| seasonal timing of reproduction in a tropical bird, the seychelles warbler: a field experiment using translocation. | reproduction of the seychelles warbler (acrocephalus sechellensis), a single-island endemic species living close to the equator, is characterized by a pronounced annual rhythm. the bird usually raises only one or two clutches of one egg each per year. observational data suggest that seasonal changes in feeding conditions are an important proximate factor controlling reproduction. this hypothesis could be tested by transferring breeding pairs from cousin island to islands previously unoccupied at ... | 1996 | 8946261 |
| experimental evidence for innate predator recognition in the seychelles warbler. | nest predation is a major determinant of fitness in birds and costly nest defence behaviours have evolved in order to reduce nest predation. some avian studies have suggested that predator recognition is innate whereas others have stressed the importance of learning. however, none of these studies controlled for the genetic origin of the populations investigated and the effect of unfamiliarity with the predator. here we determined whether experience with a nest predator is a prerequisite for nes ... | 2000 | 11413640 |
| inbreeding in the seychelles warbler: environment-dependent maternal effects. | the deleterious effects of inbreeding can be substantial in wild populations and mechanisms to avoid such matings have evolved in many organisms. in situations where social mate choice is restricted, extrapair paternity may be a strategy used by females to avoid inbreeding and increase offspring heterozygosity. in the cooperatively breeding seychelles warbler, acrocephalus sechellensis, neither social nor extrapair mate choice was used to avoid inbreeding facultatively, and close inbreeding occu ... | 2004 | 15521460 |
| experimental evidence for density-dependent reproduction in a cooperatively breeding passerine. | temporal variation in survival, fecundity, and dispersal rates is associated with density-dependent and density-independent processes. stable natural populations are expected to be regulated by density-dependent factors. however, detecting this by investigating natural variation in density is difficult because density-dependent and independent factors affecting population dynamics may covary. therefore, experiments are needed to assess the density dependence of demographic rates. in this study, ... | 2009 | 19341143 |
| characterization of mhc-i in the blue tit (cyanistes caeruleus) reveals low levels of genetic diversity and trans-population evolution across european populations. | the major histcompatibility complex (mhc) is a vital component of the adaptive immune system in all vertebrates. this study is the first to characterize mhc class i (mhc-i) in blue tits (cyanistes caeruleus), and we use mhc-i exon 3 sequence data from individuals originating from three locations across europe: spain, the netherlands to sweden. our phylogeny of the 17 blue tit mhc-i alleles contains one allele cluster with low nucleotide diversity compared to the remaining more diverse alleles. w ... | 2011 | 21559782 |
| spatio-temporal variation in territory quality and oxidative status: a natural experiment in the seychelles warbler (acrocephalus sechellensis). | 1. fluctuations in the quality of the habitat in which an animal lives can have major consequences for its behaviour and physiological state. in poor-quality habitat with low food availability, metabolically intensive foraging activity is likely to result in increased generation of reactive oxygen species, while scarcity of food can lead to a weakening of exogenously derived antioxidant defences. the consequent oxidant/antioxidant imbalance may lead to elevated oxidative stress. 2. although the ... | 2011 | 21198588 |
| the role of group size and environmental factors on survival in a cooperatively breeding tropical passerine. | 1. variation in survival, a major determinant of fitness, may be caused by individual or environmental characteristics. furthermore, interactions between individuals may influence survival through the negative feedback effects of density dependence. compared to species in temperate regions, we have little knowledge about population processes and variation in fitness in tropical bird species. 2. to investigate whether variation in survival could be explained by population size or climatic variabl ... | 2006 | 17032364 |
| towards unbiased parentage assignment: combining genetic, behavioural and spatial data in a bayesian framework. | inferring the parentage of a sample of individuals is often a prerequisite for many types of analysis in molecular ecology, evolutionary biology and quantitative genetics. in all but a few cases, the method of parentage assignment is divorced from the methods used to estimate the parameters of primary interest, such as mate choice or heritability. here we present a bayesian approach that simultaneously estimates the parentage of a sample of individuals and a wide range of population-level parame ... | 2006 | 17032269 |
| heterozygosity-fitness correlations in a bottlenecked island species: a case study on the seychelles warbler. | we used capture-mark-recapture models to investigate the effects of both individual and parental heterozygosity, measured at microsatellite loci on the survival of seychelles warblers (acrocephalus sechellensis), an endemic island species which went through a severe population bottleneck in the middle of the last century. we found that an individual's survival was not correlated with multilocus heterozygosity, or with heterozygosity at any specific locus. however, maternal, but not paternal, mul ... | 2007 | 17651192 |
| explicit experimental evidence for the effectiveness of proximity as mate-guarding behaviour in reducing extra-pair fertilization in the seychelles warbler. | extra-pair copulations (epcs; copulations outside the pair bond) are widespread in birds and may result in extra-pair fertilizations (epfs). to increase reproductive success, males should not only seek to gain epfs, but also prevent their own females from gaining epfs. although males could reduce the number of epcs by their mates, this does not necessarily mean that they reduce the number of epfs; indeed several studies have found no association between epcs and epfs. male seychelles warblers (a ... | 2007 | 17845440 |
| assessing the cost of helping: the roles of body condition and oxidative balance in the seychelles warbler (acrocephalus sechellensis). | in cooperatively breeding species, helping close relatives may provide important fitness benefits. however, helping can be energetically expensive and may result in increased generation of reactive oxygen species. consequently, an oxidant/antioxidant imbalance can lead to higher oxidative stress susceptibility. given the potential costs of helping, it may be that only individuals with a sufficiently good body condition and/or stable oxidative balance can afford to help. knowledge about relations ... | 2011 | 22046283 |
| helpers at the nest improve late-life offspring performance: evidence from a long-term study and a cross-foster experiment. | conditions during an individual's rearing period can have far reaching consequences for its survival and reproduction later in life. conditions typically vary due to variation in parental quality and/or the environment, but in cooperative breeders the presence of helpers adds an important component to this. determining the causal effect of helpers on offspring fitness is difficult, since high-quality breeders or territories are likely to produce high-quality offspring, but are also more likely t ... | 2012 | 22496744 |
| age-dependent terminal declines in reproductive output in a wild bird. | in many iteroparous species individual fitness components, such as reproductive output, first increase with age and then decline during late-life. however, individuals differ greatly in reproductive lifespan, but reproductive declines may only occur in the period just before their death as a result of an age-independent decline in physiological condition. to fully understand reproductive senescence it is important to investigate to what extent declines in late-life reproduction can be explained ... | 2012 | 22792307 |
| telomere length and dynamics predict mortality in a wild longitudinal study. | explaining variation in life expectancy between individuals of the same age is fundamental to our understanding of population ecology and life history evolution. variation in the length and rate of loss of the protective telomere chromosome caps has been linked to cellular lifespan. yet, the extent to which telomere length and dynamics predict organismal lifespan in nature is still contentious. using longitudinal samples taken from a closed population of acrocephalus sechellensis (seychelles war ... | 2013 | 23167566 |
| the impact of reproductive investment and early-life environmental conditions on senescence: support for the disposable soma hypothesis. | several hypotheses have been put forward to explain the evolution of senescence. one of the leading hypotheses, the disposable soma hypothesis, predicts a trade-off, whereby early-life investment in reproduction leads to late-life declines in survival (survival senescence). testing this hypothesis in natural populations is challenging, but important for understanding the evolution of senescence. we used the long-term data set from a contained, predator-free population of individually marked seyc ... | 2013 | 23961923 |
| the impact of translocations on neutral and functional genetic diversity within and among populations of the seychelles warbler. | translocations are an increasingly common tool in conservation. the maintenance of genetic diversity through translocation is critical for both the short- and long-term persistence of populations and species. however, the relative spatio-temporal impacts of translocations on neutral and functional genetic diversity, and how this affects genetic structure among the conserved populations overall, have received little investigation. we compared the impact of translocating different numbers of found ... | 2014 | 24689851 |
| museum dna reveals the demographic history of the endangered seychelles warbler. | the importance of evolutionary conservation - how understanding evolutionary forces can help guide conservation decisions - is widely recognized. however, the historical demography of many endangered species is unknown, despite the fact that this can have important implications for contemporary ecological processes and for extinction risk. here, we reconstruct the population history of the seychelles warbler (acrocephalus sechellensis) - an ecological model species. by the 1960s, this species wa ... | 2014 | 25553073 |
| senescence in the wild: insights from a long-term study on seychelles warblers. | senescence--the progressive age-dependent decline in performance--occurs in most organisms. there is considerable variation in the onset and rate of senescence between and within species. yet the causes of this variation are still poorly understood, despite being central to understanding the evolution of senescence. long-term longitudinal studies on wild animals are extremely well-suited to studying the impact of environmental and individual characteristics (and the interaction between the two) ... | 2015 | 26344178 |
| no association between personality and candidate gene polymorphisms in a wild bird population. | consistency of between-individual differences in behaviour or personality is a phenomenon in populations that can have ecological consequences and evolutionary potential. one way that behaviour can evolve is to have a genetic basis. identifying the molecular genetic basis of personality could therefore provide insight into how and why such variation is maintained, particularly in natural populations. previously identified candidate genes for personality in birds include the dopamine receptor d4 ... | 2015 | 26473495 |
| social pairing of seychelles warblers under reduced constraints: mhc, neutral heterozygosity, and age. | the prevalence and significance of precopulatory mate choice remains keenly debated. the major histocompatibility complex (mhc) plays a key role in vertebrate adaptive immunity, and variation at the mhc influences individual survival. although mhc-dependent mate choice has been documented in certain species, many other studies find no such pattern. this may be, at least in part, because in natural systems constraints may reduce the choices available to individuals and prevent full expression of ... | 2017 | 26792973 |
| telomere length reveals cumulative individual and transgenerational inbreeding effects in a passerine bird. | inbreeding results in more homozygous offspring that should suffer reduced fitness, but it can be difficult to quantify these costs for several reasons. first, inbreeding depression may vary with ecological or physiological stress and only be detectable over long time periods. second, parental homozygosity may indirectly affect offspring fitness, thus confounding analyses that consider offspring homozygosity alone. finally, measurement of inbreeding coefficients, survival and reproductive succes ... | 2016 | 27184206 |
| the cost of prospecting for dispersal opportunities in a social bird. | understanding why individuals delay dispersal and become subordinates within a group is central to studying the evolution of sociality. hypotheses predict that dispersal decisions are influenced by costs of extra-territorial prospecting that are often required to find a breeding vacancy. little is known about such costs, partly because it is complicated to demonstrate them empirically. for example, prospecting individuals may be of inferior quality already before prospecting and/or have been evi ... | 2016 | 27330175 |
| the impact of conservation-driven translocations on blood parasite prevalence in the seychelles warbler. | introduced populations often lose the parasites they carried in their native range, but little is known about which processes may cause parasite loss during host movement. conservation-driven translocations could provide an opportunity to identify the mechanisms involved. using 3,888 blood samples collected over 22 years, we investigated parasite prevalence in populations of seychelles warblers (acrocephalus sechellensis) after individuals were translocated from cousin island to four new islands ... | 2016 | 27405249 |
| age-specific haemosporidian infection dynamics and survival in seychelles warblers. | parasites may severely impact the fitness and life-history of their hosts. after infection, surviving individuals may suppress the growth of the parasite, or completely clear the infection and develop immunity. consequently, parasite prevalence is predicted to decline with age. among elderly individuals, immunosenescence may lead to a late-life increase in infection prevalence. we used a 21-year longitudinal dataset from one population of individually-marked seychelles warblers (acrocephalus sec ... | 2016 | 27431430 |
| delayed dispersal and the costs and benefits of different routes to independent breeding in a cooperatively breeding bird. | why sexually mature individuals stay in groups as nonreproductive subordinates is central to the evolution of sociality and cooperative breeding. to understand such delayed dispersal, its costs and benefits need to be compared with those of permanently leaving to float through the population. however, comprehensive comparisons, especially regarding differences in future breeding opportunities, are rare. moreover, extraterritorial prospecting by philopatric individuals has generally been ignored, ... | 2016 | 27641712 |
| exploration is dependent on reproductive state, not social state, in a cooperatively breeding bird. | personality is an intriguing phenomenon in populations because it constrains behavioral flexibility. one theory suggests that personality could be generated and maintained if dependent on asset protection. it is predicted that trade-offs with fitness expectations and survival probability encourage consistent behavioral differences among individuals (personality). although not mutually exclusive, the social niche specialization hypothesis suggests that a group of individuals that repeatedly inter ... | 2017 | 28028379 |
| toll-like receptor variation in the bottlenecked population of the seychelles warbler: computer simulations see the 'ghost of selection past' and quantify the 'drift debt'. | balancing selection can maintain immunogenetic variation within host populations, but detecting its signal in a post-bottlenecked population is challenging due to the potentially overriding effects of drift. toll-like receptor genes (tlrs) play a fundamental role in vertebrate immune defence and are predicted to be under balancing selection. we previously characterised variation at tlr loci in the seychelles warbler (acrocephalus sechellensis), an endemic passerine that has undergone a historica ... | 2017 | 28370771 |
| prevalence and diversity of plasmodium and haemoproteus parasites in the globally-threatened aquatic warbler acrocephalus paludicola. | the diversity and prevalence of malaria parasites of the genera plasmodium and haemoproteus were determined in the globally-threatened aquatic warbler acrocephalus paludicola. birds were sampled during migration in portugal and at the wintering quarters in senegal and parasites were detected using molecular methods. only three generalist parasite lineages (plasmodium) were found. there were no significant differences in the prevalence of parasites between sexes in europe, but adults had higher p ... | 2015 | 25924680 |
| mhc-based patterns of social and extra-pair mate choice in the seychelles warbler. | the existence and nature of indirect genetic benefits to mate choice remain contentious. major histocompatibility complex (mhc) genes, which play a vital role in determining pathogen resistance in vertebrates, may be the link between mate choice and the genetic inheritance of vigour in offspring. studies have shown that mhc-dependent mate choice can occur in mammal and fish species, but little work has focused on the role of the mhc in birds. we tested for mhc-dependent mating patterns in the se ... | 2005 | 15870038 |
| testosterone, cuckoldry risk and extra-pair opportunities in the seychelles warbler. | in male birds, testosterone (t) plays an important role in aggressive and mate-attraction behaviour. in the cooperatively breeding seychelles warbler, acrocephalus sechellensis, extra-group copulations (egcs) occur frequently, but are not accompanied by sexual courtship displays as in within-pair copulations. paternity is nearly always gained by primary males. we investigated whether t levels and sperm storage capability (cloacal protuberance (cp)) in adult primary and subordinate males were rel ... | 2004 | 15293855 |
| experimental evidence that kin discrimination in the seychelles warbler is based on association and not on genetic relatedness. | in cooperative breeding systems driven by kin selection, effective kin-recognition cues are important. recognition could be achieved by the direct assessment of the genetic relatedness of individuals or by learning through association. in the seychelles warbler, acrocephalus sechellensis, female subordinates maximize indirect fitness by preferentially helping genetically related nestlings. help seems to be based on the continued presence of the primary female who previously fed the subordinate i ... | 2004 | 15255052 |
| daughters on request: about helpers and egg sexes in the seychelles warbler. | the seychelles warbler (acrocephalus sechellensis) was an endangered endemic of the seychelles islands where, until 1988, the entire population of ca. 320 birds was restricted to the one island of cousin island (29 ha). additional breeding populations were successfully established on the islands of aride (68 ha, 1988) and cousine (26 ha, 1990) and now with the existence of ca. 2000 warblers on three islands the conservation status of the warbler has improved from endangered to vulnerable. emigra ... | 2003 | 12590765 |
| sex-specific associative learning cues and inclusive fitness benefits in the seychelles warbler. | in cooperative breeding vertebrates, indirect fitness benefits would be maximized by subordinates that accurately assess their relatedness to group offspring and preferentially help more closely related kin. in the seychelles warbler (acrocephalus sechellensis), we found a positive relationship between subordinate-nestling kinship (determined using microsatellite marker genotypes) and provisioning rates, but only for female subordinates. female subordinates that helped were significantly more re ... | 2003 | 14635900 |
| direct benefits and the evolution of female-biased cooperative breeding in seychelles warblers. | inclusive fitness benefits have been suggested to be a major selective force behind the evolution of cooperative breeding. we investigated the fitness benefits selecting for cooperative breeding in the seychelles warbler, acrocephalus sechellensis. a microsatellite-based genotyping method was used to determine the relatedness of subordinates to group offspring in an isolated population of seychelles warblers. the indirect and direct breeding benefits accruing to individual subordinates were then ... | 2002 | 12487360 |
| pre-ovulation control of hatchling sex ratio in the seychelles warbler. | females of some bird species have a high degree of control over the sex ratio of their offspring at laying. although several mechanisms have been put forward to explain how females might control the sex of their eggs, virtually nothing is known. as females are the heterogametic sex in birds, adjustment of the clutch sex ratio could arise either by pre- or post-ovulation control mechanisms. the seychelles warbler (acrocephalus sechellensis) exhibits extreme adaptive egg sex ratio bias. typically, ... | 2002 | 12028765 |
| mate guarding in the seychelles warbler is energetically costly and adjusted to paternity risk. | males may increase their fitness through extra-pair copulations (copulations outside the pair bond) that result in extra-pair fertilizations, but also risk lost paternity when they leave their own mate unguarded. the fitness costs of cuckoldry for seychelles warblers (acrocephalus sechellensis) are considerable because warblers have a single-egg clutch and, given the short breeding season, no time for a successful replacement clutch. neighbouring males are the primary threat to a male's genetic ... | 2001 | 11600074 |
| evidence that helping at the nest does not result in territory inheritance in the seychelles warbler. | in an environment that has a shortage of territories, helping to rear younger siblings ('alloparenting') is proposed to facilitate territory acquisition in two ways: (i) through group augmentation that leads to an increase of the territory with subsequent partial inheritance (budding); and (ii) through site dominance that leads to greater success when competing for the natal or a nearby territory after the death of the territory owner (complete territory inheritance). most young seychelles warbl ... | 2001 | 11571047 |
| parentage assignment and extra-group paternity in a cooperative breeder: the seychelles warbler (acrocephalus sechellensis). | we describe the development and initial application of a semiautomated parentage testing system in the seychelles warbler (acrocephalus sechellensis). this system used fluorescently labelled primers for 14 polymorphic microsatellite loci in two multiplex loading groups to genotype efficiently over 96% of the warbler population on cousin island. when used in conjunction with the program cervus, this system provided sufficient power to assign maternity and paternity within the seychelles warbler, ... | 2001 | 11555268 |
| fifty seychelles warbler (acrocephalus sechellensis) microsatellite loci polymorphic in sylviidae species and their cross-species amplification in other passerine birds. | | 2000 | 11123666 |
| spatio-temporal variation in lifelong telomere dynamics in a long-term ecological study. | understanding individual-level variation in response to the environment is fundamental to understanding life-history evolution and population dynamics. telomeres, the protective caps at the ends of chromosomes, shorten in response to oxidative stress, and telomere shortening is correlated with reduced survival and lifespan. investigating telomere dynamics may help us quantify individual variation in the costs experienced from social and ecological factors, and enhance our understanding of the dy ... | 2017 | 28796902 |
| socio-ecological conditions and female infidelity in the seychelles warbler. | within socially monogamous breeding systems, levels of extra-pair paternity can vary not only between species, populations, and individuals, but also across time. uncovering how different extrinsic conditions (ecological, demographic, and social) influence this behavior will help shed light on the factors driving its evolution. here, we simultaneously address multiple socio-ecological conditions potentially influencing female infidelity in a natural population of the cooperatively breeding seych ... | 2020 | 31579133 |
| experimentally induced antipredator responses are mediated by social and environmental factors. | nest predation is a common cause of reproductive failure for many bird species, and various antipredator defense behaviors have evolved to reduce the risk of nest predation. however, trade-offs between current reproductive duties and future reproduction often limit the parent's ability to respond to nest predation risk. individual responses to experimentally increased nest predation risk can give insights into these trade-offs. here, we investigate whether social and ecological factors affect in ... | 2020 | 31289428 |
| age-dependent changes in infidelity in seychelles warblers. | extra-pair paternity (epp) is often linked to male age in socially monogamous vertebrates; that is, older males are more likely to gain epp and less likely to be cuckolded. however, whether this occurs because males improve at gaining paternity as they grow older, or because "higher quality" males that live longer are preferred by females, has rarely been tested, despite being central to our understanding of the evolutionary drivers of female infidelity. moreover, how extra-pair reproduction cha ... | 2020 | 32706433 |
| breeders that receive help age more slowly in a cooperatively breeding bird. | helping by group members is predicted to lead to delayed senescence by affecting the trade-off between current reproduction and future survival for dominant breeders. here we investigate this prediction in the seychelles warbler, acrocephalus sechellensis, in which mainly female subordinate helpers (both co-breeders and non-breeding helpers) often help dominants raise offspring. we find that the late-life decline in survival usually observed in this species is greatly reduced in female dominants ... | 2019 | 30899016 |
| compensatory and additive helper effects in the cooperatively breeding seychelles warbler (acrocephalus sechellensis). | in cooperatively breeding species, care provided by helpers may affect the dominant breeders' investment trade-offs between current and future reproduction. by negatively compensating for such additional care, breeders can reduce costs of reproduction and improve their own chances of survival. alternatively, helper care can be additive to that of dominants, increasing the fledging fitness of the current brood. however, the influence helpers have on brood care may be affected by group size and te ... | 2019 | 30891231 |
| subordinate females in the cooperatively breeding seychelles warbler obtain direct benefits by joining unrelated groups. | in many cooperatively breeding animals, a combination of ecological constraints and benefits of philopatry favours offspring taking a subordinate position on the natal territory instead of dispersing to breed independently. however, in many species individuals disperse to a subordinate position in a non-natal group ("subordinate between-group" dispersal), despite losing the kin-selected and nepotistic benefits of remaining in the natal group. it is unclear which social, genetic and ecological fa ... | 2018 | 29750837 |
| joint care can outweigh costs of nonkin competition in communal breeders. | competition between offspring can greatly influence offspring fitness and parental investment decisions, especially in communal breeders where unrelated competitors have less incentive to concede resources. given the potential for escalated conflict, it remains unclear what mechanisms facilitate the evolution of communal breeding among unrelated females. resolving this question requires simultaneous consideration of offspring in noncommunal and communal nurseries, but such comparisons are missin ... | 2020 | 29622934 |
| repeatable and heritable behavioural variation in a wild cooperative breeder. | quantifying consistent differences in behaviour among individuals is vital to understanding the ecological and evolutionary significance of animal personality. to quantify personality, the phenotypic variation of a behavioural trait is partitioned to assess how it varies among individuals, which is also known as repeatability. if pedigree data are available, the phenotypic variation can then be further partitioned to estimate the additive genetic variance and heritability. assessing the repeatab ... | 2020 | 29622921 |
| extra-pair parentage and personality in a cooperatively breeding bird. | why so much variation in extra-pair parentage occurs within and among populations remains unclear. often the fitness costs and benefits of extra-pair parentage are hypothesised to explain its occurrence; therefore, linking extra-pair parentage with traits such as personality (behavioural traits that can be heritable and affect reproductive behaviour) may help our understanding. here, we investigate whether reproductive outcomes and success are associated with exploratory behaviour in a natural p ... | 2019 | 29491549 |
| kinship and familiarity mitigate costs of social conflict between seychelles warbler neighbors. | because virtually all organisms compete with others in their social environment, mechanisms that reduce conflict between interacting individuals are crucial for the evolution of stable families, groups, and societies. here, we tested whether costs of social conflict over territorial space between seychelles warblers (acrocephalus sechellensis) are mitigated by kin-selected (genetic relatedness) or mutualistic (social familiarity) mechanisms. by measuring longitudinal changes in individuals' body ... | 2017 | 29073100 |
| population regulation in group-living birds: predictive models of the seychelles warbler. | a major challenge for population ecology is to predict population responses to novel conditions, such as habitat loss. this frequently involves understanding dispersal decisions, in terms of their consequences for fitness. however, this approach requires detailed data, and is thus often inappropriate for urgent problems on poorly known species. this may be resolved by developing a predictive framework based on well-studied species, for applying to those that are less well understood. population ... | 2003 | 30893959 |
| sex-ratio selection in species with helpers at the nest: the repayment model revisited. | we reexamine the theoretical and empirical basis for the "repayment model" of emlen, emlen, and levin, which predicts that the overall sex ratio of offspring in cooperative-breeding species with helpers at the nest should be biased toward the more helpful sex. we conclude that in theory the model may yield a biased sex ratio but only under restricted conditions that are unlikely to be met in most populations. in those cases where the model is potentially applicable, estimates of both direct and ... | 1999 | 29578772 |