Mating scheme for the transfer of B. jarvisi markers into a B. tryoni background. (a) Mating scheme for transfer of B. jarvisi (white) mitochondria into B. tryoni (black) background. The mitochondrial type is indicated by small circle (white - B. jarvisi origin; black - B. tryoni origin). (b) Mating scheme for transfer of B. jarvisi (white) Y chromosome into B. tryoni (black) background. P, parents; F1, first filial generation; B1, backcross generation and number; and BF7, intercross of offspring from backcross generation 6. The proportion of the parental genomic contribution in the hybrids is indicated by the size of the corresponding black and white segments.