Social polyandry, parental investment, sexual selection, and evolution of reduced female gamete size

• Sexual selection in the form of sperm competition is a major explanation for small size of male gametes. Can sexual selection in polyandrous species with reversed sex roles also lead to reduced female gamete size? Comparative studies show that egg size in birds tends to decrease as a lineage evolves social polyandry. Here, a quantitative genetic model predicts that female scrambles over mates lead to evolution of reduced female gamete size. Increased female mating success drives the evolution of smaller eggs, which take less time to produce, until balanced by lowered offspring survival. Mean egg size is usually reduced and polyandry increased by increasing sex ratio (male bias) and maximum possible number of mates. Polyandry also increases with the asynchrony (variance) in female breeding start. Opportunity for sexual selection increases with the maximum number of mates but decreases with increasing sex ratio. It is well known that parental investment can affect sexual selection. The model suggests that the influence is mutual: owing to a coevolutionary feedback loop, sexual selection in females also shapes initial parental investment by reducing egg size. Feedback between sexual selection and parental investment may be common.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Keyword

classical polyandry

coevolution

feedback

mating scrambles

quantitative genetic model

reversed sex roles

trade-off

potential reproductive rates

role-reversed pipefish

genetic mating system

egg size

charadrius-alexandrinus

spotted sandpiper

clutch size

kentish plovers

brood desertion

arrival times

Publication and Content Type

ref (subject category)

art (subject category)