The impact of regional diversity on local diversity: an experimental test

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The impact of regional diversity on local
diversity an experimental test
Brian Starzomski School for Resource and
Environmental Studies Dalhousie University
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Two parallel lines of thought in Ecology
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Two parallel lines of thought in Ecology Local
control -competition -predation Major work
MacArthur and Levins 1967
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Two parallel lines of thought in Ecology Local
control -competition -predation Major work
MacArthur and Levins 1967 Regional
control -dispersal -patch dynamics -mass
effects -evolution Major work MacArthur and
Wilson 1967
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Two parallel lines of thought in Ecology Local
control -competition -predation Major work
MacArthur and Levins 1967 Regional
control -dispersal -patch dynamics -mass
effects -evolution Major work MacArthur and
Wilson 1967 Known as MacArthurs
Paradox -- MacArthur 1972, Schoener
1983
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Local Control
Regional Control
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Ricklefs 1987
Terborgh and Faaborg 1981
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Local Control
Regional Control
Expect this if local processes dominant
Expect this if regional processes dominant
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Experimental test
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Tullgren funnel
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Experimental test
4 regional richness treatments 10 samples in time
(16-Jun-03 to 23-Aug-04) 3 replicates of each
regional richness treatment
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Region collections
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Region collections
y 22.87x 61.97 R2 0.74
Starzomski, Parker Srivastava 2008 Ecology
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Region collections
ANOSIM R 0.797 Sig. 0.1
Starzomski, Parker Srivastava 2008 Ecology
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Samples in time

• 10 Samples in Time
• 2 weeks- 16-Jun-2003
• 8 weeks- 28-Jul-2003
• 16 weeks- 22-Sep-2003
• 32 weeks- 12-Jan-2004
• 48 weeks- 4-May-2004
• 64 weeks- 23-Aug-2004

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Transitory coexistence
Early competitive effects
Competition for resources
Local species richness
Colonization effects
Community assembly time
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• N 44 60 samples
• Total number of morphospecies 234
• Total number of individuals 20079 32718

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Local Richness vs Time Graph
F6,76 20.74, p lt 0.0001
Starzomski, Parker Srivastava 2008 Ecology
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Local Richness vs Time Graph
neither regional richness nor composition
determined changes in local richness over time
(2-way ANOVA F3,56 0.85, p 0.47 for Number
of sites X Time F9,70 0.82, p 0.60 for
Identity of site X Time).
F6,76 20.74, p lt 0.0001
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Local vs Regional Graph
12 January 2004
23 August 2004
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Local vs Regional Graph
12 January 2004
23 August 2004
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Local vs Regional Graph

• What does happen here, however
• big difference between wet and dry seasons
• communities change dramatically
• wet winter and dry summer- drives the relationship

12 January 2004
23 August 2004
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Seasonality

• divided into
• wet season (September through April)
• dry season (May through August)

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Seasonality

• divided into
• wet season (September through April)
• dry season (May through August)
• Local species richness was affected by the
  composition of the original regional community in
  the wet season (ANOVA, F9,14 2.89, p 0.04),
  though not in the dry season (F9,49 0.55, p
  0.83).
• By contrast, local richness was not affected by
  the regional richness treatments in either the
  wet (F3,20 1.10, p 0.31), or dry season
  (F3,55 0.75, p 0.39).

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Seasonality

• divided into
• wet season (September through April)
• dry season (May through August)
• Effectively
• Species can aestivate until the conditions
  improve, and move from region to local
• Seasons reset the community dynamics

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Conclusions

• No good relationship between local and regional
  richness
• Seasonality can change local richness more than
  either local or regional influence
• Regional composition control is important, but
  seen through a seasonal filter different
  communities present in the regional pool make up
  wet and dry season communities

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Acknowledgements

• Diane Srivastava
• Raenelle Parker
• Aimée Pelletier
• Ben Gilbert
• Jackie Ngai
• Derek Tan
• Jon Shurin
• Ross Thompson
• NSERC