BIOL 4120 Principles of Ecology Lecture 11 Species

BIOL 4120: Principles of Ecology Lecture 11: Species Interaction Dafeng Hui Office: Harned Hall 320 Phone: 963 -5777 Email: dhui@tnstate. edu

An example of species interaction: Prickly pear cactus population is controlled by its predator, the cactus moth Prickly pear cactus was introduced into Australia as ornamental plant, and out of control. Cactus month was introduced in 1920 s Now prickly pear cactus maintain a low level of equilibrium, mosaic isolated inlands.

Species interactions Consumer-resource interactions: fundamental ecological relationship between species, organize biological communities into food chains; include predator-prey, herbivore-plant, parasite-host. Competition: two consumers share the same resource, each reduces the availability of resources of the other. Mutualism: interactions benefit both species (pollinator-plant) Commensalism: benefit one, but do no harm on another (bird nests on a tree) Amensalism: elephant crushes a grasshopper under foot.

Topics (Chapter 14) 11. 1 All organisms are involved in consumerresource interactions 11. 2 Dynamics of consumer-resource interactions reflect mutual evolutionary responses 11. 3 Parasites maintain a delicate consumerresource relationship with their hosts 11. 4 Herbivory varies the quality of plants as resources 11. 5 Competition may be an indirect results of other types of interactions 11. 6 Individuals of different species can collaborate in mutualistic interactions

11. 1 All organisms are involved in consumer-resource interactions Consumer-resource interactions are the most fundamental interactions, as all non-photosynthetic organisms must eat, and all organisms are at risk of being eaten. Consumer organisms: Predator, Parasite, Parasitoid, Herbivore, Detritivore Resource organisms: plants, animals etc

Predation n n Consumption of all or part of one living organisms by another Serve as energy transfer; Predators are agents of mortality and feed on organisms • Carnivory n Direct taking of animal prey for immediate consumption • Hawk or an owl taking a mouse • Decrease prey population, gain nutrition to support reproduction. • Parasitism n Predator lives in or on a host and consumes, consumers part of a living host, but does not usually kill the host • Ticks on mammals • Parasites that can cause disease symptoms: pathogens • Parasitoidism n Predator lives in or on a host and eventually kills to provide a food source • Parasitic wasps • Herbivory n n n Consumption of whole or parts of plant material Consumption of nuts and seeds (predator) or leaves of plants (parasite) Grazing (when apply to grasses and herbaceous vegetation) or browsing (wood vegetation)

• Detritivores: consume dead organic material – such as leaf litter, feces, and carcasses • No direct effects on the populations that produce resource (commensal interaction)

11. 2 Dynamics of consumerresource interactions reflect mutual evolutionary responses From evolution point of view, resource organisms should develop many tactics to avoid being eaten (for consumer-resource relationships). Consumers (like predators) should develop better ways to hunt prey. Plants: produce thorns and defensive chemicals that dissuade herbivore. Animals: hide or seek refuge in a safe microhabitats; produce foulsmelling or stinging chemical secretions (scorpions) to dissuade predators; armored body covering (armadillos).

Boomnardier beetle sprays a noxious liquid at the temperature of boiling water toward a predator.

Avoiding predators may result in reduced growth rates: Bullfrog experiments by Relyea and Werner, 1999 Grew tadpoles in aquaria with caged dragonfly larvae or fish. Fish and dragonfly larvae are predators here.

11. 3 Parasites maintain a delicate consumer-resource relationship with their hosts n n Parasitism: a relationship of two organisms living together (symbiosis) and one derives its nourishment at the expense of the other Parasite and host Parasitism has • Negative effect on hosts • But do not usually kill hosts Parasite consists of a wide range of organisms, including • Virus, bacteria, protists, fungi, plants, and invertebrates (include arthropods) • 50% of the species on Earth (typically feed on only one or a few host species).

Hosts provide diverse habitats for parasites n n Hosts are the habitats for parasites Depends on the places: • Ectoparasites: live on the skin within the protective cover of feathers and hair • Endoparasites: live within the host Examples: Fleas, ticks, are ectoparasites Liver flukes, lung flukes, flatworms, are endoparasites

Parasite life cycles Many parasites have complex life cycles Life cycle of the malaria parasite Plasmodium Two hosts: mosquito and Human (or other mammal, bird or reptile) Malaria: 300 -500 m cases/yr, 1 Millon died.

Parasite virulence and host resistance n n n Virulence: a measure of the capacity of a parasite to invade host tissues and proliferate in them Balance between parasite and host populations is influenced by the virulence of the parasite and the immune response and other defenses of the host. Virulence can be reduced by actions of the host’s immune system, including inflammation responses and production of antibodies. n Inflammation response (produce certain chemical, increase flood flow) n Immune response. White cells produce anti-body: bind to foreign proteins, helping counter infects.

11. 4 Herbivory varies with quality of plants as resources Nutrient quality and digestibility of plants is critical to herbivores. Herbivores usually select plants according to nutrient content, preferring young leaves (low cellulose), fruits and seeds. n Defenses of herbivory: n Inherently low nutrient value of most plant tissue n Toxic compound n Structure defenses: spines, hairs, tough seed coats, sticky gums and resins Digestibility: secondary compounds such as tannin.

n Secondary compounds n Three major classes based on chemical construction n Nitrogen compound (derived from amino acid), such as lignin, alkaloids Terpeniods: include essential oils, latex, and resins. Phenolics: simple phenols have antimultimicrobial properties (carbolic acid).

n Two type of defenses n Constitutive defenses • Fixed features of the organisms n n Some type of defense chemicals are maintained at high levels in plant tissues at all times Induced defenses • Defenses are brought about or induced by the presence or action of predators, herbivores n Chemical defense n Behavior defense

Structure and chemical defenses protect the stems and leaves (catus and milkweed plants) (constitutive defenses)

Induced defenses Plant defenses can be induced by herbivory Mean number of the mite were lower on cotton plants that have previously exposed to a closed related mite species. Cost to produce.

11. 5 Competition may be an indirect result of other types of interactions n Direction interaction: direct relationships between two species (e. g. , predator and prey) Consumer (+) resource (-) Indirection interaction: Ex 1. : predator (+) herbivore (-) plant (+) Multiple trophic levels in a food web, trophic cascade n Ex. 2: Consumer 1 (+) resource (-) consumer 2(+) seems like consumer 1 (-) consumer 2(-) Exploitation competition or indirect competition

A competitionfacilitation continuum Facilitation: nurse plants Individuals of one species facilitate the germination and growth of a second species An example: ironwood in desert provides protected sites for the establishment of cacti (later competition for nutrient, water and light)

11. 6 Individuals of different species can collaborate in mutualistic interactions Mutualism: interaction benefits both species involved honeybee and plants (plants provide honeybee with nectar, bees carry pollen between plants) Can be symbiosis: lichens (algae and fungi) or non-symbiosis: seed dispersal (birds and plants) Could involve more species Humans extract honeycombs (for honey) Birds eat the wax left behind Bacteria in the guts to digest the wax Three categories Trophic, defensive and dispersal mutualisms Trophic mutualisms: feeding relationship, bacteria in rumens of cows

Defensive mutualism Food and shelter, defend partners against their consumers Cleaning fish or shrimp

A wonderful story of Acacias plants and ants in Central America, see textbook (298). Some mutualists need their partners to survive and grow. Ants can’t survive without plants; and plants can’t survive without ants. Adaptation improved the efficiency of their association: Ants work day and night to protect plants. Acacias retain leaves all year. (both unusually)

Dispersive mutualism: Birds and mistletoe

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