ECOLOGY PRINCIPLE EACH SPECIES HAS A SPECIFIC ROLE TO PLAY IN THE ECOSYSTEM WHERE IT IS FOUND THAT ROLE THE SPECIES PLAYS IS ITS ECOLOGICAL NICHE A SPECIES.

SPECIES INTERACTIONS OR THE ROLES SPECIES PLAY IN AN ECOSYSTEM (SLIDES 1 – 22 NEW)

http://savannabiomeassignment.weebly.com/food-web.html

ECOLOGY PRINCIPLE• EACH SPECIES HAS A SPECIFIC ROLE TO PLAY IN THE

ECOSYSTEM WHERE IT IS FOUND• THAT ROLE THE SPECIES PLAYS IS ITS ECOLOGICAL

NICHE • A SPECIES WAY OF LIFE IN A COMMUNITY OR • ITS PATTERN OF LIVING• INCLUDES EVERYTHING THAT AFFECTS THE SPECIES

SURVIVAL & REPRODUCTION• THE NEEDS OF THE SPECIES SUCH AS AMOUNT OF WATER,

SUNLIGHT, SPACE, FOOD, OPTIMUM TEMPERATURE AND WHAT FEEDS ON IT

CLASSIFYING NICHES

• GENERALISTS – BROAD NICHES,• LIVE IN MANY DIFFERENT PLACES• EAT A VARIETY OF FOODS• OFTEN TOLERATE A WIDE RANGE OF

ENVIRONMENTAL CONDITIONS• FLIES, COCKROACHES, MICE, RATS,

WHITE-TAILED DEER, RACCOONS, HUMANS

CLASSIFYING NICHES• SPECIALISTS – OCCUPY NARROW NICHES• MAY BE ABLE TO LIVE IN ONLY ONE TYPE OF HABITAT• USE JUST ONE OR A FEW TYPES OF FOOD• TOLERATE A NARROW RANGE OF CLIMATIC & ENVIRONMENTAL

CONDITIONS• SHOREBIRDS OCCUPY SPECIALIZED NICHES – FEEDING ON

CRUSTACEANS, INSECTS & OTHER ORGANISMS UNIQUE TO SANDY BEACHES & COASTAL WETLANDS

• MORE PRONE TO EXTINCTION WHEN ENVIRONMENTAL CONDITIONS CHANGE

• GIANT PANDA HIGHLY ENDANGERED DUE TO HABITAT LOSS, LOW BIRTH RATE AND SPECIALIZED DIET OF BAMBOO

5 MAJOR SPECIES ROLES WITHIN ECOSYSTEMS

• NATIVE SPECIES – NORMALLY LIVE AND THRIVE IN A PARTICULAR ECOSYSTEM

• NONNATIVE SPECIES – MIRGRATE INTO, DELIBERATELY OR ACCIDENTALLY INTRODUCED INTO AN ECOSYSTEM (INVASIVE, ALIEN, EXOTIC)

• NONNATIVE SPECIES CAN COMPETE WITH & REDUCE A COMMUNITY’S NATIVE SPECIES, CAUSING UNINTENDED & UNEXPECTED CONSEQUENCES

• CAN SPREAD RAPIDLY DUE TO NO PREDATORS OR DISEASES FACED IN NATIVE NICHES

• EXAMPLES: WILD AFRICAN HONEYBEES, KUDZU


• INDICATOR SPECIES – PROVIDE EARLY WARNINGS OF DAMAGE TO A COMMUNITY OR ECOSYSTEM

• EXCELLENT BIOLOGICAL INDICATORS INCLUDE BIRDS, BUTTERFLIES, AMPHIBIANS

• WHY?


In ecological communities there are little players and big players. The biggest players of all are referred to as keystone species.

A keystone species may be defined as one whose presence/ absence, or increase/decrease in abundance, strongly affects other species in the community.

Evidence usually comes from the addition or removal of species.

Removal of the keystone in the arch will cause the structure to collapse.

Starfish as Keystone Predators

http://life.bio.sunysb.edu/marinebio/rockyshore.html

Photo by Raymond Seed

In the rocky intertidal zone, mussels are superior at occupying space, crowding out other species. Starfish are effective predators of mussels, and thereby make room for other species.

A starfish removal experiment in Washington State demonstrated that the mussels are competitive dominants. Starfish predation opens up enough space for various barnacles, echinoderms and other marine invertebrate species to maintain a presence. When starfish are experimentally removed, mussels take over and other species are excluded.

A hoard of hungry starfish converge on a mussel bed. A starfish curls its body around the mussel, using its tube feet to pry apart the valves enough to insert its extensible stomach. Digestive enzymes break down the mussels’ muscles, and the starfish consumes its prey.

Starfish as Keystone Predators

Fig. 5-1, p. 79

Fig. 5-1, p. 79

Fig. 5-A, p. 82

Core Case Study: Endangered Southern Sea Otter

• Santa Cruz to Santa Barbara shallow coast• Live in kelp forests• Eat shellfish• ~16,000 otters around 1900• Hunted for fur • Hunted because they were considered competition for

abalone and shellfish• 1938-2008: otter population declined• 1977: otters declared an endangered species

http://library.thinkquest.org/J001418/urchin.html

Science Focus: Sea Urchins Threaten Kelp Forests

• Kelp forests– Can grow two feet per day– Require cool water– Host many species – high biodiversity– Provide essential habitat for entire ecosystem– Fight beach erosion– Algin – gelatinous polysaccharide from brown

algae used as a thickener in foods (ice cream)

Science Focus: Sea Urchins Threaten Kelp Forests

• Kelp forests threatened by– Sea urchins– Pollution– Rising ocean temperatures

• Southern sea otters eat urchins– Keystone species

• The keystone species effect is the best-known example of indirect interactions. One cannot have a keystone species effect without the presence of indirect interactions.– Keystone species produce strong indirect effects, out of proportion

to their abundance.

• If a predator strongly suppresses its prey (e.g., herbivores), one expects the trophic level below (e.g., plants) to benefit. Such top-down trophic cascades are well-known in lakes.

Other Indirect Species Interactions

Other Indirect Species Interactions

• Removal of one species causes other species to be lost from the system

•Aka “ripple effect”

• When the dodo (a 25 kg pigeon) was exterminated on Mauritius, the tree Calvaria major ceased to recruit. Its seeds needed to be abraded in the dodo’s gizzard to germinate.


• FOUNDATION SPECIES – PLAY A MAJOR ROLE IN SHAPING THEIR COMMUNITY BY CREATING AND ENCHANCING THEIR HABITATS IN WAYS THAT BENEFIT OTHER SPECIES

• ELEPHANTS PUSH OVER, BREAK AND UPROOT TREES WHICH CREATE OPENINGS IN GRASSLANDS AND WOODLANDS OF AFRICA

• THIS STIMULATES THE GROWTH OF GRASSES AND OTHER FORAGE PLANTS THAT BENEFIT SMALLER GRAZING SPECIES SUCH AS ANTELOPE

• IT ALSO ACCELERATES NUTRIENT CYCLING RATES• OTHER FOUNDATION SPECIES INCLUDE BEAVERS,

ALLIGATORS,

Interspecific Competition

• No two species can share vital limited resources for long

• Resolved by:– Migration– Shift in feeding habits or behavior– Population drop– Extinction

• Intense competition leads to resource partitioning

Cape May Warbler

Stepped Art

Blackburnian Warbler

Black-throated Green Warbler

Yellow-rumped Warbler

Bay-breasted Warbler

Fig. 5-2, p. 81

Resource Partitioning of 5 species of insect eating warblers

Mutualistic Interactions• A mutualism is an

interaction where both species benefit

• facultative mutualisms are beneficial but not essential to either species’ survival

• obligate mutualisms are essential to the survival of one or both species

Pollination is a classic mutualism. The plant gains through gamete transfer. The pollinator receives a reward of nectar and pollen.

The Boran - Honeyguide Mutualism• Example of a facultative

mutualism between an African people, and a bird, Indicator indicator.

• Borans find bee colonies more quickly when guided by the bird

• Honeyguides get larvae, wax, and are in less danger from bees

The bird informs on direction, distance to, and arrival at bee colony. Search time is reduced from 8.9 to 3.2 hrs

• Example of an obligate mutualism between ants and a thorny, small tree of dry tropical forests.

• Acacia provides shelter (hollow thorns) and food (nectar, protein bodies) to ant.

The Ant - Acacia Mutualism

Ants remove herbivorous insects, vines, others plants, and leaf litter (which reduces risk of fire).


An acacia ant (Pseudomyrmex ferruginea) sipping nectar from the petiolar nectary of a swollen thorn acacia (Acacia collinsii) in Costa Rica. http://waynesword.palomar.edu/acacia.htm#antleafb.gif


Plants also supply ants with protein and fat-rich food in the form of “Beltian bodies”, shown here being harvested by ants (arrows) from the tips of newly expanding leaflets of Acacia cornigera (Photo by T.W. Sherry)


•Newly developing bull’s horns (evolutionarily enlarged thorns)

•Filled with a pith that ants easily remove, creating hollow interiors

•Ants chew small hole into each thorn for use as home

The Ant - Acacia MutualismPseudomyrmex ants provide two services to Acacia trees:

•24-hour patrolling of leaves for protection against insects and mammals

•Clearing of plants from ground and from Acacia trees themselves as protection from competitors and fire

Fig. 5-6, p. 85

Fig. 5-6, p. 85

Commensalism

• When one species benefits, and the other neither benefits nor is harmed.

• A “+/0” interaction Cattle egrets follow cattle, consuming the

insects disturbed by the cows’ movements. It is unlikely that the cows benefit.

Fig. 5-7, p. 85

ECOLOGY PRINCIPLE EACH SPECIES HAS A SPECIFIC ROLE TO PLAY IN THE ECOSYSTEM WHERE IT IS FOUND THAT ROLE THE SPECIES PLAYS IS ITS ECOLOGICAL NICHE A SPECIES.

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