Ecology and Biodiversity Notes

Communities at Scale

  • Biosphere → Biome → Habitat → Niche.
  • NVC classifies habitats by plant communities (286 in 12 major categories).

Biomes

  • Large-scale communities of plants and animals with common characteristics.

Community Dynamics

  • r/K selection:
    • r-selected: Fast growth, early maturity, highly fecund; good in variable environments.
    • K-selected: Slower growth, delayed maturity, parental care.

Survivorship Curves

  • Type I: K-selected organisms.
  • Type III: r-selected organisms.

Community Dynamics

  • Succession: Sequence of species to a climax community.
  • Disturbance resets succession, creating a patchwork; cycles occur.

Cycles

  • Example: Limestone flats with Fucus, barnacles, limpets, and dogwhelks; barnacle settlement influencing Fucus settlement and grazing.

Disturbance and Succession

  • Disturbance reduces competition, creates habitats; essential for some species.
  • Non-equilibrium communities: Disturbance exceeds recovery rate (e.g., coral reefs).
  • Multiple stable states exist.
  • IDH.

Community Structure

  • Influenced by bottom-up (primary production, nutrients) and top-down (predation) factors.

Trophic Cascade

  • Reintroduction of wolves in Yellowstone led to tree growth and songbird nesting by controlling deer populations.

Keystone and Foundation Species

  • Foundation species: Structure communities (e.g., seagrass).
  • Keystone species: Significant impact relative to abundance (e.g., sea otters, beavers).

Behavioural Ecology

  • Explores animal behavior in relation to environment and evolutionary pressures.
  • Considers: What, why, and advantages of behaviors; heritability.

Innate vs. Learned

  • Innate: Developmentally fixed (e.g., cuckoo chicks).
  • Learned: Influenced by habitat and maternal foraging (e.g., dolphin tool use).

Individual vs. Social

  • Individual: Foraging strategies.
  • Social: Competitive, cooperative (pack hunting), altruistic (reciprocal altruism).

Optimal Foraging

  • Maximizing net energy intake.
  • Example: Crabs and mussel sizes; energy vs. effort.

Marginal Value Theorem

  • Model for patchy environments.
  • Considers currency (what organism maximizes), patch productivity and distance.

Mating Systems

  • Conflict between sexual and natural selection.
    • Monogamy, Polygamy (Polygyny, Polyandry), Promiscuity.

Mating Systems

  • Mammalian mating systems related to female dispersion.
  • Influenced by male assistance, female range size/stability/density.

Life History Strategies

  • Maximizing lifetime reproductive success.
  • Sequential hermaphrodites (e.g., slipper limpet, cuckoo wrasse).

Biodiversity: Importance

  • SDGs: SDG 14 (Life below Water), SDG 15 (Life on Land).
  • Planetary boundaries: Biodiversity integrity; genetic diversity extinction rate is x1000 times natural rate.

Keystone/Foundation Species, Ecological Role/Function

  • Three ‘E’s: Extant, Extinct.

Measuring Biodiversity

  • Species richness, relative abundance.
  • Shannon's index of diversity: H = - \sum (pi ln pi)
  • Simpson's index of diversity: 1 - D, where D = \sum (p_i)^2

Biodiversity Patterns

  • Biogeography: species distribution.
  • Distribution reasons: never dispersed, failed establishment, range retraction.
    -- Latitudinal gradients: Decreases away from equator, strongest for carnivores. Hypotheses include greater productivity at the equator.
  • Species-area curves: S = c A^z; Log S = log c + z(log A).

Climate Change Effect

  • Species range shifts in response to temperature.
  • Ocean acidification: Biodiversity loss.

Invasive Species

  • Lionfish: voracious predators.
  • Grey squirrel: Disease vectors, restricted range for native red squirrels.

Managing Biodiversity

  • Protected areas (SSSIs, SACs, SPAs, MPAs).
  • Convention on Biological Diversity.

Conservation Biology

  • Principles: Preserve diversity, prevent extinctions, maintain complexity, intrinsic value.

Conservation Biology

  • Conserve species: Maintain population size and genetic diversity; Minimum viable population.
  • Conserve communities: Diversity promotes resilience.
  • Conserve habitats: Size, shape (edge effects), connectivity.

Extinctions and Key Species

  • Current extinction rates are x1000 times the natural background rate.
  • Indicator species, umbrella species protect the wider ecosystem.