SLIDE 1
Native species: Native species: Squirreltail Squirreltail - - PowerPoint PPT Presentation
Native species: Native species: Squirreltail Squirreltail - - PowerPoint PPT Presentation
Native species: Native species: Squirreltail Squirreltail Squirreltail Squirreltail ( Elymus elymoides ) ( Elymus elymoides ) Invasive species: Invasive species: Cheatgrass Cheatgrass Cheatgrass Cheatgrass ( Bromus tectorum ) ( Bromus
SLIDE 2
SLIDE 3
- E. A. Mordecai, unpublished
SLIDE 4
Competition between diatoms A i ll f Synedra ulna Asterionella formosa Cyclotella meneghiniana
SLIDE 5
A longstanding theoretical result: g g Number of species ≤ number of limiting factors
Volterra 1928, Levin 1970
SLIDE 6
A longstanding theoretical result: g g Number of species ≤ number of limiting factors Limiting factors include:
- resources (food space)
- resources (food, space)
- physical factors (temperature, pH)
- other species
Volterra 1928, Levin 1970
SLIDE 7
Models: Number of species ≤ number of limiting factors N t N b f i b f li iti
Photo credit oceanworld.tamu.edu
Nature: Number of species >> number of limiting resources
- G. Evelyn Hutchinson (1961): “The paradox of the plankton”
SLIDE 8
What’s missing?
- Spatial heterogeneity (Tilman 1982, Tilman & Pacala 1993)
T hi ( d ) (J 1970 H l 1984)
- Trophic structure (predators) (Janzen 1970, Holt 1984)
- Recruitment limitation (Levins & Culver 1971, Hastings 1980)
- Non‐equilibrium dynamics (Armstrong & McGehee 1980)
- Movement behavior (Abrams & Wilson 2004)
E i t l fl t ti (Ch 1994)
- Environmental fluctuations (Chesson 1994)
- Differences among individuals (Clark et al 2007)
SLIDE 9
Peter Chesson, 2000. “Mechanisms of maintenance of species diversity” Annual Reviews of Ecology and Systematics diversity . Annual Reviews of Ecology and Systematics Species will coexist if each species has a positive growth rate when rare. “Mutual invasibility.” equalizing mechanisms are those that reduce fitness q g differences between competitors. stabilizing mechanisms are those that cause a species stabilizing mechanisms are those that cause a species population growth rate to increase when rare. (a common example might be niche differences). destabilizing mechanisms are those that cause a species population growth rate to increase when common. p p g
SLIDE 10