Biology subjects

Dugdale, H. L.

Publications and source records attributed to Dugdale, H. L..

7 recordsLinked to original sources

bioRxiv2026

Inbreeding depression by polygenic load following a severe population bottleneck

It is poorly understood how populations survive extreme bottlenecks despite severe inbreeding. We investigate the genomic architecture of inbreeding in the once critically endangered Seychelles warbler (Acrocephalus sechellensis) using 37 years of individual-based monitoring and 1.8 million SNPs. Linkage disequilibrium patterns reveal a historical effective population size of [~]270 that plummeted to [~]13 coinciding with human colonisation events of the Seychelles archipelago. Contemporary genomes are over one-third inbred from recent inbreeding measured by runs of homozygosity (ROH) formed since human colonisation of the Seychelles, 50 generations ago (mean FROH < 50 generations ago = 0.38), and we identify significant inbreeding depression across cross key fitness traits. On average, a 17.9% reduction in lifespan and a 15.1% reduction in lifetime offspring production were associated with each 10% increase in individual inbreeding. Genome-wide scans reveal this depression is caused by a polygenic load. Our results suggest that a history of small population size could have facilitated the selective purging of severe genetic load, while mildly deleterious alleles escaped selection via drift. A partitioned genetic load architecture potentially enabled species recovery despite the inbreeding depression that followed near-extinction.

evolutionary biology↗

bioRxiv2025

Life-history traits as predictors of expected genetic contributions 15 years later in a cooperatively breeding bird

An individuals life history plays an important role in how successful individuals are in passing on their genes to future generations. However, exactly which life-history traits best approximate an individuals long-term genetic contributions remains poorly studied, especially in cooperative breeders. Here, we use a genetic pedigree and long-term data of the closed population of the Seychelles warbler (Acrocephalus sechellensis) to calculate the expected individual genetic contributions (IGC) after 15 years (or [~]3 generations) across 11 cohorts. Using a Bayesian analysis we then quantified and compared how well six important life-history traits predict IGC in each sex of this cooperatively breeding species. The life-history traits compared were: acquisition of a dominant breeding position, age at first breeding attempt, tenure as a dominant breeder, lifespan, and LRS (measured as both the number of independent [surviving 3 months+] and recruited [surviving 1 year+] offspring produced over an individuals lifetime). An individuals lifetime reproductive success (LRS) was the strongest predictor of IGC and this predictive power did not differ across the different measurements used. However, this predictive power did differ between sexes, explaining [~]61-62% of IGC variation in males versus [~]47-49% in females owing to the larger variation among males in their annual reproductive success. Across other life-history traits the predictive power of IGC was similar across both sexes but differed between life-history traits considerably (2-37%). Comparing these predictive powers suggested that lifespan and the duration of a dominant breeding position are far more important in shaping long-term genetic contributions than if and when in their life they acquired dominance. Overall, these findings give insight into the individual and population-level processes influencing future gene pools and illustrate how life-history evolution is shaped by sex-specific reproductive patterns and cooperative breeding dynamics.

evolutionary biology↗

bioRxiv2025

Genetic variation in life-history traits is not correlated with estrogen-receptor positive breast cancer risk

Estrogen receptor-positive breast cancer (ER+ BC) is one of the most prevalent cancers, but the evolutionary processes shaping genetic variation in ER+ BC risk are poorly understood. Both evolutionary life-history theory and evidence from studies of individual ER+ BC risk variants suggest that increased genetic ER+ BC risk is associated with faster maturation, earlier reproduction, and/or increased reproductive success (i.e., there is a trade-off), but it is unclear how well this pattern is replicated when considering the polygenic architecture of these traits after controlling for potential biases. Here, we estimate genome-wide genetic correlations between ER+ BC risk and three reproductive traits (age at menarche, age at first birth, and the number of children) using genomic restricted maximum-likelihood analyses on Lifelines biobank data and linkage disequilibrium score regressions on population and family-based genome-wide association study data. Regardless of the data or method used, genetic correlations were low and not statistically significant. Further analyses decomposing genome-wide genetic variance into local regions detected only three loci exhibiting significant pleiotropy between ER+ BC risk and age at menarche, suggesting little shared genetic architecture between ER+ BC risk and reproductive traits. Thus, the role of life-history trade-offs in shaping ER+ BC risk in European populations appears, at most, small, and the evolutionary processes giving rise to this life-threatening disease remain unclear. Future studies could examine the impact of evolutionary mismatches in shaping ER+ BC risk, where conducting longitudinal studies on populations transitioning to reproductive patterns observed in contemporary European populations would be most useful.

evolutionary biology↗

bioRxiv2024

Lifespan costs of reproduction increase during the Great Finnish Famine

Evolutionary theory of aging predicts that women with increased reproductive effort live shorter lives, but evidence is inconsistent. These inconsistencies could be because environmental conditions influence how much a mothers life span is reduced when having more children, i.e. their life-span cost of reproduction. Using a structural equation measurement model, we compare how reproductive effort affects the life span of 4,684 women exposed across different life-stages, or not at all, to the Great Finnish Famine. We find that life span costs of reproduction became higher in mothers exposed to the famine during reproduction, and for these mothers amounted to lower life expectancy of [~]0.5 years per child. Conversely, reproduction did not shape the life spans of mothers not exposed to the famine, or exposed post-reproduction or during development. This natural experiment reveals how environmental adversity can influence reproductive costs, providing a biological explanation for previous inconsistent findings, while showing how reproductive behavior has shaped the evolution of aging in humans. TEASERMothers with more children had shorter lives during a famine, suggesting that harsh conditions increase costs of reproduction.

evolutionary biology↗

bioRxiv2024

A path analysis disentangling determinants of natal dispersal in a cooperatively breeding bird

Delayed offspring dispersal is an important aspect of the evolution of cooperative breeding. By applying a path-analysis approach to the long-term Seychelles warbler (Acrocephalus sechellensis) dataset, we studied whether and how delayed dispersal is affected by territory quality, the presence of helpers and non-helping subordinates, maternal breeding status, age and fecundity, and offspring sex ratio. We found that offspring are more likely to disperse when their genetic mothers are co-breeders, helpers are absent and territory quality is high. In contrast to earlier findings, our analysis does not support the idea that offspring sex ratio is affected by territory quality and helper presence. Our findings suggest that a complex interplay of ecological and social factors shapes dispersal decisions. Our study underscores the importance of considering proximate factors in understanding cooperative breeding dynamics, and it shows that path analyses offer valuable insights into dissecting the intricate relationships influencing dispersal in wild populations.

ecology↗

bioRxiv2022

Lifetime reproductive success is an imprecise but largely unbiased predictor of long-term genetic contribution in historical humans

An individuals lifetime reproductive success (LRS) measures its realised genetic contributions to the next generation, but how well does it predict these over longer periods? Here we use human genealogical data to estimate expected individual genetic contributions (IGC) and quantify the degree to which LRS, relative to other fitness proxies, predicts IGC over longer periods in natural populations. This allows an identification of the life-history stages that are most important in shaping variation in IGC. We use historical genealogical data from two non-isolated local populations in Switzerland to estimate the stabilised IGC for 2,230 individuals ~10 generations after they were born. We find that LRS explains 30% less variation in IGC than the best predictor of IGC, the number of grandoffspring. However, albeit less precise than the number of grandoffspring, we show that LRS does provide an unbiased prediction of IGC and overall predicts IGC better than lifespan and similarly when accounting for offspring survival to adulthood. Overall, our findings demonstrate the value of human genealogy data to evolutionary biology and showing that reproduction - more than lifespan or offspring survival - impacts the long-term genetic contributions of historic humans, even in a population with appreciable migration.

evolutionary biology↗

bioRxiv2018

Compensatory and additive helper effects in the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis).

O_LIIn cooperatively breeding species, helper aid may affect dominant breeders investment trade-offs between current and future reproduction. By compensating for the care provided by helpers, breeders can reduce the costs of reproduction and improve chances of survival. Also, helper care can be additive to that of dominants, resulting in higher success of the current brood.\nC_LIO_LIHowever, the influence of helpers on offspring care itself may be the by-product of group size and territory quality. Therefore to make conclusive inferences about causation of additive and compensatory care as a result of help per se requires disentangling the impact of helping from other factors determining parental investment.\nC_LIO_LIIn this study, we use 20 years of offspring provisioning data to investigate the effect of helping on breeder and overall offspring provisioning rates in the facultative cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). Our extensive dataset allowed us to effectively control for the effects of living in a larger group and in territories with higher food availability.\nC_LIO_LIWe show compensatory and additive care in response to helper aid. Helpers lightened the provisioning load of the dominant male and female and increased the total provisioning to the nestlings. This was irrespective of group size or territory quality (food availability).\nC_LIO_LIOur results illustrate how multiple benefits of helping behaviour can simultaneously be fundamental to the evolutionary maintenance of cooperative behaviour.\nC_LI

animal behavior and cognition↗