Understanding the multiple meanings of ‘inbreeding’ and ‘effective size’ for genetic management of African rhinoceros populations Stanton Braude* and Alan R. Templeton Biology Department, Washington University in St Louis, Box 1137, One Brookings Drive, St Louis, MO 63130-4899, U.S.A. Abstract Although some African rhinoceros populations are cur- rently increasing, others are critically endangered. Even healthy populations are extensively managed in the wild and in captivity. While political and demographic consid- erations are of primary concern, many decisions are made in the name of genetic management. Such decisions should be informed by a full understanding of the multiple meanings of inbreeding and effective population size. In this essay, we examine inbreeding and effective size of wild and captive populations of African rhinoceroses. We con- clude by showing how misunderstanding of effective size and Franklin’s 50 / 500 rule can make a crucial difference in informing management decisions. Key words: effective size, genetic management, inbreeding, rhinoceros Re ´sume ´ Bien que certaines populations de rhinoce ´ros africains soient actuellement en augmentation, d’autres sont en danger critique. Me ˆme les populations saines sont ge ´re ´es tre `s activement dans la nature et en captivite ´. Alors que les conside ´rations politiques et de ´mographiques soient les principaux motifs d’inquie ´tude, de nombreuses de ´cisions sont prises au nom de la gestion ge ´ne ´tique. Ces de ´cisions devraient se faire en pleine connaissance des multiples implications de l’inbreeding et de ce qu’est une taille de population ne ´cessaire. Dans cet essai, nous examinons l’inbreeding et la taille ne ´cessaire des populations sauvages et captives de rhinoce ´ros africains. Nous concluons en montrant comment une mauvaise compre ´hension de la taille ne ´cessaire et de la re `gle 50 / 500 de Franklin peut entraı ˆner une diffe ´rence cruciale lorsqu’il s’agit de prendre, en connaissance de cause, les de ´cisions opportunes. Introduction Species survival plans (SSPs) coordinate management of rare and endangered species to maintain healthy breeding populations, retain genetic variation and minimize ‘inbreeding’. SSPs often have the conflicting goals of pre- serving species in a captive environment while at the same time minimizing evolutionary change in the species and minimizing loss of genetic diversity from ‘inbreeding’ or drift (Templeton, 1991a,b). These can be significant forces affecting in situ and captive populations that are entering or emerging from population bottlenecks. The captive population of Speke’s gazelle, Gazella spekei, and in situ populations of southern white rhinoceros, Ceratotherium simum simum, have weathered such bottlenecks in recent times (Templeton & Read, 1984; Roomaaker, 2002). However, black rhinoceros, Diceros bicornis, and northern white rhinoceros, Ceratotherium simum cottoni, populations are currently entering bottlenecks. With the refusal of the Congolese government to allow the airlift of the last few northern white rhinoceroses from Garamba reserve in 2006, this bottleneck may in fact have already become the end of an extinction vortex for the northern white rhi- noceros. To fully appreciate the consequences of this situation, we will first review the multiple meanings of the term ‘inbreeding’ and examine the available data on inbreeding and inbreeding depression in captive African rhinoceros populations. Next, we will review the various meanings of the term ‘population effective size’ and how these terms reflect very different aspects of populations of African rhi- noceros. Finally, we will examine Franklin’s 50 / 500 rule *Correspondence: E-mail: braude@wustl.edu 546 Ó 2009 The Authors. Journal compilation Ó 2009 Blackwell Publishing Ltd, Afr. J. Ecol., 47, 546–555