Lecture 3: Human Vectors of Dispersal

Question 1

Recap. What is the difference between natural and human mass invasions?

Answer 1

• prehistoric mass invasions were episodic and regional. The current invasion phenomenon is global and continuous
• human assisted dispersal frequently occurs over much greater distances than natural dispersal
• human assisted dispersal events involve larger numbers of introduced organisms
• current invasion rates are orders of magnitude more rapid than in geological history

Question 2

If something is native to an area, is it native to that entire country/ continent?

Answer 2

• NO
• ## it might not be native to all of it. Scale matters when talking about these things

Question 3

Describe an example of a sp that is native to one area of a continent but not the entire continent.

Answer 3

• small mouth bass
• eastern and midwestern NA is where it naturally occurs but when it moved across the rockies it was in areas it had no evolutionary history. It is a NA sp but it is only native to a PART of NA.

Question 4

If a mammal sp was introduced to an area 100 years ago, is it native now?

Answer 4

• NO. bc it would take longer to actually evolve a new form that is adapted to this new region, thus making it native. Especially true with mammals, because evolution is slow in them
  Ex: Dingos in Australia..new behaviours developed by native fauna in reaction to it being introduced could be a sign of some threshold that the dingo is becoming native / is. Because there is evolutionary accommodation

Question 5

What aids in speciation?

Answer 5

• extinctions

- freak environmental disturbances

Question 6

Explain why the great lakes are a special case of natural invasion?

Answer 6

• invasions leads to diversification to some areas and losses in others
  ex: group of crustaceans and molluscs evolved in NA, canalized great lakes thousands of years ago. We don’t call them alien. Why? Bc great lakes was formed thousands of years ago via glacial melt water with living things in it. Geologically young, this area evolves rapidly, invasion occurs of species in the margins/colonise it. But there wasn’t a system to invade bc it was in formation, it was missing whole parts and it didn’t exist thousands of years before that. It took thousands of years to stabilize. There are some sp endemic to it. The diff with this is that the area was young and didn’t have anything native in it, therefore a new system was formed by invasion mech but it’s not invasion of non native sp.

Question 7

Are all successful introduced exotic sp, equal in establishment

Answer 7

• no
• number of success/ number of total introduction events
• great variation in success ut not so much in plants it vries somewhere between 5-10% for them
• most sp introduced fail (lower than 50% success), esp with fail it tends to be 10-25 in plants

Question 8

Explain the stages of invasion with the tens rule

Answer 8

• multiple stages where things can fail
• if a variety of conditions are met, they will form a report pop and can sustain itself
• if there are firm boundaries, expansion can be limited
• the rate of spread tends to be related to production of individuals
• ## 10% become established, after you become established, the chance of further population expansion + spread 10%

Question 9

Explain the tens rule

Answer 9

• most invasions FAIL
• ~ 10% of introduced species become established
• ~ 10% of those established become
  Ex: Introduced 100spp -> established 10spp -> invasive 1sp

Question 10

Why is the tens rule useful?

Answer 10

• to remind us that successful invasions are relatively rare.
• it’s a yard stick to assess which groups of species are unusually successful or prone to failure.

Question 11

What explains the tens rule?

Answer 11

• factors that determine survival (at low densities) and abundance (ability to increase in numbers).
• many species are introduced into unsuitable habitats
• many species are introduced in small numbers

Question 12

What organisms does the tens rule seem to work best for ?

Answer 12

• introduced plants

* * there really isn’t a pattern in establishment and spreading across various taxa

Question 13

What organism were found to violate the tens rule by Jeschke (2008)?

Answer 13

• mammals and birds
• upward bias
• concluded that most invasions fail but some sp are more predisposed to spread and establish better esp if they are good with living with hemans
• some do better than what is expected by tens rule
• *keep in mind most people are not around to see the failures so these establishments could be erroneous , can’t trust the numbers

Question 14

Explain the overestimation of establishment success of non native birds in Hawaii and Britain

Answer 14

-the lack of information about failed species introductions and the tendency to report species that have become invasive more than those that have not, result in an overestimate of the establishment success and invasion rates of non native species.

Question 15

What are the barriers to species invasion?

Answer 15

1. Geographic barrier
2. Physiological barrier
3. Demographic barrier
4. Biotic resistance

Question 16

Explain geographic barriers

Answer 16

• responsible for defining the native region originally, preventing the sp from going elsewhere. Can be overcome by natural means like earthquakes or storms etc

Question 17

Explain what physiological barriers are?

Answer 17

getting past the geographical barrier is not enough. They need a SUITABLE environment, physiologically for them to persist, survive, reproduce etc

Question 18

Explain what demographic barriers are

Answer 18

• they need to be there in sufficient numbers to start a population take off. For ex: need enough of both sexes or could be a fault of genetics

Question 19

Explain what the biotic resistance barrier to species invasion is

Answer 19

• resistance from natives. Meet predators or parasites they have no evo history with, that could wipe them out or stop them from establishing

Question 20

What is a main reason how introduced sp are getting through the four barriers preventing introduction?

Answer 20

• HUMAN VECTORS

- we punch holes in geo barriers , giving OPPORTUNITY

Question 21

Explain snake fish failed invasion in the USA

Answer 21

• sold illegally through pet trade
• established in some ponds of NE USA, they are adapted to temps in china, so fine with cold therefore no physiological barrier.
• they have not established bc of the demographic barrier, not enough have been dumped

Question 22

What would it take for a marine mollusc to establish in a marine environment ?

Answer 22

• they need a planktonic larvae
• probs transported as one
• • larvae will disperse with ocean current SO they need to be confined in one area so they don’t float off far. A lot will die
• if some settle and develop, now they are all separated. They will reproduce via broadcast spawning BUT if separated by 100skm this won’t happen SO assuming enough ere dumped, , they cannot be separated too far apart, A LOT CAN GO WRONG
• *enough need to be dumped in a confined area

Question 23

Describe the exchange of species from the red sea to the mediterranean.

Answer 23

• The Suez canal was built allowing passage from the red sea to the mediterranean, uniting two geographic realms that were separated historically.
• lots of sp moved in both directions without human help
• 100-200sp from the red sea invaded the mediterranean, less than 50 moved in the other direction
• mediterranean has a lower elevation, creating a difference in hydrological regimes THEREFORE more sp can be transported passively to the med from the red sea. They had more opportunity to move, so more have the chance to establish in that direction.

Question 24

What are the reasons why there are more exotic plants on larger islands vs small?

Answer 24

• bc larger areas have more niches, resources to exploit.
• Species area effect theory
• larger areas are like dart boards.
• larger areas have larger barriers to cross, more entry points. Random dispersal, larger areas will tend to intersect more sp. They offer more opportunities
  ex: tibet is surrounded by mountains, which means its harder to get into. So even though it is a larger area, it could not have many non native sp because of these.

Question 25

Discuss some natural animal vectors of dispersal.

Answer 25

• passive transport of aquatic invertebrates by birds is a frequent process
• organisms may be attached to plumage or to feet, regurgitated or defecated as resting eggs for ex, or carried directly (e.g. fish dropped into the water by a hawk)

Question 26

What are the two main causes of invasion?

Answer 26

• intentional release

- Unintentional release

Question 27

What are the main causes of intentional release.

Answer 27

• stocking of wildlife
• cultured organisms
• release of biocontrol agents
• pet release

Question 28

What are the main causes of unintentional release.

Answer 28

• hitchhikers with animal imports, hitchhikers with human transport, escapees from culture facilities, container traffic, fishing and boating activities

Question 29

Intentional Release: Fish stocking

Answer 29

• done to enhance sport fishing
• ## over 25% of FW fish caught by anglers in the US is from non native stock

Question 30

Intentional Release:

Agriculture, Horticulture, Mariculture

Answer 30

• example with oyster stocks
• larger and adults from Pacific US hatcheries have been used to establish shellfisheries around the world
• culturing**

Question 31

Intentional Release: Biological Control agents

Answer 31

• attempt to control a nuisance sp through the introduction of enemies (predators, parasites, pathogens)
• often is a non native sp THUS can perpetuate cycles of invasion, where you are now trying to control two for ex

Ex: Grass carp used to control weeds

Question 32

Intentional Release: Pet release. Explain it.

Answer 32

• intentionally but non authorized releases , like dumping aquaria
• ex: pythons in Florida, lionfish ex

Question 33

What’s up with Giant African Rats in Florida.

Answer 33

• Gambian Pouch Rat
• breeding population reported in florida keys
• vector= pet release

Question 34

What are hitchhikers?

Answer 34

• parasites, predators etc
  ex: for salmon pens, salmon escaping into the wild. You could also be relating diseases they have esp bc the pens can be incubators for disease due to the stress of being held there.
• things can live inside wood a palate boxes for another ex: container traffic

Question 35

Unintentional release: Hitch-hikers associated with animal imports

Answer 35

• organisms arriving with imported selfish
  ex:
  1. Japanese oyster drill: snails that bore into and feed on oysters
  2. MSX: protozoan that infect oysters
  3. Shrimp virus IHHN: first observed in Hawaii in shrimp introduced from Panama
  4. disease organisms associated with pet trade like West Nile Virus, Monkey Pox Virus.

Question 36

Unintentional release: Hitchhikers associated with human transport examples?

Answer 36

• South American Ants disperse across US in soil stuck to mud flaps of trucks
• Asian cockroaches spread through Florida in cars
• tourist vehicles spreading weeds in remote areas
• dispersal of tiger pear cactus by vehicles

Question 37

Unintentional release: Hitchhikers associated with human transport: Brown tree snake

Answer 37

• transported to Guam by military cargo planes
• arboreal (climbs trees), nocturnal predator
• native to Indonesia/Australia
• Invaded Guam in 1950s
• Caused many extinctions in birds, lizards and bats
• *shy snake and hide in crevice areas like wheel wells
• fauna on this island had no evolutionary history with arboreal predators
• *it is a generalist predator

Question 38

Unintentional Release: Aquaculture escapees, Salmon ex

Answer 38

• each year during the 1990s, 150000-400000 adult salmon escaped from salmon pens in Washington and BC into pacific coastal waters

Question 39

Unintentional Release: Ex: Asian bigheaded carp in Lake Erie

Answer 39

• multiple sighting since fall 2000

- can consume 40% of their weight in plankton daily

Question 40

Unintentional Release: Recreational fishing and boating activities
- Ex: Baitfish

Answer 40

• european minnows brought to N America for culture and Sale as live bait are now established in many lakes
• *Rudd = ex

Question 41

Unintentional Release: Recreational fishing and boating activities
- Ex: Weeds and Zebra

Answer 41

• overland dispersal of weeds and zebra mussels on boat trailers

Question 42

Unintentional Release: Container Traffic. Ex?

Answer 42

• Asian longhorn beetle
• introduced to NA this way
• Also emerald ash borer
• If wood is not treated, things can burrow, pupate
• therefore surviving the trip
• 80% of the worlds trade is by shop
• USA and Canada introduced legislation to ban importation of any lumber form not treated bc of this threat.

Question 43

Explain rafting of marine sp on ocean litter

Answer 43

• drifting debris can carry sp to shores of islands for ex
• In a study 20-80% if debris was human made and persists longer than natural debris
• attached are inverts,: barnacles, bryozoans, hydroids, worms, molluscs
• floating trash enables raft dispersal by marine sp to double in the tropics and triple at high latitudes

Question 44

Explain the risk of marine bioinvasion via global shipping

Answer 44

• the rate of bio invasions has strongly increased during the last decade due to the accelerated spread of sp by increasing global trade and transport.
• invasion risks vary widely between coastal ecosystems
• ## the invasion probability is highest for intermediate geographic distances between donor and recipient ports

Question 45

Describe the issue with shipping patterns in the pacific

Answer 45

• shipping connects what would be isolated regions around the world
• constant movement of people and trade
• merchandise itself could be sp moved into non native regions either as part of live trade, moving plants, fish etc around to be sold either as food or pets, biocontrol agents, ornamental sp etc these can carry hitchhikers as well, or they can be moved unintentional with whats in the ballast water or haul

Question 46

What is hull fouling?

Answer 46

process of organisms attaching themselves to ship hulls and other submerged appendages of the ship, creating small living communities that travel with he ship to areas where they can be introduced as invasive species.

Question 47

Explain ship ballast water?

Answer 47

• can carry more sp and different types like those that don’t attach vs hauls
• it’s used to help balance boats
• in the beginning soil and rocks were used = risk of introducing plants and insects but in the 21st century we switched to ballast water
• 1m3 of ballastt water contains 10^4 zooplankton and 10^6 phytoplankton
• ballast tanks carry sediment containing various resting stages of organisms
• some sediment can decant , providing habitat for inverts in the tank
• resting stages allow some sp to survive the trip like resting eggs, cysts (to survive temp, lack of food, lack of light etc)

Question 48

Explain carlton’s estimate wrt ballast water

Answer 48

• ~ 50% of all registered ships are at sea at any given time
• at least 10% are fully ballasted
• most vessels carry hundreds of animals and plant sp
• assuming that at least each vessel has two unique species at a given time =
  3500 ships x 2 sp/ship = 7000sp at a given time.

Question 49

Issue with carlton’s estimate of ballast water?

Answer 49

-underestimated bc those ships that are not fully blasted still carry sp too

Question 50

Explain physical factors contributing to successful transport of organisms in ballast water.

Answer 50

• increasing ship traffic = more opportunity
• better ship design (bigger ships aka larger volumes of ballast water, which means higher oxygen concentration and a more stable temp).
• increased oxygen is good bc ballast water is in complete dark conditions, therefore oxygen runs out eventually and is only recovered when new water is added.
• dying/decomp organisms take oxygen
• no PS occurring
• carry more sp
• ships are faster, meaning more sp can survive
• opening of the Panama and Suez canals
  L> cuts travel time
• better water quality received = greater abundance of organisms in ports can be picked up and more likely introduced. Good quality = better env to survive in as well
• most ports are near estuaries, usually near a city, with water that has a gradient of salinity and temp WHICH means organisms in these tend to have a broader salinity tolerance which is good since ballast water means they are exposed to different sanity changes……

Question 51

Explain the relationship between the number of species present and the age of ballast water.

Answer 51

• diversity of what is in the ballast tank decreases with the age of the water
• the older the water gets, the more stressful it gets
• shorter voyages lead to more sp surviving and being transported to a new site

Question 52

Explain the relationship between the abundance of zooplankton groups in ballast water at the beginning and end of ship voyages.

Answer 52

• some sp do better than others
• long voyages you lose more of a given sp
  -higher initial abundance allows for a more successful introduction bc if they are dying off, they have a buffer demographically
• BUT if too low, they may have too few of numbers arriving at the dumping site to start a new pop
• dinoflagellates can form a resting stage, and often are introduced at this stage, if sediments are stirred up in the tank and released into the water column, they can come out of this stage
  L> usually they also produce toxic compounds

Question 53

List biological traits for successful transport in ballast water.

Answer 53

• planktonic life stages
• broad temp and salinity tolerance
• tolerance to anoxic conditions
• ability to feed in the dark
• pref for cryptic habitats = more likely to be picked up in ballast water
• ability to withstand starvation (e.g. large with large lipid reserves and non-feeding larval stages)
  L> oysters and mussels are good examples for lipid reserves
  L> barnacle larvae for non feeding stages
• ability to delay metamorphosis
  L> marine mussels can do this up to 70 days
• ability to encyst (or form dormant stages)
  L> trade off= the longer in this stage, the longer you might not come out
  L> ex: dinoflagellates, planktonic crustaceans

Question 54

Explain how sediments in ballast tanks are a dispersal vector

Answer 54

• mud forms at the bottom of tank harbouring many inverts in resting stages (can remain viable for a long time in many conditions) and active stages
• very low oxygen in the mud
• accumulate over time as water is taken and dumped
• • ex = Daphnia, Chydoridae and Brachionus

Question 55

Based on biological considerations what might we predict for the most/least abundant taxa being in ballast water?

Answer 55

1. Most abundant = crustaceans (barnacles), bivalves, dinoflagellates
   L> esp if brought in at larval stages
   L> bivalves with planktonic larvae don’t need to feed much
   L> dings can form cysts
2. Least = sponges, bryozoans, echinoderms, fish
   L> all have low env tolerances
   L> hardly have a larval stage thats not planktonic and it’s usually a short period
   L> most fish won’t get into the tank
   L> echinoderm larvae won’t live long bc of low tolerances

Question 56

What makes up the highest abundance of organisms in ballast water? (Chesapeake Bay ex)

Answer 56

Copepods> DIatoms>Barnacles>Bivalves>Dinos>Polychaetes

• ** copepods are the most abundant animal on the planet and have very broad tolerances.
• *diatoms live plank tonically

Question 57

Give a brief summary of human mediated vectors of dispersal.

Answer 57

-any habitat accessible to humans is accessible to exotic species –> can tell you WHAT is likely to invade BUT not when.
- given the huge variety of dispersal opportunities provided by human activities, a large number of invasions must go unnoticed
L> ex: pine cones for christmas decorations, imported from India, things were crawling outside of them, got onto shelves of supermarkets = non native beetles.
- most human mediated dispersal vectors are linked with trade, therefore, as global trade expands, species introductions will increase in frequency.