American Bison - Buffalo Field Campaign

exchangeability, move beyond traditional trinomial taxonomy
to incorporate evolutionary considerations. Conservation
biologists are reconsidering definitions of conservation units that
incorporate both the history of populations reflected in molecular
analysis, and adaptive differences revealed by life history and
other ecological information (Crandall et al. 2000; DeWeerdt
2002). For example, the geminate evolutionary unit identifies
conservation units that are genetically similar but ecologically
or behaviourally distinct (Bowen 1998). Crandall et al. (2000)
argue for a broad categorisation of population distinctiveness
based on non-exchangeability of ecological and genetic traits.
Each of these concepts presents challenges, as does any
concept that attempts to divide the biological continuum for
the convenience of human interests. Essentially, differentiation
on any level within a species warrants a formal decision
and recognition. Of note, The U.S. Endangered Species Act
recognises this conservation issue and provides for protection
of “distinct population segments”. Similarly, the Committee
on the Status of Endangered Wildlife in Canada (COSEWIC),
which is responsible for assessing the status of wildlife, includes
any indigenous species, subspecies, variety or geographically
defined population of wild fauna or flora as a “species”.
While there appear to be sufficient grounds for formal
recognition of American bison subspecies, the debate may
continue. This, however, should not preclude conservation of
the two forms as separate entities (van Zyll de Jong et al. 1995;
Wilson and Strobeck 1999). Regardless of current genetic,
18 American Bison: Status Survey and Conservation Guidelines 2010
biochemical or other evidence about the subspecies question,
there are notable phenotypic differences, and potentially other
types of variation that may not be detectable with technologies
available at this time. Geneticists predict that genetic analysis in
the future will be able to better identify groupings within species
(Wilson 2001).
Although genetic and morphological evidence often correspond,
this is not always the case (Winston 1999). This can lead to
debate over recognising variation that cannot be measured using
alternative morphological or molecular methods. Nevertheless,
all forms of geographic and ecological variation within a species
contribute to biodiversity (Secretariat of the Convention on
Biological Diversity 2000). All variants of a species may carry
evolutionarily important ecological adaptations (Chapter 4), and
possess the potential to develop genetic isolating mechanisms
leading in evolutionary time to new species (O’Brien and Mayr
1991). Prediction of which variants will evolve to become
species is not possible; this is an outcome of natural selection
and chance. Therefore, to maintain biodiversity and evolutionary
potential, it is important to not dismiss any form of differentiation
within a species, and to maintain the opportunity for evolutionary
processes to function (Crandall et al. 2000). Debating whether a
name is warranted within a relatively arbitrary taxonomic system
does not absolve humans of the responsibility to recognise and
maintain intraspecific diversity as the raw material of evolution.
The risk of losing evolutionary potential suggests it would not be
prudent to prematurely dismiss existing groupings such as the
plains and wood bison.