Post on 25-Jan-2015
description
“As species of the same genus usually have some similarity in habits and structure, the struggle will generally be more severe between species of the same genus.”
C. Darwin 1859
Environmental filteringCompetitive interactions
Over-dispersion Under-dispersion
Webb et al. 2002 Annu Rev Ecol Syst
Vamosi et al. 2009 Mol Ecol
Environmental filteringCompetitive interactions
Over-dispersion Under-dispersion
Webb et al. 2002 Annu Rev Ecol Syst
Phylogenetic dispersion patterns vary widely from study to study
Vamosi et al. 2009 Mol Ecol
Adler et al. 2006: Species differences both promote and deter coexistence
NICHE DIFFERENCESPROMOTE COEXISTENCE
FITNESS DIFFERENCESDETER COEXISTENCE
Adler et al. 2006 Ecol Lett
Evolutionary trajectories of niche (α) to fitness (λ) differences
1
Phylogenetic distance
Coex
iste
nce
met
ric
(Δα/
Δλ)
COEXISTENCE ZONE
EXCLUSIONZONE
Mayfield and Levine 2010 Eco Lett
Evolutionary trajectories of niche (α) to fitness (λ) differences
Coex
iste
nce
met
ric
(Δα/
Δλ)
COEXISTENCE ZONE
EXCLUSIONZONE
Phylogenetic distance
Exotics?
Mayfield and Levine 2010 Eco Lett
1
How do species interactions and biogeography combine to regulate
diversity?
I hypothesize that niche and fitness evolution depends on biogeographic origin
sympatric
allopatric
Niche difference Fitness difference
BEASTITS1/5.8S/ITS2 regionrelative time tree
Bayesian tree
Spain
California
Biogeographic origin
Estimating niche and fitness differences
Niche pots Fitness pots
Adler et al. 2006 Ecol Lett
− 20 pairwise combinations− density ~70 individuals
− each species grown alone at low density
BEASTITS1/5.8S/ITS2 regionrelative time tree
Bayesian tree
Spain
California
Biogeographic origin
Pairs of competitors selected to represent phylogenetic independent contrasts
Beverton-Holt annual plant model
intrinsic growth rate in the absence of competition
Niche difference = avg(αii/αij,αjj/αji) Fitness difference = max(λi,j)/min(λi,j)
intra- and inter-specific competition
There is no relationship between niche difference and phylogenetic distance
Phylo dist: F1,15 = 1.42, P = 0.252; Origin: F1,15 = 0.86, P = 0.370
Cali vs Cali
Cali vs Spain
Fitness differences scale with phylogenetic distance but not biogeographic origin
Phylo dist: F1,13 = 4.87, P = 0.046; Origin: F1,13 = 0.001, P = 0.971
Cali vs Cali
Cali vs Spain
…but, Spanish species have consistently higher fitness than Californian species
Phylo dist: F1,13 = 4.87, P = 0.046; Origin: F1,13 = 0.001, P = 0.971
Cali vs Cali
Cali vs Spain
Pop. growth rates decrease by 43% when focal species are grown with exotic species
F = 45.27, P < 0.001
Summary
• No reason to expect overdispersion via competition – coexistence becomes less likely with phylogenetic distance– factors other than competition may give rise to
overdispersion in nature• e.g., host-specific fungal pathogens
• Species invasions and phylogeny– Strauss et al.: exotic taxa less related to native species are
more invasive
Liu et al. 2012 Ecol Lett
Implications for phylogenetic community assembly
Strauss et al. 2006 PNAS
Moving forward
• But, are these results incompatible with Webb et al.’s original framework?– fitness is shaped in part by the underlying
environment– coexistence may be possible if different species
are favored in different environments
Phylogenetic signal in the change in fitness across environments
Webpage: rgermain.wordpress.comEmail: rachel.germain@mail.utoronto.ca
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