Transcript
Limits to plant diversity: an experimental decoupling of local and regional control
Rachel M. Germain1, Sharon Y. Strauss2, and Benjamin Gilbert1
1. Dept. Ecology & Evolutionary Biology, University of Toronto; 2. Dept. Ecology & Evolution, UC Davis
A metacommunity perspective of diversity
diversity ~ local processes + regional processes + their interaction
Metacommunity diversity
Modified from Leibold et al. 2004 EcoLett
Species sorting Source-sinkDispersal limitation
Identifying the processes that structure metacommunity diversity is challenging, because different processes can lead to similar outcomes
dispersal
Manipulating dispersal in a natural system
Speciesmixer
? ?
? ?
Diversity responses to the removal of dispersal limitation
Species sorting
Loca
l div
ersit
y
small large
Loca
l div
ersit
y
small large
Spatial scale of mixing
Spec
ies-
envi
ronm
ent
rela
tions
hips
small large
Spatial scale of mixing
Spec
ies-
envi
ronm
ent
rela
tions
hips
small large
Source-sink
?
?
Dispersal limitation
Loca
l div
ersit
y
small large
Spatial scale of mixing
Spec
ies-
envi
ronm
ent
rela
tions
hips
small large
Research questions1. Which metacommunity process best explains
diversity patterns in natural communities?
2. How does removing dispersal limitation at multiple scales affect metacommunity diversity?
: McLaughlin
serpentine metacommunity ▪ water limited ▪ many annual species
Experimental design: seed vacuuming procedure
Vacuuming procedure modified from Coiffait-Gombault et al. 2010 Restor Ecol
Environmental parameters were measured concurrent to the community survey
% soil moisture
Experimental design: plot locations
1 m 5 m 100 m 5 km 10 km
Each plot in a block received seed that were mixed from plots at five different spatial scales (the other three plots were control plots)
30 serpentine sitesarranged in six clusters offive sites
Each site contained a block of eight 0.75 x 0.75 m plots
Spatially nested plot arrangement
1 m = essentially natural diversity patterns 10 km = dispersal limitation completely removed
1 m5 m100 m5 km10 km
1 m
Result 1: Plot-level species richness increased with the spatial scale of seed mixing
lmer(species richness ~ treatment + (1|site))
NS
NS
Result 2: Community composition shifted with the spatial scale of seed mixing
1 m5 m100 m
10 km5 km
Example of spatial scaling effects on diversity
1 m 10 km
Plantago erectaHemizonia congestaMicroseris douglasiiLepidium nitidium
Plantago erectaHemizonia congestaMicroseris douglasiiLepidium nitidium
Rigiopappus leptocladusLasthenia califoricaCollinsia sparsifloraLotus wranglianus
What can the effects of removing dispersal limitation reveal about the specific metacommunity class that structures diversity?
Result 3: Species-environment associations increase with the spatial scale of seed mixing
5 km
100 m
Result 4: Species composition shifts with % soil moisture
0.45 0.35 0.05 0.20 0.20 R2
1 m5 m
10 km
lmer(axis scores ~ % sm *treatment + (1|site))
5 km
Community level
Species- vs. community-level environmental associations
1 m5 m100 m
10 km5 km
1 m
Species level
P = 0.011
0%
Even in communities with strong environmental determinism, dispersal limitation can still be widespread
Summary of results
Diversity increases non-linearly with the spatial scale of removed dispersal
Species-environment associations increase with the scale of the species pool
x x
The shifting importance of metacommunity processes with spatial scale of dispersal removal
1 m 5 m 100 m 5 km 10 km
dispersal limitation source-sink species sorting
Figure modified from Bell & Lechowicz 1991 JEcol
x x
The shifting importance of metacommunity processes with spatial scale of dispersal removal
1 m 5 m 100 m 5 km 10 km
dispersal limitation source-sink species sorting
suitable
Figure modified from Bell & Lechowicz 1991 JEcol
AcknowledgementsThe Gilbert LabThe Strauss lab
Susan HarrisonCaprice LeeErica CaseStella CopelandBrian Anacker
Webpage: rgermain.wordpress.com Email: rachel.germain@mail.utoronto.ca
Paola ArenasLaurren SergisonKate LeCroy
Cathy Koehler
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