Evolutionary rate shifts suggest species-specific adaptation events in HIV-1 and SIV

Maoz Gelbart; Adi Stern

A method for identification of evolutionary rate changes has been previously established and 51 was used to study intra-subtype HIV adaptation events [18] . To date, the lack of SIVcpz and 52 group O full genomic sequences limited the ability to study adaptation across cross-species 53 transmission events. Here, we utilized the growing availability of diverse and full HIV-1 and SIV 54 genomes to identify many sites in various SIVcpz/SIVgor/HIV-1 clades whose evolutionary rate 55 changed across clades [19] . We demonstrate how cross-species transmissions are correlated 56 with abundant evolutionary rate shifts and how known adaptation events are manifested in 57 different amino acid substitution rates between lineages. Based on the rate shift patterns, we 58 suggest previously unknown adaptation events, and highlight the exceptional amount of 59 evolutionary rate shifts observed in HIV-1 group O, possibly due to a more extreme host species 60 barrier. 61