Abstract

Whilst there has been considerable research focusing on the kinship of wolves, data on free-ranging dogs was sparse and there has been a long standing controversial debate over their ability to form packs. One of the aims of this project was to reconstruct kinship relationships in a population of free-ranging dogs, assessing the genetic variability and inbreeding level. For this purpose, I studied a population inhabiting a nature reserve at the outskirts of Rome in Italy. Analysis of twelve microsatellite loci revealed low number of alleles per locus, low levels of heterozygosity and difficulties in assigning parentage, possibly resulting from high levels of inbreeding in the population. Results from parentage analysis suggested multiple breeding individuals to be present in the social groups. One explanation for this is a result of the domestication process as free-ranging dogs no longer follow seasonal reproductive behaviour and have a plentiful supply of human waste to scavenge reducing competition. Although parentage analysis suggested multiple paternity for two litters, results had low statistical support and could be due to low genetic variability in the population.
Recent research has found MARCH7 as a common candidate gene under diversifying selection between free-breeding dogs and either East Asia or European dog breeds, with a SNP labelled in the intronic region of the gene. MARCH7 belongs to the membrane-associated RING-CH (MARCH) family, a RING finger protein family of E3 ubiquitin ligases, consisting of 11 members in mammals. The second aim of this study was to test for the possible signals of diversifying selection between free-ranging dogs, pure-breed dogs and wolves in the MARCH7 gene. This was achieved through three main routes: Sanger sequencing of a targeted region previously identified as being under selection, evolutionary comparison through investigation of nonsynonymous and synonymous patterns and phylogenetic analysis of mammalian species and ab initio prediction of protein structure . Sequence analysis demonstrated the possibility of copy number variation and alternative splicing in MARCH7 but failed to show polymorphism at the previously identified intronic SNP. Comparative analysis demonstrated MARCH7 to have highly conserved regions, most notably the RING-CH domain, but also polymorphic regions, where a multitude of both synonymous and nonsynonymous mutations are present across mammalian species studied. Comparison of nonsynonymous and synonymous mutations demonstrated MARCH7 to be under purifying selection across mammalian species. Ab initio prediction of protein structure indicated a highly disordered structure across the majority of the gene, with the exception of the RING-CH domain.