Utilization of microsatellite markers in genotyping of Saudi Arabian camels for productivity and conservation

Camels are considered as integral and notable components of the heritage of the Kingdom of Saudi Arabia. Genetic variabilities within and among four camel populations in Saudi Arabia were evaluated using 21 simple sequence repeat (SSR) loci of 122 unrelated individuals, including three indigenous breeds [Humur (HA), Zurg (ZR), Shuguh (SG)] and one exotic breed [Sudanese (SN)]. Nineteen SSR markers generated multilocus fingerprints with a total of 225 alleles, a range of 4–23 alleles per locus, and an average of 9, 7, 7, and 6 alleles per locus in HA, ZR, SG, and SN populations, respectively. The mean multilocus FST value (0.034 ± 0.005) showed non-significant population differentiation. Mean observed heterozygosity values were 0.908 for HA, 0.860 for ZR, 0.919 for SG, and 0.887 for SN, which were higher than the expected heterozygosity. An excess of heterozygotes was observed, suggesting the presence of overdominant selection or the occurrence of outbreeding. Pairwise genetic distances indicated that the three indigenous camel breeds were genetically close to each other and genetically distant to the SN population. This genetic variability assessment by microsatellite analysis is important and useful for the conservation of local camel genetic resources as well as the future development of breeding programs.

Segregation and the Evolution of Sex Under Overdominant Selection

The segregation of alleles disrupts genetic associations at overdominant loci, causing a sexual population to experience a lower mean fitness compared to an asexual population. To investigate whether circumstances promoting increased sex exist within a population with heterozygote advantage, a model is constructed that monitors the frequency of alleles at a modifier locus that changes the relative allocation to sexual and asexual reproduction. The frequency of these modifier alleles changes over time as a correlated response to the dynamics at a fitness locus under overdominant selection. Increased sex can be favored in partially sexual populations that inbreed to some extent. This surprising finding results from the fact that inbred populations have an excess of homozygous individuals, for whom sex is always favorable. The conditions promoting increased levels of sex depend on the selection pressure against the homozygotes, the extent of sex and inbreeding in the population, and the dominance of the invading modifier allele.