Species Diversity and SuccessionSpecies Diversity and Succession

The Dynamics of Community The Dynamics of Community StructureStructure

CompetitionCompetition

• When two or more individuals attempt to When two or more individuals attempt to use an essential, common resource.use an essential, common resource.

• May be May be intraspecificintraspecific (within a species) or (within a species) or interspecificinterspecific (between species). (between species).

Effects of Competition on Realized Effects of Competition on Realized NichesNiches

The The Competitive Exclusion PrincipleCompetitive Exclusion Principle states that completely equivalent states that completely equivalent competitors cannot coexist; two species competitors cannot coexist; two species cannot have the same niche.cannot have the same niche.

Species 2 outcompetes species 1Species 2 outcompetes species 1and restricts the niche of species 1and restricts the niche of species 1

Effect of Competition on Realized Effect of Competition on Realized NicheNiche

AmoebaAmoeba

Species “1”Species “1”

Species “2”Species “2”

Species “1” + “2”Species “1” + “2”

Resource PartitioningResource Partitioning

Resource partitioning is reduced competition by evolving differences in resource use.

Resource partitioning Resource partitioning occurs when natural occurs when natural selection acts to favor selection acts to favor individuals of species individuals of species that reduce competition that reduce competition by becoming more by becoming more specialized.specialized.

Warblers as Warblers as examples of examples of Resource Resource PartitioningPartitioning - - each species each species spends at least spends at least 50% of foraging 50% of foraging time in time in designated areasdesignated areas

CoevolutionCoevolution

CoevolutionCoevolution is is reciprocal evolution. That is, an reciprocal evolution. That is, an interdependent evolution of two or more species interdependent evolution of two or more species that occurs as a result of their interactions (suggests that occurs as a result of their interactions (suggests the importance of interactions for the structure of the importance of interactions for the structure of biotic communities - if one species is lost, the co-biotic communities - if one species is lost, the co-evolved species will be affected).evolved species will be affected).

For predator/prey = “Arms race” (i/.e., The evolution of predator strategies to catch prey, and the responding prey strategies to escape predators.).

Evidence of CoevolutionEvidence of CoevolutionEach of the following either improves the chance of Each of the following either improves the chance of catching prey or avoiding predator.catching prey or avoiding predator.

Predators:Predators:Rapid pursuitAmbush

Prey:SpeedSpeedCrypsis (camouflage)Crypsis (camouflage)Aposematic coloration - warningAposematic coloration - warningDistasteful nature - Monarch butterfliesDistasteful nature - Monarch butterfliesDangerous nature - Dangerous nature - wasps, beesMimicryMimicryGroup livingGroup living

Aposematic ColorationAposematic Coloration

Cryptic ColorationCryptic Coloration

Dangerous NatureDangerous Nature

Distasteful Distasteful NatureNature

MimicryMimicry

MimicryMimicry

Herbivory (i.e., when organisms eat Herbivory (i.e., when organisms eat plants - plants are not usually killed)plants - plants are not usually killed)

Herbivore:Herbivore:

Avoidance of chemical defenses:Avoidance of chemical defenses: choice of tissue. choice of tissue.

Specialized adaptations:Specialized adaptations: horse teeth and skull. horse teeth and skull.

Use of plant chemicals:Use of plant chemicals: sequestering chemicals; sequestering chemicals; digesting chemicalsdigesting chemicals

Plant: Plant:

Physical Defenses:Physical Defenses: Thorns/spines/prickles, toughness Thorns/spines/prickles, toughness (grass)(grass)

Chemical Defenses: Chemical Defenses: digestibility reducers, toxinsdigestibility reducers, toxins

Recruitment of Predators:Recruitment of Predators: extra-floral nectaries, food extra-floral nectaries, food bodies.bodies.

Plant ToxinsPlant Toxins

MutualismMutualism

Is an interaction between two species where Is an interaction between two species where both benefit (often co-evolved relationship)both benefit (often co-evolved relationship)

Examples:Examples:

Lichens: fungi/algae (or cyanobacteria). Protected environment in exchange for photosynthates.

Mycorrhizae: plants/fungi make connections with the roots of plants. Get photosynthates in return for nutrients, especially phosphorous.

Rhizobium bacteria/some plants: nitrogen/photosynthates

LichensLichens

Rhizobium bacteriaRhizobium bacteria

CommensalismCommensalism

Interaction wherein one species benefits, while Interaction wherein one species benefits, while the other is unaffected.the other is unaffected.

Examples:Examples:

Cattle and cattle egretsCattle and cattle egrets

Eyelash mitesEyelash mites

Cattle EgretsCattle Egrets

Eyelash MitesEyelash Mites

Benefits from DiversityBenefits from Diversity

Utilitarian Utilitarian FoodFoodDrugs and MedicinesDrugs and Medicines

AestheticAestheticRecreation/tourismRecreation/tourism

EcologicalEcologicalCommunity StabilityCommunity Stability

MoralMoral

Diverse Food SourcesDiverse Food Sources

Drugs and MedicinesDrugs and Medicines

Some natural medicinal productsProduct Source UsePenicillin Fungus AntibioticBacitracin Bacterium AntibioticTetracycline Bacterium AntibioticErythromycin Bacterium AntibioticDigitalis Foxglove Heart stimulantQuinine Chincona bark Malaria treatmentDiosgenin Mexican yam Birth-control drugCortisone Mexican yam Anti-inflammation treatmentCytarabine Sponge Leukemia cureVinblastine, vincristine Periwinkle plant Anticancer drugsReserpine Rauwolfia Hypertension drugBee venom Bee Arthritis reliefAllantoin Blowfly larvae Wound healerMorphine Poppy Analgesic

Drugs and MedicinesDrugs and Medicines

Recreation/TourismRecreation/Tourism

Determinants of Species DiversityDeterminants of Species Diversity

1.1. Abundance of ecological nichesAbundance of ecological niches

2.2. Dominance of individual species Dominance of individual species

3.3. Environmental stress of habitatEnvironmental stress of habitat

Effect of Abundance of NichesEffect of Abundance of Niches

SuccessionSuccession

SuccessionSuccession is the directional changes in the is the directional changes in the community through time. Changes occur community through time. Changes occur because species alter the soil, shelter, because species alter the soil, shelter, humidity, etc. It results from the humidity, etc. It results from the differential ability of organisms to colonize differential ability of organisms to colonize disturbed areas and from environmental disturbed areas and from environmental changes.changes.

Move from Move from pioneerpioneer community through community through successional communities to a successional communities to a climaxclimax community.community.

Primary SuccessionPrimary Succession

Primary succession is at a new, sterile site. Primary succession is at a new, sterile site.

Conditions that may cause primary Conditions that may cause primary succession are glaciers, winds, fires, or succession are glaciers, winds, fires, or volcanoes producing glacial moraines, volcanoes producing glacial moraines, dunes, and lava fields. The key point is dunes, and lava fields. The key point is that the soil has been disturbed.that the soil has been disturbed.

Indiana DunesIndiana Dunes

Glacial MoraineGlacial Moraine

Mount Saint HelensMount Saint Helens

Mount Saint HelensMount Saint Helens

Lake Obscurity Lake Obscurity 10 miles N10 miles N

Secondary SuccessionSecondary Succession

Secondary succession is recovery of a Secondary succession is recovery of a disturbed site back to a climax disturbed site back to a climax community. The soil remains relatively community. The soil remains relatively intact (e.g., cause of secondary intact (e.g., cause of secondary succession is cutting oak trees from a succession is cutting oak trees from a forest)forest)

ProgressionProgression

Examples of Examples of ProgressionProgression

Lichens and Mosses of Early Lichens and Mosses of Early SuccessionSuccession

Plants of Middle Succession Plants of Middle Succession

Timeline for Hardwood Climax ForestTimeline for Hardwood Climax Forest

Succession Often is the Result of Succession Often is the Result of Human InterventionHuman Intervention

Succession May Be FacilitatedSuccession May Be Facilitated

““Nurse plants”Nurse plants” may often facilitate the may often facilitate the progression toward a climax system.progression toward a climax system.

The idea of facilitating species is important The idea of facilitating species is important concept for restoration ecology).concept for restoration ecology).

Facilitation of One Species by AnotherFacilitation of One Species by Another

e.g., Saguaro Cactuse.g., Saguaro Cactus need nurse plants need nurse plants (mesquite) to shield (mesquite) to shield seeds from seeds from consumption and to consumption and to protect young plants protect young plants from cold nights.from cold nights.

Question? Does Succession Apply Question? Does Succession Apply Only to Restoration of Land Only to Restoration of Land

Ecosystems?Ecosystems?

No!! No!! – Aquatic ecosystems go through – Aquatic ecosystems go through progressive stages to reach a stable progressive stages to reach a stable community structure.community structure.