Fitness consequences of hybridization between house sparrows (Passer domesticus) and tree sparrows (P. montanus) (original) (raw)
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Behavioral Ecology, 2006
The occurrence of extrapair paternity (EPP) in birds is often attributed to the action of good-genes sexual selection whereby females ''trade up'' on male genetic quality by allocating fertilizations to males with better genes than those possessed by their social mate. To date, most studies of EPP in birds focus on absolute measures of male quality as a criterion for female choice, although multiple mating by females in other taxa is more commonly ascribed to benefits associated with the individual optimization of offspring genotypes. Here, we examine whether the genetic similarity of social mates predicts female mating patterns in a population of Savannah sparrows (Passerculus sandwichensis) where as many as 70% of adults produce extrapair young (EPY). We consider the influence of genetic similarity across all stages of a female's decision-making process, from pair formation through the decision to produce EPY, to the allocation of fertilizations to specific extrapair sires. In a 4-year study of 175 males, 206 females, and 506 offspring, females were more likely to produce EPY when paired to genetically similar males, but they did not appear to be influenced by the size, age, mass, individual heterozygosity, and genetic diversity of their social mates. In paired comparisons, females were almost twice as likely to decrease their genetic similarity to males when producing EPY as they were to increase it. Nonetheless, females did not select especially dissimilar males when mating outside the pair-bond nor did they pair disassortatively with respect to genetic similarity. Relative measures of male quality may influence mating patterns in birds, but only at some points in a female's decision-making process.
Biological Journal of the Linnean Society, 1999
Despite the many studies that have investigated the genetic mating system of socially monogamous birds, very little is known about the underlying causes of extra-pair paternity and few studies have attempted to test those hypotheses which have been suggested. This study describes the analysis of the genetic mating system of two populations of the house sparrow (Passer domesticus), and uses the results from four other populations to test existing hypotheses using an intra-specific comparative approach. The parentage analysis was conducted using a combination of published and newly presented microsatellite loci isolated from the house sparrow. One population in Kentucky, U.S.A. was found to contain what may be considered to be a typical level of extra-pair paternity for this species (10.5%, 19/ 185 offspring). The second, a population on the island of Lundy, UK, exhibited a very low level (1.3%, 4/305 offspring), significantly lower than that in all the other populations studied so far. The finding of such diverse rates of extra-pair paternity, along with the existing estimates from other populations, has allowed us to test the effects of breeding density and genetic variation on the level of extra-pair paternity. We found no effect of either factor on the frequency of extra-pair paternity in the house sparrow, leaving the cause of this variation open to fresh ideas.
Tests of Ecological, Phenotypic, and Genetic Correlates of Extra-Pair Paternity in the House Sparrow
The Condor, 2006
We performed a two-year study of extra-pair paternity in the House Sparrow (Passer domesticus) to test a suite of hypotheses relating to ecological factors associated with breeding conditions and parental phenotypes and genotypes. Extra-pair fertilizations (EPFs) accounted for 45 of 419 (11%) nestlings and occurred in 33 of 126 (26%) broods. EPFs were not correlated with breeding synchrony or breeding density, although they were significantly more common toward the end of each breeding season. Body size and the size of the bib, a secondary sexual character, were no different between males that were cuckolded and those that achieved full paternity in their nests. Older males were cuckolded as frequently as yearlings, and there was no difference between males that were cuckolded and those that were not with regard to two measures of individual genetic diversity. There was no evidence that females sought EPFs to avoid inbreeding, since EPFs were equally likely to be present among pairs that were closely related and those that were only distantly related, and females were equally related to their extra-pair mates as they were to their within-pair mates. Furthermore, extra-pair sires did not possess alleles that were rare in the population. In sum, despite a substantial sample size, we found few correlates of extra-pair paternity in House Sparrows.
The use of genetic markers for parentage analysis in Passer domesticus (House Sparrows
Heredity, 1992
The relationships between 420 Passer domesticus (house sparrow) nestlings from 144 broods and the adults which fed them were determined using genetic markers. The inheritance and independence of six polymorphic enzymes observed with starch gel electrophoresis and the component bands of DNA fingerprint profiles were investigated, and the probabilities of detecting incorrect parental assignments calculated. Allozymes were capable of detecting cuckoldry by males unrelated to the attendant adult in 54 per cent of cases whilst fingerprints could reveal virtually every occurrence. Fingerprinting uncovered some instances of erroneous parental exclusion based on the allozyme data, highlighting the problems caused by null alleles and post-translational modification. However, both techniques clearly showed that incorrect paternity as a result of extra-pair copulation (EPC) was the sole cause of multiple genetic incompatibilities, and that the cuckoldry rate varied little over 4 years [11.5 per cent (s.d. 2.3)].
Hybrid speciation in sparrows II: a role for sex chromosomes?
Molecular Ecology, 2011
Homoploid hybrid speciation in animals is poorly understood, mainly because of the scarcity of well-documented cases. Here, we present the results of a multilocus sequence analysis on the house sparrow (Passer domesticus), Spanish sparrow (P. hispaniolensis) and their proposed hybrid descendant, the Italian sparrow (P. italiae). The Italian sparrow is shown to be genetically intermediate between the house sparrow and Spanish sparrow, exhibiting genealogical discordance and a mosaic pattern of alleles derived from either of the putative parental species. The average variation on the Z chromosome was significantly reduced compared with autosomal variation in the putative parental species, the house sparrow and Spanish sparrow. Additionally, divergence between the two species was elevated on the Z chromosome relative to the autosomes. This pattern of variation and divergence is consistent with reduced introgression of Z-linked genes and ⁄ or a faster-Z effect (increased rate of adaptive divergence on the Z). F ST-outlier tests were consistent with the faster-Z hypothesis: two of five Z-linked loci (CHD1Z and PLAA) were identified as candidates for being subject to positive, divergent selection in the putative parental species. Interestingly, the two latter genes showed a mosaic pattern in the (hybrid) Italian sparrow; that is, the Italian sparrow was found to be fixed for Spanish sparrow alleles at CHD1Z and to mainly have house sparrow alleles at PLAA. Preliminary evidence presented in this study thus suggests that sex chromosomes may play a significant role in this case of homoploid hybrid speciation.