Behavioural Processes 84 (2010) 745–749 Contents lists available at ScienceDirect Behavioural Processes journal homepage: www.elsevier.com/locate/behavproc Multiple paternities increase genetic diversity of offspring in Brandt’s voles Ying-jun Huo a,b , Xin-rong Wan a,∗ , Jerry O. Wolff c,1 , Guiming Wang d , Shawn Thomas e , Raymond B. Iglay d , Bruce D. Leopold d , Wei Liu a a State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing 100101, China b Graduate School of Chinese Academy of Sciences, Beijing 100039, China c Department of Biological Sciences, St. Cloud State University, St. Cloud, MN 56301, USA d Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Mississippi State, MS 39762, USA e Department of Biological Sciences, College of St. Benedict/St. John’s University, Collegeville, MN 56377, USA article info Article history: Received 21 November 2009 Received in revised form 10 April 2010 Accepted 4 May 2010 Keywords: Genetic relatedness Inner Mongolia Microsatellite markers Multi-male mating Population genetics abstract Mating system and philopatry influence the genetic structure of a social group in mammals. Brandt’s vole (Lasiopodomys brandtii) lives in social groups year-round and has male biased dispersal, which makes the vole a model system for studies of genetic consequences of mating system and philopatry. This study aimed to test the hypotheses that: (1) multiple paternity (MP) would exist in Brandt’s voles, enhance offspring genetic diversity and reduce genetic relatedness between littermates; (2) promiscuity would occur in this species in that males and females mate with multiple partners; and (3) plural breeders of a social group would be genetically related because of philopatry of female juveniles in Brandt’s voles. Paternity analysis indicated that MP occurred in 11 (46%) of 24 social groups examined and that promis- cuity existed in this species. Multiple paternity litters had twice the offspring genetic diversity and half the average within-litter genetic relatedness of single paternity litters. We also found plural breeding females in six social groups. Average pairwise genetic relatedness of plural breeders ranged from 0.41 to 0.72 in four social groups, suggesting first-order kinship. Future studies need to investigate effects of reproductive skew and MP on population genetic structure of Brandt’s voles. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Genetic consequences of social behavior are critical to under- standing social organizations of rodents. Mating systems and philopatry of females are the two main factors influencing genetic structure of a social group in mammals. A common social system among murid rodents, especially the arvicolines, is for females to be territorial and males to have large home ranges that overlap those of several females as well as several other males (Wolff, 1985). However, exceptions exist such as in prairie voles (Micro- tus ochrogaster), in which a pair of bonded male and female shares a home range (Getz et al., 1993; Ophir et al., 2008). Mating systems are frequently flexible ranging from monogamy to polygyny and promiscuity, often within the same species (McEachern et al., 2009; Solomon and Keane, 2007; Waterman, 2007). Multi-male mating ∗ Corresponding author at: State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang, Beijing 100101, China. Tel.: +86 010 64807106; fax: +86 010 64807099. E-mail address: Wanxr@ioz.ac.cn (X.-r. Wan). 1 Deceased. appears also to be relatively common in the murid rodents, partic- ularly the arvicolines (Solomon and Keane, 2007; Boonstra et al., 1993b; Gordon et al., 1998; Solomon et al., 2004; Borkowska et al., 2009). Multiple paternity (MP—multiple males siring a litter) has many direct and indirect benefits including increased offspring genetic diversity (Wolff and Macdonald, 2004; Reynolds, 1996) and effective population sizes (Karl, 2008), which may subsequently enhance survival of offspring (Yasui, 1998). Kinship plays a major role in the evolution of group living (Griffin and West, 2003; Hamilton, 1964). Philopatry of juveniles, particu- larly female pups, is the proximate cause of social group formation in rodents (Lacey and Sherman, 2007; Nunes, 2007; Solomon, 2003). Natal dispersal is typically male biased in mammals; more male juveniles disperse from their natal habitat to a new one than do female juveniles (Greenwood, 1980). Daughters remain in their natal groups, delay sexual maturity, and assist in care of offspring of parents or siblings (i.e., alloparental care). As a result, female group mates may be kin (e.g., mother–daughter and siblings). Kin- ship enhances the fitness of social group members through either direct or indirect benefits of group living (Griffin and West, 2003; Hamilton, 1964; Lacey and Sherman, 2007). Direct benefits can include increased female reproductive success owing to cooper- ative breeding or alloparental care (Hamilton, 1964; Lacey and 0376-6357/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.beproc.2010.05.002