Biology Reference
In-Depth Information
Hediona Lagoon and Huntington Harbor (Jousson et al. 2000; Anderson 2005). The
source of both infestations was hypothesized to be personal aquaria, and the DNA
forensics found that Californian
C. taxifolia
virtually was identical to the
Mediterranean aquarium strain (Jousson et al. 2000). Already at high density,
the Huntington Harbor invasion is thought to have started at least 2 years earlier,
while the timing of the invasion in Agua Hediona Lagoon remains unknown
(Williams and Grosholz 2002). Eradication efforts began immediately in both
California locations and, to date, the USA is the only country with complete
C.
taxifolia
eradication. A large celebration was held on12 July 2006 for this victory
in spite of the price tag of over 7 million dollars and the necessary, but seemingly
temporary, associated environmental harm (Anderson 2005; R. Woodfield, personal
communication).
15.3 WhyIs
Caulerpa
Such a Potent Invasive Species?
15.3.1 ReproductiveCapacity
“Invasive success” refers to traits of a species that promote establishment, spread,
and proliferation in the new range (Inderjit 2005). One hallmark trait of an invasive
plant or macrophyte is its ability to rapidly spread to both close and distant locations.
Short-range expansion occurs regularly via the basal rhizome in
C. taxifolia
. Long-
range dispersal can occur via sexual or asexual reproduction. Sexual reproduction
occurs in
C. taxifolia
with separate male and female individuals releasing gametes
that are fertilized externally (Zuljevic and Antolic 2000). However, only male gam-
etes, probably from a single clone that initially entered Monaco waters, have been
documented in the Mediterranean (Zuljevic and Antolic 2000). No sexual reproduc-
tion has been described for any other invasive population either because only single
sex clones entered the waterways or from the lack of site-specific research.
Many diverse genera of marine macroalgae excel at asexual reproduction via
vegetative fragmentation (e.g., Fig. 15.4, Walters and Smith 1994; Herren et al.
2006). For this type of reproduction to be important, fragments must be generated
regularly, have the ability to disperse widely, land safely, and then rapidly attach
and grow under the new suite of biotic and abiotic conditions (Smith and Walters
1999; Walters 2003). With the genus
Caulerpa
, the capability is especially impres-
sive as all members of the genus are siphonous, with no internal cell walls to reduce
loss of cytoplasm when damage occurs that leads to fragmentation. Long before the
genus
Caulerpa
became well known because of invasive characteristics, research
was focused on understanding the underlying chemical properties that healed
wounds in less than 1 min and kept fragments and the parent thallus from losing all
the nucleus-rich cytoplasm (Dreher et al. 1978; Goddard and Dawes 1983).
Laboratory bioassays have confirmed that very small fragments of
C. taxifolia
can survive wounding and continue growing by producing new attachment rhizoids
