esa 2013 minneapolis, mn

“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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