Biodiversity, Species Interactions, and Population Control Chapter 5

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? Habitat Live in giant kelp forests (California, West Coast) Prey on many kelp-eating shellfish Hunted: early 1900s Fur traders Competition with local shell-fisherman Partial recovery (still endangered, though) FWS declared endangered, numbers grew from 50 to 2,654 Why care about sea otters? Ethics Tourism dollars Keystone species Control population of shellfish that would otherwise exploit the kelp forests

Southern Sea Otter Figure 5.1: An endangered southern sea otter in Monterey Bay, California (USA), uses a stone to crack the shell of a clam (left). It lives in a giant kelp bed (right). Scientific studies indicate that the otters act as a keystone species in a kelp forest system by helping to control the populations of sea urchins and other kelp-eating species. Fig. 5-1a, p. 104

5-1 How Do Species Interact? Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

Species Interact in Five Major Ways Interspecific Competition- members of different species compete for resources Predation-one species feeds directly on another Symbiotic Interactions Parasitism-one species uses a another as a host to gain nutrients in a way that it harms the host. Usually on or in the host Mutualism- interactions between two different species in which both species benefit from each other Commensalism- interaction between 2 species where one species benefits and the other is neither helped nor harmed (neutral)

Most Species Compete with One Another for Certain Resources Competition: Actual fighting Mostly one species becoming more efficient at gaining resources Remember every species occupies a special ecological niche Some niches overlap When they both require the same resources The greater amount of shared resources, the more intense competition

Overlapping Niches Result in… When one species is much more efficient at obtaining resources, the other must either: Move (if possible) Alter (reduce or shift) its niche through natural selection Suffer population decline Become extinct

Some Species Evolve Ways to Share Resources Resource partitioning Using only parts of resource Using at different times Using in different ways

Black-throated Green Warbler Yellow-rumped Warbler These different species of birds feed on different parts of the spruce tree to partition their resources. Some feed on different insect species Black burnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler Figure 5.2: Sharing the wealth: This diagram illustrates resource partitioning among five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion (yellow highlighted areas) of the spruce trees, and by consuming somewhat different insect species. (After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,” Ecology 36 (1958): 533–536.) Fig. 5-2, p. 106

Specialist Species of Honeycreepers Honeycreepers of Hawaii descended from one common ancestor, now have differentiated in beak shapes to partition their resources Figure 5.3: Specialist species of honeycreepers: Through natural selection, different species of honeycreepers developed specialized ecological niches that reduced competition between these species. Each species has evolved a specialized beak to take advantage of certain types of food resources. Fig. 5-3, p. 107

Most Consumer Species Feed on Live Organisms of Other Species Predators capture prey several ways Herbivores: Swim, walk, fly up to plants they feed on Carnivores: 2 options: pursuit and ambush Cooperative hunting: pack of lions hunting giraffes Camouflage: Hide in plain sight and ambush Examples: praying mantis, snowy owls Chemical warfare: Poisonous snakes and spiders (examples)

Predator-Prey Relationships Figure 5.4: Predator-prey relationship: This brown bear (the predator) in the U.S. state of Alaska has captured and will feed on this salmon (the prey). Fig. 5-4, p. 107

Prey species have evolved ways to avoid predators Exceptional ability to run, swim, fly away Highly developed senses (sight and smell) Protective physical features: Shells Thick bark Spines Thorns Lizard tails Break off when attacked and give extra time to escape

Prey species have evolved ways to avoid predators Camouflage Chemical Warfare Poison Irritants Foul-smelling, bad tasting Squids, octopus emit ink clouds to confuse predators Warning coloration Mimicry Non-harmful prey that mimic more risky prey Ex. The Viceroy butterfly looks and acts like monarch which is poisonous Deceptive looks and behavior Moths, blow fish

(b) Wandering leaf insect (a) Span worm (b) Wandering leaf insect (c) Bombardier beetle (d) Foul-tasting monarch butterfly (e) Poison dart frog (f) Viceroy butterfly mimics monarch butterfly (g) Hind wings of Io moth resemble eyes of a much larger animal. (h) When touched, snake caterpillar changes shape to look like head of snake. Stepped Art Fig. 5-5, p. 109

Science Focus: Threats to Kelp Forests Kelp forests: biologically diverse marine habitat Extract the substance algin from kelp for use as a renewable resource Used in toothpaste, cosmetics, ice-cream, and more Major threats to kelp forests Sea urchins- feed on kelp Pollution from water run-off Global warming

Purple Sea Urchin Figure 5.A: This purple sea urchin inhabits the coastal waters of the U.S. state of California. Fig. 5-A, p. 108

Predator and Prey Interactions Can Drive Each Other’s Evolution Intense natural selection pressures between predator and prey populations Both prey and predator evolve adaptations to survive Coevolution Definition: when two species interact with each other over a long period of time, changes in the gene pool of one species can lead to changes in the gene pool of the other species. Interact over a long period of time Bats and moths: echolocation of bats and sensitive hearing of moths

Coevolution: A Langohrfledermaus Bat Hunting a Moth Fig. 5-6, p. 110

Some Species Feed off Other Species by Living on or in Them Parasitism Parasite is usually much smaller than the host Parasite rarely kills the host Mostly draw nourishment from host and gradually weaken them over time Parasites may have a negative reputation, but they never-the-less add to species biodiversity May live inside or outside host Examples: tapeworms, ticks, sea lampreys, fleas, mistletoe plants

Parasitism: Trout with Blood-Sucking Sea Lamprey Fig. 5-7, p. 110

Mutualism Two interacting species benefit each other by doing so Examples: Bees/butterflies/mosquitos/hummingbirds and flowering plants (pollination) Clownfish and sea anenomes Oxpeckers and black rhinoceros Gut inhabitant mutualism: beneficial bacteria in digestive systems Note: mutualism is not a cooperative agreement. Unintentional benefit by exploiting each other Each species is in it for themselves

Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish Fig. 5-9, p. 111

Commensalism Examples: Interaction where one species benefits and the other is neither helped, nor harmed (just neutral) Examples: Epiphytes: “air plants” attach themselves to trunks or branches of large trees Gain better access to sunlight, nutrients; gain a solid base on which to grow Birds nesting in trees Bromeliad Epiphyte

5-2 What Limits the Growth of Populations? Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

Most Populations Live Together in Clumps or Patches (1) Population: group of interbreeding individuals of the same species Population distribution Clumping Uniform dispersion Random dispersion

Most Populations Live Together in Clumps or Patches (2) Why clumping? Species tend to cluster where resources are available Groups have a better chance of finding clumped resources Protects some animals from predators Packs allow some to get prey

Populations Can Grow, Shrink, or Remain Stable (1) Population size governed by Births Deaths Immigration Emigration Population change = (births + immigration) – (deaths + emigration) Negative value means population is shrinking Positive value means population is growing 0 means stable

Populations Can Grow, Shrink, or Remain Stable (2) Age structure: Distribution of individuals among various age groups in a population Can have strong effects on how fast a population grows or shrinks Age groups described as: Pre-reproductive age Reproductive age Post-reproductive age Population most likely to grow fast the more individuals there are in the reproductive age group

Age Structure Graphs Why is taking gender into account important? Would a population grow faster with more men than women or women than men at reproductive ages? What does this depend on?

Some Factors Can Limit Population Size Range of tolerance Variations in physical and chemical environment Some individuals within a population can be slightly more tolerant (see next slide Limiting factor principle Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance Precipitation Nutrients Sunlight, etc

Trout Tolerance of Temperature Figure 5.13: This diagram illustrates the range of tolerance for a population of organisms, such as trout, to a physical environmental factor—in this case, water temperature. Range of tolerance restrictions prevent particular species from taking over an ecosystem by keeping their population size in check. Question: For humans, what is an example of a range of tolerance for a physical environmental factor? Fig. 5-13, p. 113

Limiting Factors control population sizes Important Land Limiting Factors: Precipitation/water Soil nutrients Temperature Important Aquatic Limiting Factors Sunlight Nutrient availability Dissolved oxygen levels Salinity

No Population Can Grow Indefinitely: J-Curves and S-Curves (1) Size of populations controlled by limiting factors: Light Water Space Nutrients Exposure to too many competitors, predators or infectious diseases There will always be limits to population growth No population can grow indefinitely

No Population Can Grow Indefinitely: J-Curves and S-Curves (2) Environmental resistance All factors that act to limit the growth of a population Determines a population’s carrying capacity Carrying capacity (K) Maximum population a given habitat can sustain When populations near the (K), growth RATE begins to slow/decline

No Population Can Grow Indefinitely: J-Curves and S-Curves (3) Exponential growth (J-curve) Starts slowly, then accelerates to carrying capacity when meets environmental resistance Logistic growth (S-curve) Decreased population growth rate as population size reaches carrying capacity

Logistic Growth of Sheep in Tasmania Note how the population size fluctuates, it never truly stabilizes. Overshoot usually occurs, knocks the population back down, and up again. Figure 5.15: This graph tracks the logistic growth of a sheep population on the island of Tasmania between 1800 and 1925. After sheep were introduced in 1800, their population grew exponentially, thanks to an ample food supply and few predators. By 1855, they had overshot the land’s carrying capacity. Their numbers then stabilized and fluctuated around a carrying capacity of about 1.6 million sheep. Fig. 5-15, p. 115

Science Focus: threat on California’s southern sea otter Low reproductive rates Sexual maturity between 2-5 years old 1 pup per yea Threats Predation from Orcas Parasites from cat litter Thorny-headed worms from seagulls Toxic algal blooms Biomagnification from PCB’s Oil Spills They serve as indicator species why?

Population Size of Southern Sea Otters Off the Coast of So Population Size of Southern Sea Otters Off the Coast of So. California (U.S.) Figure 5.B: This graph tracks the population size of southern sea otters off the coast of the U.S. state of California, 1983–2009. According to the U.S. Geological Survey, the California southern sea otter population would have to reach at least 3,090 animals for 3 years in a row before it could be considered for removal from the endangered species list. (Data from U.S. Geological Survey) Fig. 5-B, p. 114

Case study: white tailed deer populations White Tailed Deer were greatly threatened in the early 1900’s Due to habitat destruction and hunting Laws were passed in 1920’s-30’s to protect remaining deer Methods used included Restricted hunting Elimination of predators Protection methods worked too well Population boom

Case study: white tailed deer Problems with deer population explosion Deer are exploiting suburban areas (feeding on suburbanite’s gardens and farmer’s land) Spreading Lyme disease to humans (via ticks) Increased vehicular accidents, human fatalities Control methods: Hunting re-opened Spray predator-scented sprays as a scare tactic Trapped and moved Birth control darts

Population crash after exceeding carrying capacity Some populations temporarily exceed the (K) known as OVERSHOOT A drastic crash may occur if there is a reproductive time lag Period needed for the birth rate to fall and for the death rate to rise in response to over consumption This is known as a population Crash, or dieback

Carrying capacity is not fixed Factors may increase or decrease (k) Seasonality Presence/absence of predators Abundance/scarcity of competitors Habitat degradation

Species have different reproductive rates Some species reproduce many, small offspring Do not need to provide significant parental care  Why not? Many offspring = greater chances of survival The number of pre-reproductive deaths will most likely always remain less than the total offspring produced Conserves time/energy for parent offspring Some species reproduce later in life and have few offspring Mature slowly Require parental care Which are most susceptible to extinction? Why?

Survivorship Curves http://ap-biology.chsd218.richards.schoolfusion.us/modules/groups/homepagefiles/gwp/805395/918350/File/Unit_01_Ecology/Survivorship_Curves.swf?sessionid=44c50c7ebdcd89a975e40de7289bbd56 I. Humans and other large mammals; those who fit this curve produce few offspring, but provide them with good care II. Ground squirrels, rodents, invertebrates, lizards, annual plants; this curve includes animals with a constant death rate III. Oysters; those within this survivorship curve produce many offspring, but provide little to no care for them http://ap-biology.chsd218.richards.schoolfusion.us/modules/groups/homepagefiles/gwp/805395/918350/File/Unit_01_Ecology/Survivorship_Curves.swf?sessionid=44c50c7ebdcd89a975e40de7289bbd56

Reproductive Strategies (R & K) R - Unstable environment, density independent K - Stable environment, density dependent interactions small size of organism large size of organism energy used to make each individual is low energy used to make each individual is high many offspring are produced few offspring are produced early maturity late maturity, often after a prolonged period of parental care short life expectancy long life expectancy each individual reproduces only once individuals can reproduce more than once in their lifetime type III survivorship pattern  in which most of the individuals die within a short time  but a few live much longer type I or II survivorship pattern in which most individuals live to near the maximum life span http://www.bio.miami.edu/tom/courses/bil160/bil160goods/16_rKselection.html

Reproductive Patterns r-selected species tend to be opportunists while K-selected species tend to be competitors. Figure 8-10

R-selected vs. K-selected

Population Density Population Density: number of individuals in a population found in a particular area or volume

Density-Dependent vs Density Independent factors Density Dependent factors Have a greater effect as a population increases in density Examples: infectious disease, competition, space, predation, parasitism Musical Chairs! Density-Independent Factors Does not matter how dense a population is Examples: seasonal change, catastrophic event, habitat destruction Think of a population of plants that experience a winter freeze does not matter if there are 50 members in the population or 100 members. The freeze will affect the entire area

4 Different Types of Population Change Occur in Nature Stable- population size slightly fluctuates above and below (k) Ex. Species in undisturbed tropical rainforests Irruptive Population surge, followed by crash Common of short-lived rapidly reproducing organisms Cyclic fluctuations, boom-and-bust cycles Top-down population regulation Bottom-up population regulation Irregular- no particular pattern

Population Cycles for the Snowshoe Hare and Canada Lynx Figure 5.18: This graph represents the population cycles for the snowshoe hare and the Canadian lynx. At one time, scientists believed these curves provided evidence that these predator and prey populations regulated one another. More recent research suggests that the periodic swings in the hare population are caused by a combination of top-down population control—through predation by lynx and other predators—and bottom-up population control, in which changes in the availability of the food supply for hares help to determine their population size, which in turn helps to determine the lynx population size. (Data from D. A. MacLulich) Cyclic fluctuation patterns Fig. 5-18, p. 118

Estimating Population Sizes Scientists need to consider several limitations when attempting to estimate population sizes Mobility/immobility Distribution patterns Migration rates Some methods scientist use to estimate ecological populations: Random Sampling (best for stationary organisms) Normally use quadrats Mark Recapture

Mark Recapture P=(M*C)/R P= estimated population size M=# of 1st Sample that were marked C= Total number caught in 2nd sample R= # recaptured (marked) found in sample 2

Mark recapture Example A biologist caught 16 cichlid species from a lake and tagged all of them. He released them back into the lake. A week later, he went back and caught 13 cichlid fish in the same lake and found that 4 of them were tagged individuals he had recaptured. The estimated population of cichlids in the lake would be: M=16 C=13 R=4 P= (16*13)/4= 52 This method helps with estimating mobile species population sizes

Random Sampling Example Since the area is 4x4, take 4 samples Find the average number of individuals per square Multiply is times total number of area (16) Total Sampled = 29 Average/sample = 7.25 Est. Population = 7.25*16 = 116 10 8 4 7 This method is best for evenly dispersed, stationary populations… why?

Humans Are Not Exempt from Nature’s Population Controls Ireland Potato crop in 1845 Bubonic plague Fourteenth century AIDS Global epidemic

5-3 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? Concept 5-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

Communities and Ecosystems Change over Time: Ecological Succession The normally gradual change in species composition in a given area after the area has been disturbed o destroyed in some way Response to such instances as Fire Volcanic eruption Climate change Clearing of forests 2 types: Primary succession Secondary succession

Some Ecosystems Start from Scratch: Primary Succession Establishment of biotic community in a lifeless area No soil in a terrestrial system No bottom sediment in an aquatic system Takes hundreds to thousands of years Need to build up soils/sediments to provide necessary nutrients Pioneer species: first species to inhabit the area Examples: Moss, Lichens Occurs after such instances as Volcanic eruption Retreating glaciers Abandoned highway/parking lot Newly created or shallowed pond/reservoir

Primary Ecological Succession Figure 5.19: Primary ecological succession: Over almost a thousand years, these plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern Lake Superior. The details of this process vary from one site to another. Question: What are two ways in which lichens, mosses, and plants might get started growing on bare rock? Fig. 5-19, p. 119

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession Some soil remains in a terrestrial system Some bottom sediment remains in an aquatic system Much more common than primary succession Restoration is also much faster than in primary succession Occurs after disturbances such as Abandoned farmland Burned/cut forests Heavily polluted streams Flooded land

Natural Ecological Restoration of Disturbed Land Figure 5.20: Natural ecological restoration of disturbed land: This diagram shows the undisturbed secondary ecological succession of plant communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. See an animation based on this figure at CengageNOW. Questions: Do you think the annual weeds (left) would continue to thrive in the mature forest (right)? Why or why not? Fig. 5-20, p. 120

Secondary Ecological Succession in Yellowstone Following the 1998 Fire Figure 5.21: These young lodgepole pines growing around standing dead trees after a 1998 forest fire in Yellowstone National Park are an example of secondary ecological succession. Fig. 5-21, p. 120

Ecological succession Succession Primary and secondary succession Tend to increase biodiversity Increase species richness and interactions among species Important natural service Both (primary and secondary) are examples of ecological restoration Primary and secondary succession can be interrupted by Fires Hurricanes Clear-cutting of forests Plowing of grasslands Invasion by nonnative species

Science Focus: How Do Species Replace One Another in Ecological Succession? Facilitation- One set of species makes an area more suitable for other species and less suitable for itself Inhibition- Early species hinder the establishment of other species growth Succession can proceed when these species are removed Tolerance- Plants in the late stages of succession are unaffected/no direct competition with earlier species

Succession Doesn’t Follow a Predictable Path Traditional view- Equilibrium Balance of nature and a climax community Climax community: dominated by few long-lived plant species and is in balance with its environment Current view Ever-changing mosaic of patches of vegetation Reflects on-going struggle by species Mature late-successional ecosystems State of continual disturbance and change

Living Systems Are Sustained through Constant Change Stability is achieved through change Environment is constantly changing, thus to keep it stable, living systems must parallel the change by change 2 aspects of stability: 1. Inertia (persistence) Ability of a living system to survive moderate disturbances 2. Resilience Ability of a living system to be restored through secondary succession after a moderate disturbance Some systems have one property, but not the other

Some ecosystems have one or the other: resilience or Inertia Ranforests (example) High Inertia High resistance to change due to species diversity and richness Once severely damaged, have low resilience Reaches ecological tipping point Grasslands (example) High Resilience Low species diversity makes them susceptible to destruction Because most plant matter stored in underground roots, they may recover quickly via secondary succession

Three Big Ideas Certain interactions among species affect their use of resources and their population sizes. There are always limits to population growth in nature. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession).