Invasion Biology Lectures
Dr.
James Danoff-Burg
Dept. Ecology, Evolution,
and Environmental Biology
Columbia University
INTRODUCTORY
FACTS AND FIGURES ABOUT INVASIVES FROM COX
Lecture
1 – Introduction to Invasion Biology
Lecture
2 – Terms and Language
Lecture
3 - Accidental species introduction
Lecture
4 – Intentional introductions
Lecture
5 – Introduced parasites
Lecture
6 – Characteristics of invasive species
Lecture
7 - Community and ecosystem - structure and function
Lecture
8 - Diffusion models
Lecture
9 – Traveling Waves in Heterogeneous environments
Lecture
10 – Stratified Diffusion
Lecture
11 - Application and testing of models: Types of data needed to construct
models
Lecture
12 - Application and testing of models: Choosing between models
Lecture
13 – Exotics and Evolution
INTRODUCTORY
FACTS AND FIGURES ABOUT INVASIVES FROM COX
STATISTICS
ABOUT INTRODUCED SPECIES
1)More
have been introduced into North America than any other continent - approximately
6,600 species of terrestrial, freshwater, and marine organisms have been
introduced into NA (VERY conservative estimate - doesn't account for those
brought before European immigration, doesn't really account for many insects,
freshwater orgs, or plant pathogens in Canada; also underestimates those
organisms that are not pests and does not include those that are of uncertain
origin "cryptogenic" species - "hidden origin")
2)aa.
This trend is continuing in that between 1980 and 1993, more than 205 new
species were discovered in the US - again probably an underestimate
3)aaa.
This process of introductions began early on during human evolution, post
domestication of commensal and agricultural species, but only really picked
up after World War II. After the second war to end all wars ended, the
world began to become much more of a global marketplace and international
trade increased -- international trade is one of the main reasons why we
have the problem with introduced species we have currently
4)In
the US, introduced species have either caused or contributed to the decline
of approximately 49% of all species on the threatened or endangered species
lists - from Wilcove et al. 1998, Bioscience article
5)Of
those listed approximately 15.8% were due to introduced predators or herbivores,
7.1% competitors, 0.8 diseases are the primary threat (total of 23.7% with
exotics as primary threat) from Simberloff 1996, Consequences vol. 2 online
journal
6)The
distribution of invasive species in N.A. is of course not uniform - any
guesses as to what would be the most likely locations? Why do you think
there? -- Hawaii is first (4,598 spp established! - approx another at least
3,300 spp in cultivation, but not established!) -- Florida & Gulf coast
next most heavily invaded (over 2,000 spp established, with another 25,000
plants in cultivation but not established! incl. 8% of all insects) --
Calif & pacific coast states with at least 674 spp of exotic plants
(11% of the flora)
a)cc.
also, Coastal marine areas and inland freshwater lakes are also strongly
affected by exotics
7)The
groups of organisms that are of the most interest to the public are disproportionately
impacted by exotics -- of the listed species above, fish are most severely
impacted (57% of listings are due at least in part to exotics), mammals
next (36%), and plants least (22%)
8)Among
plants, not all species are equally likely to invade (DON'T TELL WHY I
THINK THAT THE TAXA ARE LIKELY TO INVADE) -- those that are most likely
to invade are grasses (r-selected, disturbed habitat specialists - account
for 11.2% of grass species in US), composites (r-selected, disturbed habitat
specialists), legumes (able to grow in poor soil conditions, disturbed
habitat specialists), and crucifers (no idea?) -- why do you think that
these species are the most prone to invade?
a)ee.
similarly, the geographic origin of the terrestrial invader species is
not uniformly distributed around the world (WHY DO YOU THINK THAT THIS
IS THE CASE? WHAT PATTERNS WOULD YOU PREDICT?) - primarily Eurasia for
Northern North America - primarily tropicalCentral & South America
for Florida - primarily Asia for Hawaii -- likely because of combination
of recent human traffic (hence paucity from Australia and Africa) and climatological
similarity to place of origin (hence the similarities in latitude)
9)N.A.
is not the only location for exotic spp. wars - in terms of the ratio of
native to exotics, Australia and New Zealand have a worse problem than
N.A. (even though they have a smaller total number of species introduced)
-- Australia has around 1,700 exotic plants (approx 21-43% of flora o S.
Australia) and New Zealand has around 1,570 plants (about 47% of total
flora!). -- it is particularly a problem there, as the biota of these regions
are disproportionately comprised of exotic species, given the essentially
island characteristic of both countries.
FACTS
ABOUT SPECIFIC INTRODUCED SPECIES:
a.
Pigeons (Columba livia), a.k.a. rock doves, introduced into New France,
present day New Foundland in 1605, used as food, for keeping as pets, as
navigation, and deliveries - for a long time, there was debate as to whether
the pigeons were native or introduced
b.
Honeybees (Apis mellifera)
c.
Sea Lamprey (Petromyzon marinus), introduced into the Great Lakes with
the formation of the Welland Canal near Niagara Falls, Canada in 1920s,
bridging the gap in height
Lecture
1 – Introduction to Invasion Biology
Notes
from Board:
Deliberate
Introductions – why introduce?
Marketable
products in preexisting market
comfort
/ familiarity
ignorance
of how to use native species / comfort and familiarity with using introduced
species previously
cultural
utility & comfort
religious
reasons & utility
biological
control
ecological
remediation
ornamentals
agricultural
domestics
sport
Accidental
introductions – how are they introduced?
travel
(primary mode)
trade
(primary mode)
parasites
augmenting
natural dispersal abilities
removal
of natural barriers
escapes
of domestics
ballast
water
unprocessed
natural products
Native
Invasives – how can this occur? Primarily through human action
removal
of some restraining forces (e.g., predators)
augmenting
resources – food
augmenting
resources – habitat (fragmentation and increased edges)
grazing
fire
suppression
Agenda
for day:
a
story about doomed people
structure
of the course for the semester and introduction of JDB
introduction
of the concept of invasive biology
reasons
why people bring species to novel areas
statistics
about invasive species and their impact
invasive
species language
invasion
steps
Doomed
People:
(take
home: were not able or willing to make a go of it using the native biota,
were only able to last, for as little as they did before investors withdrew
support, based on the assistance of introduced species, particularly bees,
-
idea of America's political system being reflected by both the ethnicities
& the Biota
-
read off the percentage of native vs. Nonnative people in the US &
their ethnicities
-
people grow homesick, want to bring some of the old country over with them
-
people prefer to work with the plants & animals that you know in the
ways in which you know than to learn anew how work with new spp.
-
this lack of familiarity w/the local biotawas the main reason that the
first few colonists in New France (1604) and Jamestown (1620-1624) (the
so called “lost colony”) either failed or had such difficulties
-
reasons for introductions are diverse : list off
1.
Intentional for agriculture,
2.
Intentional for sport,
3.
Intentional for decorative,
4.
Intentional for land stability
5.
Accidental - fellow travelers
6.
Accidental - as a consequence of land changes
-also
have pest species that are not introduced, that are in fact native to the
area, but who have expanded their ranges because of human activities –
particularly because of fire suppression, grazing, fragmentation, or other
alterations of the habitat.
oExamples
of this include red maples (due to fire suppression – leading to a decline
in the germination success of many oaks)
oMesquite
in the desert southwest (due to fire suppression and increased grazing
– leading to a loss in many species of desert grassland plants and their
animal associates
Lecture
2 – Terms and Language
Announcements:
1.
No class on 27 September (Yom Kippur), 6 Nov (Election Day), 22 Nov (Thanksgiving)
2.
Be thinking about which species that you would like to begin working on
for the class – it should not be one with which you are already familiar
or have worked on already
GENERAL
IDEAS ABOUT INVASIVES
1)Current
attitude towards introduced species: WAR! INVASION!
a)Think
of some of the dire quotations about the current view of introduced species,
akin to war and terminology of conflict
2)current
attitude about invasives is fueled by threats to biodiversity and estimations
about the roles that invasives play in species loss
3)role
of language in science structures our look at the subject - think about
the facts of the case and try to recouch them in terms that are the opposite
of Invasion Biology as we talk about matters in the course -could these
facts be interpreted so that they are not as bombastic and negative?
4)Some
Invasion Language definitions:
a)-introduced:
species that come from one location and are brought to a new location
b)-exotic:
usually ditto a, but also a species from another location
c)–alien:
ditto a
d)–
nonnative: ditto a
e)-invasive:
a species that becomes abundant and influential invaders of a community
of native species
f)adventive: Located
outside habitat, though a reproductive population may not be established
g)-tramp: An
widespread ant species spread by human commerce with a specific syndrome
of life history characteristics: extreme polygyny, unicolonial or highly
polydomous nest structure, and colony reproduction by budding (sensu Passera
1994)
h)-commensal:
a species that lives with another
i)-pest:
any species that is not wanted by humans – exclusively a human construct
j)-domesticate:
any species that we have domesticated and have around us by choice – sometimes
used as a counterpoint to commensal or tramp
k)Native:
not introduced into that area by humans (the delineator that we could use
to determine a native vs. non-native plant.
9.
Notes about presentations:
a)Sign
up for two presentations, all of which will be done in pairs
b)Write
up a sheet that has the following format – fill in the blanks
i)Hypothesis
Tested / General Goal / Theme(s) of Paper:
ii)Structure
of Paper:
iii)Comments:
iv)Questions
for Discussion:
c)Make
up a total of at least 5 questions for discussion that can be used to trigger
discussion, if it is flagging
d)You
should plan on giving a quick review of the paper (10-15 minutes or so)
and hopefully the discussion will either begin during your review or will
begin and grow after your presentation – don’t be upset if we start talking
about the paper before you finish all you had to present.You can work it
into the discussion as we go along, or as the discussion slows.
Lecture
3 - Accidental species introduction
1.three
main phases of the invasion process: Dispersal and introduction, Establishment,
Integration
l)the
current most likely modes of dispersal for exotic species occurs in a number
of ways, nearly all of which involve or occur because of humans, particularly
for long-distance dispersal (WHAT ARE THEY?)
m)not
all species that are introduced are successful - have two perspectives
about this: 1. the Tens Rule: 3 10% relationships, only 10% of the species
will make each of the steps to become a pest: only 10% of those dispersed
will appear in the wild, only 10% of those will become established, only
10% of those will become problem species - therefore only 0.1% of the species
that arrive on the shore will become a pest species -- this is a gross
generalization from the observed statistics -- ex: Hawaii Plants (11.2%
of established plant species have become pests)
n)OR
2. approximately only 1 in 7 (14.3%) are successful enough to cause problems
to human endeavors - Simberloff 1996, Consequences vol. 2 online journal
5)the
spread of species often does not happen in an orderly and progressive way,
with the range gradually expanding each year like ripples on a pond - there
are several models that have been advanced to account for this. Often there
will be an incubation period or a long lag time between the time when a
species has been introduced until it explodes in population size (akin
to a logistic growth curve)
6)successful
integration of species into a community leads to long term impacts on the
evolution of the species that live in that area - they impose new patterns
of selection on the native species - the natives also evolve in response
to the introduced species of course, if and once they survive the initial
onslaught of the exotics, a process called counteradaptation
-Recap
the ideas for modes of accidental dispersal that the class came up with
in lecture –
ospecies
often escape from cultivation (Kudzu - Pueraria lobata) or from labs (African
Clawed Frog, Xenopus sp.)
-Add
to them that the movement of species (both intentionally and accidentally)
is not a novel phenomenon.
ospecies
have moved around since humans began migrating and dispersing around the
globe
oa
variety of seeds, vermin, and other human associates have accompanied them
continually - most of the early movements did not move around large quantities
of species, typically only a few individuals.
-Shipping
and exploration have greatly accelerated the pace of movement.
oThe
large-scale movement of species via ships even predates the use of ballast
(originally dry ballast consisting of rocks, soil, or other stones, now
essentially unfiltered seawater) for shipping.
oEncrusting
species (barnacles, etc.) and boring species (isopods, barnacles, etc.)
have moved around even with the earliest of European explorers.
oBefore
1820, over 90% of the insect introductions were beetles - attesting to
the importance of dry ballast in the movement. These can also be traced
to ports in Southwest England and to their arrival points in Nova Scotia,
PEI, and St. Lawrence area. (later 1840-1860 leps became most common invaders,
with the increase in commerce in living plants)
-Between
travel, shipment, and war (large scale movement of huge machines and the
organisms inadvertently contained within them), we are accelerating the
arrival of the Homogocene (from Rosenzweig).
-many
species were introduced so early into the northeast that their names seemingly
reflect nativeness (Kentucky bluegrass [Poa pratensis], Canada bluegrass
[Poa compressa], Canada thistle [Cirsium arvense], common
dandelion [Taraxacum officinale]
-Given
that Ecology, even in its earliest of modern Naturalistic roots, did not
begin until well after the earliest of these movements, and even is the
case currently if we work with organisms about which little is known, we
have a problem.
oWhat
is the true distribution of species?
oPotentially,
many of the species that we currently think of as having a Holarctic distribution
may have originally been very limitedin their distribution (say to the
northern European seas).
oAn
impact of this realization is that many of us rely upon the distribution
of species to conduct biogeographic studies. as a consequence, many of
these studies may be flawed, possibly leading to erroneous conclusions
about phylogeny, if these characters are used in analyses.
oThese
errors could in turn lead to errors in studies of evolutionary or conservation
biology. If the latter is the case, we may make errors of judgment in the
design of conservation preserves or some similar applied question.
Notes
on Prep readings for Hudson valley article (by Will and Erin) – from Cox
-
many of the introductions into the Northeast have been ecological time
bombs, with long lag times before becoming invasive (our fourth stage of
the invasion process, after integration), great example is Purple loosestrife.
-
Purple loosestrife (Lythrum salicaria) was introduced into North America
before 1814 (when Asa Gray and John Torrey surveyed Northeastern NA. plants
first noticed it). It did not become an invasive until 130 years later,
with the advent of the US highway system in the 1940s and irrigated farming
- both of which disturbed and created wetlands. Now it is essentially continent-wide
in distribution.
Much
of the disturbances (nationwide as well as in the NE) are due to land alterations.
in the NE, this began in earnest in the 1600s. Clearing forests, farms
established, wetlands drained, etc. Facilitated the establishment and integration
of species that were introduced with the movement of property and ballast
and livestock feed and bedding and in and on the colonists and domesticates
-
Carp, although intentionally introduced for sport and food, have been of
major importance in the Hudson Valley.they were first intentionally introduced
into the Hudson in 1831. Propagated on a small scale until 1870s. federal,
state, and private hatcheries began in the 1870s and led to the widespread
cultivation of this species and dissemination of the species across NA.
Now they are viewed as less desirable because they destroy aquatic vegetation
and lead to increased turbidity, which leads to increased egg and larval
mortality of various native species. control of them depends on killing
the entire water body / watershed with rotenone or other piscicides and
then restocking native species (since all are killed).
Lecture
4 – Intentional introductions
Cox’s
chapters 14 – 16 form Part III, which details intentional introductions
for game purposes, native invasives (Cox’s “homegrown exotics”), and human
domesticates (respectively)
A.
Game introductions -
i)Main
threats:
competition and ecological replacement, land degradation, genetic hybridization,
importation of exotic illnesses (which we’ll talk about next week) – also
beneficial
aspects: could replace species that have been extirpated by human activity
(eg. Gemsbok and horses)
1.From
1948 – 1977, the US F&WS encouraged the introduction of exotic species
into N.A. for the purposes of game – The federal program was stopped in
1970 and in 1977 Carter stopped the use of federal funds and resources
for exotic introductions (but what about fish stocking…?)
a.African
Gemsbok (Oryx gazella) was introduced into New Mexico and have successfully
competed with pronghorn (Antilocapra americana) and feral horses
(which are themselves reintroduced)
b.Reindeer
into Alaska competing with Caribou and destroying native tundra
c.Game
Ranching is popular in west, particularly Texas of axis, sika, and fallow
deer, blackbuck and nilgai antelope, Barbary sheep, Ostriches, emus, Eurasian
wild boar – were all introduced into Texas in 1930’s to 1950’s because
of the extreme depletion of native game species by hunters
2.Fur
bearing animals have been introduced in many areas, particularly nutrias
– these southern South American rodents devastate the local salt-marsh
vegetation through over reproduction and then over grazing and in the process,
competing with the native wintering waterfowl – also serious predators
on bald cypress seedlings, and could lead to the elimination of this type
of vegetation in coastal Louisiana
3.Game
birds – ring necked pheasant into NW US – nest cuckolder in the endangered
prairie chicken nests
4.Sport
fish – carp (huge despoiler of native vegetation and the local shore ecology),
brown trout outcompeting the native golden trout (Onchorhynchus aquabonita)
in California’s Kern River
B.
Homegrown exotics (local invasives)
Definition:
those species that are native to the general area (say the continent) but
were brought to other areas by human activities and have exploded in population
size – usually this occurred because humans have brought them over or around
natural barriers (e.g., the great plains or the Rocky Mountains)
all
of these species could lead to the loss of many species through predation,
outcompeting locals, and diseases
also,
because they are often closely related with the species with whom they
are competing, they can also lead to frequent hybridization, more so than
most other introductions
and
as a consequence, their control is very difficult in that what works to
control the homegrown exotic also controls the native species we are trying
to conserve.
In
marine areas, the species are usually those that have been transported
from one coast to the other
butterfly
releases at weddings of species that are not normally found in that area
– even if the species is local, the genes they introduce may not be locally
adapted and lead to the death of those individuals as well as of their
progeny, once they mate with locally-adapted lineages
fish
are the majority of the homegrown exotic species that have been transported
in this way – lead to the death or extirpation of many local plant, amphibian,
insect species, as well as many dramatic changes in the local ecological
balance
many
mammalian associates have greatly expanded their ranges as a consequence
of hitching rides on our movements – raccoons, coyotes, cottontail rabbits,
elk, mountain goats, red foxes, opossum
C.
Domesticates
Issues:
how and whether to reduce these species? Animal rights people frequently
run afoul of the biologists and conservationists who try to restrict the
population growth of these species, as being violations of the animals’
right to exist and as being animal abuse.
cats
and dogs are the largest problem, particularly the former (as we saw in
Pimentel et al.)
feral
livestock, like hogs in Hawaii (after interbreeding with the Eurasian wild
Boar), lead to major damage when they forage, as their rooting uproots
many species and spread the seeds of exotic plants and they can outcompete
native species (white-tailed deer, wild turkey, gray squirrels, and black
bear)
feral
horses – an interesting case, as this is a species that had originally
evolved in North America, subsequently went extinct, and was brought over
by Spaniards in 1500s – is this a problem as a consequence? They may be
thought to be only refilling a native niche that they filled until human
intervention about 8,000 yrs ago.
feral
burros have overgrazed Grand Canyon and Death Valley (growing at a rate
of 18% per year in the latter place), outcompeting many native species
(like desert bighorn sheep) and impacting the native plants – however,
Wild Horse and Burro Act of 1971 makes it a felony to kill feral burros
and horses on most federal lands
Free-range
livestock on public lands in west – is this a problem? How does it impact
upon the native plants, erosion rates, riverbank disruptions, and altered
seasonal patterns of water flow?
A
major occurrence in the west – use up 268 million acres of BLM and Forest
Service lands
Alters
ecological communities, and makes it possible for other exotics to enter.
Rats
and mice (refer back to Pimentel et al.)
house
sparrow, pigeons, starlings, swan,
exotic
pets that are subsequently released into the wild
discuss
the Buddhist practice of releasing captive species
Lecture
5 – Introduced parasites
(diseases
– epidemics and epizootics – viruses, bacteria, endosymbiotic organisms)
or Emerging Infectious Diseases (EIDs from Daszak et al. 2000, Science)
1.
Unique features to these phenomena:
a)Biological
modes are a bit different – quick review of life history of many species
i)Often
infect more than one species and as a consequence need normal host as well
as intermediate host(s)
ii)Often
spread by the intervention of one or more vectors
iii)Obligately
symbiotic (parasitic, parasitoidal, etc.)
iv)Often
have diseases go between humans and other animals in both directions –
these are called Zoonotic illnesses (from Latin for “animal” “disease”
“alteration” –[otic])
b)Similar
modes of spread and introduction are necessary (hurdle #1)
c)In
addition, before the parasite causing the epidemic or epizootic can become
established, and certainly before it can become integrated into the population
(following the scenario that we discussed at the beginning of the class),
the following are needed:
i)Vector
(if any)
ii)the
intermediate hosts (if any) are needed
iii)Proper
environmental conditions needed for all of the host(s) and vector(s)
d)Consequently,
the deck is stacked against parasites becoming established, much more so
than for free-living species
e)Have
several ecological types of parasites (decreasing ease of establishment
in novel areas)
i)Opportunistic
ii)Facultative
iii)Obligate
f)However,
the spread of these diseases is being increased with increasing shipping
and travel rates, particularly between areas that were not previously exposed
to shipping and travel
i)Of
particular importance for the spread of epidemics is adventure travel to
novel areas
2.
Examples of introduced epidemics (Read Guns, Germs and Steel, by Jared
Diamond, which talks about this quite a bit):
a)Smallpox,
which is believed to have been introduced into the Roman Empire from Asia,
which wiped out ¼ of the Roman Empire’s population, and is hypothesized
to have been one of the factors which ended the Roman Empire
b)Bubonic
plague in the 1300s in Asia, which decimated the population in central
Asia, spread by the invading Mongols, who picked up the illness from Europe
(where it wiped out 1/3 of Europe)
c)AIDS
today
d)<