Inbreeding in the last ruling dynasty of Portugal: The house of Braganza

Abstract

ObjectivesTo determine whether: (1) there are high levels of inbreeding in a European royal dynasty that continues until the 20th century, and (2) whether inbreeding is negatively associated with pre‐reproductive survival and longevity.MethodsGenealogical information of all Braganza monarchs (1640‐1910) was used to compute the individual's inbreeding coefficient (F) and the coefficient of kinship (θ) of the marriage which were examined in relation to two life‐history traits.ResultsMean F of the monarchs was 0.0530, close to that corresponding to the progeny of first cousins (F = 0.0625). A statistically significant effect of maternal inbreeding on offspring longevity (P = 0.037) and a significant effect of individual's F on survival from birth to 10 years (P = 0.023) were detected.ConclusionsAnother European royal dynasty besides the Habsburgs had high levels of inbreeding, especially high during a period after the early modern age. The lineage showed evidence of inbreeding depression. Results support the hypothesis that an increase in maternal homozygosity affects the lifespan of the progeny.