In-depth Notes on Adaptation in the Anthropocene

Learning Objectives

• Habitat Fragmentation
  • Examine how it limits relocation in response to climate change.
• Vulnerability of Small Populations
  • Explore how small populations are particularly susceptible to extinction.
• Climate Change Effects
  • Consider how climate change can act as both a direct and indirect selective force.
• Mechanisms of Evolution
  • Examine the possible mechanisms of evolution due to climate change.
• Examples of Adaptation
  • Review specific instances of adaptation to climate change.

Responses of Species to Environmental Changes

• When environments change, a species can:
  • Relocate
  • Acclimate
  • Adapt
  • Go extinct

Climate Change and Range Shifts

• Species Movement: As climates change, species may migrate to find more suitable habitats.
  • Possible outcomes include:
  • Range Expansion: Species moving into new areas.
  • Range Shift: Species altering their existing range.
  • Range Contraction: Decrease in the area a species occupies.
• Example: Arthropods in the UK have shown measurable average range shifts as evidenced in various studies.

Challenges of Movement in the Anthropocene

• Human Modifications: Landscape changes hinder plant and animal movement:
  • Habitat Fragmentation:
  • Reduces access to food and mates.
  • Limits population growth.
  • Restricts dispersal abilities.
  • Creates edge effects that affect local biodiversity.

Biodiversity and Habitat Fragmentation

• Biodiversity Reduction: Habitat fragmentation leads to decreased species richness:
  • Common species may become absent from fragments, and fewer species migrate into fragmented habitats.

Extinction Rates and Influencing Factors

• Increased Extinction Rates: Since the industrial revolution, extinction rates have significantly risen due to various anthropogenic factors, with climate change being a critical contributor.

Risks for Small Populations

• Genetic Decline: Small populations are particularly vulnerable to extinction:
  • Loss of just a few individuals can have significant impacts.
  • Genetic variation is less within small populations, leading to:
  • Increased genetic drift, causing shifts in allele frequencies.
  • Increased chances of inbreeding, reducing heterozygosity and possibly expressing harmful alleles.
  • Reduced evolutionary flexibility, limiting opportunities for adaptation to new conditions.

Climate Change as a Selective Force

• Direct Selection: Higher temperatures can select for:
  • Increased mutation rates.
  • More thermotolerant phenotypes.
  • Greater phenotypic plasticity.
• Indirect Selection: Changing habitats, resources, and species interactions due to climatic changes also affect species adaptation strategies.

Evolutionary Opportunities in the Face of Climate Change

• Rapid Resilience: Selection for resilient lineages can occur during extreme weather events.
• Hybridization: This may lead to novel genotypes and break down reproductive isolation.
• New Niches: The creation of new ecological niches can promote adaptation and speciation, as seen in Anole lizards that evolved larger toepads in response to frequent hurricanes.

Evidence for Adaptation to Global Change

• Case Study: In pink salmon, strong selection against late-migrating phenotypes correlates with increased stream temperatures, demonstrating how climate change can lead to evolutionary changes in species.