Restoration Ecology, Part 2 Lecture 19 Spring 2014

Transcription

1 Restoration Ecology, Part 2 Lecture 19 Spring 2014

2 Restoration Ecology 1 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?

3 Biological Diversity 3 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

4 Species Diversity 4 Which community is more diverse? Fig

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6 Biodiversity Hot Spots 6 See IG 9.5 Endemic species A species found only one location in the world

7 Genetic Diversity 7 Do subspecies matter?

8 Restoration Ecology: Diversity & Functional Groups 8 Functional groups Groups of species that have the same function within an ecosystem Functions?

9 Functional Group: Seed Dispersers 9 Is functional equivalency sufficient? Case study: seed dispersal Frugiverous animals Transport seeds long distances Scarification

10 Functional Group: Seed Dispersers 10 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

11 11 Functional Group: Seed Dispersers Seed size decline in palms Loss of large, large-gaped frugiverous birds Smaller seeds, lower survival

12 Functional Group: Seed Dispersers 12 Re-caching by rodents Seed predators

13 Functional Group: Seed Dispersers 13 Replacement of extinct Mauritian tortoises with Aldabran tortoises

14 Functional Group: Seed Dispersers Seeds dispersed to different habitat Spurge olive 14 Lilford's Wall Lizard Pine marten

15 Symbiotic Relationships 15 Symbiosis intimate living together of members of two or more species. Mutualism Parasitism pathogen Commensalism Fig. 54.8

16 Interactions between Species 16 Species A Species B Predation + - Herbivory + - Competition - - Mutualism + + Parasitism + - Commensalism + 0

17 Species Interactions 17 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

18 Avoiding competition 18 Resource partitioning or Niche differentiation Species evolve more specialized traits that allow them to use shared resources differently

19 Avoiding competition 19 Generalists: Broad ecological niche Examples? Specialists: Narrow ecological niche Examples?

20 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

21 Predator-Mediated Coexistence 21 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

22 Predator-Mediated Coexistence 22 Test Remove Pisaster from some areas Results Species richness decreased in areas with no Pisaster Conclusion Pisaster allows for coexistence of competing species See Fig

23 Competition Examples 23 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.

24 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 25 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 26 Removal of invasive organisms Restoring native organisms Or functional equivalents Ongoing Management

27 Invasive species & competition 27 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 28 Channel Islands Galapagos of North America Many endemic species Invasive Species Sheep & pigs introduced in mid-1800s Golden Eagle s

29 Restoration Case Study: Santa Cruz Island 29 Restoring native organisms Santa Cruz island fox Bald Eagle

30 Invasive Species & Biological Control 30 Biocontrol Reduction of an invasive species by using its natural enemies Introduction of a new species Goal Reduce rather than eradicate

31 Invasive Species & Biological Control 31 Criteria Narrow host range Climatic adaptability Synchrony with host (prey) life cycle High reproductive potential Efficient search ability Survival at low host (prey) density

32 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 33 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)

34 Invasive Species & Biological Control 34 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)

35 35 Restoration Ecology When is an ecosystem considered restored?