TITLE:
Phylogenetic Relationship and Molecular Divergence Dating Using SRY Gene Polymorphism about Four Ladoum Sheep Lineages in Senegal
AUTHORS:
Pape Madiop Sembène, Fatimata Mbaye, Mama Racky Ndiaye, Mbacké Sembène
KEYWORDS:
Genetic Diversity, Phylogenetic Relationship, Molecular Dating, SRY Gene, Sheeps, Ladoum, Senegal
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.13 No.2,
April
6,
2023
ABSTRACT: Animal genetic resources are playing a vital role in livestock production
and are essential to food security. The present study aims to contribute to a
better understanding genetic local sheep breeds and to elucidate the
phylogenetic relationships through the evolution of the SRY gene in four
different lineages of Ladoum sheep raised in Senegal. After a brief analysis of
genetic diversity, the phylogenetic relationships and molecular dating were
inferred through haplotype networks and four phylogenetic reconstruction
methods. The different haplotype networks are constructed with NETWORK ver.
5.0.0.0 using the Median-Joining method. Phylogenetic trees were reconstructed
using neighbor-joining, maximum parsimony, maximum likelihood and Bayesian
inference. The robustness of the nodes in phylogenetic trees of the three first
methods was assessed by 1000 bootstraps. For Bayesian inference, the posterior
probability distribution of the trees was estimated by 4 MCMC chains. 5,000,000
generations were performed for each of the chains by sampling the different
parameters every 1000 generations. Results show a low polymorphism. Haplotypic
diversity is much higher than the average nucleotide divergence between all
pairs of haplotypes. The majority and central haplotype indicates a close
relationship between “Batling” and “Tyson” individuals. “Birahim” lineage is
very distinct from the rest. Phylogenetic trees confirm two genetically
separate clades between “Birahim” and the other lineages. The period of
divergence between “Birahim” lineage versus the common ancestor of the other three lineages was 2504 years
ago. The polyphyly revealed in “Birahim” lindicates that this lineage does not
contain the common ancestor of all individuals who compose it. It could
therefore be derived from two or more sheep breeds with a common ancestor, Ovis aries. The monophyletic clade
appears to be a group including a common ancestor and all of its genetic
descendants. This group, bringing together the other three lineages, is in the
process of being structured into sub-lineages. This study is the first to show
that there are only two genetic lines within ladoum sheep in Senegal.