The value known as "mean kinship" (MK) describes
the overall degree of
relatedness of a given individual to the remainder of the captive population.
Therefore, a wild-caught individual that has not yet bred has a mean kinship of
O.O, while an individual that has a large number of líiving offspring has a
relatively higher MK value (up to a theoretical maximum of 1.0). The table above
indicates those wild-caught individuals that should be given high priority for
breeding: those animals with a mean kinship value of O.O and that are relatively
young adults that will have a higher probability of breeding success. A brief
analysis of the table indicates that individuals with studbook numbers 48 and 49
satisfy these criteria. Fortunately, both of these animals are in Guatemala, so this
will facilitate a successful pairing. These factors are very commonly considered in
many captive population management plans and can serve as the basis for very
effective genetic and demographic management of captive populations.
Finally, it is important to recognize that a total of three litters have come from
inbred mating. While this is not a particularly high frequency of inbreeding, there
could be more inbred litters produced in the future as the overall captive population
becomes more related through the continued skewed genetic representation of wild-
caught individuals. Again, relatively simple computer methods of studbook
analysis can be used to calculate the current levels of inbreeding among living
animals and, more importantly, the inbreeding coefficient that can be expected
from potential mating designed by population managers.
We hope that this brief summary of the analysis of the captive Mesoamerican
jaguar population provides a broad summary of the genetic status of the population,
and demonstrates the valuable and sophisticated tools available for effective
genetic management of captive populations. Experienced use of these tools can
provide very valuable guidance for the population manager as mating are designed
to maximize the amount of genetic variation derived from the wild population.
Appendix I:
Simulation Modeling and Population Viability Analysis
A model is any simplified representation of a real system. We use models in all
aspects of our lives, in order to: (1) extract the important trends from complex
processes, (2) permit comparison among systems, (3) facilitate analysis of causes
of processes acting on the system, and (4) make predictions about the future. A
complete description of a natural system, if it were possible, would often decrease
our understanding relative to that provided by a good model, because there is
"noise" in the system that is extraneous to the processes we wish to understand. For
example, the typical representation of the growth of a wildlife population by an
annual percent growth rate is a simplified mathematical model of the much more
complex changes in population size. Representing population growth as an annual
percent change assumes constant exponential growth, ignoring the irregular
fluctuations as individuals are born or immigrate, and die or emigrate. For many
purposes, such a simplified model of population growth is very useful, because it
captures the essential information we might need regarding the average change in
population size, and it allows us to make predictions about the future size of the
population. A detailed description of the exact changes in numbers of individuals,
while a true description of the population, would often be of much less value
because the essential pattern would be obscured, and it would be difficult or
impossible to make predictions about the future population size.
In considerations of the vulnerability of a population to extinction, as is so often
required for conservation planning and management, the simple model of
population growth as a constant annual rate of change is inadequate for our needs.
The fluctuations in population size that are omitted from the standard ecological
models of population change can cause population extinction, and therefore are
often the primary focus of concern. In order to understand and predict the
vulnerability of a wildlife population to extinction, we need to use a model which
incorporates the processes which cause fluctuations in the population, as well as
those which control the long-term trends in population size (Shaffer 1981). Many
processes can cause fluctuations in population size: variation in the environment
(such as weather, food supplies, and predation), genetic changes in the population
(such as genetic drift, inbreeding, and response to natural selection), catastrophic
effects (such as disease epidemics, floods, and droughts), decimation of the
population or its habitats by humans, the chance results of the probabilistic events
in the lives of individuals (sex determination, location of mates, breeding success,
survival), and interactions among these factors (Gilpin and Soulé 1986).
Models of population dynamics which incorporate causes of fluctuations in
population size in order to predict probabilities of extinction, and to help identify
the processes which contribute to a population's vulnerability, are used in
"Population Viability Analysis" (PVA) (Lacy 1993/4). For the purpose of
predicting vulnerability to extinction, any and all population processes that impact
population dynamics can be important. Much analysis of conservation issues is
conducted by largely intuitive assessments by biologists with experience with the
system. Assessments by experts can be quite valuable, and are often contrasted
with "models" used to evaluate population vulnerability to extinction. Such a
contrast is not valid, however, as any synthesis of facts and understanding of