Biology Reference
In-Depth Information
introduced from California. An examination of historical records then
revealed that the bark of tanoak (
Lithocarpus densiflorus
) was shipped from
California in large quantities to tanneries on Vancouver Island in the late
1800s. Since clouded salamanders are good climbers and often hide under
the loose bark of trees, they were likely transported to Vancouver Island
with the bark of tanoak.
Jackman's study not only revealed the source of the British Columbia
populations but also showed that the Oregon populations were distinct
from those of California and British Columbia in many genetic features.
He also located a zone of overlap between the two salamanders near the
Smith River in northern California. Hybridization occurred in this zone
but was quite limited. Jackman concluded that the two forms deserved
recognition as separate species.Thus, a new species name was proposed for
the California and British Columbia form:
Aneides vagrans
,the wandering
salamander, an appropriate name for a species that traveled north from
California and invaded British Columbia!
Molecular genetic analysis now provides a very powerful set of tools
for characterizing populations of alien species and relating them to pop-
ulations in their native range. Genetic analyses also hold the potential for
distinguishing cryptic species, aliens as well as natives. Of great practical
importance is the ability to pinpoint the locality of origin and route of
invasion of alien forms. As we shall see, pinpointing the locality of origin
is often of great value because it can help narrow down the search area
for potential biological control agents of harmful aliens. Knowledge of the
precise region of origin of alien species can also help us understand the
degree to which release from competitors, predators, parasites, and dis-
eases has enabled alien species to do well in their new homes.
Genetic Analyses and Discovery of Cryptic Species
Cryptic aliens are species that were not recognized as alien in origin or,
in some cases, not distinguished from other aliens. Many cryptic species
are probably the products of recent evolutionary divergence, although
some may be strongly conserved genotypes of ancient origin. Many
examples of cryptic aliens involve marine invertebrates. Marine poly-
chaete worms of the genus
Marenzelleria
, for example, are native to the
Atlantic coast of North America.They appeared in coastal waters of Scot-
land in 1979 and in the Baltic Sea in 1985 (Bastrop et al. 1998). These
polychaetes have since become a major component of coastal and estuar-
ine habitats throughout much of western Europe. Mitochondrial DNA
