Biology subjects

Hoareau, T. B.

Publications and source records attributed to Hoareau, T. B..

4 recordsLinked to original sources

bioRxiv2025

A framework for integrating genomic profiles into captive breeding and reinforcement programmes: A case study on captive saker falcons

Ex-situ conservation is crucial for preserving endangered species by breeding to preserve genetic diversity and provide surplus for translocation, thereby supporting in-situ conservation and enhancing wild populations. Genomic tools can assist breeding strategies and ensure long-term success of ex-situ conservation efforts by assessing genetic introgression, determining genetic origin and status, and inferring genetic relatedness of potential founders. This study aims to develop a comprehensive genomic approach for assessing the genetic profiles of candidate founders for ex-situ breeding, with the goal of releasing surplus individuals while using the endangered Saker Falcons (Falco cherrug) as a study model. Genetic clustering of 31 captive sakers revealed both diverse origins, some matching wild Asian individuals (Mongolia), and a lineage (Group III) divergent from wild populations. Comparative analyses detected hybridisation signals in 61.3% of individuals, including three with gyrfalcon (F. rusticolus) introgression and Group IIIs pronounced divergence indicating past interbreeding with an unknown falcon species. All captive birds exhibited severe inbreeding (FROH = 0.352), far exceeding wild population levels (FROH = 0.131). Using the partial pedigree data of the captive sakers, we established a genetic relatedness threshold of 0.154 (95% CI: 0.096-0.211) to identify cases of related dyads (both full and half-siblings). At this threshold, 18.3% of captive dyads showed relatedness, with asymmetric genetic contributions between pairs, reflecting a functionally small breeding flock. To avoid risks from releasing admixed or inbred individuals, we recommend excluding introgressed birds, strategically pairing purebreds, and sourcing new founders from genetically validated wild sources, especially underrepresented Central Asian lineages. Applying this genomic framework, we demonstrate its role in safeguarding genetic integrity and preventing genetic erosion in conservation breeding programmes, thereby establishing a standard for genomic-led ex-situ conservation.

genomics↗

bioRxiv2021

Contraction-expansion dynamics of reef species in response to sea-level changes

The contraction-expansion model (CEM) describes the dynamics of species that survived in refugia during the last glacial maximum (LGM) and expanded their range when environmental conditions slowly improved from the Late Glacial through to the Holocene. The CEM has been proposed to describe the dynamics of reef species in response to sea-level fluctuations from a range of disciplines, but genetic inferences rather suggest stable population sizes since the last glacial period. Here, we address this paradox by providing a new model of modern reef development, by assessing the effect of LGM bottlenecks using genetic simulations, and by using a survey of the literature on reef species to compile both estimates of times to expansion and applied rates of molecular evolution. Using previously published radiocarbon dates of core data, we propose a synthetic model for the dynamics of modern coral reefs in the Indo-Pacific region. This model describes both an initiation at 9.9 ka and subsequent development that confirms a strong influence of sea-level fluctuations on reef dynamics. Simulations based on mtDNA datasets showed that pre-LGM genetic signatures of expansion are lost. Recent literature shows that, although genetic expansions of tropical marine species are frequent (>95%), the onset of these expansions is old (median ~110 ka), which indicates that most populations have remained stable since before the LGM. These pre-LGM expansions are explained by the low mutation rates (1.66% changes/site/Myr) known to be inadequate to calibrate time at population level. Specific calibrations should help solve the paradox and generalise the CEM for reef species.

genetics↗

bioRxiv2020

Reef development and Sea level changes drive Acanthaster Population Expansion in the Indo-Pacific region

Molecular clock calibration is central in population genetics as it provides an accurate inference of demographic history, whereby helping with the identification of driving factors of population changes in an ecosystem. This is particularly important for coral reef species that are seriously threatened globally and in need of conservation. Biogeographic events and fossils are the main source of calibration, but these are known to overestimate timing and parameters at population level, which leads to a disconnection between environmental changes and inferred reconstructions. Here, we propose the Last Glacial Maximum (LGM) calibration that is based on the assumptions that reef species went through a bottleneck during the LGM, which was followed by an early yet marginal increase in population size. We validated the LGM calibration using simulations and genetic inferences based on Extended Bayesian Skyline Plots. Applying it to mitochondrial sequence data of crown-of-thorns starfish Acanthaster spp., we obtained mutation rates that were higher than phylogenetically based calibrations and varied among populations. The timing of the greatest increase in population size differed slightly among populations, but all started between 10 and 20 kya. Using a curve-fitting method, we showed that Acanthaster populations were more influenced by sea-level changes in the Indian Ocean and by reef development in the Pacific Ocean. Our results illustrate that the LGM calibration is robust and can probably provide accurate demographic inferences in many reef species. Application of this calibration has the potential to help identify population drivers that are central for the conservation and management of these threatened ecosystems.

genetics↗

bioRxiv2020

Whales and Men: genetic inferences uncover a detailed history of hunting in bowhead whale

After millennia of hunting and a population collapse, it is still challenging to understand the genetic consequences of whaling on the circumarctic bowhead whale. Here I use published modern mtDNA sequences from the Bering-Chukchi-Beaufort population and a new time calibration to show that late-glacial climate changes and whaling have been the major drivers of population change. Cultures that hunted in the Arctic Seas from as early as 5000 years ago appear to be responsible for successive declines of the population growth, bringing the effective size down to 38% of its pristine population size. The Thules and the Basques (year 1000-1730) who only hunted in the North Atlantic had a major impact on this North Pacific population, indicating that bowhead whale stocks respond to harvesting as a single population unit. Recent positive growth is inferred only after the end of commercial whaling in 1915, and for levels of harvesting that are close to the current annual quota of 67 whales. By unfolding the population history of the bowhead whale, I provide compelling evidence that mtDNA yields critical yet undervalued information for management and conservation of natural populations.

genetics↗