Life history and the evolutionary loss of parental care

The Evolutionary Loss of Paternal Care Is Associated With Shifts in Female Life-History Traits

Parental care can increase the fitness of parents through increased offspring survival but can also reduce reproductive output by limiting time and energy allocated to additional mating opportunities. The evolutionary origin of parental care is often associated with shifts in life-history traits (e.g., high investment in few, large offspring, slow offspring growth), but little is known about whether the evolutionary loss of care is associated with reciprocal shifts in the same life-history traits. Here, we capitalize on the divergence of parental care between ecotypes of three-spined stickleback (Gasterosteus aculeatus) to test for associations between parental care and life-history traits. While males from most stickleback populations provide care, an unusual "white" ecotype has recently lost paternal care. We found support for the hypothesis that the evolutionary loss of paternal care is associated with shifts in female life-history traits; relative to females of the ecotype with paternal care, females of the white ecotype that lack paternal care produced clutches with a similar overall mass and a greater number of smaller eggs, despite their smaller body size, suggesting lower per-offspring investment. We did not detect an ecotypic difference in embryonic development rate, metabolic rate, or offspring age at hatching, contrary to the 'safe harbor hypothesis'. These results support the theory that behavioral traits such as parental care co-evolve with other life-history traits and highlight opportunities for future study of the underlying causal mechanisms.

Divergence in Reproductive Behaviors Is Associated with the Evolutionary Loss of Parental Care

AbstractThe mechanisms underlying the divergence of reproductive strategies between closely related species are still poorly understood. Additionally, it is unclear which selective factors drive the evolution of reproductive behavioral variation and how these traits coevolve, particularly during early divergence. To address these questions, we quantified behavioral differences in a recently diverged pair of Nova Scotian three-spined stickleback (Gasterosteus aculeatus) populations, which vary in parental care, with one population displaying paternal care and the other lacking this. We compared both populations, and a full reciprocal F1 hybrid cross, across four major reproductive stages: territoriality, nesting, courtship, and parenting. We identified significant divergence in a suite of heritable behaviors. Importantly, F1 hybrids exhibited a mix of behavioral patterns, some of which suggest sex linkage. This system offers fresh insights into the coevolutionary dynamics of reproductive behaviors during early divergence and offers support for the hypothesis that coevolutionary feedback between sexual selection and parental care can drive rapid evolution of reproductive strategies.