Two eggs, two different constraints: a potential explanation for the puzzling intraclutch egg size dimorphism in Eudyptes penguins.

摘要: Phenotypic plasticity and phenotypic stability are major components of the adaptive evolution organisms to environmental variation. The invariant two-egg clutch size Eudyptes penguins has recently been proposed be a unique example maladaptive stability, while their egg mass is plastic trait. We tested whether this during reproduction might result from constraints imposed by migration (migratory carry-over effect) breeding (due depletion female body reserves). For first time, we examined these differ between eggs within clutches (yolk albumen). interval colony return initiation positively influenced yolk mass, albumen subsequent total first-laid eggs. This time had only slight negative influence on second-laid no masses. both eggs, at laying Female investment into entire was not related in before but increased with mass. These novel results suggest that intraclutch dimorphism exhibited penguins, being consistently smaller than due combination constraints: migratory effect reserve egg. Both explain why timing reproduction, especially formation, narrow capital breeders.