Division: |
Rhodophyta |
Very ancient division, as can be seen on the Tree of Life |
Class: |
Rhodophyceae |
There is only one class in the Division |
Subclass: |
Florideophyceae |
Only other subclass is Bangiophyceae |
Order: |
Gigartinales (Plocamiales) |
Although some still consider Plocamium to belong to the Gigartinales (Sze 1998), there is molecular evidence for the Plocamiales, (Saunders & Kraft 1994.) |
Family: |
Plocamiaceae |
Silva 1980b, showed that Thamnophoraceae decaisne 1330, was a taxonomic synonym and Plocamiaceae was retained. |
Genus: |
Plocamium |
Only other Genus is Plocamiocolax, which is parasitic on Plocamium. (Goff 1997) |
Species: |
Plocamium pacificum Kylin 1925 |
Currently there are 47 species of Plocamium
distributed around the globe. |
For centuries one of the four species of Plocamium that grows
on the pacific coast of Northern America was referred to as
Plocamium cartilagineum, which inhabits most of Europe and the
Indian Ocean. However, in 1925 Kylin collected a specimen of what
should have been P. cartilagineum from San
Juan Island, Washington. After analyzing that specimen he pointed out
that the eastern Pacific version is more robust, has a more
cartilaginous appearance, has a rounder cross section and has more
branching in the tetrasporangia.
Based on these observations Kylin assigned the new species name P.
pacificum to what is today commonly referred to as P.
cartilagineum. The latter species still exists, but not on the
western coast of northern America. This was confirmed by leading
phycologist Paul Silva of the Jepson Herbarium.
Plocamium cartilagineum has undergone many name changes over the years. Linnaeus, the same Linnaeus who created the scientific binomial naming system, first named the species Fucus cartilagineus in 1753. Fucus, however, was a catchall genus used to describe most large fleshy algae. The name has evolved through a pattern of confusing personal opinions, faulty identifications and more recently, through molecular research.
The table below summarizes the many names that have been used to
refer to P. cartilagineum. It is because P. pacificum
is often referred to as P. cartilagineum that the entire
nomenclatural history of P. cartilagineum is also given
below. Plocamium pacificum was referred to as Plocamium
angustum J. (Linnaeus) Agardh 1863 until the Eastern Pacific
population was renamed P. pacificum (Linnaeus) Kylin 1925.
P. angustum went through a series of name changes, and in 1967
Dixon renamed it P. cartilagineum. This name included changing
P. pacificum by including the Eastern Pacific in the
distribution of P. cartilagineum. However, there are physical
characteristics that have been reported to separate the two species
and P. cartilagineum is not found in the Eastern Pacific. Even
though P. pacificum is the correct name for the species
appearing on America's northwestern coast, it is still often referred
to as P. cartilagineum.
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Fucus cartilagineus |
Linnaeus |
1753 |
Type (original reference specimen) allegedly from "Oceano australiore," but probably actually from Northern Europe |
Conferva rubra |
Hudson |
1762 |
Illegitimate synonym for Plocamium cartilagineum, according to Silva |
Fucus plocamium |
Gmelin |
1768 |
|
Fucus coccineus |
Hudson |
1778 |
Illegitimate name |
Plocamium vulgare |
Lamouroux |
1813 |
|
Plocamium coccineum |
Lyngbye |
1819 |
Illegitimate name, but was used extensively in the literature |
Plocamium pussillum |
Sonder |
1845 |
Taxonomic synonym |
Plocamium brachiocarpum |
Kützing |
1849 |
Taxonomic synonym |
Plocamium cruciferum |
Harvey |
1855 |
Taxonomic synonym |
Plocamium angustum |
J. Agardh |
1863 |
Taxonomic synonym |
Plocamium leptophyllum |
V. May |
1965 |
Taxonomic synonym |
Plocamium cartilagineum |
Dixon |
1967 |
Plocamium cartilagineum is in Indian Ocean and Europe - NOT the Pacific Americas. |
Plocamium pacificum |
Kylin |
1925 |
Plocamium pacificum is on Pacific coast of northern
America only. |
|
Table compiled, in part, from information from the Jepson Herbarium.
Note:
Taxonomic Synonym means that someone believes two different specimens are actually the same species.