Species Diversity in Communities

Photo from Wikimedia Commons

Community Assembly – Ecological Filters

Cain, Bowman & Hacker (2014), Fig. 19.4

Co-occurrence Coexistence

Species “able to persist indefinitely together are deemed to ‘coexist’…”

“If some mechanism promotes the coexistence of two or more species, each species must be able to increase when it is rare and the others are at their typical abundances; this invasibility criterion is fundamental evidence for

species coexistence regardless of the mechanism.”

“some subset of the co-occurring species are either slowly being driven extinct by others in the assemblage… stochastically [drifting] to extinction via

neutral dynamics… or maintained in a local area by dispersal from other areas (i.e., sink populations…)…”

Quotes from Siepielski & McPeek (2010) Ecology

Species-packing mechanismsthat illustrate

“resource-partitioning” or “niche-differentiation”

explanations for differences in diversity

between two sites

Coexistence – Resource Partitioning

Figure from Remsen (1991) Univ. Calif. Publ. Zool.

Coexistence – Resource Partitioning

Species-packing mechanismsthat illustrate

“resource-partitioning” or “niche-differentiation”

explanations for differences in diversity

between two sites

Figure from Remsen (1991) Univ. Calif. Publ. Zool.

Coexistence – Resource Partitioning

Species-packing mechanismsthat illustrate

“resource-partitioning” or “niche-differentiation”

explanations for differences in diversity

between two sites

Figure from Remsen (1991) Univ. Calif. Publ. Zool.

Coexistence – Temporal Variability

Quote from Chesson (2000) Ann. Rev. Ecol. Syst.

G. E. Hutchinson’s (1961) “Paradox of the Plankton” i.e., that many more species of plankton apparently coexist in

lakes than there are limiting nutrients; concluded that plankton rarely achieve equilibrium owing to

ever-changing environmental conditions

Storage Effect“models in which stable coexistence results from environmental fluctuations are

models of temporal niches: species are not distinguished by the resources they use but by when they are most actively using them…”

(Chesson 2000)

Temporal variability can foster coexistence

Coexistence – Intermediate Disturbance Hypothesis

Cain, Bowman & Hacker (2014), Fig. 19.14, after Connell (1978) Science

Disturbance can foster coexistence

Coexistence – Intermediate Disturbance Hypothesis

Cain, Bowman & Hacker (2014), Fig. 19.15, after Sousa (1979) Ecology

Disturbance can foster coexistence

Coexistence – Dynamic Equilibrium Model

Cain, Bowman & Hacker (2014), Fig. 19.12, after Huston (1979) The American Naturalist

Disturbance can foster coexistence

Coexistence – Keystone Predation

Enemies can foster coexistence

“The removal of Pisaster has resulted in a pronounced decrease in diversity… from a 15 to an eight-species system”

Quote from Paine (1966) The American Naturalist; photo of Paine from http://naturalhistoriesproject.org/conversations/anemone-like

Coexistence – Janzen-Connell Model

Enemies can foster coexistence

Adapted from Janzen (1970) The American Naturalist

Coexistence – Facilitators

Cain, Bowman & Hacker (2014), Fig. 19.17, after Hacker & Gaines (1997) Ecology

Positive interactions can foster coexistence

Coexistence – Facilitators

Positive interactions can foster coexistence

Cain, Bowman & Hacker (2014), Fig. 19.18, after Hacker & Gaines (1997) Ecology

Coexistence – Facilitators

Cain, Bowman & Hacker (2014), Fig. 19.19, after Menge & Sutherland (1987) The American Naturalist

A combination of predators and disturbance/stress can foster coexistence

Long-term co-occurrence:Lottery and Neutral Models

Cain, Bowman & Hacker (2014), Fig. 19.20, after Sale (1979) Oecologia

Experimental removal and numbers of replacements by 3 species of fishes

Diversity-Ecosystem Function (e.g., Productivity) Relationships

Cain, Bowman & Hacker (2014), Fig. 19.21A after Tilman & Downing (1994), Fig. 19.21B after Tilman et al. (1996)

Drought resistance (measured as biomass change) in plots that varied in pre-drought

species richness

Separate experiment in which plots were constructed with varying numbers of

species and cover after 2 yr was measured

Cain, Bowman & Hacker (2014), Fig. 19.22, after Peterson et al. (1998) Ecosystems

Diversity-Ecosystem Function

Relationships