Genomic insights into racing camels: inbreeding levels and positive selection linked to athletic traits

Racing dromedary camels are widely distributed across the Arabian Peninsula, predominantly concentrating in its northern and southeastern regions. Phenotypically, they are differentiated from other dromedary types, characterised by their smaller body size, longer limbs, reduced hump size, and thinner chest girth. In this study, the whole genome sequences of 34 racing camels were analysed to assess their genetic relationship with non-racing populations, estimate levels of inbreeding, calculate Wier and Cockerham's fixation index (Fst), assess effective population size (N_e), and identify candidate regions with signatures of positive selection. Both racing and non-racing camels exhibited comparable levels of genomic inbreeding (F_ROH = 0.21), with no significant genetic differentiation detected between them. The estimated Fst value between the two camel groups also revealed minimal genetic differentiation. A declining trend was observed in N_e estimations of both groups over the past 5 000 years, with slightly lower recent N_e in racing camels compared to their non-racing counterparts. Signatures of positive selection in the genomes of racing camels were identified through the application of two haplotype-based statistics, namely the integrated haplotype homozygosity score (iHS) and extended haplotype homozygosity between-populations (Rsb), along with runs of homozygosity (ROH) analysis. A total of 33 regions under selection were detected via iHS, 19 via Rsb, and 24 through ROH. Candidate regions under selection were found to overlap with genes involved in diverse biological pathways potentially linked to athletic performance, e.g., musculoskeletal development, lipid metabolism, stress response, bone integrity, as well as endurance and power. These findings provide a foundation for further exploration of the racing dromedary genome, with the goal of defining variants and haplotypes that might be associated with athletic traits. Such insights could assist the development of genetically informed breeding programmes aimed at developing specialised racing dromedary lines, contributing to the broader understanding and preservation of animal athletic performance and selection in domesticated species worldwide.