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| Ecology of the green macroalga Codium fragile (Suringar) Hariot 1889: invasive and non-invasive subspecies |  |
| Trowbridge, C.D. (1998). Ecology of the green macroalga Codium fragile (Suringar) Hariot 1889: invasive and non-invasive subspecies Oceanogr. Mar. Biol. Ann. Rev. 36: 1-64 |
| In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: Aberdeen. ISSN 0078-3218, meer |
| Abstract |
The large, green, branching macroalga Codium fragile (Suringar) Hariot 1889
(Chlorophyta: Codiaceae) is one of the most abundant and widespread species in
the morphologically and taxonomically diverse genus of Codium. Six distinct
subspecies of C. fragile have been recognized, in addition to morphologically
heterogeneous populations (with no subspecific name) on temperate and boreal
shores throughout the world. Three of the subspecies appear to occur primarily as
revealed that the spores released from 4 and 6 cm above the substrate show a
normal disc development, whereas those released from 2 cm produced rhizoids
and smaller disc than the former. The spores released from 6 cm show the greatest
growth. The spores with a greater density of fixation show distortions in the development of normal pattern and a smaller growth of microthalli. rom 2 cm produced rhizoids
and smaller disc than the former. The spores released from 6 cm show the greatest
growth. The spores with a greater density of fixation ss from this region are
not necessarily applicable to the alga in other temperate and boreal regions.
Furthermore, much of the work on ssp. tomentosoides is unrelated to the invasion
ecology of this alga, and many authors remain unaware of its exotic origins. In this
review, I examine the ecological differences among and within subspecies and
evaluate their relative invasiveness. Variation among subspecies of C. fragile
occurs in the following attributes: (a) sexual reproduction v. parthenogenesis, (b)
apparent ploidy level of the macroscopic adult thallus, (c) salinity tolerance, and (d) thallus buoyancy in germs both of tissue density and propensity to trap gases.
There is little reported evidence, however, that subspecies vary substantially in
length of their reproductive period, growth, phenology, vegetative propagation,
physiological ecology, herbivore palatability, competitive ability, host-epiphyte
interactions, or natural products production. Comparative studies are needed to
understand the variable invasiveness of the three introduced subspecies and the
non-invasiveness of indigenous forms as well as geographic variation in ecological
attributes of ssp. tomentosoides. |
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