Genetic rescue of an isolated African lion population

Miller, Susan M.; Druce, Dave J.; Dalton, Desiré L.; Harper, Cindy Kim; Kotzé, Antoinette; Packer, Craig; Slotow, Rob; Bloomer, Paulette

doi:10.1007/s10592-019-01231-y

“…Therefore, a rescue program integrated with measures that prompt early demographic restoration is expected to be helpful both in the short and the long term (Hufbauer et al 2015). If the population recovery is less prosperous, one or two migratory events may be helpful to reduce the extinction risk before purging restores the population fitness, but periodic migration, advised in order to prevent the progressive loss of genetic diversity (Miller et al 2020), could increase the extinction risk in the long term due to random accumulation of migration events introducing large amounts of inbreeding load. Then, a compromise should be achieved by favoring donor populations that are expected to be purged but that still contribute to enrich the genetic diversity of the recipient one.…”

Section: The Relevance Of Purging To Rescue Success Under Different Conservation Scenariosmentioning

confidence: 99%

Reviewing the consequences of genetic purging on the success of rescue programs

Pérez‐Pereira

¹

,

Caballero

²

,

García-Dorado

³

2021

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Genetic rescue is increasingly considered a promising and underused conservation strategy to reduce inbreeding depression and restore genetic diversity in endangered populations, but the empirical evidence supporting its application is limited to a few generations. Here we discuss on the light of theory the role of inbreeding depression arising from partially recessive deleterious mutations and of genetic purging as main determinants of the medium to long-term success of rescue programs. This role depends on two main predictions: (1) The inbreeding load hidden in populations with a long stable demography increases with the effective population size; and (2) After a population shrinks, purging tends to remove its (partially) recessive deleterious alleles, a process that is slower but more efficient for large populations than for small ones. We also carry out computer simulations to investigate the impact of genetic purging on the medium to long term success of genetic rescue programs. For some scenarios, it is found that hybrid vigor followed by purging will lead to sustained successful rescue. However, there may be specific situations where the recipient population is so small that it cannot purge the inbreeding load introduced by migrants, which would lead to increased fitness inbreeding depression and extinction risk in the medium to long term. In such cases, the risk is expected to be higher if migrants came from a large non-purged population with high inbreeding load, particularly after the accumulation of the stochastic effects ascribed to repeated occasional migration events. Therefore, under the specific deleterious recessive mutation model considered, we conclude that additional caution should be taken in rescue programs. Unless the endangered population harbors some distinctive genetic singularity whose conservation is a main concern, restoration by continuous stable gene flow should be considered, whenever feasible, as it reduces the extinction risk compared to repeated occasional migration and can also allow recolonization events.

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“…Fitness data are often not readily available, and it may be impossible to gather these data within a reasonable timeframe and/or given available resources, considering that extinction risk rises rapidly in an inbred population (O’Grady et al, 2006). There are a few case studies dealing with genetic rescue in lions (Miller et al, 2020; Trinkel et al, 2008) and other felids (Johnson et al, 2010). Large source populations are generally seen as the most effective way to increase diversity in a genetically depauperate population (Frankham, 2015).…”

Section: Discussionmentioning

confidence: 99%

Genetic guidelines for translocations: Maintaining intraspecific diversity in the lion (Panthera leo)

Bertola

¹

,

Miller

²

,

Williams

³

et al. 2021

Evolutionary Applications

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Conservation translocations have become an important management tool, particularly for large wildlife species such as the lion (Panthera leo). When planning translocations, the genetic background of populations needs to be taken into account; failure to do so risks disrupting existing patterns of genetic variation, ultimately leading to genetic homogenization, and thereby reducing resilience and adaptability of the species. We urge wildlife managers to include knowledge of the genetic background of source/target populations, as well as species‐wide patterns, in any management intervention. We present a hierarchical decision‐making tool in which we list 132 lion populations/lion conservation units and provide information on genetic assignment, uncertainty and suitability for translocation for each source/target combination. By including four levels of suitability, from ‘first choice’ to ‘no option’, we provide managers with a range of options. To illustrate the extent of international trade of lions, and the potential disruption of natural patterns of intraspecific diversity, we mined the CITES Trade Database for estimated trade quantities of live individuals imported into lion range states during the past 4 decades. We identified 1056 recorded individuals with a potential risk of interbreeding with wild lions, 772 being captive‐sourced. Scoring each of the records with our decision‐making tool illustrates that only 7% of the translocated individuals were ‘first choice’ and 73% were ‘no option’. We acknowledge that other, nongenetic factors are important in the decision‐making process, and hence a pragmatic approach is needed. A framework in which source/target populations are scored based on suitability is not only relevant to lion, but also to other species of wildlife that are frequently translocated. We hope that the presented overview supports managers to include genetics in future management decisions and contributes towards conservation of the lion in its full diversity.

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“…Therefore, a rescue program integrated with measures that prompt early demographic restoration is expected to be helpful both in the short and the long term (Hufbauer et al 2015). If the population recovery is less prosperous, one or two migratory events may be helpful to reduce the extinction risk before purging restores the population fitness, but periodic migration, advised in order to prevent the progressive loss of genetic diversity (Miller et al 2020), could increase the extinction risk in the long term due to random accumulation of migration events introducing large amounts of inbreeding load. Then, a compromise should be achieved by favoring donor populations that are expected to be purged but that still contribute to enrich the genetic diversity of the recipient one. Finally, the third scenario corresponds to rather extreme situations within the unfortunately paradigmatic case of an isolated population whose size has progressively declined over time, often beginning with a period where the decline was cryptic.…”

Section: Discussionmentioning

confidence: 99%

Reviewing the consequences of genetic purging on the success of rescue programs

Pérez‐Pereira

¹

,

Caballero

²

,

García-Dorado

³

2021

Preprint

View full text Add to dashboard Cite

Genetic rescue is increasingly considered a promising and underused conservation strategy to reduce inbreeding depression and restore genetic diversity in endangered populations, but the empirical evidence supporting its application is limited to a few generations. Here we discuss on the light of theory the role of inbreeding depression arising from partially recessive deleterious mutations and of genetic purging as main determinants of the medium to long-term success of rescue programs. This role depends on two main predictions: (1) The inbreeding load hidden in populations with a long stable demography increases with the effective population size; and (2) After a population shrinks, purging tends to remove its (partially) recessive deleterious alleles, a process that is slower but more efficient for large populations than for small ones. We also carry out computer simulations to investigate the impact of genetic purging on the medium to long term success of genetic rescue programs. For some scenarios, it is found that hybrid vigor followed by purging will lead to sustained successful rescue. However, there may be specific situations where the recipient population is so small that it cannot purge the inbreeding load introduced by migrants, which would lead to increased fitness inbreeding depression and extinction risk in the medium to long term. In such cases, the risk is expected to be higher if migrants came from a large non-purged population with high inbreeding load, particularly after the accumulation of the stochastic effects ascribed to repeated occasional migration events. Therefore, under the specific deleterious recessive mutation model considered, we conclude that additional caution should be taken in rescue programs. Unless the endangered population harbors some distinctive genetic singularity whose conservation is a main concern, restoration by continuous stable gene flow should be considered, whenever feasible, as it reduces the extinction risk compared to repeated occasional migration and can also allow recolonization events.

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Genetic rescue of an isolated African lion population

Cited by 19 publications

References 63 publications

Reviewing the consequences of genetic purging on the success of rescue programs

Reviewing the consequences of genetic purging on the success of rescue programs

Genetic guidelines for translocations: Maintaining intraspecific diversity in the lion (Panthera leo)

Reviewing the consequences of genetic purging on the success of rescue programs

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