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CHAPTER 10 Community Ecology 1 Learning Outcome 1. Describe the predation, cannibalism and mutualism 2. Explain the types of defense mechanism in carnivore relationship 3. Distinguish between the functional types 2 What is Predation? The transfer of energy and nutrients in community. 3 Example of Predation 1. Herbivory 2. Carnivory 3. Parasitism Predator numbers are dependent on prey and predator may regulate number of prey 4 Predation (Fitness) Fitness of predator – is the ability to capture the prey Fitness of prey - is the ability to elude or hide from predator 5 Predation- Mechanism Plant Herbivore System Defoliation and consumption of fruits/seeds Defoliation – destruction of plant tissue (leaf, bark, stem, sap, roots) Feeding on seeds can be detrimental but it helps their dispersal (seed) mostly via feces 6 Predation- Effect on Prey (Plant) Fitness The effects of the predation are strong at the juvenile stages of plant development Grazers concentrate on young leaves and thus remove nutrients Loss of nutrients – young leaves and meristems are dependent structures – get nutrients from reserves in roots and other tissue 7 Predation- Plant response after defoliation Defoliation and subsequent growth alter the trees physiologically 1. 2. 3. 4. Can cause changes in hormonal growth regulators that control bud dormancy Causes increased attack by insects and disease (plant is not established yet) Reduces resources available to reproduction (loss of nutrient and mature cell) In some instances in coniferous trees defoliation causes death because these trees do not have physiological traits that allows them to recover 8 Plant response after defoliation Example 1 (-ve): Plant response after attack by predator - Plant attacked by a moth (Alsophila pometaria) - Leaves are smaller and canopy area is reduced as much as 30 – 60% Some trees end up with only 20-40% of original leaf area 9 Example 2 (-ve): Aphids that suck sap can cause reduction in growth rate and biomass by 25% Example 3 (+ve): Defoliation can be beneficial for some grasses where grazing stimulates production by removing older tissue that have low rate of photosynthesis – exposes younger leaves to light 10 Effects on Herbivore Fitness Herbivore biomass, consumption and reproduction are correlated to primary production For herbivore the quality of food is low (low in N) but not quantity (high in number) Low quality food – tough woody, fibrous and indigestible High quality – young, soft and green or storage organs (roots, tubers, seeds) Food of herbivore is low quality and also hindered by plant defences – makes food unavailable, hard to digest, unpalatable, and toxic 11 1. Prey Defenses- chemical defences Example 1(venom and pheromone): Snakes (venom) – to avoid predators or capture prey Fish e.g. sea lamprey release pheromones that act as alarm and induces fright and flight 12 Prey Defenses- chemical defenses Example 2 (secretion): Arthropods/amphibians/reptiles – take up secretions to repel predators like birds/mammals/other insects Copious amounts – strongly odorous secretion and easily detectable Secretion of slimy substance/mucous may come out of body wall – millipede May be released in air – beetles Sprayed as in grasshoppers and stink bugs 13 Prey Defenses- chemical defenses Example 3 (odor and toxic secondary substance) Skunks and shrews’ odor – produce secretions that discourage predation cause bad smell Toxic secondary substances – in arthropods – eg saponins, glossypol, cynogenic glycosides Some arthropods can take in the above substances and infuse in their tissue The monarch caterpillar feeds on milkweed (cardiac glycosides) – when birds eat the caterpillar they fall sick or even die Toxic secondary substances in plants – alkaloids, terpenes, phenolics, cynogenic steroids, mustard oil, glycosides, tannins, resins 14 2. Prey Defenses- warning coloration Warning Coloration (Aposematic Coloration) Animals that possess pronounced toxicity (toxins) and other chemical defences (sting) often possess warning coloration – bold colors or designs Bees/wasps’ (sting) serve notice to danger . 15 3. Prey Defenses- mimicry One sp resembling another species for predator avoidance – usually live in the same habitat (mimic and model) Eg: Passiflora (plant) have evolved glandular outgrowths on its stipules that mimic the size, shape and colour of Heliconius sp (butterfly) eggs – female butterfly will reject shoots that carry eggs of other females so the plant receives a measure of protection by egg mimicry. 16 Prey Defenses- mimicry 1. Batesian (harmless vs harmful) Harmless species (mimic) imitate the warning signals of a harmful species (model) directed at a common predator Predator leaves to avoid model (harmful)– it also avoids mimic (harmless) The Ash Borer (Podosesia syringae), a moth of the Clearwing family (Sesiidae), is a Batesian mimic of the Common bee - it resembles the bee, but is not capable of stinging. Podosesia syringae (mimic) 17 Bee (model) Prey Defenses- mimicry 2. Mullerian (two or more harmful sp.) Mutual resemblance of two or more harmful species, that are not closely related and share one or more common predators, have come to mimic each other's warning signals Usually members of the same genus and family eg the viceroy butterfly mimics the monarch butterfly (distasteful to birds) Model Mimic 18 Viceroy butterfly Monarch butterfly Prey Defences- mimicry (different phylogenetic lines) Some butterflies and butterfly larvae posses eye spot patterns that suggest the eye of snakes or eyes of large avian predators (that attack small birds) Juvenile lizards & snakes mimic highly unpalatable millipedes, insect larvae mimic snakes snakes even mimic snakes Models and mimics are from different phylogenetic lines 19 4. Prey Defences- Cryptic Coloration Concealing Coloration or protective coloration Allows prey to hide from predators Involves pattern, shape, posture, movement and behavior that make prey less visible Common among fish, reptiles and ground nesting birds Stick insects – resemble stick or twigs Ibexes in the Israeli desert. 20 Lizard fish (to the right of the green rock), Big Island of Hawaii Stick insect Leaf insect 21 5. Prey Defences- Flashing Coloration Butterflies, grasshoppers, birds and ungulates display visible color patches when disturbed and put predator to running away Colour may distract and disorientate predators In deer the colours may signal to provide group organization when confronted by predator Harmless Scarlet king snake Poisonous Coral snake 22 6. Prey Defences- Armour & Weapon Clams, armadillos, turtles, beetles withdraw in their armour, coats or shells Porcupines/hedgehogs/echidnas – have modified hairs (quills) – sharp and painful Armadillos Echidnas Hedgehog Porcupines Armadillos 23 Armadillos Porcupines 7. Prey Defences- Alarm call (Behavioral Defences) Alarm call – when a predator is sighted - If alarm exposes the caller it attracts predator attention away from conspecific (same sp.) or - could attract more conspecifics for cooperative defence Alarm calls do function to warn close relatives eg in squirrels 24 Belding’s Ground Squirrel Prey Defences- Alarm call (Behavioral Defences) 1. Alarm calls do bring in number of potential prey that respond by mobbing (grouping) or harassing predator - e.g. harassment of owls by small birds The mobbing may be at a safe distance or by direct attack The distraction display diverts attention of predators from eggs and young – very common in birds 2. Living in groups is the most simplest defense – sudden movements of flight or running away in many directions will confuse predator 25 8. Prey Defences- Predator Satiation Synchronization of births/eggs predation of new born to reduce Most offspring are produced in a short period of time to enhance their numbers e.g. strategy employed by caribou and wildebeest - Collective defense of young by breeding adults - Production of increase number of prey so that predator only takes a fraction of them - Remaining young will grow quickly beyond size easily handled by predator caribou 26 wildebeest Cannibalism -Terrestrial cannibal (50% herbivorous) -Aquatic/marine cannibal (predaceous) 27 Cannibalism (Intraspecific Predation) Definition: - killing or consumption of - either all or part of the individual - that is from the same sp. Common in animal kingdom and even in humans 50% of terrestrial cannibals are herbivorous – most appropriate to encounter shortage of protein. - E.g. snail CoelophysisCannibalism became a way of surviving 28 Cannibalism (Intraspecific Predation) in aquatic and marine habitats cannibalistic species are predaceous i) Usually cannibalism is found in stressed populations (rabbit, sea lion, hippo)/facing starvation/hunger (lion, tiger) ii) Crowded/dense population even when food is available (hippo) 29 Cannibalism (Intraspecific Predation) Potential cannibal? Not all individuals in a population become cannibals – usually older and larger individuals In some species of organisms the young may cannibalize or consume older or bigger individuals Why? Cannibalism is a mechanism to regulate/control their population that reduces intraspecific (same sp.) competition as food gets scarce E.g. Larger crocs prey on the juveniles, which keeps their numbers stable, and their other food sources and resources from becoming scarce. How long? Usually short term extinction of species so no chance 30 of Cannibalism (Intraspecific Predation) Cannibalism promotes selective fitness advantage, increase longevity Eliminates potential intraspecific competition and provides a meal 31 Mutualism Symbiotic Non symbiotic 32 Mutualism is a positive, reciprocal relationship at the individual or population level between 2 different species both species enhance their survival, growth and fitness may be symbiotic or non symbiotic i. Symbiotic - two organisms live in close physical association – both derive benefit – at least one member of the pair cannot lead an independent life Non symbiotic – the species do not live together, both members benefit each other – relationship is either facultative or opportunistic ii. 33 Other Forms of Mutualisms 1. Obligatory - organisms cannot survive in the absence of the other partner. - E.g. fungi and algae that combine to form lichen are obligate symbiotic - E.g. yucca moth and yucca plant are obligate non-symbiotic 2. Facultative - organism can lead an independent existence, interacting species derive benefit without being fully dependent. Mutualism is not essential for the survival of either sp Both of the sp will engage when both of the sp is present - E.g. Many plants produce fruits that are eaten by birds. Birds would be the pollinator in 34 return. Obligate Symbiotic- Mycorrhizae mycorrhizae is association between a fungus and plants (roots) - plant supplies energy (photosynthesis) to fungi - fungal hyphae take up mineral nutrients from the soil and transport them into plant’s roots 35 Obligate Symbiotic- Coral reefs anthozoans+ photosynthetic zooxanthellae Trophic mutualism Coral reefs – corraline anthozoans and photosynthetic dinoflagellates (zooxanthellae) Zooxanthellae provide the photosynthetic products to the heterotrophic anthozoans Coral anthozoans remove, retain and recycle essential nutrients from the water used by zooxanthellae The chemical interaction between the coral cells and the zooxanthellae facilitates crystalization of calcium carbonate - zooxanthellae help the corals grow 36 zooxanthellae Obligate NonsymbioticYucca moth/plant Dispersive mutualism Yucca flowers are a certain shape so only -that tiny moth can pollinate them. yucca moth placing pollen on yucca stigma The moths lay their eggs in the yucca ovary and - the larvae (caterpillars) live in the developing ovary and eat yucca seeds. 37 Obligate NonsymbioticAcacia ant/plant Defensive mutualism ants protect the plant from herbivores – at the least disturbance they swarm from shelters and produce disgusting odours and attack intruder Acacia gives ants more than thorns to live in. She feeds them sweet sap through special organs called nectaries. Here three ants sip38 nectar from their host tree. Functional responses Relationship between prey and predators. 3 types of functional responses: Type I Type II Type III 39 II III I 40 Type I (Linear) The no of prey eaten per predator increases linearly to a maximum but then suddenly reaches a constant value when the predator is satiated Based on the Lotka-Voltera equation (dN1/dt = r1N1(K1 – N1)/K1) Best demonstrated in the lab Exhibit by the long-eared owl (Asio otus) and the Microtus vole population Microtus vole Asio otus 41 Type II (cyrtoid) Corophium Tringa totanus Functional response in which the attack rate increases at a decreasing rate of prey density until it becomes constant at satiation. Cyrtoid behavioral responses are typical of predators that specialize on one or a few prey. E.g amphipod crustaceans (Corophium) being eaten by a shorebird (Tringa totanus) E.g the 1st instar of spider (Linyphia triangularis) feeding on Drosophila 42 Drosophila Linyphia triangularis Type III (sigmoid) i. ii. iii. No of prey taken is low at 1st, then the attack rate accelerates and finally decelerate towards satiation approaching asymptote Predator may require a learning period (i) to develop searching and handling skills for a particular food item before they can feed on it efficiently (ii) E.g, bay-breasted warbler (Dendroica castanea) feeding on spruce budworm (Choristoneura fumiferana) Dendroica castanea Choristoneura fumiferana budworm 43