J. Avian Biol. 39: 579583, 2008 doi: 10.1111/j.2008.0908-8857.04331.x # 2008 The Authors. J. Compilation # 2008 J. Avian Biol. Received 27 July 2007, accepted 7 November 2007 Genetic monogamy in two long-lived New Zealand passerines Sabrina S. Taylor, Sanne Boessenkool and Ian G. Jamieson S. S. Taylor, S. Boessenkool and I. G. Jamieson (correspondence), Dept. of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand. Email: ian.jamieson@stonebow.otago.ac.nz High rates of extra-pair paternity (EPP) can be relatively common in passerines whereas low rates or absence of EPP are often associated with taxa that are long-lived and exhibit obligatory paternal care. We examined EPP in an under- represented category: passerine species with relatively long life spans (or low annual mortality rates). Specifically, we studied EPP in New Zealand saddlebacks Philesturnus carunculatus and robins Petroica australis, two species with unusually low annual mortality rates (6.511% and 1020% respectively). No EPP (0%) was detected in saddlebacks (39 pairs, 202 offspring) and only one case of EPP (1.9%) was detected in robins (54 pairs, 198 offspring). Genetic monogamy in these passerine species supports the hypothesis that low annual mortality rates play an important role in explaining variation in rates of EPP across species. The detection and frequency of extra-pair paternity (EPP) in avian species is so widespread (e.g. 86% of all socially monogamous passerine species are not genetically mono- gamous; Griffith et al. 2002) and its benefits so varied (e.g. Petrie and Kempenaers 1998, Tregenza and Wedell 2000, Griffith et al. 2002, Foerster et al. 2003), that recent research has tried to identify factors explaining its absence in some species (Arnold and Owens 2002, Griffith et al. 2002). More than 50% of inter-specific variation in EPP can be explained by phylogeny, making the identification of particular traits difficult (Owens and Bennett 1995, Arnold and Owens 2002, Griffith et al. 2002). Nevertheless, the degree of paternal care required and low annual mortality rates (i.e. long life spans) appear to be key predictors of genetic monogamy (Arnold and Owens 2002, Griffith et al. 2002). The need for paternal care to successfully raise offspring affects whether a female will seek EPP and risk reduced effort or even desertion by her social mate. Females that can rear offspring with little or no paternal care (e.g. many passerines), should be likely to seek EPP (Griffith et al. 2002). If paternal care is essential (e.g. seabirds), rates of EPP should be low. These theoretical predictions are borne out by comparative analyses that have controlled for the effect of phylogeny (Arnold and Owens 2002). Similarly, phylogeny-based methods using evolutionarily independent contrasts show that longevity explains 25% of the variation in rates of EPP across species (Arnold and Owens 2002, Griffith et al. 2002). Males of short-lived species should stay with their mate, even when paternity is uncertain, because the probability of finding a new mate and breeding again is low. In contrast, males of long-lived species should never tolerate EPP because they have many future opportunities in which to find new mates. Indeed, inter-specific analyses demonstrate that species with annual mortality rates below 30% usually have EPP rates below 20% (Mauck et al. 1999). Phylogeny-based analyses have been constrained by limited data for species with low annual mortality rates. Most documented EPP for long-lived species exists for non- passerines, especially species in which longevity and obligatory paternal care co-occur (Appendix A in Arnold and Owens 2002). Therefore correlations between longevity and genetic monogamy are biased by certain taxonomic groups and relatively little information is available for passerines, a group that is usually short-lived. In their dataset, Arnold and Owens (Appendix A, 2002) listed only three passerine species with mortality rates below 20%, while the remaining 39 species had values well above this level. In New Zealand, saddlebacks Philesturnus carunculatus and robins Petroica australis are relatively long-lived passerines when introduced predators are absent. Saddle- backs are known to live for 1721 years (Higgins et al. 2006) with estimated annual adult mortality ranging between 6.511% (Armstrong et al. 2005, I. Jamieson unpubl. data). Robins can live up to 14 years (D. Armstrong unpubl. data) with annual adult mortality rates between 1020% (Dimond and Armstrong 2007, I. Jamieson unpubl. data). We examined the frequency of EPP in saddlebacks and robins over several seasons and for robins, across several populations. We predict that low annual mortality rates in both passerine species should result in genetic monogamy. 579