Fig. 1: Sex ratios at various life stages and their consequences.
From: Adult sex ratios: causes of variation and implications for animal and human societies
Males (M) and females (F) flow through stages from birth (b) through development into juveniles (or subadults) for up to j time steps, maturation (m), and adulthood. Adults include newly mature individuals and individuals who reached sexual maturity at an earlier time. Adults are classified as breeders (br), nonbreeders (nbr) that are capable of breeding but at present are not reproductively active, and post-reproductive individuals (pr) that are senescent. Transitions between stages are shown with white arrows and within stages with black arrows. The number of females and males, respectively, are depicted at birth (Fb and Mb), one (Fb+1 and Mb+1) and j time steps later (Fb+j and Mb+j), at maturation (Fm and Mm), breeding (Fbr and Mbr), non-breeding (Fnbr and Mnbr) and post-reproduction (Fpr and Mpr). Different sex ratios emerge from various combination of the sexes at different stages: (1) Birth sex ratio = Mb / (Fb + Mb); (2) Juvenile sex ratio = (Mb+1 + Mb+j) / (Fb+1 + Fb+j + Mb+1 + Mb+j); (3) Maturation sex ratio (MSR) = Mm / (Fm + Mm); and (4) Adult sex ratio (ASR) = (Mm + Mnb + Mbr + Mpr) / (Fm + Fnb + Fbr + Fpr + Mm + Mnb + Mbr + Mpr). Consequences of sex ratios discussed in the paper are shown.
