Molecular Genetic Approaches in Wildlife Conservation

*Ranjana Bhaskar and E. Agnita Sharon*

### **Abstract**

Wildlife conservation is of major biological importance due to the survivability of organisms in an ecosystem and population stability. The primary concern of the management and genetics of populations is inbreeding. The small population size can play a diminishing role in genetic variability and increasing inbreeding in animal populations. Inbreeding depression can be due to major factors such as rare, deleterious, recessive alleles which can be repressed under heterozygous conditions. The decreasing effect in heterozygosity can be significant upon severe bottleneck effect. The genetic variations between populations could be assessed using molecular techniques. Mitochondrial DNA variations for determining the founder's effect can be widely applicable in the management of wild populations. The maternal lineages in a captive population can signify the variations in the population as well as the number of males contributing to the gene pool of the various population. Molecular markers can be used to differentiate between populations and identify the individuals contributing to the gene pool of the species.

**Keywords:** genetic biodiversity, populations, inbreeding, mitochondria, evolution

#### **1. Introduction**

Wildlife populations are faced with several anthropogenic pressures such as climate change, habitat fragmentation, destruction of habitat, pollution, the threat of invasive species, harvesting, and ill effects of novel pathogens. This contributes to high extinction and challenges in sustaining wild populations [1]. While habitat fragmentation has been fundamentally the prime concern for conservation research. The evolutionary consequences of fragmentation are underestimated due to a reduction in the levels of gene flow among the formerly connected fragments of the forest. An increase in genetic drift and selection by the evolutionary processes may lead to differentiation among populations would [2]. Increased tendency for genetic differentiation and local adaptation are not considered for resource-based management. Fragmentation of habitat combined with management efforts may create a source or sink dynamics which is vital for selection [3].

The loss of genetic diversity often leads to affect individual fitness and poor adaptability to their surroundings [4]. A small population size is at risk of genetic changes within the population. The captive breeding programs of vulnerable or endangered animals are necessary for their conservation to increase their chances of long-term survival; however, this methodology often increases the chances of inbreeding causing poor fitness in populations [5]. It is under stood that inbreeding causes a decreased genetic diversity and leads to a reduction in reproductive rates resulting in increased extinction or survival risks. To recover genetically impoverished endangered populations, they may breed with individuals from other populations [6]. If genetic diversity is too low any wildlife population can be at a greater risk of extinction [7]. There are many molecular techniques for genetics studies that can reduce the extinction risk by suggesting localized monitoring population and management mechanisms wherever necessary that can reduce the chances of inbreeding. Breeding initiative programs are started assuming that the founders of the captive population are distinct from each other.

#### **2. Wildlife genetics**

Small population size contributes to inbreeding and loss in genetic variation. Thus, the measure of genetic variation in a given population serves as a measure of the extent to which the population is inbred. Effective recombination occurs only in individuals heterozygous at many loci. Inbreeding reduces the frequency of heterozygotes, thereby reducing the effective rate of recombination. Inbreeding causes an increase in homozygosity resulting in increased expression of deleterious effects of recessive homozygous genotypes and decreased frequency of heterozygous combinations which may be over dominant.

Random fluctuation in gene frequencies of alleles resulting in random genetic drift reduces the genetic variation, increasing the homozygosity and the loss of evolutionary adaptability to environmental changes within small populations. The maintenance of genetic variability in a real population can be understood by Wright's concept of effective population size [8]. Populations with different selection effective population sizes are predicted to develop profoundly different genome architectures [9].

#### **3. Genetic variation**

Species in general are a set of individuals that are capable of interbreeding and producing fertile offspring which can be genetically alike. According to Darwinism, the species instead of being constant changes according to its environment causing variation over time. Genetic variation in biodiversity means that variation at all levels of biological organization [10] including diversity within or among species.

Genetic variation in populations results in short-range fitness and long survival rates (population level). Genetic variation is caused due to evolutionary driving forces like natural selection and genetic drift etc. which results in variability among individuals causing differentiation at the population level, species, and higher-order taxonomic groups. The study of variation among individuals, populations, and species is population genetics. Population genetics relates to the analysis of evolutionary and demographic factors affecting the genetic composition of a population [11] increasing the chance of an organism to survive and adjust to the ever-changing environment. However, genetic-based molecular markers are a powerful tool in analyzing the genetic distinctiveness of individuals, populations, or species [12]. For genetic analysis, modern sequence-based marker systems are being used now like single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSRs) [13]. However, for fish

population genetic studies, microsatellites have become the marker of choice [14]. Molecular markers are commonly used for wild-population studies [15].

### **4. Factors of evolution**

Various evolutionary factors such as allele frequency, genetic drift, and mutation are affecting the wildlife populations. The Hardy-Weinberg theory proves that the relative frequencies of several gene alleles in a Mendelian population tend to remain constant [16]. The genotypic variability present in a population is passed on from one generation to the next. Evolution is defined as a change in the genetic composition of populations. If the genes frequencies in populations remained constant that means evolution could not occur.

The genetic forces that modify the gene frequencies in populations


The assumption in the Hardy-Weinberg law is that the population is infinitely large. If the populations are small, it consists of small numbers of breeding individuals which tend to lose genetic diversity. That is true in populations from one generation to other. We assumed that the population is isolated and there is no immigration or emigration that carriers of some genotypes in preference to others. Migration in individuals of genetically diverse populations can increase or decrease the gene frequencies in a population gene pool.

#### **5. Mutants in populations**

In mendelian populations, mutation provides the ultimate source of genetic variation in that no two individuals have the same genotype. Genetic variability owes to mutation, unfixed genes which are represented in a population by two or more alleles. The existence of diverse alleles is because of a genetic mutation which is the fundamental force of evolution. Mutant alleles can persist in the gene pool of a population depending on natural selection for many generations according to Hardy Weinberg's theory [16].

Most mutants that arise naturally in the populations are deleterious mutations and are harmful to the organism; in some cases, they are completely lethal. The accumulation of harmful mutations of hereditary diseases is opposed by natural selection. According to the theory of natural selection which is based that the progeny of any species survives and interbreed and produces a variety of surviving offspring. The population of a species includes genetic variables which occur more or less by natural selection in a given environment [17]. The better-adapted variants will constitute from one generation to another. Artificial selection is also a process similar to natural selection except that the variants leave the larger progeny which is chosen by human beings rather than the environmental factors.
