Community ecology

Community

a grouping of many populations that live in the same place at the same time

Community ecology

studies the factors that influence the number and abundance of species in a community

keystone species

is a species whose impact on its community is much greater than its total mass or abundance would indicate.

Keystone species have a disproportionately large effect on their ecosystem relative to their abundance.

Keystone species examples

sea stars (control mussel populations, maintain species diversity along rocky shores)

•Sea otters: the decline of sea otters off the western coast of Alaska allowed populations of sea urchins, their main prey, to increase.

oThe greater abundance of sea urchins, which consume seaweeds such as kelp, has resulted in the loss of many of the kelp “forests” and the diversity of marine life that they support.

•Other examples:

oBees: because their role in pollination maintains plant reproduction, biodiversity, and entire food webs

oGray wolves (Yellowstone): Regulate herbivore populations (elk), allow vegetation and river ecosystems to recover

oBeavers: Create wetlands by building dams, increasing habitat diversity for plants and animals

oPrairie dogs: Burrowing aerates soil, provides habitat for many other species

oFigs (fig trees): Provide year‑round fruit for many animals, support entire food webs in tropical forests

Species interactions

are r

relationships

between different

species in an

ecosystem that affect

survival and population

dynamics

Competition

Competition occurs when two species compete for the same limited

resources (food, space, light, mates), and both are negatively affected

ex, lions vs hyenas, plants for sunlight

Ecological Significance

• Drives natural selection and adaptation

• Prevents overcrowding

• Leads to niche differentiation (species specialize)

Mutualism

Both species benefit from the interaction

1. Bees and Flowers (Pollination)

• Bees get nectar (food)

• Flowers get pollinated

2. Clownfish and Sea Anemones

• Clownfish get protection

• Anemone gets cleaning + nutrients

3. Ecological Significance

• Increases biodiversity

• Essential for ecosystems (e.g., pollination)

• Drives co-evolution between species

Commensalism

Commensalism

One species benefits, the other is unaffected

Remora fish and sharks

• Remora gets food scraps + transportation

• Shark unaffected

2. Barnacles on whales

• Barnacles gain mobility and feeding access

• Whale not affected

Ecological Significance

• Helps species survive without harming others

• Supports ecosystem complexity

Predation

One organism (predator) kills and eats

another (prey) .

Ecological Significance

• Controls population sizes

• Maintains food chains

• Drives evolution (speed, camouflage)

Parasitism

Gne organism (parasite) benefits while harming

the host, usually without killing it

Ecological Significance

• Regulates population health

• Influences evolution (immune defenses)

• Can affect entire ecosystems

Native species

Species that originated and

developed in the habitat

• Adapted to living with the

environment that surrounds them.

• Also, play a balanced role in the

ecosystem

Non-native species

Species that originated in other

parts other than their current

living.

• Also called Exotic species

• Species living in habitats where

they do not naturally exist

invasive species

Species that outcompete other

species cause damage to the

ecosystem.

• Species that cause harm to the

environment of the habitat.

EXPLAIN HOW INVASIVE SPECIES ALTER ECOLOGICAL

INTERACTIONS (COMPETITION, PREDATION, NUTRIENT

CYCLES, BIODIVERSITY)

Competition: Outcompete native species for food, space, and

resources

Predation: Introduce new predators or disrupt existing food webs

Nutrient Cycles: Alter soil chemistry and ecosystem processes

Biodiversity Loss: Reduce native species populations and ecosystem

stability

ARE THERE ANY LEGISLATION OR

REGULATIONS IN THE USA TO PREVENT

OR MITIGATE THE IMPACT OF INVASIVE

SPECIES?

yes, lacey act s responsible for preventing harmful

invasive plants and animals from entering the country.

2. National Invasive Species Act, It mostly deals with

water invasive species.

3.There is also Executive Order 13112 instructing agencies

to cooperate in the prevention of the invasive species

introduction, their detection and rapid response to them.

BURMESE PYTHON Ecological, economic and human Impacts:

Sharp decline in small native mammals (raccoons, rabbits, etc).

• Impacts wildlife tourism and ecosystem health.

• Reduces biodiversity significantly

BURMESE PYTHON Native Range

Southeast Asia (Thailand, India) but now it is invasive in Florida,

particularly in the Everglades.

BURMESE PYTHON Mechanisms of Invasion:

Introduced through the exotic pet trade, some escaped or were

released into the wild.

• Reproduces quickly (large # egg), and spreads trough water systems.

• Very large size and strong predator, camouflage makes it hard to find.

• No natural predator in the Everglades

BURMESE PYTHON Control Efforts

Hunting programs and removal events

• Traps and tracking methods

• Public reports when they see the animal.

BURMESE PYTHON Limitations:

Hard to find and capture

• Live in large, dense wetlands

• Reproduce quickly

BRAZILIAN PEPPER TREE Native Range:, Native ecological role:

ropical South

America, especially Brazil,

Argentina, and Paraguay

• Native ecological role: Has a crucial

role in restoration and soil

stabilization

BRAZILIAN PEPPER TREE Mechanism of invasion

How was it introduced?: It was imported to Florida

in the late 1890s, and later in 1926, became a

landscape ornamental

• Spread?: It spread widely because birds and

mammals eat their bright red berries.

• Competitive Traits and Ecological interactions:

They prevent the growth of native species, also can

harm or kill wildlife if they just eat their berries, and

have a high growth rate.

BRAZILIAN PEPPER TREE Ecological Impacts

n Brazil, they support

biodiversity, providing habitat

and sustenance for native

wildlife.

• In Florida, can alter native plants,

decrease biodiversity, and the

variety of animals and plants

• Also, increased the risk of

invasion of non native species,

and increased habitat

degradation

BRAZILIAN PEPPER TREE Economic and human impacy

his plant is a highly invasive plant that has caused

severe ecological and economic damage, causing

monocultures that displace native biodiversity.

• In mangrove areas, this tree reduces the quality of the

habitat for coastal fish and wildlife

• They grow fast and dense, requiring high maintenance.

• Remove seedlings by hand-pulling or herbicide

treatment

• USDA has been working on reducing their growth rates

and flower production by introducing Brazilian

peppertree thrips

LIONFISH Native Range

South Pacific and Indian Oceans.

They have a big range from Western Australia and

Malaysia to the UK, Japan, and Korea.

LIONFISH Mechanism of invasion

How was it introduced?: It was introduced in the Atlantic

Ocean through the aquarium trade in the 1980s.

• Spread?: They have high reproduction rates, they also lack

predators in invaded areas.

• Competitive Traits and Ecological interactions: The lack of

predation in invaded areas allows them to grow in population.

In addition, females mature in a year and can release around

2 million eggs per year. On the other hand, they cause

declines in native reef fish up to 79%.

LIONFISH Ecological Impacts

n their native habitat, they control

small reef fish.

• As an invasive species, they

drastically reduce Atlantic biodiversity

by consuming their native fish,

disrupting food webs by having no

predators in these areas, and having a

high reproductive rate.

• Also, they adapt really fast to their

environment, not just reefs, but also

mangroves.

LIONFISH Economic and human impacy

Also causes damage to the coral health due that

they eat herbivorous fish, causing algal overgrowth.

• Their presence makes the management of Marine

Protected Areas and tourism operations more

difficult and expensive.

• Also, they are important for the commercial market

for human consumption incentive fuasherman to

target them. This also helps to the reduction of them

in the reefs.

AFRICAN GIANT LAND SNAILS Economic & Human Impacts

severe agricultural damage (fruits,

vegetables, ornamental plants)

• Health risk due to parasite transmission

• Control efforts: Quarantine, pesticide

use, manual removal

• Costs: Millions spent in eradication

programs in Florida

• Limitations: Eggs are difficult to detect;

rapid reinfestation

AFRICAN GIANT LAND SNAILS Native range: \

• Native ecological role:

Native range: East Africa

• Native ecological role: Decomposer; feeds

on plant material and organic matter

AFRICAN GIANT LAND SNAILS Ecological Impacts

estroys native plants and agricultural

crops

• Alters food webs by reducing plant

availability

• Threatens native snail species and

biodiversity

AFRICAN GIANT LAND SNAILS Mechanism of Invasion

introduction: Brought through pet trade and accidentally

via cargo

• Spread: Lays hundreds of eggs multiple times per year;

spreads through soil, plants, and human transport

• Competitive traits: Extremely high reproduction rate,

broad diet (500+ plant species)

• Ecological interactions:

⚬ Competition: Competes with native snails and

herbivores

⚬ Herbivory (predation on plants): Consumes crops and

native vegetation

⚬ Parasitism: Carries parasites harmful to humans (rat

lungworm)