Cothurnia limnoriae - NSCEP | US EPA - US Environmental ...

Unknown: A species was classified as unknown when there was insufficient information
to make a judgment as to its origin. This was the default classification in the absence of
any evidence. In addition, taxa with an uncertain taxonomy (e.g., species complexes,
taxon only identified to genus) were assigned an unknown classification except in cases
when there is evidence that the taxon was recently introduced into an area (e.g., recent
appearance of genus never observed within a region). Species with uncertain taxonomies
have also been classified as “unresolved” (CANOD, 2009).
Transient: Transient species are those that temporarily migrate into an area as a result of
unusual climatic conditions, such as El Niño (e.g., Rosales-Casian, 2004). Their
movement into the area is via natural mechanisms rather than mediated through direct
human activities. The terms “vagrant” or “migrant” have been used in a similar fashion.
Transient species were not included in the counts of NIS in regions or ecoregions.
Conflict: In some cases, invasion experts disagree as to whether a species is
nonindigenous versus native or cryptogenic within an area. If the available information
was insufficient for us to make a decision among the conflicting classifications, species
were assigned a “conflict” classification. Our use of “conflict” instead of “cryptogenic” is
to highlight cases where some, but not all, of the experts believe that there is sufficient
information to consider a species introduced. “Conflict” species were included in the
counts of NIS in regions or ecoregions.
Definitions for Species’ Population Status
In addition to classifications related to origin, species were also classified in terms of their
population status. Lee et al. (2012) present a set of criteria to evaluate population status. The
following definitions were used in the Atlas and PICES database:
Established: A species with a self-maintaining population as indicated by its population
size, occurrence over time, widespread geographical distribution, presence of juveniles,
and/or presence of reproductive adults. Pragmatically, the occurrence of a species in a
probability-based survey (vs. targeted sampling of optimum habitat type) is reasonably
strong evidence that the species is established based on the relatively small areas sampled
in such random surveys (e.g., tens of square meters for benthic surveys). Native species
are assumed to be established.
Not Established: A species that has been reported from an area but that does not
constitute a self-maintaining population or that has gone extinct within the region. One
indication of non-establishment is not observing the species for ≥25 years, assuming that
the appropriate habitat types were surveyed. Other indications include lack of juveniles or
reproductive adults. By definition, transient species are considered not established.
Nonindigenous species classified as not established were not included in the counts of
NIS in regions or ecoregions.
Unknown: A species for which there is insufficient spatial and/or temporal records to
assess population status. This was the default population status. Nonindigenous species
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