As monotocous and polytocous species are not monophyletic, the inference of episodic evolutionary history from which their traits formed through convergent evolution is somewhat complicated.
Mutually exclusive AA substitution for monotocous and polytocous species
Amino acid substitution sites in multiple sequence alignments, which are mutually exclusive between monotocous and polytocous species that could assert molecular convergent evolution for the trait, are termed 'mutually exclusive AA substitutions' in this study.
We selected the orthologous gene sets which have undergone adaptive evolution that were also on the site of mutually exclusive AA substitution to identify convergent evolution by adaptive selection pressure for the monotocous or polytocous traits.
We investigated the monotocous specific and polytocous specific genes for expansion as it is possible that the trait was acquired by gene expansion.
We collected monotocous and polytocous specific orthologous gene sets by selecting genes that only existed in the monotocous species or the polytocous species.
After filtering, 10 monotocous specific orthologous gene sets and 12 polytocous specific orthologous gene sets were collected.
We explored genes which have evolved differently between monotocous and polytocous species in a number of different scopes, specific amino acid substitution with site-wise adaptive evolution, gene expansion and specific orthologous group.
Although such an interaction between year and family effects has not been reported in other polytocous mammals, it is expected to play an important role in population dynamics.
Firstly, the variance of female lifetime reproductive success will be expected to be greater in polytocous than in monotocous species because, for the latter, family effects cannot occur within a single year.
Because this is the first demonstration of the role of family effects in polytocous mammals, these are predictions that will need to be explicitly tested in the future.