Reclassification ‘a risk’ to wildlife
determines the underlying health and long-term survival of a population.
Populations with higher genetic diversity have more options (different alleles) for adapting to ever-changing environmental conditions.
“Genetic diversity is, therefore, essential for the evolutionary process of natural selection to occur. However, if only the so-called ‘best’ alleles (from a game breeders’ perspective) are passed on to each successive generation, it would eventually lead to a population with reduced genetic diversity.”
The current National Environmental Management: Biodiversity Act Threatened or Protected Species regulations controls breeding of the listed species to safeguard their gene pool for the long-term conservation of wild populations. “However, intensive breeding through artificial (non-random) selection of individuals for commercially valuable traits (eg horn size/ shape, coat colour) represents humans taking over this natural process.
“Such artificial selection by humans is even more powerful than natural selection in creating distinct phenotypes within very short time frames ... Intensive and semi-intensive breeding invariably leads to small isolated (closed) populations because it’s the quickest way to produce a desired phenotype.
“These populations lose genetic diversity through artificial selection for the so-called superior traits, as well as through genetic drift (a consequence of small populations) and lack of gene flow (a consequence of isolation).
“The full negative impact of reduced population genetic diversity then becomes clear as most individuals in the population become so closely related that they all possess the same lethal or deleterious allele copies for the same genes.”
This increases the chance that an individual will receive harmful copies of a gene from both parents in a phenomenon known as inbreeding depression.
Intensive and semi-intensive breeding often leads to hybridisation because individuals from other parts of the species range (other subspecies), or other closely related species, are also present on the same land.
This is a common in SA. “Although hybridisation is the opposite of low genetic diversity and inbreeding, as it leads to increased genetic diversity, its negative consequences for longterm population survival should not be understated.” Attempting to increase population genetic diversity on wildlife reserves in this way is unethical.
“While managed gene flow may be required, and even essential, to maintain long-term genetic diversity of many wild large mammals, gene flow between evolutionary divergent populations can disrupt local adaptability and lead to the loss of unique alleles in receiving populations.
“It is disingenuous to claim that genetic diversity of intensively managed populations can be maintained through translocations if, in reality, the translocations are undermining locally evolved adaptive traits. Hybridisation between species, or very distantly related subspecies, compounds this effect even more because the hybrid will not be adapted to either parental environment, which leads to reduced fitness and survival.”
The authors state that a “logical end point of this legislation is that we will have two populations of each species: one wild and one domesticated. We suggest that maintaining this distinction will be expensive, if it is actually possible.”
This week, the Conservation Action Trust reported that the Department of Agriculture ignored the recommendations of the government’s own scientific authority, which warned against intensively breeding wildlife species.