Biology Reference
In-Depth Information
have documented a positive correlation between fragment retention and structural
complexity (e.g., A.R. Davis unpublished data). Wright and Davis (2006) deter-
mined experimentally that stolon growth and fragment success were linked in
Australian
C. taxifolia
, and fragment recruitment was enhanced when stolons were
present. Ceccherelli et al. (2002) found that dense, low-growing (turf) species pro-
moted spread of aquarium
C. taxifolia
, while habitats with encrusting and erect
macrophytes were less likely to be invaded.
15.3.3
Temperature and Salinity Tolerances of C. Taxifolia
Tolerance of a wide range of temperatures is another attribute of a successful
invasive species.
Caulerpa
is endemic in tropical and subtropical regions around
the world (Fig. 15.3), and latitude is a significant predictor of native occurrences
(Creese et al. 2004; Glardon et al. 2008). Silva (2003) stated that members of the
genus
Caulerpa
also can grow in locations up to 34°N along the southeastern US
coastline, where the Gulf Stream typically warms the water. From known histori-
cal temperatures, Keppner (2002) suggested that the potential thermal distribu-
tion for
C. taxifolia
in the USA is (1) just south of Virginia Beach, VA on Atlantic
coast, (2) Stonewall Bank, OR on the Pacific Coast, (3) throughout the Gulf of
Mexico, (4) Hawaii, (5) Puerto Rico, (6) the US Virgin islands, (7) American
Samoa, (8) Guam, and (9) the Northern Mariana Islands. In Europe, Ivesa et al.
(2006) reported that invasive
C. taxifolia
was first recorded in Malinska (Island
of Krk), Croatia in 1994, the highest northern latitude (45°7
) documented for
C. taxifolia
. However, only a few thalli were present in 2004 surveys, and low tempera-
tures (9.5-10.5°C) in the previous winter were the suspected cause of the decline.
Many lab and field studies have determined experimentally the thermal toler-
ance range for
C. taxifolia
. Komatsu et al. (1997) determined that the upper tem-
perature limit was 31.5-32.5°C, allowing
C. taxifolia
to thrive in tropical waters
around the globe. The lower lethal temperature is much more important for under-
standing the potential range of
C. taxifolia
, and Komatsu et al. (1997) found the
lower threshold to be between 9 and 10°C for fragments of the Mediterranean
C. taxifolia
. Additionally, Komatsu et al. (1997) found that minimum temperatures
of 15 and 17.5°C were required for new growth of blades and stolons, respectively,
for aquarium
C. taxifolia
. At the Monaco Oceanographic Museum, winter daily
seawater temperatures from 1978 to 1991 were only below 11°C for 3 days
(Meinesz and Hesse 1991). Minimum water temperatures in Moreton Bay,
Australia are similar to minimum temperatures in the Mediterranean Sea (12°C)
(Wright and Davis 2006). Chisholm et al. (2000) reported that
C. taxifolia
from
Moreton Bay had a lower lethal temperature between 9 and 11°C. The lower limit
for Lake Conjola was 11°C while it was 14°C for Port Hacking (Phillips and Price
2002; Wright and Davis 2006). Fragments did not grow at temperatures less than
20°C and had 100% mortality at 15°C or less in NSW trials (West 2003). When
introduced into the Sea of Japan,
C. taxifolia
failed to establish where the mean
′
30
′
