Conservation Biology

Challenges to Conserving Small Populations

• Loss of Genetic Variability

  • Genetic variability is crucial for adaptation.

  • Genetic Drift:

    • Random changes in allele frequency that can lead to the loss of rare alleles.

  • Example:

    • In a population of 1000, 100 copies of a rare allele at 5% frequency; in a population of 10, only 1 copy remains.

  • Inbreeding:

    • Mating among relatives leads to similar genotypes.

    • Results in inbreeding depression and loss of heterozygosity.

• Demographic Stochasticity:

  • Random fluctuations in birth and death rates, which can significantly impact small populations.

  • Example:

    • Three individuals each with a 50% survival rate might all go extinct.

• Environmental Stochasticity:

  • Variability in environmental conditions affecting populations.

Loss of Heterozygosity

• H0: Original heterozygosity (=1)

• H1: Heterozygosity remaining after one generation:

  • H1 = [1 – 1/(2Ne)] * H0

• Proportion of heterozygosity remaining over generations:

  • Ht/H0 = [1 – 1/(2Ne)]^t

• Inbreeding Coefficient:

  • Related to heterozygosity and contributes to inbreeding depression.

  • Can lead to high mortality and fewer offspring.

• Outbreeding Depression:

  • Occurs when mating between different populations leads to incompatibility.

  • Example: The different reproductive strategies of various orchid species based on pollination methods.

Effective Population Size (Ne)

• Calculating Ne:

  • Examples:

  • Monogamous species with unequal sex ratios.

  • Consider the implications of sex ratios on effective population size.

  • Assess fluctuating populations through cumulative effective populations over time.

Demographic Stochasticity

• Random Variability in survival probabilities can disproportionately affect small populations leading to extinction risks.

• Example: Kakapo population experiences significant challenges due to low numbers.

Environmental Stochasticity

• Factors include food availability, predator numbers, and natural disasters.

• Severe climatic events can drastically reduce populations, e.g., Przewalski’s horse in Mongolia.

Extinction Dynamics

• Types of Extinction:

  • Globally extinct, extinct in the wild, extirpated (locally extinct), ecologically extinct.

• IUCN Red List Categories includes species evaluation and tracking extinction risk.

• Understand the concept of extinction debt related to imminent species loss due to habitat degradation.

Island Biogeography and Extinction Vulnerability

• Island Species:

  • Species on islands often have narrow ranges, few populations, and vulnerable life histories.

  • Factors include limited dispersal, low genetic variation, and no prior exposure to human presence, often leading to higher extinction rates.

Invasive Species Challenges

• Control Measures:

  • Use of mechanical, chemical, and biological control methods.

  • Recognize the impact of invasive species on native populations and their ecosystems, such as competition and habitat alteration.

Overexploitation Risks

• Modern Overexploitation:

  • Influenced by human population growth and advancements in harvesting technologies.

  • Address issues such as by-catch and the unsustainable use of marine resources.

Sustainable Seafood Practices

• Importance of Sustainability:

  • Promote sustainable seafood sources to protect marine biodiversity.

  • Legal frameworks such as the International Whaling Commission aim to manage and ideally restore vulnerable whale populations.

Convention on the International Trade in Endangered Species (CITES)

• Goals:

  • Regulate international wildlife trade to prevent species extinction through strict tracking and management of trade activities.

  • Be aware of illegal trade impacts on wildlife, including demand-driven factors in various cultures.

Zoonotic Diseases from Wildlife

• Increased zoonotic disease risks associated with wildlife consumption amid ongoing conservation challenges.