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Teton County�Master Naturalist

Ecological Concepts

Catherine Black

Idaho State University

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Defining Ecology (p.1-2)

Ecology:

Study of relationships between organisms and the environment
Environment includes abiotic (nonliving) & biotic (living) factors

What are some useful applications of Ecology?

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Levels of Biotic Organization (p.2-3)

Niche: range of environmental factors in which a species can survive and reproduce
Habitat: geographic area that provides all aspects of the niche within a reasonable distance given the organism’s mobility

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Population Dynamics (p.25-26)

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MN Paragraph 12: Population Dynamics

Carrying Capacity

When habitat quality improves, its carrying capacity increase so quality of wildlife habitat is critical to maintaining wildlife popoulations and why managers “manage” habitat, not wildlife
Drought, pollution, etc. can decrease K

Change in abundance/age distribution or dispersal due to B, I, D, E

Intrinsic factors affecting population growth = sex and age distribution, age-specific fecundity and social structure; territorial species have limited # of breeding pairs

Extrinsic factors affecting population growth: competition, predation, disease, pollution, hunting and carrying capacity

Dispersal replenishes populations even if just a few individuals: wind, water, fur, digestion (birds/mammals), caching (ants/mammals), mechanical (leafy spurge)

Decrease inbreeding
Increase gene flow

Population Cycling of Lynx/Hare – overshoot K (lag in reproduction, etc.) and then start to crash

Shows that we cannot think of populations without other species in their environment
Based on trapping records of 200 years of Hudson Bay Company
Cycling by plants: no evidence that plants cycle—cycles don’t match sunspots
Hares limit themselves? Need 300 g/day; reduced biomass from 530 kg/ha in Nov to 160 kg/ha in Mar; Or crash due to other crowding issue (parasites, pathogens, stress); Hare browsing increases plant chemical defenses – chemicals produced for two years
Lynx specialist: 1.2 hares/day at peak
Combination: hares more susceptible to predation if weakened by lack of food
Coyote generalist: 2.3 hares/day so they do not cycle

May cache & return 4 months later to finish

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Population Growth Models (p.26-27)

Exponential growth: population growth pattern when growth is independent of density

Assumptions/Conditions: unlimited resources; no limiting biotic interactions (predation, competition, etc.)
Limiting factors: species constraints (gestation) & abiotic conditions (rainfall, temperature, etc.)
Examples?

Logistic population growth: population growth pattern when density-dependent factors apply

Assumptions/conditions: limited resources create a K
Limiting factors: predation, disease, competition
Examples?
When is growth fastest?
How is it best to manage populations that we want to use/harvest (fish/elk)?
How is it best to manage populations that are pests (mosquitoes, rats)?

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MN Paragraph 13: Population Growth Models

Implications for management:

Yield: forestry, fisheries, or wildlife set appropriate harvest rates (maximum sustained yield = usually ½ K)

Density-independent growth (exponential)

Same equation as compound interest
Exponential examples? Bacteria (old don’t die), forest trees, humans, rabbits? Graph = whooping cranes

Density-dependent growth (logistic) = environmental resistance; intrinsic factors (social stress leads to lower natality, survivorship and higher emigration) and extrinsic (predation, disease)

Assumptions: conditions allow for gradual slowing; if not, population will crash instead of level off
Limits: bioting factors: Limited resources (energy, nutrients, habitat, space)
Graph is Logistic is N0 = 20, rmax = 0.1, K = 50
Yr 8 = 241; yr 9 = 291 (can harvest 50); year 19 = 494, year 20 = 496 (can harvest 2)

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Ecological Relationships (p.23-24)

Community: interacting species inhabiting an area

Competition: interaction in which both species have negative impact on fitness

Gause’s Competitive Exclusion Principle: two species with identical niches cannot coexist indefinitely

One will be a better competitor and thus have higher fitness and eventually exclude the other

Exploitation: interaction in which one species gains fitness while the other loses it

Predators, parasites, pathogens
Exploiters can increase diversity by decreasing competition among prey species (if most palatable food is best competitor)

E.g. native grasses vs. invasive knapweed, thistles, etc.

Keystone species: increase species diversity disproportional to their biomass (removal of a top predator affects everything below it on the food web)

E.g. Wolves

Mutualism: interaction which both species gain fitness

Pollinators, seed dispersers, mycorrhyizae (fungus interacting with plant roots help plants absorb nutrients)

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Species Diversity (p.27-28)

Two factors define species diversity:

Species Richness: number of species in the community
Species Evenness: relative abundance of species

Homogeneous environment

E.g. crops, lawns, high nutrient lake, intense fire or replanted clearcut
Essentially 1 niche; competitive exclusion 🡪 1 species
Wide fluctuations in populations of those few species
Outbreaks of pests and diseases more common

Heterogeneity: environmental complexity

Forest/meadow/ with different types/ages of plants
↑ # of niches 🡪 ↑ diversity
Plant diversity 🡪 animal diversity
What causes plant diversity?

Bottom line: greatest diversity is found where there are the greatest number of niches

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Endangered Species (p.29-32)

Biodiversity

1.5 million named species (5-30 million unnamed)

Factors that affect risk of extinction:

Geographic Range of Species: extensive vs. restricted

Endemic species: found in only 1 place (e.g. Bear Lake cisco)

Habitat Tolerance (niche breadth): broad vs. narrow
Local Population Size: large vs. small

Why preserve biodiversity?

Species we use directly for commercial use (many still undiscovered & genetic diversity important)

Food, fiber, fuel, materials and medicines
Drugs: aspirin, quinine (malaria), vincristine (leukemia), antibiotics (from fungi)

Indirect uses – loss of one species may harm another we need

Pollinators & seed dispersers for crops (bees, birds)
Natural pest control (spiders, birds)
Species that clean air & water (wetlands)
Decomposers

Aesthetic pleasure, recreation & scientific study (these have value, too)
Harder & more expensive to fix than to prevent (sustainability > short-term profits)

NYC spent $1 billion to restore habitat that saved $8 billion for new treatment plants
$2 billion to retrain & support unemployed cod fisherman in MA when cod decline

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Endangered Species (p.29-32)

Endangered: species nearly extinct throughout their range

Worldwide 12% of 10,000 known birds; 21% of 5,500 known mammals

Threatened: likely to become endangered
Protections under state and federal law: see p. 32 of PDF
Species of Greatest Conservation Need: https://idfg.idaho.gov/species/taxa/list/sgcn

Human-caused decreases in biodiversity greatly exceed natural causes

Habitat loss – we occupy, clear for ag/mining, degrade
Commercial hunting/fishing
Predator/pest control
Exotic pet/plant trade
Introduction of alien species and pollution

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Idaho Threatened/Endangered Species List

Endangered in Idaho

Woodland caribou

Sockeye salmon

White sturgeon

3 types of snails

Threatened in Idaho

Lynx

Grizzly bear

Northern Idaho ground squirrel

Yellow billed cuckoo

Bull trout

Steelhead trout

Chinook salmon (Spring & Fall)

Bliss Rapids snail

Whitebark pine

3 perennial/1 annual plant

MN Bullet #9 Understand the laws and procedures necessary for protecting species

MN Paragraph 16: Endangered species

Threatened and endangered species lists
Species of greatest conservation need: keeps species from becoming eligible for Endangered or Threatened list https://idfg.idaho.gov/species/taxa/list/sgcn
Protection: state & federal: illegal to take, possess, transport or sell any animal species designated as endangered or threatened without a permit; state: prohibit commerce or collection of plants from public land w/o a permit; federal protects habitat of endangered species and recovery plan is required

https://species.idaho.gov/listed-species-in-idaho/

Endangered snails = Banbury springs limpet, Bruneau Hot Springsnail, Snake River Physa
Threatened plants = Macfarlane’s four o’clock, Slickspot peppergrass (annual/biennial), Spalding’s catchfly, Ute ladies’ tresses
Candidate: Monarch, little brown bat, lemming, 2 bumblebees and a mussel

Delisted:

Peregrine falcon (1999)
Bald eagle (2007)
Grey Wolf (2011)
Water Howellia (2021) – in PDF as threatened
Utah Valvata snail (2010) in PDF as endangered
Idaho Springsail (2007) in PDF as endangered