AE2001 Fundamentals of ecology / 3 Genetic diversity

Genetic diversity

Variety of genetic traits within a species or population.

Essential for adaptation and survival.

Alleles

Different versions of a gene within a population.

Contributes to genetic diversity.

Homozygous

Two identical alleles for a specific gene.

Influences trait expression.

Recessive traits

Traits expressed only when an individual inherits two recessive alleles.

Effective population size

Number of individuals actively reproducing & contributing to next generation’s gene pool.

Inbreeding

Mating between closely related individuals

Leads to inbreeding depression: higher expression of harmful recessive traits.

Inbreeding depression

Reduced survival and fertility of offspring from closely related parents.

Caused by expression of harmful recessive genes.

Outbreeding depression

Reduced fitness when genetically distant individuals breed, disrupting local adaptations.

Example: Crossbreeding between two deer populations adapted to different climates can lower survival rates.

Hurler’s syndrome

Rare genetic disorder, disproportionately found among Irish Travellers due to consanguinity.

Genetic drift

Random changes in allele frequencies.

Impactful in small populations, due to chance loss of alleles.

Bottleneck effect

Sharp reduction in population size that causes a significant loss of genetic variation.

Founder effect

Genetic drift occurring when a small group establishes a new population

Alters allele frequencies due to limited genetic diversity.

Cavendish Banana & Gros Michel Banana

Gros Michel wiped out by fungal disease, lead to reliance on cloned Cavendish banana, susceptible to Panama Disease due to lack of genetic diversity (issue of monoculture)

Mountain gorillas

Adapted to inbreeding through genetic purging,.

Repeated inbreeding exposes harmful recessive alleles, removing them over generations.

50/500 rule

Populations need at least 50 individuals to prevent inbreeding and 500 to minimise genetic drift over time.

Genetic rescue paradox

Introducing new individuals can reduce inbreeding but may disrupt local adaptations, causing outbreeding depression.

Translocation

Moving individuals from one population to another to increase genetic diversity & prevent inbreeding.

Zoo studbooks

Records tracking captive animal pedigrees to prevent inbreeding in zoos.

Coefficient of inbreeding

Measures genetic similarity between individuals, with higher values indicating greater inbreeding risk.

Inbreeding avoidance

Behaviour preventing mating between close relatives.

Example: African wild dogs rarely mate within their natal pack, avoiding close relatives.

Consanguinity

Marriage / reproduction between close relatives, common in some societies (Middle East, Irish Travellers).

Leads to increased genetic disorders (e.g., Hurler’s syndrome).

Pedigree breeding (agriculture)

Breeding closely-related livestock for desired traits.

but increases harmful recessive traits & reduces genetic diversity.

Example: Holstein dairy cattle

Xenophobia hypothesis

Behavioural avoidance of mating with genetically distant individuals, possibly reducing outbreeding depression risk.