. Article 16. Form: A term which, if published after 1960, is deemed to denote an infrasubspecific rank and is excluded from the zoological nomenclature. Unless, prior to 1985, it has been treated as an available name and is adopted as the name of a species or subspecies, or treated as an older homonym, in which case the name is deemed to be of a subspecial rank from the date of its establishment.”
To see more clearly, let us also relate a personal communication between Professor Georges Richard and conchology specialist Michel Boutet some years ago: "Sometimes decried by some specialists, form is however regularly cited in the literature. For a mollusk to be able to "benefit" from a valid taxon, it must belong to a small group of a local population that often lives in the same geographical area as a species or subspecies, but which shows permanent distinctive characteristics. Since 1982, C. I. N. Z. (International Commission of Zoological Nomenclature) no longer recognizes forms."
Finally, here is an excerpt of communication with Gijs Kronenberg who replied to me at the time « As you know, nearly all strombids are quite variable in shape and colour pattern. This is also true for Canarium mutabile, and morphologically slightly aberrant populations of C. mutabile are known, e.g. in Western Australia. Some of these may considered to be subspecies (depending on the exact definition of subspecies). Canarium mutabile is known from all parts of French Polynesia (Society Islands; Tuamotu Islands; Gambier Islands; and Austral Islands) where it lives on sandy and muddy bottoms with seagrass near and on the fringing reefs in the high islands and on the lagoon's bottoms of atolls. The colour pattern of C. mutabile is extremely variable, but many of these named color morphs [most notorious is zebriolatus] occur throughout "normal" populations. This is also true for the aperture, that can vary from nearly red to very pale pinkish. As far as French Polynesia is concerned, you know that it is on the very edge of some wide-spread Indo-Pacific species, and even has some endemic (sub)species. If this latter were true, even then a new question should rise: what is the influence of the environment on the phenotype (turbid waters/stagnant waters; salinity; food)? In some occasions, e.g. Littorina obtusata from the European coasts it is known that exterior coloring of the shell is influenced by food; in some ovulids coloring of the animal very well related to the coral host; be while in other species exterior (and interior) color is very constant. More questions then answers right now I am afraid. »
Now I shall call this morph Canarium mutabile roseoparvum for convenience, for that’s what it is. The set of names given to forms of life by authors are merely commodities destined to make the living world intelligible. The creation of the notion of species responds to an attempt to represent biodiversity by the human mind. If certain specialists still question this notion, it is because the practical binominal terminology is only a human concept.
When one looks at nature, when one studies its immense diversity and attempts to characterize the multitude of life forms, one is necessarily limited by the primordial notion of species. This essential point, this fundamental concept of naturalistic thought is, however, only a classification tool with its weaknesses on the field. The species is also reflecting, if used alone, a certain fixism that is incapable of studying the true path of evolution. The morph is not on the scale of a rank which can represent millions of individuals, but on the particular and singular level of the living being which is an exception in the group.
If the spatial condition is decisive for the subspecific rank, it is also its weak point since many species permanently change their range. This characteristic of the subspecies is also undermined by the explosion of biological invasions, the voluntary introductions of exotic entities and the standardization of biotopes. The term subspecies has an obsolete connotation and should, in my opinion, disappear from the language of naturalists for symbolic, ethical and practical reasons.
Each eukaryote is composed of the same primary elements and is developed subject to common physicochemical laws. The only thing that differs from one species to another is the arrangement of these elements, on the atomic, molecular or even genetic scale. These differences are also visible within a species, to a less decisive extent in biological terms. Here is the origin of the individual’s peculiarities, which enable him to evolve in a singular manner among his fellows. This is how the phenotype prevails in determining an identity. The attitude of grouping under the same name individuals of the same species with similar characteristics is quite justified.
In his letter, Mr Kronenberg also stressed the importance of the impartiality of sampling, noting that sometimes the most colored, larger or found in most accessible habitats are considered typical. In our case this scenario is not applicable, because the morph roseoparvum is small, passing easily for a juvenile in the eyes of people. It is also light colored, living in white sand or coral debris, and is found often with calcareous crusts and algae on the shell. Objectively, this form passes virtually unnoticed during a snorkeling search, while much more visible morphs share exactly the same distribution zones. However, if one changes the method of harvesting, one quickly realizes that in some localities, the form roseoparvum is much more represented than other phenotypes.
So I will stay with my morph.