Data from: Where are all the moms? external fertilization predicts the rise of male parental care in bony fishes

Parental care shows remarkable variation across the animal kingdom, but
while maternal and biparental care are common in terrestrial organisms,
male-only care dominates in aquatic species that provide care. Using the
most complete phylogenetic tree of bony fishes to date, we test whether
the opportunity for external fertilization in aquatic environments can
explain the more frequent evolution of male care in this group. We show
that paternal care has evolved at least 30 times independently in fish and
is found only in externally fertilizing species. Male care is positively
associated with pair spawning, suggesting that confidence in parentage is
an important determinant of the evolution of care. Crucially, while female
care is constrained by other forms of reproductive investment, male care
occurs more frequently when females invest heavily in gamete production.
Our results suggest that moving control of fertilization outside of the
female reproductive tract raises male confidence in parentage and
increases the potential for paternal care, highlighting that in an aquatic
environment in which fertilization is external, paternal care is an
effective reproductive strategy.