Download Slides

Restoration Ecology, Part 2
Lecture 19
Spring 2014
1
Restoration Ecology
Major questions:
• Will an ecosystem return to the same ecosystem
after disturbance?
– Succession
• How is balance maintained in food webs?
– bottom up vs. top down models
– Competition & predator-mediated co-existence
• What are invasive species, how do they affect
ecosystems and, should they always be
removed?
• What makes an ecosystem resilient?
• Which is more important to consider; species
diversity or functional groups?
Biological Diversity
Species diversity: variety of species in an area;
includes
• Species richness
– Total number of different species in a
community
• Species evenness (relative abundance)
– The proportion each species represents of the
total number of individuals in the community
3
Species Diversity
Which community is
more diverse?
Fig. 54.10
4
5
Biodiversity “Hot Spots”
See IG 9.5
Endemic species
A species found only one location in the world
6
Genetic Diversity
• Do subspecies
matter?
7
Restoration Ecology: Diversity & Functional
Groups
Functional groups
• Groups of species that have the same
function within an ecosystem
Functions?
8
Functional Group: Seed Dispersers
• Is functional equivalency sufficient?
• Case study: seed dispersal
– Frugiverous animals
• Transport seeds long
distances
• Scarification
9
Functional Group: Seed Dispersers
Hypotheses:
• Plants whose seed dispersers go extinct will also
go extinct
• “megafaunal-syndrome”: plants with very large
fruits and seeds may have evolved to attract the
megafauna to consume and (often exclusively)
disperse them
10
11
Functional Group: Seed Dispersers
• Seed size decline in palms
– Loss of large, large-gaped frugiverous birds
– Smaller seeds, lower survival
Functional Group: Seed Dispersers
• Re-caching by rodents
– Seed predators
12
13
Functional Group: Seed Dispersers
• Replacement of extinct
Mauritian tortoises with
Aldabran tortoises
Functional Group: Seed Dispersers
Spurge olive
• Seeds dispersed to
different habitat
Lilford's Wall Lizard
Pine marten
14
Symbiotic Relationships
Symbiosis – intimate living
together of members of two
or more species.
• Mutualism
• Parasitism
– pathogen
• Commensalism
Fig. 54.8
15
Interactions between Species
Species A
Predation
Herbivory
Competition
Mutualism
Parasitism
Commensalism
+
+
+
+
+
Species B
+
0
16
17
Species Interactions
Competition
• Attempts by two or more individuals to use
the same limited resources in an
ecosystem
• Interspecific (between different
species)
• Intraspecific (within same species)
• -/- species interaction
Avoiding competition
Resource partitioning or
Niche differentiation
• Species evolve more
specialized traits that
allow them to use shared
resources differently
18
Avoiding competition
Generalists: Broad ecological niche
Examples?
Specialists: Narrow ecological niche
Examples?
19
20
Predator-Mediated Coexistence
• When the presence of a predator allows
for the coexistence of two (or more)
competing species in a community
• Increases species diversity
Predator-Mediated Coexistence
Observation
• Mytilus (mussel) is most abundant
species
• Many other species present, but in
much lower abundance
• Pisaster (sea star) feeds on Mytilus
Hypothesis
• Pisaster is a keystone species that
allows for greater species diversity
in community
21
Predator-Mediated Coexistence
Test
• Remove Pisaster from
some areas
Results
• Species richness
decreased in areas with no
Pisaster
Conclusion
• Pisaster allows for coexistence of competing
species
22
See Fig. 19.14
23
Competition Examples
Invasive species
1) non-native (or alien) to the ecosystem
under consideration and
2) whose introduction causes or is likely to
cause economic or environmental harm or
harm to human health.
Invasive species & competition
Zebra Mussel (Dreissena
polymorpha)
• Native to Russia
• Introduced to U.S. in 1988 by
ballast water
• Huge number of offspring
• Competes for space
24
25
Invasive species & competition
North American gray squirrel
vs. red squirrel in Britain
• N.A. gray squirrel
introduced early 19th C
• Larger, more aggressive
• Can eat newly fallen
acorns
26
Restoration Ecology & Invasive Species
• Removal of invasive organisms
• Restoring native organisms
– Or functional equivalents
• Ongoing Management
27
Invasive species & competition
Saltcedar or Tamarisk
(Tamarix spp.)
• Introduced to
Southwestern U.S. ~
1850s
• Forms monospecific
stands
• Outcompetes native
plants for water
28
Restoration Case Study: Santa Cruz
Island
• Channel Islands
“Galapagos of North
America”
• Many endemic species
• Invasive Species
– Sheep & pigs introduced
in mid-1800s
– Golden Eagle - 1990s
29
Restoration Case Study: Santa Cruz
Island
• Restoring native
organisms
– Santa Cruz island fox
– Bald Eagle
Invasive Species & Biological Control
•
Biocontrol
– Reduction of an invasive species by using
its natural enemies
– Introduction of a new species
•
Goal
– Reduce rather than eradicate
30
Invasive Species & Biological Control
•
Criteria
–
–
–
–
–
–
Narrow host range
Climatic adaptability
Synchrony with host (prey) life cycle
High reproductive potential
Efficient search ability
Survival at low host (prey) density
31
32
Invasive Species & Biological Control
• Extensive testing
• Possible outcomes
– No sustainable population
– Sustainable population, but limited control
– Sustainable population, successful control
– Host switch
33
Invasive Species & Biological Control
• European rabbits
introduced to Australia in
1859
Biocontrol
• Myxomatosis virus
(1950s)
– Resistance rabbits
– Evolution of less virulent
strains
• European rabbit
calicivirus disease (RCD)
or rabbit haemorrhagic
disease (RHD), (1995)
Invasive Species & Biological Control
• Purple loosestrife (Lythrum
salicaria)
• Introduced to US in 1800s
– Native to Europe & Asia
– Ballast water
• Impacts
– Disrupts hydrological cycle
– Displaces native birds and
plants
• Biocontrol: Leaf beetle
(Galerucella calmariensis)
34
35
Restoration Ecology
When is an ecosystem considered restored?