Detecting purging of inbreeding depression by a slow rate of inbreeding for various traits: the impact of environmental and experimental conditions

Bundgaard, Jørgen; Loeschcke, Volker; Schou, Mads Fristrup; Bijlsma, Rob G.

doi:10.1038/s41437-021-00436-7

Cited by 11 publications

(4 citation statements)

References 59 publications

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Section: Discussionsupporting

confidence: 85%

“…Additionally, the inbred lines displayed inbreeding depression rates (B) for EAV in line with similar studies on D . melanogaster (Bundgaard et al, 2021; Enders & Nunney, 2010, 2012; Schou et al, 2015). Nonetheless, a large variation in inbreeding depression estimates was seen among different inbred lines, for both traits, despite an expected constant inbreeding level.…”

Section: Discussionmentioning

confidence: 99%

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Sustained positive consequences of genetic rescue of fitness and behavioural traits in inbred populations of Drosophila melanogaster

Ørsted

Kristensen

2022

J of Evolutionary Biology

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One solution to alleviate the detrimental genetic effects associated with reductions in population size and fragmentation is to introduce immigrants from other populations. While the effects of this genetic rescue on fitness traits are fairly well known, it is less clear to what extent inbreeding depression and subsequent genetic rescue affect behavioural traits. In this study, replicated crosses between inbred lines of Drosophila melanogaster were performed in order to investigate the effects of inbreeding and genetic rescue on egg‐to‐adult viability and negative geotaxis behaviour—a locomotor response used to measure, e.g. the effects of physiological ageing. Transgenerational effects of outcrossing were investigated by examining the fitness consequences in both the F1 and F4 generation. The majority of inbred lines showed evidence for inbreeding depression for both egg‐to‐adult viability and behavioural performance (95% and 66% of lines, respectively), with inbreeding depression being more pronounced for viability compared with the locomotor response. Subsequent outcrossing with immigrants led to an alleviation of the negative effects for both viability and geotaxis response resulting in inbred lines being similar to the outbred controls, with beneficial effects persisting from F1 to F4. Overall, the results clearly show that genetic rescue can provide transgenerational rescue of small, inbred populations by rapidly improving population fitness components. Thus, we show that even the negative effects of inbreeding on behaviour, similar to that of neurodegeneration associated with physiological ageing, can be reversed by genetic rescue.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Sustained positive consequences of genetic rescue of fitness and behavioural traits in inbred populations of Drosophila melanogaster

Ørsted

Kristensen

2022

J of Evolutionary Biology

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“…Obviously, purging during ex situ conservation is not expected to act upon traits that are not expressed in captivity but that could be fitness components in the wild. For example, the inbreeding load for heat shock resistance in Drosophila was not purged in lines that had been maintained in stable lab conditions (Bundgaard et al 2021). However, mutation is expected to produce unconditionally deleterious alleles much more often than alleles that are deleterious in some conditions but advantageous in others.…”

Section: Discussionmentioning

confidence: 99%

Genetic purging in captive endangered ungulates with extremely low effective population sizes

2021

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Inbreeding threatens the survival of small populations by producing inbreeding depression, but also exposes recessive deleterious effects in homozygosis allowing for genetic purging. Using inbreeding-purging theory, we analyze early survival in four pedigreed captive breeding programs of endangered ungulates where population growth was prioritized so that most adult females were allowed to contribute offspring according to their fitness. We find evidence that purging can substantially reduce inbreeding depression in Gazella cuvieri (with effective population size Ne = 14) and Nanger dama (Ne = 11). No purging is detected in Ammotragus lervia (Ne = 4), in agreement with the notion that drift overcomes purging under fast inbreeding, nor in G. dorcas (Ne = 39) where, due to the larger population size, purging is slower and detection is expected to require more generations. Thus, although smaller populations are always expected to show smaller fitness (as well as less adaptive potential) than larger ones due to higher homozygosis and deleterious fixation, our results show that a substantial fraction of their inbreeding load and inbreeding depression can be purged when breeding contributions are governed by natural selection. Since management strategies intended to maximize the ratio from the effective to the actual population size tend to reduce purging, the search for a compromise between these strategies and purging could be beneficial in the long term. This could be achieved either by allowing some level of random mating and some role of natural selection in determining breeding contributions, or by undertaking reintroductions into the wild at the earliest opportunity.

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“…If the managed population is reintroduced into the wild, it is expected that the fitness effects of past purging will change, as the expression of the inbreeding load depends on the environment (Kristensen, Loeschcke & Hoffmann, 2008; Cheptou & Donohue, 2011; Reed et al ., 2012; Pemberton et al ., 2017). For example, no purging has been detected for specific traits that are not expressed during the purging process as heat shock resistance (Bijlsma, Bundgaard & Van Putten, 1999; Bundgaard et al ., 2021). However, even though adaptation to captive conditions is likely to imply some detriment to adaptation in the wild, this trade‐off can depend on just a small fraction of the mutations affecting fitness which do not need to make substantial contributions to the fitness inbreeding load.…”

Section: Discussionmentioning

confidence: 99%

Prediction of fitness under different breeding designs in conservation programs

Pérez‐Pereira

López‐Cortegano

García-Dorado

et al. 2022

Animal Conservation

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The expected change in fitness under inbreeding due to deleterious recessive alleles depends on the amount of inbreeding load harbored by a population, that is, the load of deleterious recessive mutations concealed in the heterozygous state, and the opposing effect of genetic purging to remove such a load. This change in fitness can be thus predicted if an estimate of the inbreeding load and the purging coefficient (the parameter that quantifies the amount of purging) are available. These two parameters can be estimated in pedigreed populations, as has been shown for populations under random mating. A question arises whether these parameters can also be estimated under other breeding systems as well as whether they allow accurate prediction of the corresponding expected change in fitness. In conservation programs, it is usually recommended to preserve genetic diversity by equalizing contributions from parents to progeny and avoiding inbred matings. Regular systems of inbreeding have also been proposed as breeding conservation strategies to purge the inbreeding load. Using computer simulations, we first test a method to jointly estimate the initial inbreeding load and the purging coefficient in populations subjected to equalization of parental contributions, circular mating, and partial full-sib mating. Then, using the expected values of the inbreeding coefficient and the variance of family size, as well as the estimates of the inbreeding load and the purging coefficient, we make simple predictions of the change in fitness over generations under these breeding systems and compare them with simulation results. We discuss how these fitness predictions can help undertaking conservation designs under different breeding scenarios.

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Detecting purging of inbreeding depression by a slow rate of inbreeding for various traits: the impact of environmental and experimental conditions

Cited by 11 publications

References 59 publications

Sustained positive consequences of genetic rescue of fitness and behavioural traits in inbred populations of Drosophila melanogaster

Sustained positive consequences of genetic rescue of fitness and behavioural traits in inbred populations of Drosophila melanogaster

Genetic purging in captive endangered ungulates with extremely low effective population sizes

Prediction of fitness under different breeding designs in conservation programs

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