Predation and Parasitism

• The potential impact of predation is not questioned

• In fact, it may be one of the most studied aspects of population/community ecology

Predation and Parasitism

• Evolutionary, this is a classic ‘arms race’ where both sides are showing strong selection to get more efficient (although predator trying to end this relationship!)

Predation and Parasitism

• Long-term escalations have resulted in many complex adaptations

• Consider socialized hunting

Predation and Parasitism

• Some marvelous adaptations: the tongue

Predation and Parasitism

• Fangs, webs, angler fish

Predation and Parasitism

• Prey have also responded well with many unique adaptations

Predation and Parasitism

• Camouflage is an easy and effective deterent

Predation and Parasitism

• Many prey work to avoid predators through early detection

•

Predation and Parasitism

• Tight flocking (fig 15.1)• Prey in response to Peregrines• How do peregrines respond?

Predation and Parasitism

• Predator-prey oscillations (fig 15.2)

Predation and Parasitism

• However, these are rather simplistic approaches to the L-V population equations

• There are two separate ways in which predators respond to changes in prey density

• First, individual predators capture and eat more prey per unit time as prey density increases until full (until numbers don’t matter)…(functional response)

Predation and Parasitism

• Three types of functional response. Type I is a very linear response, 2 also responds quickly. Type 3, increases in prey density are not immediately beneficial to predator

Predation and Parasitism

• Second, prey density increases and raises the predator’s population size and they subsequently eat more prey (numerical response)

• Clearly the relationship between predator and prey is complex and not easily quantifiable

Predation and Parasitism

• A simple graphical model of the prey-predator interaction was developed by Rosenzweig and MacArthur (1963)

• Maximum prey density (K) exists, as well as minimum density (allele effect) and various levels of prey density will support various levels of predator densities

Predation and Parasitism

• Hypothetical relationship between prey and predator

• Exact shape not important, but concept of increasing/ decreasing areas is important

Predation and Parasitism

Predation and Parasitism

Predation and Parasitism

• Relative magnitudes of the changes in the population densities of prey and predator determine another important property of this model: whether equilibrium exists or not

• Using the vectors, we see 3 possible outcomes: spiral inward, oscillate, or spiral outward (fig 15.8)

Predation and Parasitism

• b

Predation and Parasitism

• Prudent predation and optimal yield• An ‘ideal’ predator would crop its prey as to

maximize the prey’s turnover rate and therefore the predator’s yield

• Human’s have this ability, although do a relatively poor job

Predation and Parasitism

• However, do predators take the demographic groups that allow for maximal yield?

• What about among competing species for a common food source?

Predation and Parasitism

• However, we do see some prudent predation occurring, what else may be occurring?

• What about looking at it from the prey’s perspective; which individuals have the highest potential reproductive value

Predation and Parasitism

• Selected Experiments and Observations• There have been a number of lab experiments

and some field experiments (can you think why these may be difficult?)

• Several microcosm studies have been conducted

• In ‘simple’ systems, predators usually overhunt

Predation and Parasitism

Predation and Parasitism

• Utida (1957) used two species of wasps and a beetle to look at competitors in a predatory-prey relationship

• Population varied, competitors fluctuated out of phase with one another

Predation and Parasitism

• Evolutionary Consequences: prey escape• Generalized predators vs. specialists and their

impact on prey escape tactics• There may be an advantage to being hunted

by more than one species… aspect diversity

Predation and Parasitism

• Cryptic coloration needs to be partnered with behavioral attributes

Predation and Parasitism

• Almost all diurnal species have countershading

Predation and Parasitism

• Many insects mimic plant parts

Predation and Parasitism

• Other examples

Predation and Parasitism

• Classic example

Predation and Parasitism

• Disruptive coloration is another great tool

Predation and Parasitism

• Flash coloration

Predation and Parasitism

• Disruptive burst

Predation and Parasitism

• Alarm signals: remember, this is NOT altruistic!

Predation and Parasitism

• Warning coloration (aposematic)

Predation and Parasitism

• Batesian and Mullerian Mimicry

Predation and Parasitism

• What about plants?• Some plants rely on the

spatio-temporal variation in abundance they are never very abundant nor predictable in their occurrence

Predation and Parasitism

• Morphological adaptations

Predation and Parasitism

• Their origin may have been by chance, with each combination potentially providing a little better defense

• As a result, most plants don’t just have a single compound…Why?

• Most have several, primarily to protect against herbivores, bacteria and/or fungi

Predation and Parasitism

• Most of these chemicals are termed ‘secondary compounds’ because most seem to lack a direct metabolic function, such as those in photosynthesis (also called allelochemics for defense at large)

Predation and Parasitism

• Alkaloids are among the most familiar and addictive drugs known

• Such drugs as cocaine (from coca), morphine (opium poppy), cannabidiol (hemp), caffeine (teas and coffees), and nicotine (tobacco) There are over 4,000 known alkaloids from >300 families and >7,500 sp

• About 20% of temperate sp contain them

Predation and Parasitism

• Phenolic compounds are often abundant in plants

• One group adds the pungency to many of well-known spices and tannins provide the basic compounds used in tanning leather

• Particularly abundant in oaks and mangroves

Predation and Parasitism

• Saponins are soaplike compounds that are relatively common in tropical plants and act to destroy the fatty component of the cell membrane. Some indigenous people utilize saponins to poison and capture fish, interfering with respiration

Predation and Parasitism

• Cyanogenic Glycosides (cyanide + sugar)• When the sugar is digested, the sugar is

released leaving the hydrogen cyanide• Consequently, these plants are avoided by

many species of herbivore

Predation and Parasitism

• Plant breeders have long exploited and taken advantage of ‘artificial selection’ by breeding preferred varieties or traits into crops and/or ornamentals

Predation and Parasitism

• Plant compounds have been utilized as well to control pests (Operopthera brumata)

Predation and Parasitism