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Jan T. Lifjeld - One of the best experts on this subject based on the ideXlab platform.
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S13-2 Do weather conditions affect the frequency of extra-pair paternity in the bluethroat (Luscinia svecica svecica)?
2020Co-Authors: Arild Johnsen, Jan T. LifjeldAbstract:Ecological factors may affect levels of extra-pair paternity (EPP) by influencing the costs and benefits of extra-pair copulation. During a 10-year study of a Norwegian bluethroat population, the frequency of EPP has varied extensively (8%- 76% nests with EPP, 7%-33% extra-pair offspring among years). Here, we investigate whether socio-ecological factors (breeding density, breeding synchrony) and weather conditions (ambient temperature, precipitation) during the peak fertile period explain some of the variation in the frequency of EPP. None of the factors assessed were related significantly to the likelihood that a nest would contain extra-pair offspring. Among broods that contained at least one extra-pair offspring, however, ambient temperature was related significantly to the frequency of EPP: broods contained more extra-pair offspring when the temperature was relatively high during the period of peak female fertility. We suggest that there is a direct link between weather conditions and the level of EPP in this population of bluethroats. Environmental conditions are often harsh when the birds start to breed, a large proportion of the ground being covered by snow and night temperatures falling well below zero. It therefore seems likely that there is a trade-off between investment in self-maintenance and extra-pair behavior, which shifts towards self-maintenance when the weather conditions are severe. In this study, we explore the relationship between the frequency of EPP and breeding density, breeding synchrony and weather variables (temperature and precipitation) in a Norwegian population of the bluethroat (Luscinia svecica). EPP occurs frequently in this population, but with consid- erable annual variation, fluctuating over the course of 10 study years between 7 and 33% of young, and 8 and 76% of broods. Here, we investigate whether ecological factors explain some of the variation in EPP between years, and between broods within years.
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Extra-pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean.
Molecular Ecology, 2019Co-Authors: Silje L. Rekdal, Jarl Andreas Anmarkrud, Jan T. Lifjeld, Arild JohnsenAbstract:: Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen-mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra-pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra-pair males in a nonrandom, self-matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra-pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade-off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra-pair mating is adaptive through altered genetic constitution in offspring.
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Genotyping strategy matters when analyzing hypervariable major histocompatibility complex-Experience from a passerine bird.
Ecology and Evolution, 2018Co-Authors: Silje L. Rekdal, Arild Johnsen, Jarl Andreas Anmarkrud, Jan T. LifjeldAbstract:: Genotyping of classical major histocompatibility complex (MHC) genes is challenging when they are hypervariable and occur in multiple copies. In this study, we used several different approaches to genotype the moderately variable MHC class I exon 3 (MHCIe3) and the highly polymorphic MHC class II exon 2 (MHCIIβe2) in the bluethroat (Luscinia svecica). Two family groups (eight individuals) were sequenced in replicates at both markers using Ion Torrent technology with both a single- and a dual-indexed primer structure. Additionally, MHCIIβe2 was sequenced on Illumina MiSeq. Allele calling was conducted by modifications of the pipeline developed by Sommer et al. (BMC Genomics, 14, 2013, 542) and the software AmpliSAS. While the different genotyping strategies gave largely consistent results for MHCIe3, with a maximum of eight alleles per individual, MHCIIβe2 was remarkably complex with a maximum of 56 MHCIIβe2 alleles called for one individual. Each genotyping strategy detected on average 50%-82% of all MHCIIβe2 alleles per individual, but dropouts were largely allele-specific and consistent within families for each strategy. The discrepancies among approaches indicate PCR biases caused by the platform-specific primer tails. Further, AmpliSAS called fewer alleles than the modified Sommer pipeline. Our results demonstrate that allelic dropout is a significant problem when genotyping the hypervariable MHCIIβe2. As these genotyping errors are largely nonrandom and method-specific, we caution against comparing genotypes across different genotyping strategies. Nevertheless, we conclude that high-throughput approaches provide a major advance in the challenging task of genotyping hypervariable MHC loci, even though they may not reveal the complete allelic repertoire.
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Is telomere length associated with mate choice in a songbird with a high rate of extra-pair paternity?
PLOS ONE, 2017Co-Authors: Arild Johnsen, Jan T. Lifjeld, Angela Pauliny, Donald BlomqvistAbstract:: Telomere length is related to aging in many eukaryotes and the rate of telomere attrition has been suggested to reflect individual genetic quality. Telomere length could thus have implications for mate choice. We investigated telomere length variation in bluethroat Luscinia svecica families with mixed paternity, including social parents, extra-pair fathers and nestlings, testing whether telomere length is associated with social and/or extra-pair mate choice through assortative mating or selection of mates with relatively long telomeres. In adults, relative telomere length (rTL) did not differ between the sexes, nor between two age categories. In chicks, however, rTL decreased with body mass at sampling (an index of nestling age). We found a positive correlation between the rTL of social mates, suggesting assortative mating with respect to telomere length or a correlative thereof. However, extra-pair males did not differ from social mates in rTL, and accordingly there was also no difference between within- and extra-pair young (i.e. half-siblings) when controlling for the effect of mass. We found no relationships between telomere length, age and fitness-related traits in adults, but an intriguing year-difference in telomere length in both sexes. In conclusion, we found no support for the idea that females choose extra-pair males based on their telomere length, but social mate choice seems to be influenced by rTL, possibly through its co-variation with aspects reflecting individual quality, like early arrival at the breeding grounds.
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Sperm performance in conspecific and heterospecific female fluid.
Ecology and Evolution, 2016Co-Authors: Emily R A Cramer, Marie-christine Eybert, Even Stensrud, Jan T. Lifjeld, Terje Laskemoen, Silje Hogner, Gunnhild Marthinsen, Lars Erik Johannessen, Tore Slagsvold, Arild JohnsenAbstract:Divergent sexual selection within allopatric populations may result in divergent sexual phenotypes, which can act as reproductive barriers between populations upon secondary contact. This hypothesis has been most tested on traits involved in precopulatory sexual selection, with less work focusing on traits that act after copulation and before fertilization (i.e., postcopulatory prezygotic traits), particularly in internally fertilizing vertebrates. However, postcopulatory sexual selection within species can also drive trait divergence, resulting in reduced performance of heterospecific sperm within the female reproductive tract. Such incompatibilities, arising as a by‐product of divergent postcopulatory sexual selection in allopatry, can represent reproductive barriers, analogous to species‐assortative mating preferences. Here, we tested for postcopulatory prezygotic reproductive barriers between three pairs of taxa with diverged sperm phenotypes and moderate‐to‐high opportunity for postcopulatory sexual selection (barn swallows Hirundo rustica versus sand martins Riparia riparia, two subspecies of bluethroats, Luscinia svecica svecica versus L. s. namnetum, and great tits Parus major versus blue tits Cyanistes caeruleus). We tested sperm swimming performance in fluid from the outer reproductive tract of females, because the greatest reduction in sperm number in birds occurs as sperm swim across the vagina. Contrary to our expectations, sperm swam equally well in fluid from conspecific and heterospecific females, suggesting that postcopulatory prezygotic barriers do not act between these taxon pairs, at this stage between copulation and fertilization. We therefore suggest that divergence in sperm phenotypes in allopatry is insufficient to cause widespread postcopulatory prezygotic barriers in the form of impaired sperm swimming performance in passerine birds.
Marie-christine Eybert - One of the best experts on this subject based on the ideXlab platform.
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Sperm performance in conspecific and heterospecific female fluid.
Ecology and Evolution, 2016Co-Authors: Emily R A Cramer, Marie-christine Eybert, Even Stensrud, Jan T. Lifjeld, Terje Laskemoen, Silje Hogner, Gunnhild Marthinsen, Lars Erik Johannessen, Tore Slagsvold, Arild JohnsenAbstract:Divergent sexual selection within allopatric populations may result in divergent sexual phenotypes, which can act as reproductive barriers between populations upon secondary contact. This hypothesis has been most tested on traits involved in precopulatory sexual selection, with less work focusing on traits that act after copulation and before fertilization (i.e., postcopulatory prezygotic traits), particularly in internally fertilizing vertebrates. However, postcopulatory sexual selection within species can also drive trait divergence, resulting in reduced performance of heterospecific sperm within the female reproductive tract. Such incompatibilities, arising as a by‐product of divergent postcopulatory sexual selection in allopatry, can represent reproductive barriers, analogous to species‐assortative mating preferences. Here, we tested for postcopulatory prezygotic reproductive barriers between three pairs of taxa with diverged sperm phenotypes and moderate‐to‐high opportunity for postcopulatory sexual selection (barn swallows Hirundo rustica versus sand martins Riparia riparia, two subspecies of bluethroats, Luscinia svecica svecica versus L. s. namnetum, and great tits Parus major versus blue tits Cyanistes caeruleus). We tested sperm swimming performance in fluid from the outer reproductive tract of females, because the greatest reduction in sperm number in birds occurs as sperm swim across the vagina. Contrary to our expectations, sperm swam equally well in fluid from conspecific and heterospecific females, suggesting that postcopulatory prezygotic barriers do not act between these taxon pairs, at this stage between copulation and fertilization. We therefore suggest that divergence in sperm phenotypes in allopatry is insufficient to cause widespread postcopulatory prezygotic barriers in the form of impaired sperm swimming performance in passerine birds.
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deplacements inattendus chez des mâles de gorgebleue a miroir blanc Luscinia svecica namnetum en periode de nidification unexpected movements of male bluethroats Luscinia svecica namnetum during the breeding period
Alauda, 2016Co-Authors: Clement Harmange, Laurent Godet, Matthieu Marquet, Julie Dietrich, Sarah Monnet, Elisa Gregoire, Marie-christine Eybert, Jerome FournierAbstract:Unexpected movements of male Bluethroats Luscinia svecica namnetum during the breeding period. During a radiotracking survey on 61 different males of Bluethroat Luscinia svecica namnetum from 2012 to 2015 in three different sites, we found that 8 males joined remote areas, at 300 to 900 meters from their regular territory and home range. These movements occurred at dawn and dusk, but also at day. Such movements are not recorded in the literature and we propose four different hypotheses to explain them: the existence of extra-pair copulation places, a male poly-territoriality, the look for food or for a shelter from predators.
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Bluethroats Luscinia svecica namnetum offset landscape constraints by expanding their home range
Journal of Ornithology, 2015Co-Authors: Laurent Godet, Matthieu Marquet, Sarah Monnet, Elisa Gregoire, Marie-christine Eybert, Jerome FournierAbstract:The highly fragmented landscape structures of coastal salinas are known to result in decreased terrestrial bird abundance, species richness and diversity but to promote original assemblages dominated by specialist species, such as the Bluethroat Luscinia svecica namnetum . This species is mainly found at the core of these salinas, where the landscape characteristics are a priori the most hostile for terrestrial birds. The aim of this study was to test whether individuals of a specialized species like the Bluethroat may offset such landscape constraints by expanding their home ranges. We therefore radio-tracked 21 males in 2013 and 2014 in the salinas of the Marais du Mès (Parc Naturel Régional de Brière, Western France). The data of the 18 best-monitored males were used to carry out a hierarchical partitioning of variance to test the relative influence of landscape characteristics, individual characteristics and distance to other males on their home-range sizes. We found that landscape characteristics were the factors that best explained home range sizes. Home-range sizes were significantly smaller in diversified landscapes composed of tidal creeks and salt-marsh patches and tended to be larger in landscapes dominated by the aquatic matrix consisting of water ponds. The results of this study demonstrate that although a few bird species are able to select a priori hostile landscapes, they can offset such constraints by expanding their home-range size. Blaukehlchen Luscinia svecica namnetum gleichen Einschränkungen im Lebensraum mit einer Erweiterung ihres Aktionsraumes aus Es ist bekannt, dass die stark fragmentierten Landschaftsstrukturen von küstennahen Salzmarschen Häufigkeit, Artenreichtum und Vielfalt von terrestrischen Vögeln verringert, aber Gemeinschaften begünstigen, die von Spezialisten wie dem Blaukehlchen Luscinia svecica namnetum dominiert werden. Diese Art ist daher hauptsächlich im Zentrum von Salzmarschen zu finden, wo die Landschaftsstrukturen für terrestrische Vögel am widrigsten sind. Ziel dieser Studie war es zu testen, ob Individuen dieser Art die Einschränkungen ihres Lebensraumes durch eine Erweiterung ihres Aktionsraumes ausgleichen. 21 Männchen wurden in 2013 und 2014 in den Salzmarschen des Marais du Mès (Parc Naturel Régional de Brière, Westfrankreich) radio-telemetriert. Die Daten der 18 best-verfolgten Individuen wurden genutzt um in einer hierarchischen Teilung der Varianz den relativen Einfluss von (i) Landschaftsstruktur (ii) Individuellen Unterschieden, sowie (iii) Abstand zu andern Männchen, auf die Größe ihres Aktionsraums. Landschaftsstruktur war dabei der Faktor, der die Größe des Aktionsraumes am besten erklärte. Aktionsräume waren signifikant kleiner in vielfältigeren Lebensräumen mit Prielen und Salzwiesen und größer in Lebensräumen mit einer aquatischen Grundsubstanz bestehend aus Teichen. Diese Studie zeigt, dass obwohl nur wenige Vogelarten fähig sind in grundsätzlich widrigen Lebensräumen zu siedeln, jene Arten die Einschränkungen durch eine Ausweitung ihres Aktionsraumes wieder ausgleichen können.
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bluethroats Luscinia svecica namnetum offset landscape constraints by expanding their home range
Journal of Ornithology, 2015Co-Authors: Laurent Godet, Matthieu Marquet, Sarah Monnet, Elisa Gregoire, Marie-christine Eybert, Jerome FournierAbstract:The highly fragmented landscape structures of coastal salinas are known to result in decreased terrestrial bird abundance, species richness and diversity but to promote original assemblages dominated by specialist species, such as the Bluethroat Luscinia svecica namnetum. This species is mainly found at the core of these salinas, where the landscape characteristics are a priori the most hostile for terrestrial birds. The aim of this study was to test whether individuals of a specialized species like the Bluethroat may offset such landscape constraints by expanding their home ranges. We therefore radio-tracked 21 males in 2013 and 2014 in the salinas of the Marais du Mes (Parc Naturel Regional de Briere, Western France). The data of the 18 best-monitored males were used to carry out a hierarchical partitioning of variance to test the relative influence of landscape characteristics, individual characteristics and distance to other males on their home-range sizes. We found that landscape characteristics were the factors that best explained home range sizes. Home-range sizes were significantly smaller in diversified landscapes composed of tidal creeks and salt-marsh patches and tended to be larger in landscapes dominated by the aquatic matrix consisting of water ponds. The results of this study demonstrate that although a few bird species are able to select a priori hostile landscapes, they can offset such constraints by expanding their home-range size.
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Rapid sperm evolution in the bluethroat (Luscinia svecica) subspecies complex
Behavioral Ecology and Sociobiology, 2013Co-Authors: Silje Hogner, Marie-christine Eybert, Javier García, Václav Pavel, Jan T. Lifjeld, Terje Laskemoen, Bohumír Chutný, Ekaterina Matsyna, Arild JohnsenAbstract:Spermatozoa are among the most variable animal cell types, and much research is currently directed towards explaining inter- and intraspecific variation in sperm form and function. Recent comparative studies in passerine birds have found associations between the level of sperm competition and both sperm length and sperm velocity. In species with sperm competition, postcopulatory sexual selection may shape the morphology of sperm as adaptations to the female environment. The speed of evolutionary change in sperm morphology at the species level is largely unknown. In this study, we analysed variation in sperm morphology among morphologically distinct and geographically isolated bluethroat subspecies in Europe. Consistent with previous studies, our analyses of mtDNA and nuclear introns suggest recent divergence and lack of lineage sorting among the subspecies. We found significant divergence in total sperm length and in the length of some sperm components (i.e. head and midpiece). There was a significantly positive relationship between pairwise divergences in sperm morphology and mitochondrial DNA, suggesting a role for genetic drift in sperm divergence. The magnitude of sperm length divergence was considerably higher than that in other geographically structured passerines, and even higher than that observed between several pairs of sister species. We hypothesize that the rapid sperm evolution in bluethroats is driven by sperm competition, and that strong postcopulatory sexual selection on sperm traits can lead to rapid speciation through reproductive incompatibilities.
Arild Johnsen - One of the best experts on this subject based on the ideXlab platform.
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S13-2 Do weather conditions affect the frequency of extra-pair paternity in the bluethroat (Luscinia svecica svecica)?
2020Co-Authors: Arild Johnsen, Jan T. LifjeldAbstract:Ecological factors may affect levels of extra-pair paternity (EPP) by influencing the costs and benefits of extra-pair copulation. During a 10-year study of a Norwegian bluethroat population, the frequency of EPP has varied extensively (8%- 76% nests with EPP, 7%-33% extra-pair offspring among years). Here, we investigate whether socio-ecological factors (breeding density, breeding synchrony) and weather conditions (ambient temperature, precipitation) during the peak fertile period explain some of the variation in the frequency of EPP. None of the factors assessed were related significantly to the likelihood that a nest would contain extra-pair offspring. Among broods that contained at least one extra-pair offspring, however, ambient temperature was related significantly to the frequency of EPP: broods contained more extra-pair offspring when the temperature was relatively high during the period of peak female fertility. We suggest that there is a direct link between weather conditions and the level of EPP in this population of bluethroats. Environmental conditions are often harsh when the birds start to breed, a large proportion of the ground being covered by snow and night temperatures falling well below zero. It therefore seems likely that there is a trade-off between investment in self-maintenance and extra-pair behavior, which shifts towards self-maintenance when the weather conditions are severe. In this study, we explore the relationship between the frequency of EPP and breeding density, breeding synchrony and weather variables (temperature and precipitation) in a Norwegian population of the bluethroat (Luscinia svecica). EPP occurs frequently in this population, but with consid- erable annual variation, fluctuating over the course of 10 study years between 7 and 33% of young, and 8 and 76% of broods. Here, we investigate whether ecological factors explain some of the variation in EPP between years, and between broods within years.
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Extra-pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean.
Molecular Ecology, 2019Co-Authors: Silje L. Rekdal, Jarl Andreas Anmarkrud, Jan T. Lifjeld, Arild JohnsenAbstract:: Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen-mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra-pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra-pair males in a nonrandom, self-matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra-pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade-off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra-pair mating is adaptive through altered genetic constitution in offspring.
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sperm morphology sperm motility and paternity success in the bluethroat Luscinia svecica
PLOS ONE, 2018Co-Authors: Camilla Lo Cascio Saetre, Arild Johnsen, Even Stensrud, Emily R A CramerAbstract:: Postcopulatory sexual selection may select for male primary sexual characteristics like sperm morphology and sperm motility, through sperm competition or cryptic female choice. However, how such characteristics influence male fertilization success remains poorly understood. In this study, we investigate possible correlations between sperm characteristics and paternity success in the socially monogamous bluethroat (Luscinia svecica svecica), predicting that sperm length and sperm swimming speed is positively correlated with paternity success. In total, 25% (15/61) of broods contained extra-pair offspring and 10% (33/315) of the offspring were sired by extra-pair males. Paternity success did not correlate significantly with sperm morphology or any aspects of sperm motility. Furthermore, sperm morphology and sperm motility did not correlate significantly with male morphological characters that previously have been shown to be associated with paternity success. Thus, the sperm characteristics investigated here do not appear to be strong predictors of paternity success in bluethroats.
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Genotyping strategy matters when analyzing hypervariable major histocompatibility complex-Experience from a passerine bird.
Ecology and Evolution, 2018Co-Authors: Silje L. Rekdal, Arild Johnsen, Jarl Andreas Anmarkrud, Jan T. LifjeldAbstract:: Genotyping of classical major histocompatibility complex (MHC) genes is challenging when they are hypervariable and occur in multiple copies. In this study, we used several different approaches to genotype the moderately variable MHC class I exon 3 (MHCIe3) and the highly polymorphic MHC class II exon 2 (MHCIIβe2) in the bluethroat (Luscinia svecica). Two family groups (eight individuals) were sequenced in replicates at both markers using Ion Torrent technology with both a single- and a dual-indexed primer structure. Additionally, MHCIIβe2 was sequenced on Illumina MiSeq. Allele calling was conducted by modifications of the pipeline developed by Sommer et al. (BMC Genomics, 14, 2013, 542) and the software AmpliSAS. While the different genotyping strategies gave largely consistent results for MHCIe3, with a maximum of eight alleles per individual, MHCIIβe2 was remarkably complex with a maximum of 56 MHCIIβe2 alleles called for one individual. Each genotyping strategy detected on average 50%-82% of all MHCIIβe2 alleles per individual, but dropouts were largely allele-specific and consistent within families for each strategy. The discrepancies among approaches indicate PCR biases caused by the platform-specific primer tails. Further, AmpliSAS called fewer alleles than the modified Sommer pipeline. Our results demonstrate that allelic dropout is a significant problem when genotyping the hypervariable MHCIIβe2. As these genotyping errors are largely nonrandom and method-specific, we caution against comparing genotypes across different genotyping strategies. Nevertheless, we conclude that high-throughput approaches provide a major advance in the challenging task of genotyping hypervariable MHC loci, even though they may not reveal the complete allelic repertoire.
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Is telomere length associated with mate choice in a songbird with a high rate of extra-pair paternity?
PLOS ONE, 2017Co-Authors: Arild Johnsen, Jan T. Lifjeld, Angela Pauliny, Donald BlomqvistAbstract:: Telomere length is related to aging in many eukaryotes and the rate of telomere attrition has been suggested to reflect individual genetic quality. Telomere length could thus have implications for mate choice. We investigated telomere length variation in bluethroat Luscinia svecica families with mixed paternity, including social parents, extra-pair fathers and nestlings, testing whether telomere length is associated with social and/or extra-pair mate choice through assortative mating or selection of mates with relatively long telomeres. In adults, relative telomere length (rTL) did not differ between the sexes, nor between two age categories. In chicks, however, rTL decreased with body mass at sampling (an index of nestling age). We found a positive correlation between the rTL of social mates, suggesting assortative mating with respect to telomere length or a correlative thereof. However, extra-pair males did not differ from social mates in rTL, and accordingly there was also no difference between within- and extra-pair young (i.e. half-siblings) when controlling for the effect of mass. We found no relationships between telomere length, age and fitness-related traits in adults, but an intriguing year-difference in telomere length in both sexes. In conclusion, we found no support for the idea that females choose extra-pair males based on their telomere length, but social mate choice seems to be influenced by rTL, possibly through its co-variation with aspects reflecting individual quality, like early arrival at the breeding grounds.
Terje Laskemoen - One of the best experts on this subject based on the ideXlab platform.
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Sperm performance in conspecific and heterospecific female fluid.
Ecology and Evolution, 2016Co-Authors: Emily R A Cramer, Marie-christine Eybert, Even Stensrud, Jan T. Lifjeld, Terje Laskemoen, Silje Hogner, Gunnhild Marthinsen, Lars Erik Johannessen, Tore Slagsvold, Arild JohnsenAbstract:Divergent sexual selection within allopatric populations may result in divergent sexual phenotypes, which can act as reproductive barriers between populations upon secondary contact. This hypothesis has been most tested on traits involved in precopulatory sexual selection, with less work focusing on traits that act after copulation and before fertilization (i.e., postcopulatory prezygotic traits), particularly in internally fertilizing vertebrates. However, postcopulatory sexual selection within species can also drive trait divergence, resulting in reduced performance of heterospecific sperm within the female reproductive tract. Such incompatibilities, arising as a by‐product of divergent postcopulatory sexual selection in allopatry, can represent reproductive barriers, analogous to species‐assortative mating preferences. Here, we tested for postcopulatory prezygotic reproductive barriers between three pairs of taxa with diverged sperm phenotypes and moderate‐to‐high opportunity for postcopulatory sexual selection (barn swallows Hirundo rustica versus sand martins Riparia riparia, two subspecies of bluethroats, Luscinia svecica svecica versus L. s. namnetum, and great tits Parus major versus blue tits Cyanistes caeruleus). We tested sperm swimming performance in fluid from the outer reproductive tract of females, because the greatest reduction in sperm number in birds occurs as sperm swim across the vagina. Contrary to our expectations, sperm swam equally well in fluid from conspecific and heterospecific females, suggesting that postcopulatory prezygotic barriers do not act between these taxon pairs, at this stage between copulation and fertilization. We therefore suggest that divergence in sperm phenotypes in allopatry is insufficient to cause widespread postcopulatory prezygotic barriers in the form of impaired sperm swimming performance in passerine birds.
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Rapid sperm evolution in the bluethroat (Luscinia svecica) subspecies complex
Behavioral Ecology and Sociobiology, 2013Co-Authors: Silje Hogner, Marie-christine Eybert, Javier García, Václav Pavel, Jan T. Lifjeld, Terje Laskemoen, Bohumír Chutný, Ekaterina Matsyna, Arild JohnsenAbstract:Spermatozoa are among the most variable animal cell types, and much research is currently directed towards explaining inter- and intraspecific variation in sperm form and function. Recent comparative studies in passerine birds have found associations between the level of sperm competition and both sperm length and sperm velocity. In species with sperm competition, postcopulatory sexual selection may shape the morphology of sperm as adaptations to the female environment. The speed of evolutionary change in sperm morphology at the species level is largely unknown. In this study, we analysed variation in sperm morphology among morphologically distinct and geographically isolated bluethroat subspecies in Europe. Consistent with previous studies, our analyses of mtDNA and nuclear introns suggest recent divergence and lack of lineage sorting among the subspecies. We found significant divergence in total sperm length and in the length of some sperm components (i.e. head and midpiece). There was a significantly positive relationship between pairwise divergences in sperm morphology and mitochondrial DNA, suggesting a role for genetic drift in sperm divergence. The magnitude of sperm length divergence was considerably higher than that in other geographically structured passerines, and even higher than that observed between several pairs of sister species. We hypothesize that the rapid sperm evolution in bluethroats is driven by sperm competition, and that strong postcopulatory sexual selection on sperm traits can lead to rapid speciation through reproductive incompatibilities.
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Is female promiscuity constrained by the presence of her social mate? An experiment with bluethroats Luscinia svecica
Behavioral Ecology and Sociobiology, 2008Co-Authors: Arild Johnsen, Henrik Pärn, Frode Fossøy, Oddmund Kleven, Terje Laskemoen, Jan T. LifjeldAbstract:Extra-pair paternity is common in birds and much research has focussed on the selective advantage of extra-pair matings for both sexes. In contrast, little attention has been given to the fact that in most species the majority of offspring are sired by the social male. We investigated whether extra-pair matings of female bluethroats ( Luscinia svecica ) are constrained by the presence of the pair male, by detaining males in cages on their territories for one morning during the peak of female fertility. The proportion of offspring sired by extra-pair males was higher in broods where males had been detained (35%) than in control broods (16%), while the proportion of broods that had at least one extra-pair offspring did not differ significantly between experimental (65%) and control broods (44%). Within the experimental group, levels of extra-pair paternity were not related to the day of experiment in relation to start of egg laying, but males caught early in the morning lost more paternity than males caught later on. Our results show that pair males exert constraints on the frequency of extra-pair paternity by being present during the period of peak fertility, which could be a direct effect of their mate guarding effort and/or due to an advantage in sperm competition for pair males.
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age related variation in primary sexual characters in a passerine with male age related fertilization success the bluethroat Luscinia svecica
Journal of Avian Biology, 2008Co-Authors: Terje Laskemoen, Frode Fossøy, Geir Rudolfsen, Jan T. LifjeldAbstract:In passerine species with frequent extrapair mating, young (second calendar year) males often have a lower fertilization success than older (after second calendar year) males. This pattern might be explained by male- or female-driven mechanisms, such as female preference for older males or higher competitive ability of older males. In this study we measured the size of the testes, the seminal glomera and the cloacal protuberance as well as the size and motility of the sperm, in individual bluethroats Luscinia svecica. In this species, nearly all extrapair fertilizations (EPFs) are obtained by older males. We found that the mass of the testes and the seminal glomera were highly positively correlated and that older males had significantly larger testes (38%), seminal glomera (15%) and cloacal protuberance (23%) than young males. In contrast, there was no difference between age groups in average sperm size or sperm motility. Our results are consistent with the idea that higher fertilization success by older males in this species is due to their higher rate of sperm production, allowing larger ejaculates and/or more frequent copulations. Unequal sperm production capacities by young and older males have important implications for the interpretation of paternity patterns in extrapair mating systems.
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functional infertility among territorial males in two passerine species the willow warbler phylloscopus trochilus and the bluethroat Luscinia svecica
Journal of Avian Biology, 2007Co-Authors: Jan T. Lifjeld, Arild Johnsen, Frode Fossøy, Terje Laskemoen, Oddmund KlevenAbstract:Information about male infertility in free-living birds is scarce, but anecdotal and circumstantial evidence suggests that it does occur regularly at a low frequency. In this paper we document three cases of azoospermia in two passerine species, the willow warbler Phylloscopus trochilus and the bluethroat Luscinia svecica at their breeding grounds in South Norway. In willow warblers, two males out of a sample of 50 territory holders had no sperm in their seminal glomera, the storage site of sperm ready for ejaculation. The two males also had very small testes. One out of 48 bluethroat males also had no sperm in the seminal glomera. This male had an extreme asymmetry of the testes, with the right testis being about twice as large as the left. He also failed to fertilize any eggs in his own nest, as well as in neighbouring nests, as revealed by microsatellite genotyping. Thus, the proportion of males without sperm seems to be at a magnitude of a few (2 � 4) percent in both species. These are among the first estimates of the frequency of azoospermia in wild birds. Our results indicate a significant risk for sexually monogamous females of laying unfertilized eggs, which could favour the evolution of extra-pair copulation as a fertility insurance strategy in females.
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Is female promiscuity constrained by the presence of her social mate? An experiment with bluethroats Luscinia svecica
Behavioral Ecology and Sociobiology, 2008Co-Authors: Arild Johnsen, Henrik Pärn, Frode Fossøy, Oddmund Kleven, Terje Laskemoen, Jan T. LifjeldAbstract:Extra-pair paternity is common in birds and much research has focussed on the selective advantage of extra-pair matings for both sexes. In contrast, little attention has been given to the fact that in most species the majority of offspring are sired by the social male. We investigated whether extra-pair matings of female bluethroats ( Luscinia svecica ) are constrained by the presence of the pair male, by detaining males in cages on their territories for one morning during the peak of female fertility. The proportion of offspring sired by extra-pair males was higher in broods where males had been detained (35%) than in control broods (16%), while the proportion of broods that had at least one extra-pair offspring did not differ significantly between experimental (65%) and control broods (44%). Within the experimental group, levels of extra-pair paternity were not related to the day of experiment in relation to start of egg laying, but males caught early in the morning lost more paternity than males caught later on. Our results show that pair males exert constraints on the frequency of extra-pair paternity by being present during the period of peak fertility, which could be a direct effect of their mate guarding effort and/or due to an advantage in sperm competition for pair males.
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functional infertility among territorial males in two passerine species the willow warbler phylloscopus trochilus and the bluethroat Luscinia svecica
Journal of Avian Biology, 2007Co-Authors: Jan T. Lifjeld, Arild Johnsen, Frode Fossøy, Terje Laskemoen, Oddmund KlevenAbstract:Information about male infertility in free-living birds is scarce, but anecdotal and circumstantial evidence suggests that it does occur regularly at a low frequency. In this paper we document three cases of azoospermia in two passerine species, the willow warbler Phylloscopus trochilus and the bluethroat Luscinia svecica at their breeding grounds in South Norway. In willow warblers, two males out of a sample of 50 territory holders had no sperm in their seminal glomera, the storage site of sperm ready for ejaculation. The two males also had very small testes. One out of 48 bluethroat males also had no sperm in the seminal glomera. This male had an extreme asymmetry of the testes, with the right testis being about twice as large as the left. He also failed to fertilize any eggs in his own nest, as well as in neighbouring nests, as revealed by microsatellite genotyping. Thus, the proportion of males without sperm seems to be at a magnitude of a few (2 � 4) percent in both species. These are among the first estimates of the frequency of azoospermia in wild birds. Our results indicate a significant risk for sexually monogamous females of laying unfertilized eggs, which could favour the evolution of extra-pair copulation as a fertility insurance strategy in females.
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intraspecific variation in sperm length in two passerine species the bluethroat Luscinia svecica and the willow warbler phylloscopus trochilus
2007Co-Authors: Terje Laskemoen, Oddmund Kleven, Frode Fossøy, Jan T. LifjeldAbstract:Laskemoen, T., Natural History Museum, University of Oslo, P.O. Box 1172 Blindern,NO-0318 Oslo, Norway. terje.laskemoen@nhm.uio.no (* Corresponding author)Kleven, O., Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, NO-0318 Oslo, Norway. oddmund.kleven@nhm.uio.noFossoy, F., Department of Biology, Norwegian University of Science and Technology,NO-7491 Trondheim, Norway. frode.fossoy@bio.ntnu.noLifjeld,J.T.,NaturalHistoryMuseum,UniversityofOslo,P.O.Box1172Blindern,NO-0318 Oslo, Norway. j.t.lifjeld@nhm.uio.noReceived 19 March 2007, revised 19 September 2007, accepted 21 September 2007
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Extrapair paternity and offspring immunocompetence in the reed bunting, Emberiza schoeniclus
Animal Behaviour, 2004Co-Authors: Oddmund Kleven, Jan T. LifjeldAbstract:Abstract Female promiscuity is widespread in birds, as well as in other taxa. It is often assumed that in bird species with a socially monogamous mating system, females engage in extrapair copulations to obtain indirect (genetic) benefits. ‘Good genes’ and ‘compatible genes’ models predict that extrapair young (EPY) should be of higher quality than within-pair young (WPY), but the empirical evidence for this effect is limited. A recent study, however, indicated an enhanced cellular immunity in EPY in a passerine bird, the bluethroat, Luscinia svecica. To assess the generality of that finding, we replicated the study using the reed bunting, a passerine with an extrapair mating system similar to that of the bluethroat. Using the same immune assay protocol, we found no indication of enhanced cellular immunity in EPY compared with WPY. Female reed buntings thus do not seem to engage in extrapair copulations to achieve the same type of genetic benefit as in bluethroats. Furthermore, EPY in mixed-paternity broods did not grow faster and were not in better body condition close to fledging than WPY. We conclude that our results do not support the hypotheses assuming indirect benefits to female extrapair copulations. It appears that the adaptive value for females of pursuing extrapair fertilizations varies, even between species with similar extrapair mating systems.
