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Monogamy in vertebrate evolution appears multiple times in separate lineages but their underlying genetic underpinnings are only recently explored. Young et al. (2019) compared differential gene expression between the transcriptomes of monogamous and polygamous species in five sets of species pairs across vertebrates (mice, voles, birds, frogs and fish). The frog pair were poison frogs Ranitomeya imitator (monogamous) and Oophaga pumilio (polygamous). Tests for differential gene expression between each pair revealed that congruent sets of genes (orthologous or genes of the same evolutionary genealogy) showed concordant changes in expression between the monogamous and the polygamous lineages. The directions of changes in expression in these gene sets were also concordant, such that genes which decreased in expression in the monogamous lineage of one taxonomic pair were likely to decrease in expression in the other monogamous lineages as well (for all pairwise comparisons). However, the frog species were unique in that some genes displayed the opposite direction of change in expression relative to other monogamous lineages. The poison frogs are the only lineage here in which male parental care is ancestral so monogamy with biparental care in this lineage evolved from male care (rather than female care, as in the other taxa). Overall, their research yielded a novel set of 24 candidate genes likely to be involved in the evolution of monogamy, many of which are involved in neural development, synaptic activity and cognitive function. The study provides evidence for widely conserved sets of shared genes and molecular genetic pathways contributing to the evolution of monogamous mating systems across vast gulfs of evolutionary time and change in the vertebrate lineage.
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