Human, chimpanzee, orangutan, macaque, panda, horse, cow and dolphin were selected as monotocous species, and mouse, rat, dog, cat, pig and Tasmanian devil were selected as polytocous species with the platypus as an outgroup.
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.
I can thus also conclude that moose allocate energy to maternal care as a monotocous species during the gestation period but as a polytocous species during the lactation period.
Lastly, because of their large size, moose cannot be a true polytocous species.
The pervasiveness of family effects in our study of roe deer suggests that family effects should occur in other polytocous species, at least in ungulates.
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.