Community ecology: History and theory
Dr. Dan Simberloff
region
landscape
ecosystem
community
population
Main goal of community ecologists: to
understand why particular species do or do
not coexist in the same community, and to
relate this to how many species are in a
community.
Series of related theories or ideas based on
the notion that species that are very similar
cannot coexist in the same local community.
Definition and measurement of “similarity”
varies, as does meaning of “very.”
a) Darwin’s naturalization hypothesis
In The Origin of Species, Darwin (1859) drew attention to observations
by Alphonse de Candolle (1855) that floras gain by naturalization far
more species belonging to new genera than species belonging to
native genera. Darwin (1859, p. 86) goes on to give a specific example:
“In the last edition of Dr. Asa Gray's `Manual of the Flora of the United
States' … out of the 162 naturalised genera, no less than 100 genera
are not there indigenous.”
“As the species of the same genus usually
have, though by no means invariably, much
similarity in habits and constitution, and
always in structure, the struggle will generally
be more severe between them” (Darwin
1859, p. 60).
a) Darwin’s naturalization hypothesis
b) species/genus ratios and related
statistics – islands
Charles Elton
1927
1958
Letter from Charles Elton to Aldo Leopold, 1941
1946, J. Anim. Ecol. 15:54
a) Darwin’s naturalization hypothesis
b) species/genus ratios and related
statistics - islands
c) Gause’s competitive exclusion principle
Georgyi Gause
1910-1986
1934
G. Gause, 1930s,
experiments on
Paramecium and
yeast.
Joseph Grinnell, 1904: "Two species of approximately the same food habits are not likely to
remain long evenly balanced in numbers in the same region. One will crowd out the other.”
(Image from: http://www.slideshare.net/docsawyer/11-ecology)
1934
(Images from: https://www.studyblue.com/notes/note/n/exam-3/deck/15957221)
(Images from: https://www.studyblue.com/notes/note/n/exam-3/deck/15957221)
Ecology 1958
by D. Kaspari
a) Darwin’s naturalization hypothesis
b) species/genus ratios and related
statistics - islands
c) Gause’s competitive exclusion principle
d) limiting similarity
- invasion
Robert MacArthur
1930-1972
Richard Levins
1930 -
“species packing”
2 species can coexist only if α (the per capita effect of each species on the other)
is less than 0.544. And a 3rd species can invade only if its α with each of the
2 existing species is less than 0.544.
Key results:
1) Harder for a new species to
invade a community the more
species are originally present.
2) A species that would be a
superior competitor if it invaded
cannot invade if α among
resident species is high enough
3)
“PRIORITY EFFECT”
a) Darwin’s naturalization hypothesis
b) species/genus ratios and related statistics - islands
c) Gause’s competitive exclusion principle
d) limiting similarity - invasion
e) priority effects
Jim Drake
Tad Fukami
“priority effects” = “historical contingency”