Copulation behaviour, paternity and genetic relatedness in common murres (Uria aalge)

Walsh, Carolyn J. (2001) Copulation behaviour, paternity and genetic relatedness in common murres (Uria aalge). Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In order to examine the relationship between extra-pair copulation (EPC) behaviour and extra-pair paternity (EPP) in Common Murres (Uria aalge). this study combined four breeding seasons of field observations on the copulation behaviour of a marked subpopulation of murres with genetic analyses of EPP in chicks. The genetic relatedness of individuals between and within two Newfoundland seabird colonies was also examined in order to determine I) if genetic relatedness among individuals within a ledge affected their EPC behaviour, and 2) the degree of micro- and macro-geographic population differentiation in these murres. -- Behavioural observations indicated that few extra-pair copulations (EPCs) attempted by males were accepted by females. Contrary to previous studies. I found no evidence that male murres could force cloacal contact with females that resisted EPCs. A disproportionate number of females that accepted EPCs were in unstable pair bonds that were terminated during the study (i.e.. the pairs divorced). Divorced female's acceptance of EPCs occurred both prior to and after divorce in most cases, suggesting that some EPCs were used by these females as a means of mate sampling. Male EPC behaviour was unrelated to pair bond stability. -- Paternity analyses were conducted using four microsatellite loci on 30 families sampled from 1996-1999. Only three cases of EPP were detected, all in 1998. indicating an overall EPP rate of approximately 10%. Two cases of EPP involved pairs which divorced in the year following the production of an extra-pair chick. In contrast to most female murres who accepted pair copulations (PCs) following EPCs. the two females with an EP chick that were observed during pre-laying refused all PC attempts by their mates. This suggests that females may modify their acceptance of PCs in order to ensure that EPCs result in extra-pair fertilization (EPF). Overall, both copulation behaviour and paternity outcome was largely controlled by females. The clustering of all EPP cases in one year may indicate significant among-year variation in EPP rates for long-lived species such as Common Murres. -- Relatedness analyses indicated that two ledges contained murres that were related at the approximate level of first cousins, but other ledges/areas showed low average relatedness coefficients. The genetic markers used were able to differentiate known first- degree relatives and unrelated dyads on average, although there was high variability among pairwise relatedness estimates. Social mates, as well as extra-pair mates, were generally unrelated.

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