GENETIC-EVIDENCE FOR UNDETECTED ALLELES AND UNEXPECTED PARENTAGE IN THE GRAY-BREASTED JAY

We performed protein electrophoresis to detect multiple parentage in broods of the Gray-breasted Jay (Aphelocoma ultramarina), a plural breeder that has been studied since 1969 in southeastern Arizona. We analyzed data from 43 nests (142 nestlings) for which we had blood, muscle, or feather samples from the nestlings and from at least one of the primary adults at a nest. Detection of multiple parentage was complicated by the apparent existence of an undetected (either null or masked) allele at the leu-gly-gly peptidase locus. The undetected allele resulted in offspring with single-banded phenotypes that were inconsistent with the phenotypes of adults with different single-banded phenotypes, assuming simple Mendelian inheritance. Including inconsistencies due to the undetected allele, we detected inconsistencies at 14 nests (33% of total), involving 29 nestlings (20%). We estimate that inconsistencies at seven nests (16%), involving 13 nestlings (8%) were due to causes other than the undetected allele. Inconsistencies at three nests were due to multiple parentage within broods, as the nestlings had double-banded phenotypes. The genetic data for these three nests did not allow us to distinguish between multiple paternity and multiple maternity. Data on clutch size and behavior indicated that multiple paternity was most likely. inconsistencies at three nests in which nestlings had single-banded phenotypes were likely due to multiple paternity. Inconsistencies at five nests were most parsimoniously explained by an undetected allele present in three generations of one lineage and inconsistencies at two additional nests were likely due to an undetected allele. We attributed inconsistencies at one nest to nest usurpation. We argue that some females may gain a phenotypic benefit from mating with more than one male. Males that mated with a female may be more likely to feed her on the nest and to feed her nestlings.