Terms

Question 1

Native Species

AKA: Indigenous Species

Answer 1

A species is native to a region if it evolved there, or if it evolved elsewhere and arrived by its own means through range expansion and without the intentional or accidental intervention of humans.

Question 2

Introduced species

AKA: Alien, exotic, non-indigenous, foreign, etc.

Answer 2

A species that is NOT native to a region and has arrived there with human assistance (intentional or accidental).

Beware that, typically a species is NOT considered INTRODUCED if it has been imported to a country but remains solely within mariculture / aquaculture / agriculture establishment.

Question 3

Types of Introduced Species

Answer 3

Casual
Naturalized
Invasive

Question 4

Casual Species

Answer 4

An INTRODUCED species that does not form self-replacing populations in the invaded region, and whose persistence depends on repeated introductions.


This term is used mainly for plants. 


Question 5

Naturalized Species

Answer 5

An INTRODUCED species that has formed self-replacing populations for several life cycles or a period of time (10 years for plants) with/without human eradication and removal attempts.

Question 6

Invasive Species

Answer 6

An INTRODUCED species that sustains self-replacing populations over several life cycles, produces reproductive offspring, often in very large numbers at considerable distances from the parent and / or site of introduction. 
Invasive species are thus a subset of Naturalized species (not all naturalized species become invasive).
 An important point of the definition of INVASIVE species is that there is NO connotation of IMPACT .


Question 7

Cryptogenic Species

Answer 7

A species that can’t be demonstrated as being either introduced or native.

• cryptogenic species are NOT introduced species of unknown origin 

• cryptogenic species are NOT introduced species whose mechanism of introduction is uncertain
  
- cryptogenic species are NOT “cryptic invaders”

Question 8

Pseudoindigenous Species 


2 types

Answer 8

An introduced species that is mistakenly considered native.

1) Introduced species that is redescribed as new (native) species after introduction although they have already been described in their native region.
Ex. Green Crab, Mediterranean Mussel, Japanese Sea Squirt, Dwarf Eelgrass

2) Species described as new after introduction and later found elsewhere.
Ex. The edible soft-shell clam Mya arenaria

Question 9

US Federal regulation defines Invasive species as:

Answer 9

an Alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.

Question 10

World Conservation Union (IUCN) defines invasive species:


Answer 10

as species introduced by man into places outside of their natural range of distribution, where they become established and disperse, generating a negative impact on the local ecosystem and species.

Question 11

Implications for Science and Conservation

Answer 11

These differences on how we understand the concept of invasive species amongst different members of society has critical implications for how we do science and how we conserve ecosystems, because the way such terms are used by managers and policy makers will greatly determine which species are regulated, for which species risk assessments and management plans are required, where the funding goes to control this species and also, how scientists develop their work (which species are studied).


Question 12

How many Introduced species are there?

Answer 12

• Hard to obtain an accurate estimate. In general it can be very difficult to quantify how many species are introduced and how many of those become naturalized and invasive, since many of the species that arrive do not survive or persist only a short while and thus go unnoticed.

Question 13

How many Invasive species are there?

Answer 13

The Tens rule emphasizes the low incidence of high impact invaders; 
since it states that only 10 % of species transition through each stage of the invasion process. 


Question 14

The Ten’s Rule

Answer 14

We should expect that 10% of the species that are introduced become naturalized, and 10% of those that have established populations spread to become invasive. Of these invaders, only 10% would have an impact. According to the “tens rule”, of all the species that are introduced only one species in a thousand should become a “pest”. 


While this rule of thumb can be useful to have an idea of what the numbers may be, we can see that it does not always work well. 
One problem is misapplying this rule using it for quantitative prediction or risk analysis 
(in fact, this rule was never meant to be used in this manner). 
Also, the rule focuses on the number of invasive species rather than on the magnitude and character of the invasive species, so it is not possible to use the Tens rule to identify important invaders or predict their impacts.

Question 15

What are the trends in time?

Answer 15

There is a clear trend of increasing rates of introduction and establishment of native species since the 1950’s from around the world.

Question 16

Why are these trends of increasing introductions through time taking place?

Answer 16

1) There has been an increase in the level of research activity regarding invasions, increased public interest and search effort, and improved tools for systematic analysis (e.g. molecular techniques), all of which enhance our detection and reporting capacity.
2) The increase in trade among humans; with increasing populations, globalization and economic growth, the world trade has been steadily increasing in the last 100 year.

Question 17

The Columbian Exchange

Answer 17

With the arrival of Columbus to America started perhaps the most rampant movement of species across the globe, which has been called the Columbian exchange.

Question 18

Where in the world are most harmful introduced marine species located?

Answer 18

We can see that the Hawaiian islands, the NE Pacific coast, as well as the Mediterranean, the North and the Irish Seas have considerable numbers (more than 30 species) of harmful marine species. 
However, this represents harmful introduced species only. in the following slides we will examine if similar patterns arise when we consider more types of introduced species. 


Question 19

Where do most seaweed invasions occur?

Answer 19

The Mediterranean and in the NE Atlantic, which we saw in the previous slide that harbored high number of harmful introduced species, also suffer important seaweed introductions. 


Question 20

Are there any general geographical patterns in species introductions?


Answer 20

One geographical pattern that has been observed is the trend of latitudinal gradients in numbers of invasive species. Elton (1950) already observed that temperate regions tended to have more introduced species than tropical regions.
 In this figure you can see marine invasion “hotspots”, and you will probably notice that many of the dark red areas are in temperate regions.

Question 21

Where do most introduced species come from in aquatic systems?

Answer 21

• Nearly half of aquatic plants introduced to the US come from Asia

• More than half of introduced freshwater fish and amphibians in the US come from within other parts of the US.

• Some of the data available suggests that marine systems tend to have more introductions than freshwater systems but some freshwater areas (e.g. Great Lakes) have higher invasion rates than several marine systems (such as the Baltic or North Seas).

Question 22

Stages of Invasion

Answer 22

Transport: A species may not survive during the transport stage, or, it survives, but it is under cultivation or captivity regimes

Introduction: Many species remain within the human-imposed confines (GEOGRAPHY) and are not introduced to the wild. but some of these species make it out of the CAPTIVITY / CULTIVAITON barrier and escape into the wild (introduction).

Establishment: During the establishment phase, 
an introduced species faces mainly two additional and significant ecological / environmental barriers: 
SURVIVAL and REPRODUCTION. IF individuals released into the wild are incapable of surviving for a significant period, they fail to invade Individuals may be able to survive in the wild in the location where they were introduced, but may fail to reproduce, failing to invade
Individuals may be able to reproduce, but although reproduction is occurring, populations are not self-sustaining Finally, individuals may survive and reproduce producing self-sustaining populations, with the potential to spread Factors influencing these two barriers can arise from the populations themselves (e.g. reproductive rate), 
from the particular location (e.g. habitat quality and interaction with other species), 
 from random features of the introduction event (e.g. frequency and magnitude of the introduction attempts), 
or of interactions amongst these factors. 


Spread: For a non-native species to spread beyond its place of initial establishment it must have some ability to disperse and so DISPERSAL can be a potential barrier.
if it manages to disperse, each subsequent novel location into which it arrives can pose additional barriers to its establishment and spread similar to those that it passed through previously.
However, as the species spreads moving away from the original location of introduction, the more dissimilar from the point of introduction the ENVIRONMENT at these new locations will be (because of spatial autocorrelation), potentially further hampering spread. 
It is also during transit through the spread stage that a population can experience “boom and bust” cycles. Changes in the barriers encountered during spread can lead to spectacular switches from decreased to increased success and may lead to population explosions, or population reduction or invasion failure. 


Question 23

Vector

Answer 23

Transport mechanism by which a species is transferred into another location

Question 24

Pathway

Answer 24

The route between the source region of the non-native species and the location where it arrives to

Question 25

2 Types of Vector

Answer 25

Deliberate: Movement to a new area for an express purpose
Unintentional: Movement to a new area is an unintended byproduct of some travel/transport activity

Question 26

Why do people deliberately introduce non-native species?

Answer 26

Food(aquaculture), Ornamental species trade, other commercial interests, management (biological control, habitat management), other motives (religious purposes, pet release, acclimatization societies)

Question 27

Unintentional introductions types

Answer 27

Shipping(ballast soil, water, rocks, fouling, canals,), Aquaculture, others, Tsunami drift debris.

Question 28

Relative importance of different vectors

Answer 28

Shipping seems to be the most predominant introduction vector in oceans and freshwaters

Question 29

Secondary Introduction

Answer 29

A non-native species which has arrived to a new area is introduced to other areas within the nonnative region

Question 30

Propagule pressure (introduction effort)

Answer 30

A measure of the number of individuals released into a region to which they are not native.

PP~ : 1) Propagule Number (# of discrete release events)
2) Propagule Size (# of individual in any one release event)