Headline News

1
Headline News

• a carnivorous snail exterminates 56 endemic
  snails in south Pacific
• Nile Perch eats endemic Lake Victoria cichlids
• brown tree snake eats birds, bats, lizards and
  skinks on Guam
• fireants attacks other ant species

2
(No Transcript)
3
Species Invasions

• What are the conservation implications of
  introduced species?
• 1) What is their impacts?
• 2) what factors influence success?
• 3) how are species introduced?
• 4) how can we best control or prevent invasions?

4
Conservation Implicationsoverview

• The scale and number of invasives is enormous
• On NAm prairies, 11 non-native, 35 in Hawaii
• 8000 shrub and herb sp in S Af
• 3000 plant sp in CA alone!!
• Worldwide, 20 of all endangered vertebrates
  threatened by exotics

5
Conservation Implications

• Intentional introductions lose by winning
• 67 of tropical and gt50 of temperate
  introductions successful
• Pattern is consistent in Mediterranean (gt160sp),
  Great Lakes (gt140sp), Black Sea (gt40sp)
• And numbers are increasing

but 77 caused native fish to decline
6
Conservation Implications

• Increase in rate of accumulation of introduced
  species in San Francisco Bay. 1851-1960 (1-55
  weeks) vs. 1961-1995 (1-14 weeks)

7
Conservation Implications

• The geographic range of all species is dynamic
  and range expansion is a natural process
• However, it typically occurs at a relatively slow
  rate (ecological)
• Like extinction, current rate of introductions
  greatly exceeds background rate

8
Conservation Implications

• There are certainly intentional introductions,
  largely for economic gain
• E.g. livestock, crops, sport fishing/hunting
• However, others can cause severe economic damage
• E.g. Eu. zebra mussel (100M/yr), gypsy moth
  (11M/yr), Eu. Shipworm (200M/yr), purple
  loosestrife (45M/yr)

9
Conservation Implications

• There are many public health threats associated
  with species introductions
• Smallpox, avian and human malaria, and red tides
  all can have devastating effects on human health
• Some are even more seriousHIV (18M dead, 5M
  annual infected), cholera
• Potential exists for yellow fever, dengue fever,
  malariato spread

10
Conservation Implications

• Impacts on biodiversity are complex
• May increase S (Essay 9.1)
• However, many have very detrimental effects and
  directly threaten a number of native species

11
Impacts of Invasions

• First, there are going to be direct and indirect
  effects of an invader
• E.g. direct immediate interactions (competition,
  predation, diseases) or indirect effects such as
  resource competition, trophic cascades, or
  habitat modification)

12
Impacts of Invasions

• Direct effects and Indirect effects

13
Impacts of Invasions

• Second, there can be multiple invasions
• Depending upon local conditions, the likelihood
  of success may differ as well as the subsequent
  impact
• European Starlings
• Multiple invaders can enhance or facilitate one
  another

14
Impacts of Invasions

• Third, impacts will occur over a range of
  ecological and evolutionary scales
• There may be direct immediate impacts
• Could also impact the genetic makeup or behavior
  of the population
• Further modification could occur and changes in
  ecosystem characteristics such as habitat
  structure or nutrient cycling

15
Impacts of InvasionsPopulations and Communities

• It is relatively easy to document population
  level impacts such as extinction or extirpation
• E.g. brown tree snake arrived on Guam
  after WWII, numbers stayed low til 60s
• Population exploded (fig 9.2) and native birds
  began to disappear, although

16
Impacts of InvasionsPopulations and Communities

• Electrical outages as a result of brown tree
  snakes crossing wires and frying

17
Impacts of InvasionsPopulations and Communities

• Spread of Boiga and loss of birds following
  invasion at the southern end of island

18
Impacts of InvasionsPopulations and Communities

• Currently, 15 bird sp. have been lost
• Densities can reach 5K/km2
• Pigs and monitor lizards eat them, but little
  impact

19
Impacts of InvasionsPopulations and Communities

• Pose a significant threat to other islands..why?

20
Impacts of InvasionsPopulations and Communities

• There are other infamous predators
• E.g. giant African snail introduced to Hawaii as
  a garden ornamental is now a garden and crop pest
• Solution Hawaiian official have introduced 15
  nonnative predatory snail species to control it
  (3 established)
• Result rosy wolfsnail annihilated 15 of 20
  endemic Achatinella snails on Oahu

21
Impacts of InvasionsPopulations and Communities

• RWS has been introduced to gt20 Pacific islands
  with similarly ineffective biocontrol results but
  surprisingly, similar loss of native snail (56
  of 61 endemic snails in French Polynesia)

22
Impacts of InvasionsPopulations and Communities

• Introduction of Nile perch has caused the
  extinction of endemic cichlids in Lake Victoria

23
Impacts of InvasionsPopulations and Communities

• Not all are obviously precarious
• Consider backyard introductions
• There have been 59 introductions of, most
  (64) of which have had detrimental effects,
  including extinctions of native species
• This is more than 2x of any other introduced
  mammal, but less on mainlands

domestic cats
24
Impacts of InvasionsIntroduced Competitors

• One of N Ams most unique faunas is the 297 sp of
  unionid mussels endemic to the eastern US
• They filter feed in shallow mud
• Currently 40-75 are extirpated or endangered
  from various causes

25
Impacts of InvasionsIntroduced Competitors

• The free-swimming larvae (vs. fish dispersal)
  actually attach to the shell of unionids,
  eventually strangling it

26
Impacts of InvasionsIntroduced Competitors

• Another competitor that has made dramatic impacts
  is the Argentine ant
• It not only competes with native ants, but also
  honeybees, preys on herbaceous insects and can
  impact survival of birds, lizards, and small
  mammals

27
Impacts of InvasionsIntroduced Competitors
28
Impacts of InvasionsIntroduced Competitors

• Some sp may interact to strengthen the impact of
  each sp
• The Asian macroalga and European bryozoan
  interacted by encrusting (bryozoan) the native
  Gulf of Maine kelp making them more brittle
• When they break in winter storms, algae colonize
  new spaces rapidly

29
Impacts of InvasionsIntroduced Competitors
30
Impacts of InvasionsIntroduced Competitors

• Alternatively, a new invader may actually depress
  the impacts of the first invader
• E.g. in the Black Sea, the ctenophore (comb
  jelly) is a generalist planktonic carnivore
  feeding upon zooplankton, fish eggs and fish
  larvae
• Anchovy, mackeral and spat all collapsed

31
Impacts of InvasionsIntroduced Competitors

• Egg and larvae abudance
• Anchovy (gray)
• Mackeral (black)
• Other (white)
• In 1999, Beroe arrived and is a voracious
  predator of ctenophores

32
Impacts of InvasionsIntroduced Competitors

• These are direct effects and easy to observe
• There are cascading effects and indirect effects
  that can be much more difficult to determine

33
Impacts of InvasionsMorphological and Behavioral
Impacts

• Invaders can cause changes in the behavior or
  morphology of natives
• E.g. green crab invaded the NW Atlantic coastline
  preying upon small snails
• They developed thick shells (but at the cost of
  body mass)
• Important?

34
Impacts of InvasionsMorphological and Behavioral
Impacts

• Sometimes the small-scale impacts propagate
  across multiple species
• Impatiens glandulifera was introduced and
  provides good nectar, and lots (10x) of it

35
Impacts of InvasionsMorphological and Behavioral
Impacts

• Visits reduced by 50 and seed set by 25

36
Impacts of InvasionsGenetic and Evolutionary
Impacts

• At the genetic level, hybridization and
  introgression by introduced species can
  fundamentally alter native species fitness or
  create an aggressive hybrid

37
Impacts of InvasionsMorphological and Behavioral
Impacts

• Larvae of the native checkerspot butterfly in NV
  now feed primarily on the introduced European
  narrowleaf plantain rather than the native figwort

38
Impacts of InvasionsMorphological and Behavioral
Impacts

• Percent of checkerspots preferring to oviposit on
  each species, suggesting evolutionary adjustments
  and influencing distribution

39
Impacts of InvasionsEcosystem Impacts

• Certain invaders have a disproportionate effect
  on ecosystem characteristics including habitat
  structure, disturbance regimes and nutrient
  cycling
• The exotic marsh grass Spartina alterniflora was
  introduced in the 1800s via ballasts
• It greatly impacts sediment-deposition rates in
  coastal marshes, impacting clams, anemones, and
  worms

40
Impacts of InvasionsEcosystem Impacts

• The European cheatgrass in N Am prairies, C Am
  grasses in Hawaii, Australian shrub in S Af, all
  are impacting the nutrient cycles and are
  impacting the fuel loads in these systems
  (thereby impacting the frequency and intensity of
  fires)

41
Impacts of InvasionsMeasuring Impacts

• How can we measure the relative impact of
  invaders on a system?
• A useful heuristic approach is as follows
• I is the impact, R is the range is occupies,
  its abundance (A) and its per capita effect (E)
• Combining these I RxAxE
• Remember the 3 ways in which a species can impact
  others

42
Impacts of InvasionsEcosystem Impacts

• Can we predict the spread of a species?
• This represents the speed at which a species may
  spread across the landscape
• It has been surprisingly accurate

dN / dt rN D (d2N / dx2) or c 2vrD
43
Factors influencing the Success

• What species are most successful?
• Which habitats or communities are the most
  vulnerable to invasion?

44
Factors influencing the Success

• Successful invasion can be thought of as a series
  of filters

45
Factors influencing the Success

• Is it important to distinguish a good invader
  from a susceptible community?

46
Factors influencing the SuccessPropagule Pressure

• All invasions require a pathway, which determines
  the propagule pressure (quantity, quality and
  frequency of arriving organisms)
• Two of the most important commonly recurring
  predictors of a successful invader are
  association with human activity and a previous
  history of successful invasion

47
Factors influencing the SuccessPropagule Pressure

• Most invasions start as a relatively small
  population (and all the potential pitfalls and
  shortcoming of associated with it)
• Consequently, the greater propagule pressure, the
  greater the chance of successful establishment
• Is propagule pressure constant across time and/or
  space?

48
Factors influencing the SuccessInvading Species
Characteristics

• Are all species equally likely to invade?
• What are some characteristics of a
  good/successful invader?
• Fast growing and adaptable
• High fecundity, spead vegetatively, broad
  physiographic tolerances, broad diet
• Having said that, many species have these
  characteristics and are not good invaders

49
Factors influencing the SuccessInvading Species
Characteristics

• Attempts have been made to classify attributes of
  many groups
• For woody plants (Table 9.3)
• For fish (table 9.4)

50
Factors influencing the SuccessPropagule Pressure
51
Factors influencing the SuccessInvading Species
Characteristics

• Novelty into the community can also be important
• Consider the richness and stability of
  communities on various sites
• E.g. Mainland vs. Island
• E.g. Reserve site vs. nonreserve sites

52
Factors influencing the SuccessInvading Species
Characteristics
53
Factors influencing the SuccessInvading Species
Characteristics

• Sometimes it can be difficult to determine
  likelihood of success
• E.g. Pacific mudsnail (Batillaria) vs. native
  mudsnail (Cerithidea) had very similar LHC
• Detailed field experiments showed
• Higher density-independent survival
• Higher food conversion efficiency
• Lower susceptibility to parasitic castrating

54
Factors influencing the SuccessInvading Species
Characteristics
55
Factors influencing the SuccessInvading Species
Characteristics

• Computer experiment showing the additive effect
  of competition and parasitism on the persistence
  of the native mudsnail

56
Factors influencing the SuccessInvaded Community
Characteristics

• Not all communities are created equally
• First, climate and habitat must be hospitable to
  potential invaders
• Second, the S, interaction strengths, and trophic
  structure must be able to accommodate the new
  species
• Predict relationship between S and invasibility
  of a community

57
Factors influencing the SuccessInvaded Community
Characteristics

• Results of the biotic resistance hypothesis have
  been mixed (e.g. sedge communities at broad and
  local scales)

58
Factors influencing the SuccessInvaded Community
Characteristics

• A complimentary hypothesis is that disturbance,
  of any kind, may make a community more easily
  invadable (plants)
• Why?
• Resources may become available (e.g. space)
• New condition may not favor natives
• Invaders may alter disturbance regime

59
Factors influencing the SuccessInvaded Community
Characteristics

• First, the disturbance may facilitate invasion
• Are human a pathway or the disturber?

• Disturbance can impact invasions in a couple of
  different ways

60
Factors influencing the SuccessInvaded Community
Characteristics

• However, reserves do have lower introduced
  species relative to nonreserve sites

61
Factors influencing the SuccessInvaded Community
Characteristics

• So what comes first, reserves in undisturbed
  areas or do reserves protects areas from
  disturbance?

62
Factors influencing the SuccessHow are Species
Introduced

• Historically there were many intentional
  introductions (e.g. livestock and crops)
• Diseases and parasites tagged along
• To better control these undesirables, we need to
  understand how they are introduced

63
Factors influencing the SuccessHow are Species
Introduced

• Unintentional Pathways
• With the advent of the Eurasian maritime traffic
  6kya, desireables and undisireables started
  moving
• Many of the old wooden ships might have a
  meter-thick layer of barnacles, mussels,
  tunicates, worms, and hundreds of other species
  associated with these communities

64
Factors influencing the SuccessHow are Species
Introduced

• Deballasting
• Most major invertebrate phlya, as well as algae,
  bacteria and viruses, have all been collected in
  ballast water
• Now ships are bigger and faster

65
Factors influencing the SuccessHow are Species
Introduced

• New routes were constructed to shorten travel
  time
• Suez Canal (Med and Red Sea), Erie and Welland
  Canal (Laurentian GLs and St. Lawrence Seaway),
  Panama Canal

66
Factors influencing the SuccessHow are Species
Introduced

• Sea lamprey have invaded from St. Lawrence Seaway
  and decimated many GL fish populations

67
Factors influencing the SuccessHow are Species
Introduced

• Intentional Pathways
• Agriculture, aquaculture, recreation and
  ornamental purposes are some of the most popular
  reasons for transport
• There have been groups (e.g. Societé Zoologique
  dAcclimatation, and the UK, Russia, NZ)
  advocated mass translocation of wildflowers,
  songbirds, and mammals for food and sport

68
Factors influencing the SuccessHow are Species
Introduced

• Govt agencies have mandated the introduction of
  species, particularly fish
• Amongst the first was the carp (CS 3.1)
• Destruction of macrophytes and H2O clarity
• Unfortunately there are many, many examples of
  poor decisions by governmental agencies

69
Factors influencing the SuccessHow to we Control
Species Invasions?

• Invasion Control
• The concept is extremely simple and
  straightforwardthe implementation of such a plan
  is not
• There are many approaches (e.g. trapping,
  hunting, digging, pulling, burning)

70
Factors influencing the SuccessHow to we Control
Species Invasions?

• Species-based Control
• For a relatively small invasion, physical control
  alone may be adequate
• (control of polychaete worm 1.6M snails)
• Widespread invasion may require a more intense
  approach (e.g. herb- or pesticide)
• See Case Study 9.3
• There is obvious non-target mortality with such
  widespread general agents

71
Factors influencing the SuccessHow to we Control
Species Invasions?

• Species-based Control
• What about biological control?
• Very widespred in agricultural systems
• Frequently nontarget species are the most
  dramatically impacted
• There are promises and pitfalls (CS 9.4)

72
Factors influencing the SuccessHow to we Control
Species Invasions?

• Species-based Control
• For many species, there may need to be several
  approaches
• Some are concerned with the ethics of inducing a
  drug or disease (e.g. blindness, sores, seizures)
• Many prefer sterilizing approaches

73
Factors influencing the SuccessHow to we Control
Species Invasions?

• Policymakers and managers must decide which
  species to focus on

74
Factors influencing the SuccessHow to we Control
Species Invasions?

• Invasion Prevention
• the precautionary principle is a policy of
  guilty until proven innocent
• Preventing invasions requires identifying and
  regulating pathways
• There are several practical approaches
• There are laws (e.g. Lacey Act of 1900 and many
  more)

75
Factors influencing the SuccessHow to we Control
Species Invasions?
76
Factors influencing the SuccessHow are Species
Introduced
77
Factors influencing the SuccessHow are Species
Introduced

• In marine and aquatic systems, the National
  Aquatic Nuisance Prevention and Control Act
  adopts a multi-species approach (largely a result
  of zebra mussels)

78
Factors influencing the SuccessHow are Species
Introduced
79
Factors influencing the SuccessHow are Species
Introduced

• Unfortunately, there is no single agency or
  comprehensive agency in charge
• Thus is remains an open area of political and
  legislative discussion

80
Factors influencing the SuccessHow are Species
Introduced