Chapter 1 Taxonomy of Seagrasses
9
Indian Ocean it is less common and restricted to
India. In the Caribbean H. wrightii is widely distributed from Cuba and the smaller Antilles; along
the coast of South America it crosses the mouth of the
Amazon River, and extends southward along the
coast of Brazil (De Oliveira et al., 1983). Other localities of this species are on the Atlantic coast of
Africa, e.g. in Mauritania, Senegal, and Angola; it
is expected that in future more locations will be discovered. It is remarkable that populations satisfying the diagnosis of this species have been found in
Kenya. In southern Brazil the species is replaced by
H. emarginata. Finally H. beaudettei occurs in the
Gulf of Mexico, and less frequently in the Caribbean.
It extends along the Atlantic coast of the USA northward up to North Carolina. This species has been
found also along the Pacific coast, from Panama up
to Mexico, where it reaches its northernmost locations in the Sea of Cortes. In the USA H. beaudettei
is traditionally referred to as H. wrightii, but it relates
in no way with the true H. wrightii which has been
described after material from Cuba. The remaining
two species are only known from one collection, H.
ciliata from Pacific Panama, and H. bermudensis
from the Bermuda Islands.
Although the identification characters show some
variability at present no other means for identification are available. Studies of chromosome numbers,
isozymes, and molecular analyses may be helpful
to establish definitively the validity of the present
species. The only chromosome count available, as
far is known, suggests that possibly polyploidy is involved (den Hartog et al., 1979). McMillan (1980,
1982) found differences in the isozyme composition
of East African and Texan Halodule populations, but
provided no morphological descriptions of the used
material.
Cymodocea K¨ onig in K¨ onig & Sims, Ann. Bot. 2
(1805) 96; nom. cons.
Type species: Cymodocea aequorea K¨ onig (= C.
nodosa (Ucria) Ascherson)
The genus, consisting of four species, has a mainly
tropical distribution. C. rotundata and C. serrulata
have a more or less similar pattern of distribution
along the coasts of the tropical Indo-West Pacific. C.
nodosa occurs in the subtropical Mediterranean and
extends its area in the Atlantic northward to Portugal
and southward to Senegal; further it is common on
the Canary Islands. The fourth species, C. angustata,
is endemic to the north-western part of Australia.
The distribution of this genus has been much
wider in the past. In the Avon Park formation, a late
Middle Eocene deposit in Florida, well preserved remains of seagrasses were found; among them were
two species of Cymodocea (Lumbert et al., 1984). C.
floridana differs from the present-day species, but is
close to C. angustata. The second species appears to
be preserved less completely; its leaf-blade is rather
similar to that of C. nodosa. Fossil fruits have been
found often in various deposits along the Mediterranean (Ruggieri, 1952). Another species, C. micheloti, has been recorded from the Miocene of Sulawesi (Celebes), Indonesia (Laurent and Laurent,
1926). This species is identical with the present-day
C. serrulata.
Syringodium K¨ utzing in Hohenacker, “Meeralgen”
(Algae Marinae Exsiccatae) 9 (1860) no. 426
Type species: Syringodium filiforme K¨ utz.
This genus contains two species. S. isoetifolium
is widely distributed in the coastal waters of the
Indian Ocean and the western Pacific; along the west
coast of Australia it penetrates far into the temperate
zone and occurs even south of Perth. S. filiforme is
restricted to the Gulf of Mexico and the Caribbean,
and it has been recorded from Bermuda.
Thalassodendron den Hartog, Sea-grasses of the
World (1970) 186
Type species: Zostera ciliata Forssk˚ al (= Thalassodendron ciliatum (Forssk.) den Hartog)
This genus contains two species. T. ciliatum is widely
distributed in the tropical Indo-West Pacific. In the
Indian Ocean it is dominant on the reefs of the coasts
of East Africa, many of the oceanic islands, and
along the Red Sea. It does hardly occur along the
northern coasts, as it absent from Pakistan, India,
Sri Lanka, and BanglaDesh. In the western Pacific
its occurrence is scattered, the northernmost locality
being in the South Chinese Sea, the southernmost
in Queensland. The other species, T. pachyrhizum,
has a small area of distribution in the temperate
south-western part of Western Australia, where it
occurs on exposed reefs in the open ocean.
A fossil species, T. auricula-leporis has been described from the Middle Eocene Avon Park formation, Florida (Lumbert et al., 1984); its rhizome,
however, does not show the regular features of the
still living representatives of the genus; probably
does it belong to an extinct genus of the Cymodoceaceae.
9
Indian Ocean it is less common and restricted to
India. In the Caribbean H. wrightii is widely distributed from Cuba and the smaller Antilles; along
the coast of South America it crosses the mouth of the
Amazon River, and extends southward along the
coast of Brazil (De Oliveira et al., 1983). Other localities of this species are on the Atlantic coast of
Africa, e.g. in Mauritania, Senegal, and Angola; it
is expected that in future more locations will be discovered. It is remarkable that populations satisfying the diagnosis of this species have been found in
Kenya. In southern Brazil the species is replaced by
H. emarginata. Finally H. beaudettei occurs in the
Gulf of Mexico, and less frequently in the Caribbean.
It extends along the Atlantic coast of the USA northward up to North Carolina. This species has been
found also along the Pacific coast, from Panama up
to Mexico, where it reaches its northernmost locations in the Sea of Cortes. In the USA H. beaudettei
is traditionally referred to as H. wrightii, but it relates
in no way with the true H. wrightii which has been
described after material from Cuba. The remaining
two species are only known from one collection, H.
ciliata from Pacific Panama, and H. bermudensis
from the Bermuda Islands.
Although the identification characters show some
variability at present no other means for identification are available. Studies of chromosome numbers,
isozymes, and molecular analyses may be helpful
to establish definitively the validity of the present
species. The only chromosome count available, as
far is known, suggests that possibly polyploidy is involved (den Hartog et al., 1979). McMillan (1980,
1982) found differences in the isozyme composition
of East African and Texan Halodule populations, but
provided no morphological descriptions of the used
material.
Cymodocea K¨ onig in K¨ onig & Sims, Ann. Bot. 2
(1805) 96; nom. cons.
Type species: Cymodocea aequorea K¨ onig (= C.
nodosa (Ucria) Ascherson)
The genus, consisting of four species, has a mainly
tropical distribution. C. rotundata and C. serrulata
have a more or less similar pattern of distribution
along the coasts of the tropical Indo-West Pacific. C.
nodosa occurs in the subtropical Mediterranean and
extends its area in the Atlantic northward to Portugal
and southward to Senegal; further it is common on
the Canary Islands. The fourth species, C. angustata,
is endemic to the north-western part of Australia.
The distribution of this genus has been much
wider in the past. In the Avon Park formation, a late
Middle Eocene deposit in Florida, well preserved remains of seagrasses were found; among them were
two species of Cymodocea (Lumbert et al., 1984). C.
floridana differs from the present-day species, but is
close to C. angustata. The second species appears to
be preserved less completely; its leaf-blade is rather
similar to that of C. nodosa. Fossil fruits have been
found often in various deposits along the Mediterranean (Ruggieri, 1952). Another species, C. micheloti, has been recorded from the Miocene of Sulawesi (Celebes), Indonesia (Laurent and Laurent,
1926). This species is identical with the present-day
C. serrulata.
Syringodium K¨ utzing in Hohenacker, “Meeralgen”
(Algae Marinae Exsiccatae) 9 (1860) no. 426
Type species: Syringodium filiforme K¨ utz.
This genus contains two species. S. isoetifolium
is widely distributed in the coastal waters of the
Indian Ocean and the western Pacific; along the west
coast of Australia it penetrates far into the temperate
zone and occurs even south of Perth. S. filiforme is
restricted to the Gulf of Mexico and the Caribbean,
and it has been recorded from Bermuda.
Thalassodendron den Hartog, Sea-grasses of the
World (1970) 186
Type species: Zostera ciliata Forssk˚ al (= Thalassodendron ciliatum (Forssk.) den Hartog)
This genus contains two species. T. ciliatum is widely
distributed in the tropical Indo-West Pacific. In the
Indian Ocean it is dominant on the reefs of the coasts
of East Africa, many of the oceanic islands, and
along the Red Sea. It does hardly occur along the
northern coasts, as it absent from Pakistan, India,
Sri Lanka, and BanglaDesh. In the western Pacific
its occurrence is scattered, the northernmost locality
being in the South Chinese Sea, the southernmost
in Queensland. The other species, T. pachyrhizum,
has a small area of distribution in the temperate
south-western part of Western Australia, where it
occurs on exposed reefs in the open ocean.
A fossil species, T. auricula-leporis has been described from the Middle Eocene Avon Park formation, Florida (Lumbert et al., 1984); its rhizome,
however, does not show the regular features of the
still living representatives of the genus; probably
does it belong to an extinct genus of the Cymodoceaceae.