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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
Coexistence – Resource Partitioning
Species-packing mechanisms
that 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 mechanisms
that 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 mechanisms
that 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
Temporal variability can foster coexistence
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
Photomontage of plankton from Wikimedia Commons
Coexistence – Temporal Variability
Temporal variability can foster coexistence
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)
Quote from Chesson (2000) Ann. Rev. Ecol. Syst.
Coexistence – Intermediate Disturbance Hypothesis
Disturbance can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.14, after Connell (1978) Science
Coexistence – Intermediate Disturbance Hypothesis
Disturbance can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.15, after Sousa (1979) Ecology
Coexistence – Dynamic Equilibrium Model
Disturbance can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.12, after Huston (1979) The American Naturalist
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 Pisaster consuming a Mytilus from Wikimedia
Commons; 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
Positive interactions can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.17, after Hacker & Gaines (1997) Ecology
Coexistence – Facilitators
Positive interactions can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.18, after Hacker & Gaines (1997) Ecology
Coexistence – Facilitators
Positive interactions can foster coexistence
“reefs with (closed symbols) and
without (open symbols) cleaner fish at
Casuarina Beach (circles) and Lagoon
(squares) sites
Figure from Grutter et al. (2003) Current Biology; photo of cleaner wrasse & client from Wikimedia Commons
Coexistence – Facilitators
A combination of predators and disturbance/stress
can foster coexistence
Cain, Bowman & Hacker (2014), Fig. 19.19, after Menge & Sutherland (1987) The American Naturalist
Long-term co-occurrence:
Lottery and Neutral Models
Experimental removal and numbers of replacements by 3 species of fishes
Cain, Bowman & Hacker (2014), Fig. 19.20, after Sale (1979) Oecologia
Diversity-Ecosystem Function
(e.g., Productivity) Relationships
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. 19.21A after Tilman & Downing (1994), Fig. 19.21B after Tilman et al. (1996)
DiversityEcosystem
Function
Relationships
Cain, Bowman & Hacker (2014), Fig. 19.22, after Peterson et al. (1998) Ecosystems