Lecture 11: Vulnerability of Small Populations Flashcards
Challenges for Small Populations
- Genetic (inbreeding/outbreeding depression, loss of evolutionary flexibility)
- Demographic (unequal sex ratios, variations of reproductive output, The Allee Effect)
- Stochastic (environmental variation, natural catastrophes)
Heterozygous
having different allele from the two parents (increased evolutionary fitness)
Homozygous
having the same allele from both parents (reduced evolutionary fitness)
Outbreeding Depression
weakness, sterility, or lack of adaptability resulting from reproduction by individuals of related species.
- liger
- mule
Minimum Viable Population (MVP)
the minimum population size needed to:
- retain 90% of genetic diversity of species for 200 years
- have 95% confidence of species survival for 100 years
Minimum Viable Area (MVA)
the area needed to sustain an MVP:
- increases with increasing body size of species
- depends on species trophic levels and requirements
Loss of Evolutionary Fitness
loss of genetic variability in small populations limits its ability to adapt to changes.
Unequal Sex Ratios
reduces the Effective Population Size - the population of breeding individuals.
Variation in Reproductive Output
disparities in reproductive output further reduce the effective population size
particularly common in highly fecund taxa (fish and trees)
The Allee Effect
The positive relationship between an individual’s fitness and it’s species density or population size.
Environmental Stochasticity
random variation in the biological and physical environment
-small populations are more prone to negative consequences from environmental variation and catastrophes.
Flapship Species
a species selected to act as an ambassador icon/symbol for a habitat, issue, campaign, or environmental issue.
- typically large and charismatic animals
- Panda for WWF
Umbrella Species
a species for which its conservation indirectly protects may other species.
Genetic Drift
change in allele frequency due to random chance
