Name: saving small populations with genetic diversity
Uploaded: 2019-08-01T08:31:57.000Z
Duration: 2 min 4 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Biology

ecosystems-interactions-energy-and-dynamics

Ecosystems- Interactions, Energy, and Dynamics

LS.Bio.5.2

Conservation of Small Populations

- [Docent] De prioriteit van natuurbeschermingsbiologie is het behoud van biologische diversiteit. Om dit doel te bereiken, moeten wetenschappers populaties identificeren die met uitsterven worden bedreigd. Vooral kleine populaties zoals die van de Floridapanter lopen risico, vanwege hun beperkte genetische diversiteit, hebben ze minder weerstand tegen ziekten en passen ze zich moeilijker aan verandering aan.

Deze katten zwierven vroeger van Florida tot Louisiana, langs de kust van de Golf van Mexico. Door ontwikkelingen van het land, werd hun habitat gereduceerd tot een klein gebied in het zuiden van Florida. In 1973 waren er nog ongeveer 23 panters over.

Het gevolg van zo'n kleine populatie was inteelt, wat leidde tot geknikte staarten, hartafwijkingen en andere genetische problemen die hun voortplantingsvermogen verminderde. Als een populatie eenmaal een kritiek laag aantal bereikt, kan het in een zogenaamde uitstervingsvortex terechtkomen, een spiraal van gebeurtenissen die elkaar opvolgen, waardoor de populatie verder reduceert tot aan extinctie. Zo werkt het.

Een kleine populatie is gevoelig voor inteelt, of het paren met naaste familieleden. Als gevolg hiervan is er minder genetische diversiteit in de populatie. Lagere genetische diversiteit leidt op den duur tot lagere overlevingskansen en voorplantingssnelheid, waardoor de populatie verder reduceert tot op het punt van uitsterving.

Eén manier om de uitstervingsvortex te voorkomen is door individuen uit andere populaties te importeren. Conservatiebiologen hebben bijvoorbeeld vrouwelijke panters uit Texas in de populatie in Florida geïntroduceerd om die groter en genetisch diverser te maken. Vandaag de dag zijn er ongeveer 125 Floridapanters als gevolg van deze inspanningen.

Hoewel de populatie groter is geworden, is conservatie nog steeds nodig. GPS-halsbanden worden gebruikt om panters te volgen, waardoor natuurbeschermers de gezondheid van de populatie in de gaten kunnen houden.

behoud van kleine populaties

Kleine populatiegroottes zorgen ervoor dat een soort extreem met uitsterven wordt bedreigd vanwege een gebrek aan variatie en een daaruit voortvloeiende afname van het aanpassingsvermogen. Dit verzwakt de overlevingskansen onder druk zoals klimaatverandering, concurrentie van andere soorten of nieuwe ziekten. Grote populaties hebben een grotere kans om dergelijke druk te overleven, omdat het waarschijnlijker is dat dergelijke populaties individuen herbergen die genetische varianten hebben die zich kunnen aanpassen aan nieuwe spanningen. Kleine populaties hebben veel minder kans op een dergelijke variatie.

Moderne genomische technieken kunnen homozygotie identificeren in schadelijke genen die wordt veroorzaakt door inteelt. Dit gebeurt wanneer nauw verwante organismen nakomelingen produceren; de nakomelingen hebben een grotere kans om twee identieke schadelijke allelen te krijgen. De wolven in het Isle Royale National Park ondergingen bijvoorbeeld een extreme populatiereductie als gevolg van een ziekte-uitbraak, wat leidde tot een toename van de inteelt. De wolvenpopulatie is blijven afnemen en bevatte op een gegeven moment slechts twee wolven.

Door middel van sequencing van het gehele genoom konden onderzoekers de afstammingslijn van de overgebleven wolven op Isle Royale identificeren, wat paringen tussen broers en zussen-en-ouders en nakomelingen-in de kleine populatie liet zien op basis van patronen van chromosomale overerving. Analyse van gensequenties toonde schadelijke single-nucleotide polymorfismen (SNP's) aan binnen functionele genen die de fitheid van deze wolven verminderen. Deze mutaties verklaren de fysieke kenmerken die te zien zijn bij Isle Royale-wolven, zoals misvormingen in hun ruggengraat en ribbenkast.

Parkwachters halen wolven van buiten het park binnen om een gezonde genetische diversiteit op Isle Royale tot stand te brengen. Gegeven een gezondere, grotere populatie zouden de wolven op Isle Royale moeten kunnen gedijen. Rangers volgen de wolven op het eiland ook met GPS-halsbanden om te bepalen of hun beschermingsmethoden effectief zijn.

Behoud van kleine populaties

Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens ...

Education

JoVE Core

Biologie

Ecology

Ecologie

Biodiversity and Conservation

Biodiversiteit en natuurbescherming

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

saving small populations with genetic diversity

Small populations can be hard to save because they often lose genetic diversity. When variation is low, a species has fewer traits that may help it adapt to climate change, competition from other species, or new diseases. That makes extinction more likely.

Large populations usually have a better chance of surviving new stresses. They are more likely to include individuals with genetic variants that are helpful in changing conditions. Small populations are much less likely to contain this kind of variation.

Genomic tools can reveal another problem in small populations: inbreeding. Inbreeding happens when closely related organisms produce offspring. The offspring then have a higher chance of inheriting two identical harmful alleles, which can make deleterious genes homozygous.

The wolves on Isle Royale National Park show how this can happen. A disease outbreak caused a sharp population drop, and increased inbreeding followed. The wolf population kept declining, and at one point only two wolves remained. Whole-genome sequencing helped researchers trace the remaining wolves' lineages and showed sibling-sibling and parent-offspring matings from chromosomal inheritance patterns.

Gene sequence analysis also found deleterious single-nucleotide polymorphisms, or SNPs, in functional genes. These mutations lower the wolves' fitness and help explain visible problems such as spinal and rib cage malformations. To improve the population, park rangers are bringing in wolves from outside the park to restore healthy genetic diversity. Rangers also use GPS collars to track the wolves and see whether the conservation plan is working.

Saving Small Populations with Genetic Diversity

saving-small-populations-with-genetic-diversity

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conservation of small populations

Small populations can be hard to save because they often lose genetic diversity. When variation is low, a species has fewer traits that may help it adapt to climate change, competition from other species, or new diseases. That makes extinction more likely. Large populations usually have a better chance of surviving new stresses. They are more likely to include individuals with genetic variants that are helpful in changing conditions. Small populations are much less likely to contain this kind...

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key terms and concepts

Learn how low genetic diversity, inbreeding, and genome sequencing affect small wolf populations on Isle Royale, and how conservation can help.

Saving Small Populations with Genetic Diversity | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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Earth and Environmental Science

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3.1.9-12.N

3.1.9-12.V

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LS.9.a

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Alabama Course of Study Science

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9-12.B.2.9.a

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Next Generation Science Standards

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Saving Small Populations with Genetic Diversity

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