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Extra-pair paternity in waved albatrosses: Genetic relationships among females, social mates and genetic sires
Abstract
Interactions among close relatives are expected to be common in colonially breeding species, species with limited geographic distributions such as island endemics, or those with limited natal or breeding dispersal. The waved albatross, Phoebastria irrorata, a colonially nesting, endemic seabird in Galápagos, Ecuador, presents an opportunity to closely examine relationships between genetic similarity of parents and extra-pair paternity. This species' mating system is characterized by high year-to-year social mate and nest site fidelity as well as an unexpectedly high level of extra-pair paternity. The probability of hatching was lower for social pairs with high genetic similarity, suggesting an apparent cost of inbreeding. Despite this apparent cost, analyses of multilocus minisatellite band-sharing coefficients revealed that genetic similarity was somewhat negatively associated with EPF probability, inconsistent with the pattern predicted by the Genetic Similarity Hypothesis (GSH) that social pairs with extra-pair offspring would be more similar than those with within-pair offspring. We found that a model with no effect of the type of dyad the female was in (female-social mate compared to female-genetic sire) on genetic similarity was as heavily weighted as one incorporating an effect, also inconsistent with the GSH. Evidence from our analyses suggested that cuckolded males were more genetically similar to randomly drawn males than to the genetic sire of their extra-pair offspring, a finding in contrast to the main prediction of our novel EPF tolerance hypothesis that males might tolerate extra-pair offspring if the actual sire is closely related. We discuss these findings in light of information about dispersal and we present some alternative explanations for extra-pair paternity in the waved albatross.
... Cuckolded males may discriminate against EPP offspring, thereby selecting against EPP (Westneat et al. 1990;Møller and Birkhead 1993;Westneat and Sargent 1996). However, males may tolerate cuckoldry if the extra-pair sires are genetically similar (the extra-pair tolerance hypothesis; Huyvaert and Parker 2010) or if they are unable to detect EPP chicks (Mauck et al. 1999). There is little evidence that male albatrosses discriminate against EPP chicks (Westneat et al. 1990;Jouventin et al. 2007), but we test for this in our study population by comparing the growth and survival rates of EPP and within-pair paternity (WPP) chicks. ...
... Breeding phenology terms including lay date, hatching date and incubation period were incorporated with brood period in multivariate models given that some breeding phenology characteristics have been associated with EPP in albatrosses (e.g. Huyvaert and Parker 2010) and also could influence time spent brooding young chicks. Some families, concurrently used in a cross-fostering experiment (Jones 2011), were excluded from parental investment analyses because experimentally altered egg provenance may confound parental investment. ...
... Genetic diversity in the Marion Island population was low, consistent with predictions that natal philopatry (Inchausti and Weimerskirch 2002) results in low genetic variability. It is possible that selection against EPP is reduced because costs to the cuckolded parent are small when sires are close relatives (Fietz et al. 2000;Huyvaert et al. 2000;Huyvaert and Parker 2010). In our study, paired individuals were more genetically similar to each other than expected from random pairings. ...
Genetic techniques have revealed surprisingly high rates of extra-pair paternity (EPP) in socially monogamous albatrosses. We sought to establish social and genetic influences on EPP in wandering albatrosses (Diomedea exulans) at Marion Island, where EPP rates were 14–24 % in three successive seasons. EPP probably resulted from both female solicited extra-pair behaviours and male forced copulations. EPP was not linked to breeding experience nor with poor reproductive performance, despite a tendency for pairs to consistently produce either EPP or within-pair paternity (WPP) chicks. Mate guarding may inhibit extra-pair behaviour; however, parental arrival date and presence in the colony prior to laying did not correlate with EPP. There was little support for genetic advantages to producing EPP chicks, but the population is characterised by low genetic variability, which may result in mate incompatibility. Mates of pairs that failed and pairs producing EPP young tended to be more similar genetically to their partners than mates producing WPP young, suggesting that EPP may counter mate incompatibility. EPP and WPP chicks grow equally well, so cuckolded males did not reduce investment in EPP chicks. The lack of discriminatory behaviour by cuckolded males together with low genetic diversity in the population may allow continued high levels of EPP. In albatrosses, pair bonds are typically long lasting and the costs of forming new pairings may discourage mate swapping. Females may undertake extra-pair copulations as an adaptive alternative to mate swapping because the costs of extra-pair behaviour are small.
... However, these issues were mostly addressed in reasonably large populations (at least several hundred pairs) of species that are unlikely to have experienced demographic or genetic bottlenecks. In some Procellariiform populations with low genetic variability, EPP rates can be surprisingly high (Huyvaert et al. 2006), because females may seek EPCs in order to avoid inbreeding (Tregenza and Wedell 2000), or because males might be tolerant to EPCs performed by males to which they are genetically related (Huyvaert and Parker 2010). Alternatively, if genetic similarity between males is high, exerting choosiness during mate choice and seeking EPCs should not yield significant benefits to females (Øigarden et al. 2010), and EPP rates should be low (Petrie and Kempenaers 1998). ...
... like many Procellariiform species (Warham 1990), and they also breed in very low numbers. However, the population from Vila islet is not inbred, and as far as we know, EPPs are not related to inbreeding avoidance in Procellariiformes (Austin and Parkin 1996, Quillfeldt et al. 2001, Bried et al. 2010, Huyvaert and Parker 2010 except perhaps in the wandering albatross . ...
As biparental care is crucial for breeding success in Procellariiformes seabirds (i.e. albatrosses and petrels), these species are expected to be choosy during pair formation. However, the choice of partners is limited in small‐sized populations, which might lead to random pairing. In Procellariiformes, the consequences of such limitations for mating strategies have been examined in a single species. Here, we studied mate choice in another Procellariiforme, Bulwer's petrel Bulweria bulwerii, in the Azores (ca 70 breeding pairs), where the species has suffered a dramatic population decline. We based our approach on both a 11‐year demographic survey (capture–mark–recapture) and a genetic approach (microsatellites, n = 127 individuals). The genetic data suggest that this small population is not inbred and did not experience a genetic bottleneck. Moreover, pairing occurred randomly with respect to genetic relatedness, we detected no extrapair parentage (n = 35 offspring), and pair fecundity was unrelated to relatedness between partners. From our demographic survey, we detected no assortative mating with respect to body measurements and breeding experience and observed very few divorces, most of which were probably forced. This contrasts with the pattern previously observed in the much larger population from the Selvagens archipelago (assortative mating with respect to bill size and high divorce rate). We suggest that the Bulwer's petrels from the Azores pair with any available partner and retain it as long as possible despite the fact that reproductive performance did not improve with pair common experience, possibly to avoid skipping breeding years in case of divorce. We recommend determining whether decreased choosiness during mate choice also occurs in reduced populations of other Procellariiform species. This might have implications for the conservation of small threatened seabird populations.
... Several studies in open, potentially outbred populations such as in tree swallows Tachycineta bicolor (Barber et al. 2005), pied flycatchers Ficedula hypoleuca (Rätti et al. 1995), and waved albatross Phoebastria irrorata (Huyvaert and Parker 2010) have provided evidence for females in less closely related pairs producing extra-pair offspring with more closely related males. ...
... Our population of American redstarts has extremely high immigration rates, especially among males (Wilson et al. 2017), suggesting the possibility of an outbred population. One prediction that arises from studies on potentially outbred populations that similarly found evidence of females in less closely related pairs producing extra-pair offspring with more closely related males (Rätti et al. 1995, Barber et al. 2005, Huyvaert and Parker 2010 is that less related social pairs should also experience reduced reproductive success (i.e. a cost associated with outbred pairings). We found no evidence of this effect: relatedness of pairs was not associated with number of eggs, nestlings, or fledglings. ...
The vast majority of bird species are socially monogamous; however, extra-pair paternity is nearly ubiquitous and a number of theories have been proposed to explain the prevalence of this mixed mating strategy. Here, we test the genetic compatibility hypothesis – the idea that females seek extra-pair copulations with males whose genes are more compatible with her own. For this study, we examined eight years of paternity data (2004–2011) from a Nearctic-Neotropical migratory bird, the American redstart Setophaga ruticilla, breeding in southeastern Ontario, Canada. We predicted that females paired with genetically similar males (higher relatedness) would be more likely to produce extra-pair offspring and that extra-pair offspring would have higher levels of heterozygosity than within-pair offspring. Alternatively, because this population experiences high levels of immigration, females may produce extra-pair offspring with more genetically similar males because of the potential for outbreeding depression. Using five highly variable microsatellite markers, we examined patterns of relatedness among social pairs as well as measures of offspring heterozygosity. In contrast to our predictions, we found no difference in relatedness between social pairs where the females produced extra-pair offspring and social pairs where the females produced only within-pair offspring. However, extra-pair offspring were significantly less heterozygous than within-pair offspring. Together, these findings suggest that females a) are not engaging in extra-pair fertilizations based on relatedness to their social mate and b) appear to be mating with extra-pair males that are more genetically similar to themselves. We suggest there may be benefits for females to mate with genetically similar extra-pair males in highly outbred populations with high rates of immigration, such as for maintaining co-adapted gene complexes or genes coding for local adaptations.
... The literature on this topic is vast and new sequencing methods will aid the development of the variable markers required for paternity assignment (e.g. Baião & Parker 2009, Wojczulanis-Jakubas et al. 2009, Huyvaert & Parker 2010. ...
Information on genetic variation within and among populations of highly mobile organisms such as seabirds is necessary for understanding their evolution and ecology, and can be a tool for conservation. Recent developments in molecular genetics, including efficient mutation-detection methods and automated sequencing, are providing detailed genetic information for non-model organisms. Furthermore, theoretical advances such as coalescent theory and molecular assignments are providing powerful tools to determine species' historical and contemporary abundance, distributions and movements. We review advances for studying phylogenetics, population genetics, hybridization, ecology and conservation in seabirds and summarize recent studies in each field. All fields will benefit from larger data sets and more sophisticated analytical methods. Phylogenetic studies will provide a more robust determination of evolutionary history, while studies of population genetics and hybridization will be elevated to genomic-level avenues of inquiry. Ecological studies may benefit from improved molecular assignments, and conservation-focussed studies will benefit from an increased understanding of seabird evolution and ecology. In addition, we highlight that combination of new molecular and analytical tools with data on morphology, behaviour and movements is especially powerful for understanding seabird evolution and ecology, and for aiding conservation.
... Bensch et al. 1994; Kempenaers et al. 1999; Blomqvist et al. 2002; Foerster et al. 2003; Freeman-Gallant et al. 2003; Masters et al. 2003; Richardson et al. 2004; Eimes et al. 2005; Tarvin et al. 2005; Oh & Badyaev 2006; Lindstedt et al. 2007; Blackmore & Heinsohn 2008; Kawano et al. 2009). In contrast to the inbreeding avoidance hypothesis, a negative influence of social mate relatedness on EPP occurrence has been reported in a few species: the pied flycatcher (FiceduIa hypoleuca; Rätti et al. 1995), the tree swallow (Tachycineta bicolor: Barber et al. 2005) and the waved albatross (Phoebastria irrorata; Huyvaert & Parker 2010). For the last species, the pattern occurred despite a low hatching rate associated with high parental genetic similarity. ...
Socially monogamous female birds routinely mate with males outside the pair bond. Three alternative hypotheses consider genetic benefits as the major driver behind the female strategy. The inbreeding avoidance hypothesis predicts that females paired with closely related males should seek copulations with distantly related extra-pair partners to avoid fitness loss from inbreeding depression; the outbreeding avoidance hypothesis predicts the opposite; the kin-selection hypothesis suggests that regardless of social mate relatedness, females should give related males extra-pair fertilization opportunities to gain inclusive fitness if the costs from inbreeding are minor. We test these hypotheses with a facultative cooperative breeder, the ground tit (Parus humilis). Social pairs of ground tits formed randomly with respect to genetic relatedness. In both bi-parental and cooperative groups, a female's engaging in extra-pair mating was independent of relatedness to her social mate; however, females preferred extra-pair sires to which they were more related than to their social mates. Moreover, females had higher relatedness with either their extra-group extra-pair sires in both bi-parental and cooperative groups, or within-group helper sires in cooperative groups, than expected by chance. When more than one potential extra-pair partner was available around a female's nest, she tended to select a relative. There was no indication of fitness reduction from extra-pair mating, which occurred at an intermediate level of inbreeding. These data support the kin-selection hypothesis, although there might be alternative nongenetic reasons associated with the extra-pair mating preference. Our finding offers a new explanation for why female birds pursue extra-pair mating. It also may broaden our understanding of the role of kin-selection in the evolution of cooperative society.
Extra-pair mating prevails among socially monogamous birds with biparental care. Theoretically, females may lay the resultant eggs in their own, their mating partners or other pairs’ nests, accordingly leading to extra-pair paternity (EPP), quasi-parasitism (QP) and extra-pair conspecific brood parasitism (CBP). Empirical evidence showed EPP to be widespread and QP rare, with extra-pair CBP having never been described. In Tibetan ground tits ( Pseudopodoces humilis ), we detected EPP, QP and extra-pair CBP in 54%, 47% and 24% of broods, which involved 20%, 16% and 8% of offspring, respectively. Cuckolding and cuckolded individuals in these events were genetically related and moderate inbreeding occurred between extra-pair partners, whereas social mates formed randomly with respect to relatedness. Promiscuity relative to genetic monogamy significantly increased annual reproductive output of both males and females, and extra-pair offspring did not differ from their within-pair siblings in body mass and heterozygosity. While the much high incidence of promiscuity can be ultimately driven by not only males but also females’ pursuit of increasing reproductive success, it may be proximately promoted by frequent kin ties in association with the species’ habit of burrow nesting and roosting, presumably kin-selected benefits may reduce the cost of arising non-descendant offspring. The fact that less than 30 altricial species have been documented with respect to extra-pair maternity (in contrast to over 360 species for EPP) suggests that more attention should be paid towards QP and extra-pair CBP to get a broader perspective on the evolution of avian mating systems.
Durante los días 5–9 de diciembre de 2016, el taller para desarrollar un Plan de Salud de la Vida Silvestre de Galápagos se llevó a cabo en Puerto Ayora, Galápagos. Al taller asistieron 43 participantes representantes de organizaciones estatales en Ecuador (Agencia de Regulacióny Control de la Bioseguridad y Cuarentena para Galápagos, Dirección del Parque Nacional Galápagos, Instituto Nacional de Biologíay Ministerio de Agricultura, Ganadería, Acuacultura y Pesca); universidades tanto del
Ecuador (Escuela Superior Politécnica del Litoral –Facultad de Ciencias de la Vida, Universidad Central del Ecuador, y Universidad San Francisco de Quito) como de Estados Unidos (Colorado State University; North Carolina State University College of Veterinary Medicine; University of California, Davis School of Veterinary Medicine; and College of Veterinary Medicine, University of Minnesota); funcionarios/as de organizaciones de conservación no gubernamentales con base en las Galápagos (Fundación Charles Darwin, Island Conservation, Galápagos Conservancy,Sea Shepherd, y WILDAID) así como otras organizaciones internacionales (Houston Zoo,San Diego Zoo Global, San Diego Zoo, Wildlife Conservation Society, Zoological Society of London y Fundación Pro Zoológicos).
La Visión del Plan de Salud para los próximos 25 años es la siguiente: “Un impacto
antropogénico menor y decreciente habilita ecosistemas funcionales y resilientes que
sostienen poblaciones silvestres saludables, en equilibrio con sus parásitos naturales, y cumplen con sus roles ecológicos.” Definimos parásitos
en el sentido ecológico amplio, incluyendo virus, bacterias, hongos, protozoos, helmintos,
artrópodos, y anélidos que tienen un ciclo de vida parasitario.
Las actividades del taller siguieron los procesos de trabajo de CBSG, donde los expertos ensalud de vida silvestre conformaron seis gruposde trabajo para analizar la situación actual y recomendaron prioriades de salud de las especiesnativas de Galápagos, especies domésticas ysilvestres, y sus ecosistemas. Estos grupos fueron
los siguientes:
Reptiles Endémicos de Galápagos
Aves Endémicas de Galápagos
Mamíferos Endémicos de Galápagos
Especies Introducidas e Invasoras en
Galápagos
Animales Domésticos
Protocolos y Recopilación de Datos cuando se Manipulan Animales Silvestres
Due to their smaller sizes and isolation, island populations generally have reduced genetic variability, which can have negative fitness consequences. The Galápagos Islands have played a unique and important role in our understanding of evolution, and the population genetics of bird species native to the islands is relatively well studied. Native Galápagos bird species exhibit a range of genetic patterns at neutral loci. For example, hawk and mockingbird population genetic variability is closely correlated with island size, demonstrating the effect of genetic drift, whereas gene flow has mitigated the effect of drift in dove and finch populations, resulting in higher genetic variability. Similarly, Galápagos seabirds exhibit a range of patterns, with some having greatly reduced variation compared to relatives outside of Galápagos (e.g., magnificent frigatebirds, penguins) and others having relatively high genetic variability (e.g., great frigatebirds). Published studies of major histocompatibility variability in hawks and penguins show a pattern of reduced variability at functional loci for Galápagos species compared to mainland congeners. Research has also demonstrated a relationship between genetic variability and fitness in some Galápagos species. Galápagos hawks have weaker innate immune function and higher louse loads than their more heterozygous mainland congener, and medium ground finches with higher heterozygosity are more likely to survive and breed. In contrast, no relationship between inbreeding and innate immune function or ectoparasite load was detected for mockingbirds. Further study of the population genetic dynamics of these species will continue to better inform management practices in the face of evolving threats.
Extrapair mating has been recorded in approximately 90% of investigated avian monogamous species. However, factors triggering
female mating decisions and potential fitness benefits from extrapair matings still remain poorly understood. Some studies
suggest that females mate socially with low-quality males but seek extrapair mates offering superior genes for their progeny.
This mating strategy may also help in mitigating the potential negative effects of pairing with a genetically similar mate.
Here, we investigate whether genetic similarity within a social pair may predict the occurrence of extrapair paternity (EPP)
in birds. Using a meta-analytical approach to a number of studies performed on birds, we found a positive relationship between
the occurrence of EPP and the relatedness of social mates. Moreover, we found that the type of molecular markers used to estimate
relatedness significantly affected the observed effect size. Specifically, we showed that only microsatellite markers were
associated with significantly positive effect sizes. Thus, failure of some of the previous studies to detect the relationship
between occurrence of EPP and the relatedness of social mates may at least partly arise due to methodological reasons.
Birds are characterized by a constant body temperature, a pulmonary respiratory system, beaks, bodies covered in feathers, two legs, and two wings. Their reproduction is oviparous.Of the 178 species recorded in Galapagos, 56 are endemic and native. At present, no birds are known to be extinct in the Archipelago, but extinctions have occurred locally on some islands. For marine species distribution data cited in the CDF Galapagos Checklists refer to the five main bioregions of the archipelago (Far Northern, Northern, Western, South Eastern and the Elithabeth Bay Bioregion). For the terrestrial species the more than 120 islands, islets and small rocks have been aggregated into Islands Groups, thus, for example, the island group "Santa Cruz" includes smaller islands like Santa Fé, Plaza Norte, Plaza Sur, Baltra, Daphne Mayor, Daphne Minor, and others. Please be aware that the distribution data presented here is automatically generated from specimen records and does not always accurately reflect the known distribution for all species. IUCN red-list assessments presented here may deviate from the global IUCN list for the following reasons: -for well known species groups like vascular plants or vertebrates updates proposed to the IUCN are shown instead of the outdated, but currently accepted status; -for poorly known species groups (e.g., lichenized fungi) a general assessment is currently not possible and the list presented here is a regional red-list list for Galapagos archipelago.
We used four variable microsatellite loci to examine the distribution of genetic variation and degree of genetic structuring among three subcolonies of Waved Albatrosses (Phoebastria irrorata). The breeding population of this species is almost entirely limited to the island of Española in the Galápagos Archipelago. Such strong philopatry could lead to population genetic structure among subcolonies on the island. Pairwise values of the FST analog, θ, calculated from microsatellite genotypes, were all less than 0.012, indicating little genetic differentiation and the presence of gene flow throughout the population.
Question: How well are genetic benefits hypotheses for extra-pair paternity supported by empirical evidence?
Data incorporated: Almost all published studies testing for genetic benefits from 1980 onwards (121 papers, 55 species).
Analysis methods: Collected key features and findings of each study in a database. Determined overall level of support for both good genes and compatible genes hypotheses. Conducted a formal meta-analysis on a subset of studies asking the following questions: (1) Do extra-pair mates of females have different phenotypes than their within-pair mates? (2) Do extra-pair offspring differ in viability from within-pair offspring? (3) Is there a correlation between the genetic similarity of a social pair and the incidence of extra-pair paternity?
Results: Both the good genes and compatible genes hypotheses failed to be supported in more than half of the species studied. The meta-analysis shows that extra-pair males are on average larger and older than within-pair males, but not different in terms of secondary sexual traits, condition or relatedness to the female. No difference was found between extra-pair and within-pair young in survival to the next breeding season. We found no significant correlation between pair genetic similarity and extra-pair paternity.
Conclusions: Genetic benefits are not strongly supported by available empirical data. New hypotheses are needed.
We use data from a long-term population study in combination with DNA fingerprint data to study the frequency of inbreeding and its effects on reproductive parameters in a blue tit population. Close inbreeding was very rare in this population. The proportion of unhatched eggs in a clutch was related to the degree of genetic similarity between the parents as determined by multilocus DNA fingerprinting. Data from blue and great tit populations studied over 15 years show that about 25-30% of blue tit and 20% of great tit nests contained at least one unhatched egg. The number or proportion of unhatched eggs in the nest was highly repeatable for pairs breeding in different years, but not for individual males or females. Unhatched eggs, therefore, were unlikely to result from functional infertility. The hypothesis that female blue tits engage in extra-pair copulations as insurance against their mate's infertility can thus be discarded. Because the genetic similarity between the female and the extra-pair male was not lower than that between the female and her social partner, our data do not support the hypothesis that females engage in extra-pair copulations to reduce inbreeding depression.
Matings between close relatives often reduce the fitness of offspring, probably because homozygosity leads to the expression of recessive deleterious alleles1, 2, 3, 4, 5. Studies of several animals have shown that reproductive success is lower when genetic similarity between parents is high4, 5, 6, 7, and that survival and other measures of fitness increase with individual levels of genetic diversity8, 9, 10, 11. These studies indicate that natural selection may favour the avoidance of matings with genetically similar individuals. But constraints on social mate choice, such as a lack of alternatives, can lead to pairing with genetically similar mates. In such cases, it has been suggested that females may seek extra-pair copulations with less related males4, but the evidence is weak or lacking4, 5. Here we report a strong positive relationship between the genetic similarity of social pair members and the occurrence of extra-pair paternity and maternity ('quasi-parasitism') in three species of shorebirds. We propose that extra-pair parentage may represent adaptive behavioural strategies to avoid the negative effects of pairing with a genetically similar mate.
AUSENCIA DE ESTRUCTURA GENéTICA ENTRE COLONIAS REPRODUCTIVAS DE PHOEBASTRIA IRRORATA Utilizamos cuatro microsatelites variables para examinar la distribución de la variación genética y el grado de estructura genética entre tres colonias reproductivas de Phoebastria irrorata. La población reproductiva entera de esta especie se limita casi totalmente a la isla de Española, en el archipiélago de Galápagos. Un grado de filopatría marcado podría llevar a la formación de estructura genética poblacional entre colonias en la isla. Todos los valores de θ, un análogo de FST, calculados a partir de genotipos de microsatelites, fueron menores de 0.012, indicando poca diferenciación genética y la presencia de flujo genético a través de la población.
We estimated the rate of extra-pair fertilizations (EPFs) in waved albatrosses (Phoebastria irrorata) on Isla Española, Galápagos, Ecuador, using multilocus minisatellite DNA fingerprinting. Waved albatrosses are socially monogamous, long-lived seabirds whose main population is on Española. Aggressive extra-pair copulation (EPC) attempts have been observed in the breeding colony during the days preceding egg-laying. Our genetic analyses of 16 families (single chicks and their attending parents) revealed evidence of EPFs in four families. In all cases males were the excluded parent. These data suggest that waved albatrosses have an unusually high rate of EPF relative to taxa with similar life histories. Future behavioural observations will determine the extent to which forced vs. unforced EPCs contribute to this high EPF rate.
Although 92% of avian species are socially monogamous, extra-pair copulation (EPC), resulting in extra-pair paternity (EPP), is a common reproductive strategy in birds. Among seabirds, in which the rate of social monogamy reaches 100%, Procellariiformes (albatrosses and petrels) show low EPP rates, with the noticeable exception of the only albatross investigated in this regard, the Waved Albatross Phoebastria irrorata. This species, in which forced copulations are known to occur, showed a surprisingly high rate of EPP (25% of chicks). We investigate here EPP rates in another albatross species, the Wandering Albatross Diomedea exulans, subject to a demographic survey conducted for 38 years. We combined data on pair bonds with analysis of ten microsatellite loci and found that 10.7% of 75 chicks had an extra-pair sire. Although there was some evidence for inbreeding avoidance, within-pair and extra-pair chicks showed similar levels of heterozygosity, and the incidence of EPP was independent of age, experience or past reproductive success. Hence, we found no evidence that females benefit from EPCs. Owing to the male-biased sex ratio in adults, widowed and divorced males required more time to find a new mate (+28 and +72%, respectively) than did females. Combined with high sexual size dimorphism, this phenomenon might promote the forced copulations observed in this species. Our data therefore suggest that EPC is beneficial to unpaired males but occurs at random in females, consistent with the hypothesis that EPP results solely from forced EPCs. However, the importance of the latter for EPP and the part played by solitary males require further investigation.
Parasitic female moorhens (Gallinula chloropus) lay from one to six eggs in the nests of conspecific neighbours. DNA fingerprinting was used to show that parasitic eggs
could be correctly identified when they appeared in addition to or outside the host’s laying sequence. Moorhen hosts accept
all parasitic eggs laid after the 2nd day of their laying period. To understand why moorhen hosts tolerate parasitic eggs,
we tested two hypotheses. (1) The quasi-parasitism hypothesis: females lay their eggs in the evening when the host males are normally in attendance at the nest, so host males may allow
parasitic females to lay in their nests in exchange for fertilizing their eggs. However, DNA fingerprinting showed that all
the parasitic eggs were sired by the parasites’ mates. Parasitic moorhens frequently continue laying a clutch in their own
nest, without a break in the laying sequence after a parasitic laying bout. The eggs laid by brood parasites in their own
nests were also sired by their own mates. Therefore this hypothesis was rejected. (2) The kin selection hypothesis: if one or both members of the host pair are close relatives of the parasite, the costs of rearing parasitic chicks will
be to some degree offset by inclusive fitness benefits. We examined the genetic relationships between parasites and their
hosts using DNA fingerprinting and genealogical data. Natal philopatry by both sexes was relatively common in this population,
and the probability that a neighbour of either sex was a first-order relative (parent-offspring) was calculated as 0.18. Although
first-order relatives were not preferentially chosen as hosts over individuals that were not first-order relatives, even through
random host selection there is almost a one-in-five chance that brood parasites in this population are closely related to
their hosts. This may facilitate host tolerance of parasitic eggs. Other hypotheses are also discussed.
Assuming that a male’s genetic characteristics affect those of his offspring, extra-pair copulation has been hypothesized to increase heterozygosity of the progeny—the “genetic compatibility” hypothesis—and the genetic diversity within litters—the “genetic diversity” hypothesis. We tested these two hypotheses in the alpine marmot (Marmota marmota), a socially monogamous mammal showing a high rate of extra-pair paternity (EPP). In a first step, we tested the assumption that a male’s genetic characteristics (heterozygosity and genetic similarity to the female) affect those of his offspring. Genetic similarity between parents influenced offspring heterozygosity, offspring genetic similarity to their mother, and litter genetic diversity. The father’s heterozygosity also influenced litter genetic diversity but did not affect offspring heterozygosity. Hence, heterozygosity seems not to be heritable in the alpine marmot. In a second step, we compared genetic characteristics of extra-pair young (EPY) and within-pair young (WPY). EPY were less genetically similar to their mother but not more heterozygous than WPY. EPY siblings were also less genetically similar than their WPY half siblings. Finally, the presence of EPY promoted genetic diversity within the litter. Thus, our data support both the “genetic compatibility” and the “genetic diversity” hypotheses. We discuss further investigations needed to determine the primary causes of EPP in this species.
Examines the argument that the evolution of breeding systems of animals and plants has been significantly influenced by the occurrence of inbreeding depression. Contemporary genetic theory of inbreeding depression and heterosis is evaluated, as are the experimental data concerning the strength of inbreeding depression. Partial dominance and epistatic interactions are key causal elements. Mechanisms of inbreeding avoidance include (in plants) homomorphic incompatibility, heterostyly and dioecy; and (in animals) incest avoidance and dispersal. -P.J.Jarvis
In lek-mating systems, males aggregate at display arenas and females visit solely for the purpose of mating. This breeding system is characterized by high variance in male mating success with one male often receiving most copulations. High reproductive skew among males has led to question why males join leks when their chances of reproductive success are so low. Kin selection has been invoked as a mechanism to explain the evolution of lekking behavior, whereby nonreproducing but genetically related males gain indirect inclusive-fitness benefits. Evidence for kin selection among lek-mating birds is, however, mixed. Here, we show that kin selection is unlikely to be an important explanation for evolution of lekking behavior in manakins (Aves: Pipridae). We found that for 4 species chosen from several major clades within Pipridae, males within leks were not significantly more related than expected from random assortment of males in the population. This means that nonreproducing males do not gain indirect inclusive-fitness benefits by joining leks. This result suggests alternative mechanisms must be invoked to explain the evolution of lek-mating systems in manakins. Copyright 2007, Oxford University Press.
Inbreeding depression should favor the ability of females to avoid inbreeding or minimize its effects. We tested for a relationship between genetic similarity of social pairs and the occurrence of extrapair fertilization (EPF) in the Mexican jay (Aphelocoma ultramarina). Multilocus minisatellite and microsatellite DNA fingerprinting was used to detect extrapair young and measure genetic similarity between social parents. We found that 12 of 31 (39%) nests had at least one EPF and 15 of 93 (16%) young were the result of EPF. The mean DNA fingerprinting band sharing score between social mates who had at least one EPF was significantly higher than the mean band sharing score between mates who did not (0.35 versus 0.25). The mean band sharing score for non-EPF dyads (0.25) was similar to the background band sharing among nonrelatives (0.23). The mean band sharing score for mates that had an EPF was significantly higher than that of nonrelatives (background) and was significantly lower than that of half-siblings (0.52). Our results showed a highly significant relationship between genetic similarity of social mates and incidence of EPF. Copyright 2005.
House mice prefer mates genetically dissimilar at the major histocompatibility complex (MHC). The highly polymorphic MHC genes control immunological self/nonself recognition; therefore, this mating preference may function to provide "good genes" for an individual's offspring. However, the evidence for MHC-dependent mating preferences is controversial, and its function remains unclear. Here we provide a critical review of the studies on MHCdependent mating preferences in mice, sheep, and humans and the possible functions of this behavior. There are three adaptive hypotheses for MHC-dependent mating preferences. First, MHCdisassortative mating preferences produce MHC-heterozygous offspring that may have enhanced immunocompetence. Although this hypothesis is not supported by tests of single parasites, MHC heterozygotes may be resistant to multiple parasites. Journal Article
Whether inbreeding affects the demography and persistence of natural populations has been questioned. However, new pedigree data from field populations and molecular and analytical tools for tracing patterns of relationship and inbreeding have now enhanced our ability to detect inbreeding depression within and among wild populations. This work reveals that levels of inbreeding depression vary across taxa, populations and environments, but are usually substantial enough to affect both individual and population performance. Data from bird and mammal populations suggest that inbreeding depression often significantly affects birth weight, survival, reproduction and resistance to disease, predation and environmental stress. Plant studies, based mostly on comparing populations that differ in size or levels of genetic variation, also reveal significant inbreeding effects on seed set, germination, survival and resistance to stress. Data from butterflies, birds and plants demonstrate that populations with reduced genetic diversity often experience reduced growth and increased extinction rates. Crosses between such populations often result in heterosis. Such a genetic rescue effect might reflect the masking of fixed deleterious mutations. Thus, it might be necessary to retain gene flow among increasingly fragmented habitat patches to sustain populations that are sensitive to inbreeding.
Simple tandem-repetitive regions of DNA (or 'minisatellites') which are dispersed in the human genome frequently show substantial length polymorphism arising from unequal exchanges which alter the number of short tandem repeats in a minisatellite. We have shown previously that the repeat elements in a subset of human minisatellites share a common 10-15-base-pair (bp) 'core' sequence which might act as a recombination signal in the generation of these hypervariable regions. A hybridization probe consisting of the core repeated in tandem can detect many highly polymorphic minisatellites simultaneously to provide a set of genetic markers of general use in human linkage analysis. We now show that other variant (core)n probes can detect additional sets of hypervariable minisatellites to produce somatically stable DNA 'fingerprints' which are completely specific to an individual (or to his or her identical twin) and can be applied directly to problems of human identification, including parenthood testing.
The amount of extra-pair paternity in socially monogamous bird species varies from 0% to 76% extra-pair offspring. The causes of this remarkable interspecific variation are largely unknown, although intraspecific analyses suggest that females seek extra-pair matings to improve the genetic quality of their offspring. If this is a general explanation for the occurrence of extra-pair matings, then proportionally more females should seek to modify the paternity of their clutch when there is more variation among males in their genetic quality. Here we test this prediction in birds and show that interspecific variation in the proportion of extra-pair offspring is positively related to the proportion of polymorphic loci as measured by protein electrophoresis, even when controlling for potentially confounding variables. Genetic variability was also assessed, for sister pairs of species and populations differing significantly in extra-pair paternity, by using random priming, which provides an estimate of genome-wide diversity. We found that genetic diversity was higher in the populations with a higher level of extra-pair paternity. These results suggest that the amount of genetic variability in a population may be an important factor influencing mating patterns.
Habitat fragmentation and global climate change are the two major environmental threats to the persistence of species and ecosystems. The probability of a species surviving such changes is strongly dependent on its ability to track shifts in the environmental, either by moving between patches of habitat or by rapidly adapting to local condition. These 'solutions' to problems posed by environmental change depend on dispersal propensity, motivating our desire to better understand this important behavior. This book is a comprehensive overview of the new developments in the study of dispersal and the state-of-the-art research on the evolution of this trait. The causes, mechanisms, and consequences of dispersal at the individual , population, and species levels are considered. The promise of new techniques and models for studying dispersal, drawn from molecular biology and demography is explored. Perspectives on the study of dispersal are offered from evolution, conservation biology, and genetics. Throughout the book, theoretical approaches are combined with empirical data, and examples are included from as wide a range of species as possible.
The DNA-fingerprinting technique was used to find the true pedigrees and to detect the overall genetic similarity between mates of great reed warblers (Acrocephalus arundinaceus) at an isolated breeding site in Sweden. The study covered 4 yr preceded by 3 yr when almost all adults and nestlings in the study area had been banded. DNA fingerprinting revealed that the putative father had sired 97% of the young (N = 455). The mate's genetic similarity, revealed as the proportion of bands shared in restriction fragment length polymorphism (RFLP) patterns, was high compared with other species of wild birds. Also, band sharing was higher between mates native to the area than between pairs in which the female was experimentally introduced from a distant breeding site. Hatching success of eggs was negatively correlated with the degree of genetic similarity between the mates, whereas pedigree data, up to the level of great-grandparents, clearly demonstrated an absence of close inbreeding. These are the first data showing a significant fitness cost associated with the choice of a mate that has high genetic similarity, even if it is not a close kin. This cost might be caused by generalized negative consequences of genomewide inbreeding in the present study, possibly accentuated by recent population bottlenecks.
DNA microsatellites are genetic markers that can be useful in addressing questions at a variety of scales, ranging from the extremely fine grained to the fairly coarse grained. More specifically, this genetic tool can help solve problems ranging from individual-specific, such as determining gender, to questions of relatedness and parentage. The rise of polymerase chain reaction (PCR)-based microsatellite markers provides abundant opportunities but also calls for caution. Because of their suitability for addressing problems at a fairly wide range of levels of organization from within individuals to among populations or species, a considerable expansion of interest in the interactions across these scales is foreseen. Differences in mutation processes and rates between microsatellites and allozymes provide both opportunities and problems for analysis of population subdivision. In allozyme analyses, new alleles arise by point mutations, and allelic variation has usually been modeled under the assumption of infinite alleles. The need for careful assessment of the fit among the demographic parameters of the population analyzed (migration, drift, mutation rate) and the assumptions of the models used to analyze it cannot be overemphasized. Application of an inappropriate model can lead to the wrong conclusions about the patterns and processes of genetic differentiation.
The DNA-fingerprinting technique was used to find the true pedigrees and to detect the overall genetic similarity between mates of great reed warblers (Acrocephalus arundinaceus) at an isolated breeding site in Sweden. The study covered 4 yr preceded by 3 yr when almost all adults and nestlings in the study area had been banded. DNA fingerprinting revealed that the putative father had sired 97% of the young (N = 455). The mate's genetic similarity, revealed as the proportion of bands shared in restriction fragment length polymorphism (RFLP) patterns, was high compared with other species of wild birds. Also, band sharing was higher between mates native to the area than between pairs in which the female was experimentally introduced from a distant breeding site. Hatching success of eggs was negatively correlated with the degree of genetic similarity between the mates, whereas pedigree data, up to the level of great-grandparents, clearly demonstrated an absence of close inbreeding. These are the first data showing a significant fitness cost associated with the choice of a mate that has high genetic similarity, even if it is not a close kin. This cost might be caused by generalized negative consequences of genomewide inbreeding in the present study, possibly accentuated by recent population bottlenecks.
Science is about discovering new things, about better understanding processes and systems, and generally furthering our knowledge. Deep in science philosophy is the notion of hypotheses and mathematical models to represent these hypotheses. It is partially the quantification of hypotheses that provides the illusive concept of rigor in science. Science is partially an adversarial process; hypotheses battle for primacy aided by observations, data, and models. Science is one of the few human endeavors that is truly progressive. Progress in science is defined as approaching an increased understanding of truth – science evolves in a sense.
Applications of molecular methods to assess parentage have revealed that the distribution of reproductive success among individuals often differs, sometimes dramatically, from expectation based on observation of behavioral association. Much theory exists on whether and when males should reduce parental care in response to level of paternity. Life-history theory predicts that trade-offs in reproductive effort should be influenced by adult survival. We used a dynamic programming approach to address how level of paternity, ability to assess paternity, and adult survival rate interact to affect male tolerance of reduced parentage in a given brood. Adult survival has the greatest influence on male decisions such that, for any given cost of reproduction and value of male care, tolerance of extrapair fertilizations (EPFs) decreases as adult survival increases. An unexpected result of these models is that an optimal response also depends on a male's ability to predict probability of parentage (i.e., uncertainty). These models better characterize the nature of paternity uncertainty and its effect on EPF tolerance than have previous models and add to our understanding of the complex relationship between uncertainty, mating strategies, and adult survival.
In theories of mate choice that rely on genetic benefits, the nature of the ''good genes'' involved has received little attention. A review of genetic studies of mate choice in a variety of species and situations suggests that individual heterozygosity is more important than previously realized. Females are predicted to value heterozygosity in their offspring and under some conditions in their males. The expression of vigor, condition-sensitive ornaments, and symmetry in males may be a direct reflection not of ''good genes'' but of individual heterozygosity at key loci or at many loci. Like sexuality itself, mate choice based on heterozygosity and genic diversity may be an adaptation that favors the production of diverse and superior competitors. Female choice is made meaningful by sexuality and the adaptive value of choice probably depends on some of the same factors that maintain sexuality.
La llegada temprana a los sitios de apareamiento puede influenciar el éxito reproductivo mediante el acceso privilegiado a los recursos críticos como los sitios de nidificación o las parejas. Una hipótesis que explica la protandria, o la llegada anticipada de los machos a los sitios de apareamiento, propone que los machos llegan primero para incrementar sus oportunidades de copulación extrapareja (CEP), lo que puede, a su vez, incrementar el éxito reproductivo de los machos mediante las fertilizaciones extra-pareja (FEP) (“hipótesis de oportunidad de apareamiento”). El comportamiento extra-pareja es inesperado en las aves longevas, en las cuales se espera que los machos abandonen las nidadas cuya paternidad sea incierta, debido a que la probabilidad de un futuro evento reproductivo es elevada. Un estudio previo del albatros Phoebastria irrorata, un ave marina longeva socialmente monógama, mostró evidencia de FEP en 4 de 16 (25%) familias. Aquí, combinamos observaciones de comportamiento de cópula con evidencias genéticas moleculares adicionales de FEP en las familias de P. irrorata para investigar las consecuencias de la protandria sobre la adecuación biológica en el marco de la hipótesis de oportunidad de apareamiento. Durante tres estaciones reproductivas, documentamos 3,661 intentos de copulación entre aves de identidad conocida. Más del 60% de las cópulas que incluyeron al menos un ave reproductiva fueron clasificadas como CEP. La protandria fue elevada en las tres áreas de estudio: 76.3– 96.6% de los machos llegaron antes (típicamente, 6–10 días antes) que sus parejas sociales. La llegada temprana se asoció con un incremento en las oportunidades de copulación: las frecuencias individuales de CEP fueron mayores para los machos reproductivos que para las hembras reproductivas, y los machos que llegaron más temprano que sus parejas sociales participaron en la mayoría de las CEP. Las fertilizaciones extra-pareja también fueron frecuentes en nuestra población de estudio; los padres sociales fueron excluidos como los procreadores genéticos en el 14–21% de las familias. Las fechas de puesta de los huevos de las FEP tendieron a darse más temprano en la estación que las fertilizaciones intra-pareja. Sin embrago, la llegada temprana de un macho no se tradujo en una mayor probabilidad de engendrar pichones tanto intra-como extra-pareja, ni tampoco los machos cornudos tuvieron un éxito reproductivo mayor. Aunque las consecuencias para la adecuación biológica de la llegada temprana permanecen poco claras, estos resultados sugieren ventajas alternativas de la llegada temprana de los machos de P. irrorata.
Extrapair paternities (EPP) are relatively common in passerines, but rare in seabirds. Like most seabirds, albatrosses are long lived, form long-term pair bonds and require biparental care for chick-rearing. Microsatellite analyses of 327 chicks from black-browed Thalassarche melanophris, grey-headed T. chrysostoma and wandering albatrosses Diomedea exulans over two breeding seasons revealed the presence of EPP in all three species. Though EPP rates varied between species and years, up to 21% of offspring were the result of extrapair matings. Rates were highest in wandering albatrosses (6–21%) followed by grey-headed (3–10%) and black-browed (0–9%) albatrosses. EPP rates were lower in 1998 compared to 1999 in both black-browed and grey-headed albatrosses, whereas the reverse was true for wandering albatrosses. Interspecific differences in EPP rates may reflect differences in breeding phenology and sexual size dimorphism. Differences in timing and frequency of breeding may promote different opportunities for interactions with birds other than their normal partner. The different breeding habitat, dispersion and mate-attraction rituals in wandering albatross, together with the disparity in size between the sexes may also offer more scope for higher rates of EPP. Despite extensive sampling within each colony, we were unable to identify sires for many of the extrapair young; however males from other colonies were involved, raising interesting questions regarding the timing and nature of such events.
As a nesting species, the Waved Albatross Diomedea irrorata is restricted to Hood Island in the Galapagos archipelago where 12,000 pairs bred in 1971. Outside the islands the species occurs over the northern parts of the Humboldt Current.
Two colonies were studied in detail (1970–1971). At the start of a season, males returned first to the colonies and defended a small territory. Copulation occurred without any elaborate ceremony and the female spent little time on land before laying. There was no fixed nest-site, even within a season, and birds moved their eggs considerable distances. This resulted in heavy egg losses. Younger birds bred later than older birds and laid longer but narrower eggs. The average incubation spell varied from four to five days at the extremes of the incubation period to 19 days in the middle. The average incubation and fledging periods were 60 and 167 days respectively. Pairs which lost an egg sometimes adopted the abandoned egg of another bird and successfully reared the chick. Most pairs nested in both seasons.
Nesting success was extremely variable, both between years and between colonies. Between 1961 and 1971 at Punta Suarez, virtually no young were reared in four seasons. Even in 1970–71, where nesting success was good, some groups of birds deserted their eggs en masse whereas in neighbouring areas up to 80% of the pairs reared young.
The main foods of the young were squid and fish.
Birds did not moult wing and tail feathers at the breeding colonies, and about 50% retained some primaries for more than one season, suggesting that successful pairs had difficulty in fitting in a complete moult between breeding attempts. Old feathers were normally found among the inner primaries and at the next moult were preferentially replaced, though adjacent newer feathers were sometimes retained for another season.
Some birds bred in their fourth years, but most not until a year or two older. Immatures were present at the colonies late in the breeding cycle, the youngest returning latest and remaining until the last young fledged.
Survival of adults and young averaged at least 95% and 93% per annum over many years. Adults and young ringed in 1961 survived equally well.
The significance of the timing of the return of immatures and of the large-scale desertion of eggs, apparently not due to food shortage or disturbance, is discussed.
Information theory and log-likelihood models - a basis for model selection and inference practical use of the information theoretic approach model selection uncertainty with examples Monte Carlo insights and extended examples statistical theory.
Paternity likelihood was tested in a population of splendid fairy-wrens Malurus splendens by allozyme electrophoresis. A total of 91 offspring of 24 dams and 37 putative sires were typed at 10 polymorphic loci. All young were compatible with their dams but at least 65% were not fathered by any of the males in their group. A long-term study of this wren population has shown that the males are sedentary, show little evidence of dispersal and help care for the nestlings and fledglings in their group. Had the senior male sired all the offspring in his group, there would have been a high incidence of close inbreeding. The promiscuous mating system demonstrated here would reduce the level of inbreeding in the population but still allow individuals the security of group-living in a stable year-round territory.
Møller and Birkhead (1992, 1993) reported that extra-pair copulations (EPCs) occur more frequently in colonial than dispersed
nesting birds. We comprehensively reviewed published data to investigate how breeding density affects extra-pair fertilizations
(EPFs). Within species EPFs appeared to increase with density: two of three studies on colonial breeders and six of eight
on dispersed nesters showed increases in EPFs with increasing density. However, comparisons among species (n = 72) revealed no evidence that EPF frequencies correlated with (1) nesting dispersion, (2) local breeding density, or (3)
breeding synchrony, even when each of these variables in turn was held constant and phylogenetic relationships were taken
into account via contrast analyses. Methodological and biological reasons for the disparity between observational studies
of EPCs and molecular genetic analyses of EPFs are discussed.
Genetic parentage studies of socially monogamous birds reveal a widespread prevalence of extra-pair paternity. Variation in
extra-pair paternity among individuals may depend on how different individuals benefit from extra-pair fertilisations and
on the opportunity to pursue extra-pair copulations. A long-term study of sand martins (Riparia riparia) in Hungary allowed us to examine patterns of extra-pair fertilisations in a large colony of over 3,000 breeding pairs with
many known age individuals. We used multi-locus DNA fingerprinting to determine whether extra-pair fertilisations occur when
females are paired to (1) presumably low quality mates, or (2) genetically similar or dissimilar mates, and whether extra-pair
fertilisations result in offspring of higher quality. Extra-paternal young were found in 38% of 47 broods and comprised 19%
of 190 offspring. Males that lost paternity did not differ significantly from others in age or body condition. Social mates
of broods containing extra-pair offspring did not differ in genetic similarity from pairs without extra-pair offspring. Furthermore,
there was no significant difference in body condition between extra-pair young and their maternal half-siblings. We were unable
to assign paternity and therefore cannot exclude the possibility that extra-pair males differed from the within-pair males
they cuckolded, in age, body condition or genetic similarity with the female. We found a positive relationship between paternity
losses and breeding density, suggesting that low breeding density may constrain opportunities for seeking extra-pair copulations.
The benefits of extrapair mating behaviour for females of socially monogamous bird species are unclear despite substantial research effort. The genetic compatibility hypothesis proposes genetic benefits such that females paired to social mates of low genetic compatibility avoid or diminish negative fitness consequences by mating with a more compatible extrapair mate, resulting in offspring of higher genetic quality. Furthermore, within the context of inbreeding depression observed in natural populations, a high degree of overall genetic similarity between social pair mates may be regarded as a special case of genetic incompatibility. We tested the hypothesis that female extrapair matings represent an adaptive behavioural response to avoid negative consequences of being paired to a genetically similar social pair male in the coal tit, Parus ater, a socially monogamous passerine with high rates of extrapair paternity. In contrast to what was predicted, we found no evidence for a positive association between the genetic similarity of social pair mates (measured as band-sharing coefficients from multilocus DNA fingerprints) and the occurrence of extrapair paternity. Furthermore, the genetic similarity of the cuckolding female with its social mate was not higher when compared pairwise to that of its extrapair mate in 63 uniquely composed triplets. Finally, three parameters of reproductive success were not related to the genetic similarity of social pair mates. We conclude that avoiding the potentially negative fitness consequences of being paired to a genetically similar social pair mate did not select for and thus cannot maintain female extrapair mating behaviour in our study population.
In common gull colonies on islands of the Vistula River, Poland, adoption of chicks is common. In 1997, we observed 81 chicks from 35 nests. Of these, 19 (23.4%) left their natal broods and were adopted by other pairs. Another 11 (31.4%) were driven from the foreign territory by the owners. Foreign chicks were adopted by 15 pairs (42.9%). Eleven pairs (31.4%) drove foreign chicks from the territory. To test if the frequent adoptions in these colonies could be explained by kin selection or the occurrence of kin groups, we calculated band-sharing coefficients and genetic relatedness (r) between interacting birds (neighbours and non-neighbours). Adults that adopted were most often neighbours of the biological parents of adopted chicks, whereas spatially segregated birds, nesting further away, usually drove off the chicks. Band-sharing coefficients between males, but not females, were higher with decreasing internest distances. The band-sharing coefficients for adopted chicks and foster parents were significantly higher than for adopted chicks and randomly selected, spatially segregated pairs from the same and another colony. Band-sharing coefficients of adopted chicks and adopting neighbours (males: r=0.20; females: r=0.16) also tended to be higher than those of rejected chicks and rejecting neighbours (both sexes: r=0.08). Our results suggest that kin groups of neighbours do occur in common gull colonies. Such social structure might lead to indirect inclusive fitness benefits of adopting pairs. Differences in genetic similarity between chicks and adopting or rejecting neighbours show that at least in common gulls we should consider kin altruism as a factor in adoptions.
The phenomenon of inbreeding depression is well documented and behavioral adaptations for inbreeding avoidance have been described. However, there is debate over whether inbreeding depression is always an important selective force on behavior. Here, we summarize recent evidence for inbreeding depression under natural conditions, review inbreeding avoidance mechanisms, and discuss how these are influenced by social structure. We also examine the idea that animals have evolved mechanisms to avoid outbreeding.
Recent developments in ecological statistics have reached behavioral ecology, and an increasing number of studies now apply analytical tools that incorporate alternatives to the conventional null hypothesis testing based on significance levels. However, these approaches continue to receive mixed support in our field. Because our statistical choices can influence research design and the interpretation of data, there is a compelling case for reaching consensus on statistical philosophy and practice. Here, we provide a brief overview of the recently proposed approaches and open an online forum for future discussion ( https://bestat.ecoinformatics.o rg/ ). From the perspective of practicing behavioral ecologists relying on either correlative or experimental data, we review the most relevant features of information theoretic approaches, Bayesian inference, and effect size statistics. We also discuss concerns about data quality, missing data, and repeatability. We emphasize the necessity of moving away from a heavy reliance on statistical significance while focusing attention on biological relevance and effect sizes, with the recognition that uncertainty is an inherent feature of biological data. Furthermore, we point to the importance of integrating previous knowledge in the current analysis, for which novel approaches offer a variety of tools. We note, however, that the drawbacks and benefits of these approaches have yet to be carefully examined in association with behavioral data. Therefore, we encourage a philosophical change in the interpretation of statistical outcomes, whereas we still retain a pluralistic perspective for making objective statistical choices given the uncertainties around different approaches in behavioral ecology. We provide recommendations on how these concepts could be made apparent in the presentation of statistical outputs in scientific papers. Copyright 2009, Oxford University Press.
The idea that extrapair paternity (EPP) in birds is part of a mixed reproductive strategy driven primarily by females is controversial. In cooperatively breeding American crows, we compared predictions of four female benefits hypotheses-the genetic diversity, good genes, genetic compatibility, and direct benefits hypotheses-to our predictions if EPP was primarily male driven. We found that genetically diverse broods were not more successful, extrapair young were not in better condition and did not have a higher survival probability, and, contrary to prediction, offspring sired by within-group extrapair males were more inbred than within-pair offspring. There was evidence of direct benefits, however: provisioning rate and number of surviving offspring were higher in groups containing within-group extrapair sires. Females therefore derived no apparent benefits from extragroup extrapair males but both direct benefits and genetic costs from within-group extrapair males. We suggest that males and females both influence the distribution of EPP in this system.
DNA-fingerprint similarity is being used increasingly to make inferences about levels of genetic variation within and between natural populations. It is shown that the similarity index--the average fraction of shared restriction fragments--provides upwardly biased estimates of population homozygosity but nearly unbiased estimates of the average identity-in-state for random pairs of individuals. A method is suggested for partitioning the DNA-fingerprint dissimilarity into within- and between-population components. Some simple expressions are given for the sampling variances of these estimators.
An abundant tandem repeat has been cloned from genomic DNA of the merlin (Falco columbarius). The cloned sequence is 174 bp in length, and maps by in situ hybridization to the centromeric regions of several of the large chromosomes within the merlin karyotype. Complementary sequences have been identified within a variety of falcon species; these sequences are either absent or in very low copy number in the family Accipitridae. The cloned merlin repeat reveals highly polymorphic restriction patterns in the peregrine falcon (Falco peregrinus). These polymorphisms, which have been shown to be stably inherited within a family of captive peregrines, can be used to differentiate the Greenland and Argentina populations of this endangered raptor species.
Over the past twenty years, several techniques from biochemical and molecular genetics, such as enzyme electrophoresis and isoelectric focusing, have been widely and successfully applied to the study of population differentiation and evolution. However, they have been less applicable to demographic problems such as assigning parentage to individuals within a population. This stems from a general weakness of data derived from enzyme loci: allele frequencies at polymorphic loci are sufficiently skewed that the majority of individuals are of one or two genotypes. Many enzyme systems can only be examined post mortem, so that the loci are of little use if the animals are to be studied in the wild. The search for new and more sensitive techniques for detecting genetic variation has continued, and recently a major discovery has come from molecular biology. Jeffreys et al. have reported the detection of a type of hypervariable 'minisatellite' DNA that is extraordinarily polymorphic in human populations. We have applied their technique to several bird species and particularly to a population of house sparrows (Passer domesticus) near Nottingham. We report here that one of the human minisatellite clones is a suitable probe for sparrow DNA and that it reveals variation as extensive as that found in man. These results suggest that analysis of minisatellite DNA will be a powerful tool in the study of demographic population genetics.
The human genome contains many dispersed tandem-repetitive 'minisatellite' regions detected via a shared 10-15-base pair 'core' sequence similar to the generalized recombination signal (chi) of Escherichia coli. Many minisatellites are highly polymorphic due to allelic variation in repeat copy number in the minisatellite. A probe based on a tandem-repeat of the core sequence can detect many highly variable loci simultaneously and can provide an individual-specific DNA 'fingerprint' of general use in human genetic analysis.