Mammalian Biology 76 (2011) 748–754 Contents lists available at ScienceDirect Mammalian Biology journal homepage: www.elsevier.de/mambio Original Investigation No inbreeding effects on body size in two captive endangered gazelles Belén Ibá ˜ nez a,∗ , Eulalia Moreno a , Andrés Barbosa b a Departamento de Ecología Funcional y Evolutiva, Estación Experimental de Zonas Áridas (CSIC), Carretera del Sacramento s/n, La Ca˜ nada de San Urbano, E-04120 Almería, Spain b Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal, 2, E-28006 Madrid, Spain article info Article history: Received 18 November 2010 Accepted 7 April 2011 Keywords: Inbreeding depression Body size Gazella cuvieri Nanger dama mhorr Captive breeding abstract Selection for body size is intricate, involving trade-offs between energy costs, reproductive output, for- aging efficiency, and interaction with other community members. In dimorphic, polygynous ungulates, body size is highly correlated with reproductive success in both sexes. Body size has been proposed as a potential phenotypic indicator of genetic change, in wild and in captive populations. We analysed the relationship between adult body size and inbreeding in two captive populations of endangered gazelles. Two estimates of inbreeding were used: individual inbreeding coefficient (F i ) and individual increase in inbreeding (F i ). Six cranial traits and eight post-cranial bones were measured in 87 Cuvier’s gazelles and 97 Mohor gazelles. The average level of individual inbreeding found for the alive population of Cuvier’s gazelle was 0.236 and for Mohor gazelle 0.260. Our study demonstrated that within our populations most variability in body size is explained by sex, but we have not found any evidence of inbreeding depression in this morphological trait. Our results are surprising in the light of a widely held belief that from an evo- lutionary point of view close inbreeding has deleterious effects. The great diversity of factors acting on the effects of inbreeding on trait values make difficult to provide a simple framework to understand them all, hence, we suggest fitness consequences of inbreeding has to be assessed considering the conditions under which one should expect inbreeding depression. © 2011 Deutsche Gesellschaft für Säugetierkunde. Published by Elsevier GmbH. All rights reserved. Introduction A wide range of genetic and environmental factors in com- plex processes affect body size diversification. Selection for body size is intricate, and involves trade-offs between energy costs, reproductive output, foraging efficiency, and interaction with other community members (Wisely et al., 2002). In wild polygynous ani- mals, body size is highly correlated with female social rank (Holand et al., 2004) and with male fighting ability, which influences access to receptive females (Mysterud et al., 2004), as male sexual com- petition is strong. Body size has been proposed as a potential phenotypic indicator of genetic change (Frankham et al., 1986; Fredrickson and Hedrick, 2002), and some authors have demon- strated that body size is affected by inbreeding in domestic and laboratory animals (Wright, 1977), and captive-born wild species (Laikre, 1999). One of the most important problems of endangered species is that their populations are small, leading to loss of genetic vari- ability from inbreeding (Bonnell and Selander, 1974; Wayne et al., 1991; Stangel et al., 1992). Thus inbreeding changes the frequency of genotypes in a population, increasing homozygote frequency ∗ Corresponding author. Tel.: +34 950281045x757. E-mail address: belen@eeza.csic.es (B. Ibá ˜ nez). (Charlesworth and Charlesworth, 1987; Wright et al., 2008), and may lead to a decline in the value of a trait. Such decline in a trait as a direct consequence of inbreeding is called inbreeding depression (Wright, 1977). This may be the result of either of two mechanisms. The dominance hypothesis states that inbreeding depression leads to the expression of recessive deleterious alleles as homozygos- ity increases, whereas the overdominance hypothesis states that inbreeding depression arises from the loss of favourable heterozy- gote combinations when heterozygotes are more frequent than homozygotes (Charlesworth and Charlesworth, 1987; Wright et al., 2008). Inbreeding depression has been found in a large propor- tion of species (Ralls et al., 1988; Lacy, 1997). Many traits, such as juvenile survival (Ralls et al., 1979, 1988), fecundity, mating suc- cess, development and health (Lerner, 1954; Falconer and Mackay, 1996; Roff, 1998; Bijlsma et al., 2000; Cassinello, 2000; Gomendio et al., 2000), are affected by inbreeding depression. But the effect of inbreeding depression on different traits depends on the genetic structural design of such traits (number of loci influencing a trait and the nature of interactions between alleles within and between loci; Merila and Sheldon, 1999; Bolund et al., 2010), and is more likely to occur for life-history traits (closely related to fitness) than for morphological traits (DeRose and Roff, 1999). Morphological traits (i.e. body size, cranial size) have been shown to be useful features for unveiling the effects of inbreeding depression in mammalian species (Leamy et al., 2001; Fredrickson 1616-5047/$ – see front matter © 2011 Deutsche Gesellschaft für Säugetierkunde. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.mambio.2011.04.002