Different genetics result in subspecies of the same species having slightly different traits and abilities. Wildlife genetics can also bring a population back to life which are near extinct
Over the past decade, wildlife production in South Africa has grown into a significant industry with huge financial investments, as wildlife is now freely available, and not limited to national parks and reserves. The best approach appears to establish a variety of populations of a given species or subspecies in more than one locality to prevent an entire genetic pool from being affected or even exterminated by a catastrophic event, such as exposure to a specific disease. This approach will also encourage the natural distribution of the animals. A nature reserve or wildlife ranch should always be as large and diverse in habitat as possible. It is important to ensure the maintenance of sufficient genetic integrity and heterogeneity, especially for small populations of animals. Furthermore, with the fencing of wildlife ranches, the possibility exists of creating genetic species or subspecies through genetic isolation rather than through reproductive isolation. The following are guidelines to determine the minimum effective size of a wildlife ranch for proper genetic management.
- Identify the key animal species or subspecies, the disappearance of which will decrease the biological diversity of the ranch. Common types of wildlife that may disappear should be given a smaller weight in the decision-making process than the rarer ones.
- Determine the minimum size of the populations that is necessary to ensure the survival and genetic diversity of the species or subspecies.
- Make use of known population densities and calculate the minimum size of the area necessary to accommodate at least a minimum population of that species or subspecies.
- Consider the social behaviour of the species or subspecies to prevent dominant males from killing young animals, as may happen in various wild herbivores, including the white rhinoceros and the sable antelope.
- Prevent competition between ecologically related herbivores that prefer the same type of habitat.
- Prevent the hybridisation of various species and subspecies of herbivores by maintaining genetically viable populations and eliminating closely related groups. For example, do not keep black and blue wildebeest in small numbers on the same wildlife ranch, nor subspecies such as the blesbok and bontebok. Do not allow different subspecies to crossbreed, and do not deliberately propagate colour variants of the same species or subspecies.
Basic Terminology
Some basic genetic terminology which needs to be understood to understand the genetics and breeding of wildlife
Here are some definitions regarding genetic concepts:
- Breeding value: The ability of an animal to transmit certain genetic traits to its offspring. In simple terms, it refers to the value of the animal as a parent.
- Coefficient of inbreeding: a measure of the level of inbreeding in a population, expressed as the expected proportion of homozygous loci in an individual of which both the alleles can be traced back to the same ancestor. This coefficient, therefore, measures the probability that an individual has both the alleles of a pair at a given locus from an identical ancestral source. The effect of a given gene or allele on the phenology of an animal depends upon whether it is dominant or not. The position of an allele on the chromosome is known as its locus
- Ecotype: A subspecific form within a true species, resulting from selection within a particular habitat and therefore adapted genetically to that habitat, but which can interbreed with other members of the species. This is also known as a genetic subspecies.
Difference between genotype and phenotype genes
- Genotype: The genetic composition of an animal. It includes all the genes that are responsible for the survival and production of the animal.
- Phenotype: The appearance of the animal. This can include all observable traits such as coat colour, horns and body conformation, and all the measurable traits such as the weight and height of the animal.
- Inbreeding: the mating of closely related animals, more closely than the mean of the population from which they originate. Inbreeding causes an increase in homozygotes with a higher chance for an animal to receive two recessive genes from the parents for a certain trait. Recessive genes are associated with a decrease in the performance of fitness traits. For example, a decrease in reproduction and survival traits is often referred to as an inbreeding depression.
The homozygous effect of inbreeding demonstrated. (Source: Understanding Evolution)
- Outcrossing: This refers to the mating of two individuals of the same breed who have had no common ancestors for several generations. This contributes to increased genetic diversity and higher resistance to sickness and genetic disorders.
- Outbreeding: Mating done between unrelated animals, which could be members of the same breed who do not share ancestors, members of a different breed, or members of a different species. It boosts genetic diversity in a population and ensures a greater survival rate and adaptability to environmental circumstances.
- Linebreeding: This is a form of inbreeding that attempts to maintain a high frequency of individuals with superior genetic qualities in a population.
Linebreeding example in dogs where new genetic material is introduced with every generation
Example of natural vs artificial selection in nature. (Source: BioDifferences)
- Natural selection: the selection process that allows some individuals to produce viable offspring while other is prevented from doing so. Social behaviour is the driving force in most animals that only allows some individuals in a group to breed. The dominant breeding animals in a social group are known as the alpha animals.
- Artificial selection: This is usually found in intensive production systems where specific individuals are selected for breeding based on their performance traits in producing offspring of an improved or specific quality.
- Genetic selection: selection that is based on the genotypic information of the animal. Genotypic information can only be obtained by performing DNA analyses.
- Phenotypic selection: selection of animals that are based on their superior performance for a specific trait. Performance is usually based on pedigree information and production records which are based on performance traits which can be measured objectively.
- Genetic diversity: This refers to genetic variation that is based on the allelic diversity for a specific trait(s) in a population, species or subspecies.
Genetic diversity can result in diverse phenotypic expression which produces animals of the same species that look different and form separate subspecies
- Genome: the total genetic information of the animal as it is carried on all the chromosomes. Each animal has a specific diploid set of chromosomes (chromosomes in pairs) which is carried in each body cell, except for the sex cells which only have a haploid set (a single set of unpaired chromosomes).
- Selection criteria: Traits that can be measured or quantified, such as weight, height and length, and which are included in the selection programme to reach a breeding goal.
- Breeding goal: The overall aim of what a breeder wants to achieve, such as the improvement of the production of the unit. To achieve the breeding goal, the breeder will set specific criteria or traits, such as horn development and size, colour, or body size in wildlife. All of these must be included in the selection of the founder animals.
- Heritability: The variation resulting from the additive portion of the total phenotypic variation that is inherited by the next generation. Heritability is a population parameter and refers to the traits within the population and not the individual.