Community and Population Ecology Chapter 6

Good Morning! Place your portfolio containing your paper and sources on the front table and then sign in using the red pen.

Why Should We Care about the American Alligator? Fig. 6-1, p. 108

Core Case Study: American Alligator Highly adaptable Only natural predator is humans 1967 – endangered species list Successful environmental comeback Keystone species

6-1 How Does Species Diversity Affect the Sustainability of a Community? Concept 6-1 Species diversity is a major component of biodiversity and tends to increase the sustainability of communities and ecosystems.

Species Diversity Species richness combined with species evenness Niche structure Varies with geographic location Species richness declines towards poles

Sustainability and Environmental Change Inertia or persistence Constancy Resilience

Science Focus: Community Sustainability No certain definition of sustainability Do communities need high inertia and high resilience? Communities may have one but not the other Equilibrium is rare

Richness and Sustainability Hypotheses Does a community with high species richness have greater sustainability and productivity? Is a species-rich community better able to recover from a disturbance? Research suggests “yes” to both

6-2 What Roles Do Species Play in a Community? Concept 6-2 Based on certain ecological roles they play in communities, species are described as native, nonnative, indicator, keystone, or foundation species.

Ecological Niche Species occupy unique niches Native species – those normally found living and thriving in a particular community Spanish moss in the south Nonnative species – plants, animals, fungi Spread in new, suitable niches

Deliberately Introduced Species Purple looselife European starling African honeybee (“Killer bee”) Nutria Salt cedar (Tamarisk) Marine toad Water hyacinth Japanese beetle Hydrilla European wild boar (Feral pig) Fig. 9-11a, p. 193

http://dnr.wi.gov/invasiveS/fact/loosestrife.htm http://www.npwrc.usgs.gov/resource/plants/loosstrf/index.htm

http://www.maxshores.com/kudzu/ Kudzu Fig. 9-12, p. 194

http://aaabeeremoval.com/photogallery_africanbeeswarm.htm http://www.invasivespeciesinfo.gov/animals/afrhonbee.shtml http://www.desertusa.com/mag98/sep/stories/kbees.html

Accidentally Introduced Species Sea lamprey (attached to lake trout) Argentina fire ant Brown tree snake Eurasian muffle Common pigeon (Rock dove) Formosan termite Zebra mussel Asian long-horned beetle Asian tiger mosquito Gypsy moth larvae Fig. 9-11b, p. 193

Indicator Species Early warning system – tell about harmful changes in biological communities Birds – found everywhere; affected by habitat problems including pesticides Butterflies – associate with various plant species becoming vulnerable to habitat loss Amphibians – multiple reasons; complex and interacting

Case Study: Why Are Amphibians Vanishing? (1) – See latest article Habitat loss and fragmentation Prolonged drought Pollution Ultraviolet radiation Parasites - chytrid fungi

Tadpole develops into frog Life Cycle of a Frog Adult frog (3 years) Young frog sperm Tadpole develops into frog Sexual reproduction Tadpole Eggs Fertilized egg development Egg hatches Organ formation Fig. 6-3, p. 112

Case Study: Why Are Amphibians Vanishing? (2) Viral and fungal diseases Climate change Overhunting Nonnative predators and competition Why we should care

Keystone Species Significant role in their food web Elimination may alter structure, function of community Pollinators Top predators

Foundation Species Create habitats and ecosystems Beavers Elephants Seed dispersers

http://www. morning-earth. org/Graphic-E/Interliv-Two http://www.morning-earth.org/Graphic-E/Interliv-Two.html great overview http://www.naturehaven.com/elephantbottom.html - Elephant site

Science Focus: Why Should We Protect Sharks? Remove injured, sick animals Many are gentle giants Provide potential insight into cures for human diseases Keystone species

6-3 How Do Species Interact? Concept 6-3A Five basic species interactions – competition, predation, parasitism, mutualism, and commensalism – affect the resource use and population sizes of the species in a community. Concept 6-3B Some species develop adaptations that allow them to reduce or avoid competition for resources with other species.

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

Resource Partitioning of Warbler Species Fig. 6-5, p. 115

Resource Partitioning and Niche Specialization Number of individuals Species 1 Species 2 Region of niche overlap Resource use Number of individuals Species 1 Species 2 Resource use Fig. 6-4, p. 114

Predation Predator-prey relationship Predators and prey both benefit – individual vs. population Predator strategies Prey strategies

How Species Avoid Predators Span worm Bombardier beetle Viceroy butterfly mimics monarch butterfly Foul-tasting monarch butterfly Poison dart frog When touched, the snake caterpillar changes shape to look like the head of a snake Wandering leaf insect Hind wings of io moth resemble eyes of a much larger animal Fig. 6-6, p. 116

Parasitism Live in or on the host http://mybloatingrelief.com/parasites/ Parasite benefits, host harmed Parasites promote biodiversity http://www.youtube.com/watch?v=rLtUk-W5Gpk

http://www.morning-earth.org/Graphic-E/Interliv-Two.html

Mutualism Everybody benefit by unintentional exploitation Nutrition and protection Gut inhabitant mutualism

Oxpeckers and black rhinoceros Clown fish and sea anemone Examples of Mutualism Oxpeckers and black rhinoceros Clown fish and sea anemone Mycorrhizae fungi on juniper seedlings in normal soil Lack of mycorrhizae fungi on juniper seedlings in sterilized soil © 2006 Brooks/Cole - Thomson

Commensalism Benefits one with little impact on other Bromeliad

6-4 How Do Communities Respond to Changing Environmental Conditions? Concept 6-4A The structure and species composition of communities change in response to changing environmental conditions through a process called ecological succession. Concept 6-4B According to the precautionary principle, we should take measures to prevent or reduce harm to human health and natural systems even if some possible cause-and-effect relationships have not been fully established scientifically.

Ecological Succession Primary succession Secondary succession Disturbances create new conditions Intermediate disturbance hypothesis

Ecological Succession Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce climax community Lichens and mosses Exposed rocks Small herbs and shrubs It is an orderly process of COMMUNITY development; it normally proceeds in a predictable, orderly direction; it represents the gradual replacement of populations by others that are better adapted to the existing conditions. 2. It results from modification of the physical environment by the populations that interact to makeup the community thus, succession is community controlled; the physical factors of the environment and climate determine the pattern and the rate of change; the climate and immediate environment often set the limit as to how far development can proceed Fig. 6-9, p. 119

3. The end result of succession is a stabilized ecosystem which is in balance with the climate and environment of the area; under these conditions the maximum number of organisms (biomass) and their symbiotic (nutritional) interactions are balanced or maintained with the energy available to the system. Thus, the strategy of succession as a short term process is very much like the strategy of long-term evolutionary development of the biosphere. It results in HOMEOSTATIC balance of organisms with the physical environment WITH THE BENEFIT of achieving a means of effectively dealing with the constant changes or pertubations presented by the environment. The Strategy of Ecosystem Development, Eugene P. Odum Science 18 April 1969: Vol. 164. no. 3877, pp. 262 - 270

Primary Ecological Succession Lichens and mosses Exposed rocks Balsam fir, paper birch, and white spruce climax community Jack pine, black spruce, and aspen Heath mat Small herbs and shrubs Time Fig. 6-9, p. 119

Secondary Ecological Succession Mature oak-hickory forest Young pine forest with developing understory of oak and hickory trees Shrubs and pine seedlings Perennial weeds and grasses Annual weeds Time Fig. 6-10, p. 120

Succession’s Unpredictable Path Successional path not always predictable toward climax community Communities are ever-changing mosaics of different stages of succession Continual change, not permanent equilibrium

Precautionary Principle Lack of predictable succession and equilibrium should not prevent conservation Ecological degradation should be avoided Better safe than sorry

6-5 What Limits the Growth of Populations? Concept 6-5 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

Population Distribution Clumping – most populations Uniform dispersion Random dispersion http://www.biology.iupui.edu/biocourses/n100/images/39dist.gif

Why Clumping? Resources not uniformly distributed Protection of the group Pack living gives some predators greater success Temporary mating or young-rearing groups

Populations Sizes Are Dynamic Vary over time population = (births + immigration) - (deaths + emigration) Age structure Pre-reproductive stage Reproductive stage Post-reproductive stage

Limits to Population Growth (1) Biotic potential is idealized capacity for growth Intrinsic rate of increase (r) Nature limits population growth with resource limits and competition Environmental resistance

Population Growth Curves Environmental resistance Carrying capacity (K) Population size (N) Biotic potential Exponential growth Time (t) Fig. 6-11, p. 121

Limits to Population Growth (1) Carrying capacity – biotic potential and environmental resistance (Number of individuals of a given species that can be sustained indefinitely in a given area) Exponential growth - logarithmic increase Logistic growth – exponential growth followed by steady decrease over time until population size levels off. Due to population meeting environmental resistance and approaching carrying capacity

Logistic Growth of Sheep Population 2.0 Overshoot Carrying Capacity 1.5 Number of sheep (millions) 1.0 .5 1800 1825 1850 1875 1900 1925 Year Fig. 6-12, p. 121

Overshoot and Dieback Population does not transition smoothly from exponential to logistic growth Overshoot carrying capacity of environment Caused by reproductive time lag Dieback, unless excess individuals switch to new resource

Exponential Growth, Overshoot and Population Crash of Reindeer Overshoots Carrying Capacity 2,000 Population crashes 1,500 Number of reindeer (millions) 1,000 500 Carrying capacity 1910 1920 1930 1940 1950 Year Fig. 6-13, p. 122

Different Reproductive Patterns r-Selected species High rate of population increase Opportunists K-selected species Competitors Slowly reproducing Most species’ reproductive cycles between two extremes

Humans Not Exempt from Population Controls Bubonic plague (14th century) – Ebola like symptoms Famine in Ireland (1845) – led to emigration to the United States (through 1848) AIDS – major player in population decline Technology, social, and cultural changes extended earth’s carrying capacity for humans Expand indefinitely or reach carrying capacity?

Case Study: Exploding White-tailed Deer Populations in the United States 1920–30s: protection measures Today: 25–30 million white-tailed deer in U.S. Conflicts with people living in suburbia