A PROPOSAL FOR A UNIFORM TERMINOLOGY
ON BIOINVASIONS FOR MEDITERRANEAN MARINE SCIENTISTS
Anna Occhipinti-Ambrogi
1*
and Bella S. Galil
2
1
University of Pavia, Department of Genetics and Microbiology, Ecology Section, Pavia, Italy - * anna.occhipinti@unipv.it
2
National Institute of Oceanography. Israel Oceanographic and Limnological Research, Haifa Israel.
Abstract
A consensual set of definitions regarding bioinvasions is essential in order to facilitate discourse among the science, policy and
management communities dealing with the issue. Considering both the extent of the impact and the mode of entry of an alien species into
a new environment, some definitions are being proposed as an operative tool for marine scientists working in the Mediterranean Sea.
Key words: biological invasions, definitions
Rapp. Comm. int. Mer Médit., 37,2004
414
The advent and spread of alien species in the Mediterranean has been
repeatedly discussed in various forums over the past three decades, and
it has been widely perceived that the littoral and infralittoral biota of the
Mediterranean Sea is undergoing a rapid and profound change (1-5).
The rapidly expanding study of marine bioinvasions raised awareness
and concern of governmental and regulatory bodies as well as the
public, and resulted in a glut of specialized terms. The words used to
describe non-native species vary among scientific disciplines, linguistic
and national borders, and frequently constitute synonyms, partial
synonyms and neologisms that hinder communication. Confronted with
a plethora of unsettled and overlapping terms for alien organisms, we
have sought to clarify the terminology for Mediterranean marine
scientists. Our goal is to compile clear and brief definitions for terms
needed by students, researchers, and policy and management personnel
interested or concerned about invasions in the marine environment. We
have combed the literature for the new terminology generated by recent
initiatives, including the proposed new IUCN categories defining the
status of alien species
1
.
Our view of native species and their natural ranges and, inter alia, of
alien species, is largely dependent on scientific knowledge of the taxa in
a certain geographic region. In the Mediterranean Sea, for instance, a
number of extensive biological surveys and identifications were
conducted after 1950, thus allowing a reasonable measure of confidence
in separating the alien from the native biota, and reducing the cases of
cryptogenic species to earlier possible introductions. A notable
exception are the Red Sea taxa, where 1920 was chosen as a cut-off
date, because the Cambridge expedition to the Suez canal furnished a
body of valuable scientific data (4).
In defining the terms we deliberately made a distinction between the
scale and impact of the alien populations on the native ecosystem, and
their mode of entry. From our studies of alien organisms in the
Mediterranean Sea, we have noted that some are known only from
chance collections of non-breeding individuals, other from breeding
populations that remain for decades in low numbers, whereas in some
cases we have witnessed rapid population growth and high impact upon
the ecosystem and risk to humans. Accordingly we have ordered our
definitions in a nested hierarchy of increasing order of the alien’s
population size and impact. As to mode of entry, we have made a
distinction between introduction, which is wholly derived from human
actions, and range expansion, which can result from natural phenomena
or from both natural and human-induced environmental changes.
Introduction is further divided into primary and secondary introduction
and each of these can be intentional or unintentional. Secondary
introduction could also result naturally.
In the course of our classification effort, we are aware that nature is a
continuum and not easily divided into objective units, we therefore aim
to produce a pragmatical tool in order to facilitate the exchange of ideas
among the scientists of the many countries bordering the Mediterranean
Sea. Moreover, the dynamics of invasion and of research progress mean
that organisms may be recognised as fitting in different categories
according to the spatial and temporal setting of their observation.
Terms and definitions
•Native : an organism occurring within its known or consensual range
(as documented in scientific publications).
•Alien : an organism, inclusive of parts, gametes or propagules that may
survive and subsequently reproduce, occurring outside of its known or
consensual range (as documented in scientific publications). It includes
established aliens, invasive aliens, nuisance aliens in increasing order of
population expansion and impact. (Synonymous terms: non-native, non-
indigenous, allochtonous, foreign, exotic, immigrant).
•Established alien : an alien organism that is reproducing in the wild
and has established a permanent population outside its natural range.
•Invasive alien : an alien organism whose population has undergone an
exponential growth stage and may threaten the diversity or abundance of
native species and the ecological stability of the impacted ecosystem.
•Nuisance alien : an alien organism that poses a risk to the well-being
of humans.
As to mode of entry:
•Expanding alien : an alien organism that has extended its range as a
result of changing environmental conditions (e.g. temperature, current
regime) or by chance events, such as the attachment to drifting objects
and phoresy.
•Introduced alien : an organism occurring outside its native range as a
consequence of intentional or unintentional human action.
•Intentional introduction : the deliberate transfer of alien organisms.
•Unintentional introduction: the unintentional transfer of alien orga-
nisms through shipping, aquaculture, canals, research etc.
•Secondary introduction : a dispersal of an alien organism beyond its
primary location of introduction; secondary introduction could be inten-
tional, unintentiona, or by natural means.
Acknowledgements. Dr. Dario Savini and Dr. Rosanna Gugliemo are
acknowledged for the help in organizing the reference material.
References
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1
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