Island Biogeography & Nutrient Subsidies

Transcription

1 Island Biogeography & Nutrient Subsidies Debora Obrist October 31, 2017 BISC204

2 Outline Island Biogeography Early theories Theory of Island Biogeography Nutrient Subsidies Land sea Sea land The 100 Islands Project

3 Why study islands? Small, simple Visibly discrete boundaries a unit the mind can pick out and understand Natural replication Unique characteristics What does this mean for species?

4 Why study islands? Nesiophilia - the inordinate fondness and hungering for islands, may be a genetic condition. E.O. Wilson

5 Early Theories Buffon s Law (1776): Environmentally similar but geographically isolated regions are comprised of distinct biotas What do you call a species that is unique to a specific geographical location? ENDEMIC SPECIES

6 Early Theories Johann Reinhold Forster (1778): Isolated biotas generally less diverse than mainland Diversity of plants increases with island area, availability of resources, variety of habitats, and heat energy from the sun

7 Number of Species Species Area Curve Why might an island reach saturation for number of species? - Limited number of niches for species to occupy Island Area (m 2 )

8 Log (Number of Species) Species Area Curve Why might an island reach saturation for number of species? Limited number of niches for species to occupy Log (Island Area (m 2 ))

9 Robert McArthur & E. O. Wilson

10 Rate of change in number of species Theory of Island Biogeography Far Near Small Immigration Extinction Large Immigration rate is determined by distance to mainland. Extinction rate is determined by island size. Number of species Intersection tells you the species richness of the island.

11 Rate of change in number of species Theory of Island Biogeography Immigration Extinction Far Large Near Small 0 2 Number of species

12 Rate of change in number of species Theory of Island Biogeography Immigration Extinction Far Large Near Small Number of species

13 Theory of Island Biogeography

14 Theory of Island Biogeography

15 Theory of Island Biogeography

16 Dynamic Equilibrium Species Richness = 2

17 Dynamic Equilibrium Species Richness = 2

18 Dynamic Equilibrium Species Richness = 2

19 Dynamic Equilibrium Species Richness = 2

20 Dynamic Equilibrium Species Richness = 2

21 Dynamic Equilibrium Species Richness = 2

22 Dynamic Equilibrium Equilibrium reached between rate of immigration of new species, and rate of extinction of established species. Determines species richness of island There is constant turnover in species present Before MacArthur and Wilson, it was thought that species richness was static

23 How did they test this? Defaunation experiment by Simberloff and Wilson Methods: Survey small mangrove islands for arthropods. Cover islands with plastic and spray with insecticide (gets rid of all arthropods) Observe colonization/ succession over one year. How many and what species return?

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26 Results Species richness on islands returned to levels similar to before defaunation Closer, larger islands had more species The precise species identity was not consistent, only the total number of species

27 Things we know increase species richness: Larger island size Closer to mainland Productivity Rate of generation of biomass in an ecosystem Measure of amount of energy available

28 Ecosystem Subsidies What is a subsidy? A resource that is passed from one ecosystem to another, increasing productivity of the recipient ecosystem. Organisms Materials (detritus) Nutrients

29 Land Sea Transfers

30 Sea Land Transfers

31 Sea Land Transfers

32 Theory of Island Biogeography

33 Theory of Island Biogeography

34 Theory of Island Biogeography

35 Theory of Island Biogeography?

36 Theory of Island Biogeography

37 The 100 Islands Project

38 The 100 Islands Project

39 The 100 Islands Project

40 Hypothesis In addition to MacArthur and Wilson s predictions, that larger, less remote islands will have higher species richness, islands receiving more marine nutrient subsidies will also exhibit higher species richness than islands receiving fewer.

41 How to test: Indirect test: Look at physical attributes that allow for more nutrient transfer Direct test: Measure amount of sea wrack washing up on shores

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43 Methods

44 Methods Sara Wickham

45 Effect of Island Shape Bird

46 Effect of Island Shape Bird

47 Effect of Sea Wrack Bird

48 Effect of Sea Wrack Bird

49 Conclusions

50 Conclusions

51 Rate of change in number of species How would subsidies affect island equilibrium? Immigration Extinction Number of species

52 Thank you PIs: Dr. John Reynolds Dr. Chris Darimont Dr. Brian Starzomski Spatial Data Team: Dr. Wiebe Nijland Luba Reshitnyk 100 Islands Researchers: Sara Wickham Dr. Crystal Ernst Owen Fitzpatrick Katie Davidson Becky Miller 100 Islands Bird Crew Members: Kate Prince Jeremiah Kennedy Ian Thomas Janine McManus Rob White Blair Dudeck Julian Heavyside Also: 100 Islands field technicians Cal Humchitt Hakai Staff Reynolds Lab Members Earth to Ocean Group Images: Sara Wickham, Kate Prince, Ian Thomas, Brian Starzomski, Wiebe Nijland, Luba Reshitnyk, Blair Dudeck, Alan Schmierer, Fred Hochstaeder, Michael Coghlan, Ben M, Bryce Mullet, Kirt L. Onthank, JR Guillaumin Moucheron