Clements argued that these climax
communities were bound together
and could be thought of as single,
complex organisms.
Clements was soon challenged
by American botanist Henry
Gleason, who agreed that plant
communities could be mapped, but
argued that since individual plant
species have no common purpose,
the idea of integrated communities
was invalid. His view found support
in the 1950s, in the field studies of
Robert Whittaker and the numerical
research of John Curtis.
In 1967, American ecologist
Richard Root proposed the idea of
the “guild,” a group of organisms—
closely related or otherwise—that
exploit the same resources. Later,
ecologists James MacMahon and
Charles Hawkins refined the
definition of a guild to speciesthat “exploit the same class
of environmental resources,”
regardless of how they do it.New ideas
Many new ideas enriched the
study of ecology in the late 20th
and early 21st centuries. The
metapopulation concept was
advanced by the Finn Ilkka Hanski,
who argued that a population of
a species is made up of differing,
dynamic components. One part of
a population may become extinct,
while another thrives. The thriving
element may subsequently help
reestablish the population that has
died out.
In the process, British ecologist
John Odling-Smee argued, so-called
“niche-constructor” species create
a more favorable environment for
themselves—as seen in countlessORGANISMS IN A CHANGING ENVIRONMENT
1967
The concept of the
“ecological guild” is
introduced in Richard
B. Root’s thesis on the
blue-grey gnatcatcher.1976
Robert May applies
chaos theory to
predicting rates of
growth and decline in
animal population
dynamics.2004
Mathew Leibold’s
“metacommunities”
concept looks at how
populations of a single
species disperse
and interact.1975
Citizen science
enables Fred and Norah
Urquhart to discover
where monarch
butterflies go in winter.1988
John Odling-Smee
suggests that “niche
constructors” actively
change their environment.1991
Ilkka Hanski outlines
his metapopulation
theory for species in
fragmented habitats.161
1989
James H. Brown and
Robert Maurer devise the
concept of macroecology,
in which ecological
patterns are analysed
across large areas.1957
The first satellite goes
into space, heralding
new technologies in
wildlife tracking.examples, from ancient oxygen-
producing cyanobacteria that altered
the composition of the atmosphere
in prehistoric times, to beavers
creating wetlands.Modern methods
Traditionally, the task of monitoring
environmental change has been
the responsibility of academics
and professional ecologists, but
millions of interested amateurs now
provide enormous amounts of raw
data on everything from flowering
dates to butterfly numbers, and
from the state of coral reefs to the
breeding populations of birds. With
computer power to quickly process
vast amounts of data, and with
Earth’s ecology changing faster
than ever, this “citizen science”
looks set to become an invaluable
resource for ecology. ■US_160-161_Ch_6_Organisms_in_a_Changing_Environment_Intro.indd 161 12/11/18 6:25 PM