PATTERN AND PROCESS IN COMPETITION
5
less constant ratio of components in a continuous flow of materials,
and the system returns to a steady state after a disturbance of stimulus
(Bray, 1958). Nevertheless, is the amount of diversity that exists in
ecosystems essential to the orderly function of its component parts, and
what mechanisms make the diversity possible? It is often observed that
older ecosystems such as those in the tropics are richest in structural
and species diversity, even though the differences in primary productivity between comparable tropic and temperate systems is not great
and may, in fact, be greater in the temperate ecosystem type (Odum,
1959). Bray (1958) advances the hypothesis that re-utilization efficiency
may offset the reduced primary productivity that occurs in the succession from simple to more complex communities. Re-utilization efficiency
reduces the relative loss that may occur through production of nonavailable energy forms and is a function of the number and kinds of
organisms and their ability to create new energy niches and thus increase the number and pathways of energy exchange (Bray, 1958). The
diversification of animal food chains is regarded as an example of this
function.
The most obvious source of species diversity among closely related
forms, or within the assemblage of organisms a t one trophic level, is
through specialization (Klopfer, 1962). Any natural community contains large numbers of specialists as well as more widely adapted nonspecialists, and it is worth noting that this kind of division seems to be
an almost universal phenomenon in every taxonomic group, even
within genera. Curiously enough, the more ubiquitous species have
asserted themselves to only a limited extent. How then does specialization confer a competitive advantage? Even though we tend to accept
the premise that specialization leads to competitive superiority, we
lack empirical evidence to show how this occurs. There is no clear
reason why the widely adapted wood mouse (Apodemus sylvaticus) has
not entirely replaced its cogener, the yellow-necked mouse (Apodemus
Jlavicollis), in Britain, or why Peromyscus maniculatus is not the only
member of this genus in North America. A. sylvaticus would appear to
be able to inhabit every woodland habitat in Great Britain, and there
is no evidence to show that A . Jlavicollis is a more efficient or more
productive species. In the absence of competition from its cogeners the
least chipmunk (Eutamias minimus) can apparently inhabit any environment in which western chipmunks are found, yet there are 16
species of this genus in North America and this more widely adapted
species seems, usually, to be displaced by its cogeners (Sheppard,
unpublished). It is obvious that genetic systems allow a rather wide
range of adaptation - most taxonomic groups contain a complement
of species that are capable of inhabiting a variety of habitats, in addition
5
less constant ratio of components in a continuous flow of materials,
and the system returns to a steady state after a disturbance of stimulus
(Bray, 1958). Nevertheless, is the amount of diversity that exists in
ecosystems essential to the orderly function of its component parts, and
what mechanisms make the diversity possible? It is often observed that
older ecosystems such as those in the tropics are richest in structural
and species diversity, even though the differences in primary productivity between comparable tropic and temperate systems is not great
and may, in fact, be greater in the temperate ecosystem type (Odum,
1959). Bray (1958) advances the hypothesis that re-utilization efficiency
may offset the reduced primary productivity that occurs in the succession from simple to more complex communities. Re-utilization efficiency
reduces the relative loss that may occur through production of nonavailable energy forms and is a function of the number and kinds of
organisms and their ability to create new energy niches and thus increase the number and pathways of energy exchange (Bray, 1958). The
diversification of animal food chains is regarded as an example of this
function.
The most obvious source of species diversity among closely related
forms, or within the assemblage of organisms a t one trophic level, is
through specialization (Klopfer, 1962). Any natural community contains large numbers of specialists as well as more widely adapted nonspecialists, and it is worth noting that this kind of division seems to be
an almost universal phenomenon in every taxonomic group, even
within genera. Curiously enough, the more ubiquitous species have
asserted themselves to only a limited extent. How then does specialization confer a competitive advantage? Even though we tend to accept
the premise that specialization leads to competitive superiority, we
lack empirical evidence to show how this occurs. There is no clear
reason why the widely adapted wood mouse (Apodemus sylvaticus) has
not entirely replaced its cogener, the yellow-necked mouse (Apodemus
Jlavicollis), in Britain, or why Peromyscus maniculatus is not the only
member of this genus in North America. A. sylvaticus would appear to
be able to inhabit every woodland habitat in Great Britain, and there
is no evidence to show that A . Jlavicollis is a more efficient or more
productive species. In the absence of competition from its cogeners the
least chipmunk (Eutamias minimus) can apparently inhabit any environment in which western chipmunks are found, yet there are 16
species of this genus in North America and this more widely adapted
species seems, usually, to be displaced by its cogeners (Sheppard,
unpublished). It is obvious that genetic systems allow a rather wide
range of adaptation - most taxonomic groups contain a complement
of species that are capable of inhabiting a variety of habitats, in addition