Foundations of Biology 2: Ch. 55 Species Interactions

Prey species have evolved defenses.

Escape mechanisms: - Flying or running away. Morphological defenses: - Tough skin and shells. - Spines - Hair. Other mechanisms...

Behavioral Mechanisms

Group behaviors such as flocking and alarm calls can provide protection from predators. ex. "Starling Clouds" allow flocks of starlings to confused and intimidate peregrine falcons. Selfish-prey keeps starling on the inside of the flock more protected.

Competitive Exclusion

If a species can prevent another species from using essential resources, the inferior competitor may become locally extinct.

Ectoparasites

Macroparasites that live outside the bodies of their hosts. ex. Ticks Some ectoparasites (leeches or mosquitoes) are only casually associated with hosts; interact just long enough to eat their fill then move on. Ectoparasites that spend their entire lives on their hosts have attributes that keep them attached: - ex. Whale lice have claws on the tips of their legs that piece skin of marine mammal host. Mosts host actively work to rid themselves of ectoparasites. - ex. Grooming behavior; especially common among primates to maintain social bonds that will ensure removal. - ex. Hairlessness in humans might be an evolutionary response to ectoparasites.

Endoparasites

Macroparasites that spend at least part of their life cycle inside the bodies of their hosts. ex. Tapeworms

Behaviors and Characteristics Affect Competition

Morphological, physiological, and behavioral differences all affect competition and the success of one species vs. another.

Predation is a trophic interaction in which predators benefit and prey are harmed.

Most familiar and most dramatic type of species interaction. Three Types of Predation: 1. Carnivory 2. Herbivory 3. Parasitism

Predators can have dramatic effects on communities.

Not just on populations! Communities are on the next largest scale, made up of several species and populations. Predators promote diversity of species within communities ex. Sea stars feed on mussels, which create space for sessil vertebrates to occupy, which creates diversity. When the sea star population is taken away, mussels start to monopolize on the space, leaving no space for other species, which means no diversity!

Nontrophic

A categorization of the effects of species interactions where the effect does NOT involve feeding.

Mimicry Systems

- Batesian Mimicry - Mullerian Mimicry

Parasitism

(+ , -) Form of predation in which the predator (a parasite) lives symbiotically on or in the prey (its host) and consumes only certain tissues without necessarily killing the host. Some parasites are pathogens that cause disease in their hosts.

Carnivory

(+ , -) Form of predation in which the predator and prey are both animals. ex. Mountain lion consuming a deer.

Herbivory

(+ , -) Form of predation in which the predator as an animal and the prey is a plant or algae. ex. Giraffe consuming the leaves of a tree.

There are two extreme results of competition.

- Competitive exclusion - Competitive coexistence.

Herbivory is a widespread but often specialized interaction.

- Herbivores can be specialists or generalists. - Herbivores can affect plant evolution. - Plants develop defenses against herbivores.

Important Things to Consider When Thinking About Competition

- Intra- vs. interspecies - Closely related species vs. distantly related species - Asymmetrical - Morphological, physiological, and/or behavioral differences impact success - Competitive success is on a continuum

The outcome of competition among species can be changed by a variety of factors.

- Physical environmental conditions: - Ecological disturbances - Predation Can cause a weakening or reversal of competitive outcomes between species if they negatively affect the competitively dominant species. By reducing the growth or survival of the competitively superior species, the physical environment, disturbance, and predation can allow the competitively inferior species a chance to acquire limiting resources, gain a foothold, and potentially increase its population size.

Predator populations can cycle with their prey populations.

- Species interactions can affect population dynamics. Figure 55.9: - Some predator-prey populations are linked and scillate in response to one another. - Predator-prey cycling in Canada lynx and snowshoe hare. - Regular cycle in population cycle in population sizes of each species; peaking every 10 years but falling low during the intervening years. - Peak of lynx population lags behind hare population 2 - 3 years. - Cycling is a result of tight coupling between predator and prey: as prey increase, so do predators - Prey decline as a result of increased mortality; predators decline in response to low resources. - When predators decline, prey populations rise again in response to low predation. - This allows the predator population (still lagging behind) to increase as well. - Prey population cycling may also be caused by environmental factors (large-scale variability in climate), as suggested by a study removing lynx from the equation or adding food for the hare.

Microparasites can affect animal behavior.

- ex. Fungi Cordyceps Many species of cordyceps that specialized in infecting a specific animal. Keeps a single species from getting the upper hand. Changes behavior of prey in order to aid in reproduction of parasitic offspring.

Trophic

A categorization of the effects of species interactions where the effect involves feeding.

Microparasites

A classification of parasites that includes viruses, bacteria, and protists. Much smaller than their hosts. Live and reproduce inside hosts. Multiple generations reside within a single individual. Host may harbor thousands or millions of them. If in process of acquiring nutrients at the expense of host, cause symptoms of disease, the microparasites are considered pathogens. Immune systems are an example of host mechanism that can limit pathogen proliferation.

Macroparasites

A classification of parasites that includes worms and insects. Much larger than microparasites. Not always intimately associated with hosts (can live and reproduce outside host). Infections to be chronic and often accumulate slowly. Two categories: 1. Ectoparasites 2. Endoparasites

Symbiosis

A condition of species interactions in which one of the species lives in or on the other species. Can occur whether the interaction is positive or negative.

Batesian Mimicry

A form of mimicry in which a benign, edible species (the mimic) closely resembles a dangerous, toxic species. The mimic benefits from the avoidance behavior of predators. ex. The harmless veceroy butterfly closely resembles the toxic monarch butterfly.

Mullerian Mimicry

A form of mimicry in which two or more species converge on a common warning signal; all benefit from providing a stronger recognition signal to predators. ex. Examples, most species of bees have a similar "yellow and black" pattern on their bodies.

Exploitation Competition

A limiting resource is available to all competitors but their use is different, affecting availability to the other species. Species interact indirectly; if one species uses a resource, it can affect how another species uses that resource. This can often lead to coexistence; two species find a balance on how each uses a resource so they can share. ex. Honeybee species that eat the same nectar harvest at different times and locations. Light can result in exploitative competition in plants.

Realized Niche

A niche defined by interactions with other species. In a realized niche, the organism is more limited by intraspecific competition caused by limited resources.

Fundamental Niche

A niche defined by its physiological capabilities. If an organism didn't have any competition, where would it be able to exist?

Competition

A nontrophic interaction in which two or more species overlap in the use of at least some of the same required limiting resources, negatively affecting their their growth, reproduction, and/or survival. Both are affected negatively. (- , -) Can occur between: - Predators that depend on the same prey species. - Herbivores that feed on the same house plant. - Pathogenic microbes attacking the same host. - Pathogens can coexist, but one of the two will grow stronger and over take which symptom the host will suffer from.

Obligate Interactions

A positive interaction in which the interaction is necessary for both parties in order for them to survive. ex. Fungus-lichen combination. Fungus provides lichen with water, while the lichen provides food for the fungus.

Facultative Interactions

A positive interaction in which the interaction is optional. ex. It is a benefit for trees if their seeds are eaten by animals and then dispersed at a greater distance.

Limiting Resource

A resource that is in short supply.

Keystone Species

A species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically. ex. Wolves of Yellowstone National Park.

Predation

A trophic interaction in which an individual of one species (a predator) kills and/or consumes individuals (or parts of individuals) or another species (its prey). One benefits, the other doesn't benefit. (+ , -) Includes: - Carnivory - Herbivory - Parasitism

Mutualism

A type of positive interaction in which both species benefit from the interaction (+ , +), sometimes in a highly dependent and symbiotic manner. ex. Clownfish live in sea anemones by developing a mucus coating for protection. - Fish gets a habitat, while the anemone get nutrients.

Commensialism

A type of positive interaction in which one participant benefits but the other is unaffected (+ , 0). Typically encompasses the provisioning of food and habitat to improve conditions for the commensal organism.

Amensialism

A type of species interaction that occurs when one participant is harmed but the other is not affected (- , 0). ex. Elephants moving through a forest and crushing plants. Elephants not affected, but plants are. ex. Understory plants that grow under trees are deprived of light but have no effect on the trees. ex. Bird droppings are toxic to plants. Birds are not affected, but plants are.

Parasite

An organism that lives in or on another organism and benefits at the host's expense. Parasitism: A predatory interaction in which a predator (a parasite) lives on or in the prey (its host). 50% of the Earth's species are parasites. Many parasite-host relationships are symbiotic.

Herbivores can affect plant evolution.

Because herbivores usually only consume parts of plants but don't kill them, this ultimately reduces plant fitness, which in turn produces fewer offspring for the plant since animals often feed on seeds.

Carnivory results in a range of capture and avoidance mechanisms.

Best strategy for predators: maximize ability to capture and consume prey. Best strategy for prey: minimize likelihood of being eaten.

Evolutionary change can occur in response to species interactions.

Biotic factors: - ex. Woodpeckers have feet, tails, beaks, and tongues adapted to catch insects under the bark of trees as a result of their long-standing interactions with their insect prey. Abiotic factors: - Unlike biotic factors, do NOT undergo change as a result of interaction. - ex. Ice and snow don't become more deadly as a result of encountering cold-resistant organisms.

Crypsis

Camouflage; one form of hiding. Allows species to resemble objects that their predators consider inedible. ex. Satanic Leaf-tailed Gecko

Closely Related Species vs. Distantly Related Species

Closely Related Species often have more competition than Distantly Related Species. This might be due to the fact that Closely Related Species are more likely to consume the same limited resources.

Resources

Components of the environment that are required by a species.

Competition is Asymmetrical

One species is usually affected more than the other, be it positive, negative, or neutral. It is usually never even.

Intraspecies vs. Interspecies

INTRAspecies refers to members within a single species. INTERspecies refers to interactions between different species.

Positive interactions can have dramatic effects on populations and communities.

In addition to influencing the physiology, behavior, and growth of a species, positive interactions have effects at the population and community levels. Affects population growth. - ex. Acacia trees depend on ants for protection against herbivores and weeds attempting to crowd the space at the bottom of the tree (reduces competition), in exchange for food and shelter for the ants. - Removal of ants means the acacia tree will lose its leaves to herbivores, decreasing the plant's growth rate and increasing the plant's mortality rate. -Mutualism has effects on population size of each partner. Affects community diversity. - Dominant species such as plants or corals and sponges provide homes to a diverse array of species that cannot survive outside a particular environment. - Species living within dominant species often have no affect on them, thus occur commensalism. - These dominant plants and animals are the very foundation of the community, which would not exist without them.

Host-pathogen interactions can have strong selective pressure.

In order for pathogens to persist in a host population, they must continually infect new host individuals. A less deadly stain that kills a smaller proportion of host individuals may be able to infect a larger number of new hosts. Thus pathogen and host may reach a state of coexistence as increased host resistance (ability to withstand the effects of a pathogen) and decreased pathogen virulence (ability to cause disease) evolve. ex. Myxoma virus introduced to European rabbits to control exploding population in Australia. After a large portion of the rabbit population died out, rabbits slowly evolved resistance to virus. Now control of populations requires new, more lethal strains of the virus.

Species interactions are not always clear-cut.

Interaction categorization is on a continuum. Continuum is a consequence of variable strength in species interactions and their asymmetrical nature. ex. In Eurasia, non-native grey squirrel interactions with native red squirrel are asymmetrical, since the grey squirrel has a much greater effect on the red squirrel than the red squirrel has on the grey squirrel. - Grey squirrel's ability to better obtain limited resources and disease (fatal to red squirrel) cause red squirrel populations to decline. Illustration: http://slideplayer.com/slide/4486576/14/images/27/Figure+12.7+A+Continuum+of+Competitive+Effects.jpg

Certain interactions are more likely to result in coevolution than others.

Interactions that are more likely to result in coevolution occur predictably with high frequency and have a strong effect on the fitness of species. More likely: - Predation - Competition - Mutualism Less likely: - Amensialism - Commensalism

Plants develop defenses against herbivores.

Morphology: - Being physically difficult for herbivores to eat. - ex. Thorns and spines are highly effective deterrents against vertebrate herbivores. Chemicals: - Consuming the plant is an unpleasant experience for herbivores. - ex. Coralline algae contain calcium carbonate within their tissues, which deters many marine herbivores. - ex. Tobacco plants protect themselves with a nicotine coating, which deters predators.

Interference Competition

One species directly interferes with or excludes another species' access to a limiting resource. - Can take many forms; from physical exclusion to chemical warfare among competitors. - ex. Desert ants will block the entrance to a honeypot nest with rocks in order to temporarily limit competition for food. - Can occur with two different species or the same species. - If a resource is patchy, there's a high chance species will participate in interference competition for said resource. - Watering holes.

Parasites specialize on hosts.

Parasites have specific hosts. However, a single host can house an array of different parasites. Parasites can even have their own parasites.

Predators may adapt to prey's chemical defenses.

Predators like Sea Slugs can become immune to the toxin of the Sea Sponge. Sea slugs have the advantage of having a resource that other animals cannot have. Additionally, the sea slug is able to concentrate the toxin in its own system to protect itself against predators.

Chemical defenses

Prey will use chemical defenses to escape or repel their predators. Often used by animal prey that are small, weak, sessile (immobile), or otherwise protected. Many insects produce sprays, oozes, or froths when attacked. Venom vs. Poison: If something is poisonous, the toxin is absorbed or ingested (touched or eaten). This is enough to deter the predator with an unpleasant experience. If something is venomous, the toxin is injected into the predator. ex. Box Jellyfish Toxin in Sting

Warning Signals

Some prey species that defend themselves with toxic chemicals advertise that fact with a warning signal. Can be: - Visual (many toxic species are bright and colorful). - Acoustical (ex. Rattlesnake's warning rattle). Predators can learn to associate specific colors and sounds with unpleasant experiences.

Herbivory Specialists vs. Generalists

Specialists feed on just one or a few, often taxonomically related, plant species. - 90 % of herbivorous insects are specialists. Generalists feed on hundreds of unrelated plant species. - Vertebrate herbivores are usually generalists; a cow grazing in a pasture can consume many different plant species in a single afternoon.

Positive Interactions

Species Interactions that occur when neither species is harmed. Mutualisms: - Both species benefit from the interaction. - Allow access to limited resources from both participants. - Often involve an exchange of food for housing or defense. ex. Gut bacteria Commensalism: - Only one species benefits, but the other is unaffected. ex. Organisms living on another's species body but the host is unaffected. Some Positive Interactions are Symbiotic. - Organisms live in close contact with each other; usually when one thing affects an organism, the other is also affected ex. Clownfish and sea anemones - Obligate or Facultative

Species interactions are characterized based on the effects species have on each other.

Species interactions can either be positive (+), negative (-), or neutral (0). Effects are Trophic or Nontrophic. Species interactions may include Symbiosis. There are four broad categories of species interactions: 1. Predation 2. Competition 3. Positive Interactions (Facilitations) 4. Amensialisms

The net outcome of an interaction depends on the ecological circumstances under which it occurs.

Species interactions do not always classify into one category. ex. The interaction between anemonefish and anemones is usually mutualistic (anemone acclimation to anemonefish and anemonefish acclimation to anemone benefits both). However, anemonefish can steal anemone's prey by eating their own defecation, which affects the fitness of the anemone. In conclusion, the net outcome of an interaction depends on the ecological circumstances under which it occurs, including the influence of other species and the existing physical conditions.

Competition is a Negative Interaction.

Species overlap in the use of some limiting resources. Virtually no species has exclusive access to any given set of resources. - Resources - Niche

Positive Interactions are more common in Stressful Situations

Stressful situations constitute as environments where limited resources become even more limited. ex. A barren ice cold mountaintop vs. it's thriving resource-dense valley. Increase in growth in harsher conditions indicates that some type of positive interaction occurred to increase growth.

Competitive Coexistence

The ability to coexist with one another despite sharing limiting resources. - Most species show competitive coexistence over competitive exclusion. - Maintained through a variety of ecological processes.

Lack of movement

The act of staying completely still, or "playing dead", in order to avoid detection or taking the chance that the predator will lose interest. ex. Possum; Eastern Hognose Snake.

Carnivore strategies involve trade-offs.

The cost of pursuing, capturing, and handling prey vs. The energetic benefit of consuming prey. "Active Pursuit" Strategy - Carnivores use strength and swiftness to actively search for and capture high-quality prey. The Trade-Off: Predatory expends a large amount of energy but has the potential to capture prey that will give a lot of energy back if caught. "Stealthy Predator" Strategy - An ability to look inconspicuous allows predator to ambush prey unlucky enough to pass its way. The Trade-Off: Little energy expenditure, but predator will have to wait a long time for prey to pass by.

Coevolution

The evolutionary process in which an adaptation in one species leads to the evolution of an adaptation in a species in which it interactions. Predators can, over evolutionary time, become swifter, more powerful, and more efficient at capturing their prey. In response, prey species become swifter, tougher, less conspicuous, ore more poisonous, all of which decrease their likelihood of being consumed. The result is back and forth evolutionary response between two interacting species.

Niche

The physical and biological conditions required for growth, reproduction, and survival. -Full set of resources determines a niche. - A species' niche defines where it can and cannot live. - There are different types of niches that every species has...

Competitive Success Is On a Continuum

There are rarely any extreme on how successful a species is.

Positive Interactions (Facilitations)

Trophic or Nontrophic interactions in which at least one species benefits from the interaction and none are harmed. Includes: - Mutualism - Commensialism

Additional Predation Strategies

ex. Jaws of some snakes open wide enough to allow them to swallow prey larger than head. The Trade-Off: Large energy expenditure and amount of time, but prey is so large that the predator will not need to feed for a month. Additionally, during periods of digestion, the snake is vulnerable to attack.