Didinium Experiments Lotka Volterra Predation Equations N 1 N 2 Contacts two coefficients of predation p 1 and p 2 plus r 1 and d 2 dN 1 dt ID: 732826
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Lotka-Volterra Predation Equations: N1 N2 = Contacts two coefficients of predation, p1 and p2 plus r1 and d2 dN1 /dt = r1 N1 – p1 N1 N2 dN2 /dt = p2 N1 N2 – d2 N2 No self damping N2 terms (no density dependence) dN1 /dt = 0 when r1 = p1 N2 or N2 = r1 / p1 dN2 /dt = 0 when p2 N1 = d2 or N1 = d2 / p2Gause’s Paramecia x Didinium Experiments Neutral StabilityLimit CyclePredator destabilizing, Prey RefugesFunctional and Numerical Responses
23rd Lecture
21 April
2020Slide2
Predator-Prey Experiments Georgy F. GauseCiliated ProtozoansDidiniumSlide3Slide4Slide5
Predator-Prey Experiments Georgy F. GauseDidiniumParameciumSlide6
Predator-Prey ExperimentsGeorgy F. GauseSlide7
Lotka-Volterra Predation Equations N1 N2 = Contacts coefficients of predation, p1 and p2 dN1 /dt = r1 N1 – p1 N1 N2 dN2 /dt = p2 N1 N2 – d2 N2 No self damping (no density dependence) dN1 /dt = 0 when r1 = p1 N2 or N2 = r1 / p1 dN2 /dt = 0 when p2 N1 = d2 or N1 = d2 / p2
Alfred J. Lotka
Vito VolterraSlide8
Neutral Stability(Vectors spiralin closed loops)Slide9
Vectors spiral inwards (Damped Oscillations)Prey self damping
dN
1
/
dt
= r
1
N
1
– p
1
N
1
N
2
– r
1
K
1
/N
1
2
dN
2
/
dt
= p
2
N
1
N
2
– d
2
N
2
dN
1
/
dt = 0 r1 = p1 N2 or N1* = – r1 K1/ N1 dN2 /dt = 0 p2 N1 = d2 or N1* = d2
o
o
o
r
1
/K
1Slide10
Mike RosenzweigRobert MacArthurWhy the prey isocline has a humpOptimal Yield Slide11
Mike RosenzweigRobert MacArthurPredator isoclinesSlide12
Moderately efficient predatorNeutral stability — Vectors form a closed ellipse. Amplitude of oscillations remains constant.<—Mike RosenzweigRobert MacArthur —>Superimposed prey and predator isoclines Slide13
Unstable — extremely efficient predatorVectors spiral outwards until a Limit Cycle is reachedRobert MacArthur —><—Mike RosenzweigSuperimposed prey and predator isoclines Slide14
Damped Oscillations — inefficient predatorVectors spiral inwards to stable equilibrium pointRobert MacArthur —><—Mike RosenzweigSuperimposed prey and predator isoclines Slide15
Functional response = rate at which Individual predators capture and eat more prey per unit time as prey density increasesC. S. HollingSlide16
Numerical response = increased prey density raises the predator’spopulation size and a greater number of predators consume An increased number of preySlide17
Gause’s Paramecia x Didinium ExperimentsLotka-Volterra Predation Equations: N1 N2 = Contacts two coefficients of predation, p1 and p2 plus r1 and d2 dN1 /dt = r1 N1 – p1 N1 N2 dN2 /dt = p2 N1 N2 – d2 N2 No self damping N2 terms (no density dependence) dN1 /dt = 0 when r1 = p1 N2 or N2 = r1 / p1 dN2 /dt = 0 when p2 N1 = d2 or N1 = d2 / p2Neutral Stability, Limit CyclePredator destabilizing, Prey RefugesFunctional and Numerical ResponsesSlide18
Adding Prey self-damping stabilizesPrey-Predator isocline analysesPredator efficiency, Prey escape abilityPrey refuges, coevolutionary racePredators usually destabilizingPredator Switching, frequency dependence, stabilizesSlide19
Prey Isocline HumpEfficient Predator —> unstableInefficient Predator —> stablePredator Switching, frequency dependence, stabilizes“Prudent” Predation and Optimal YieldFeeding territoriesConsequence of senescenceSlide20
Predator Escape Tactics Aspect Diversity Cryptic coloration (countershading) Disruptive coloration Flash coloration Eyespots, head mimicry Warning (aposematic) coloration Alarm signals Hawk alarm calls Selfish callers Plant secondary chemicalsUpside-Down CatfishSlide21
Aspect Diversity in Tide Pools Cottid Fish <— Shrimp —>Secondary Chemical Defenses of PlantsSlide22Slide23Slide24Slide25Slide26Slide27
Calligo owl butterflySlide28Slide29Slide30Slide31
Head Mimicry Papilio caterpillar Pit Viper caterpillar DeVries Snake headSlide32Slide33Slide34
Monarch(Model)Viceroy(Mimic)Batesian MimicrySlide35
Rufous-tailed JacamarGalbula ruficaudaSlide36Slide37
Batesian MimicrySlide38
Mullerian MimicrySlide39
Batesian MimicrySlide40
Aposematic (“stay away”) Warning colorationSlide41
Aposematic (“stay away”) Warning colorationDendrobatid FrogsSlide42
Parasitism > Commensalism > Mutualism(+, –) < (+, 0) < (+, +)Host-Altered BehaviorEvolution of VirulenceBiological ControlSlide43
Parasitism Slide44
HIVVirionsSlide45
1. Physiological dependence on host most parasites are highly specialized many have complex life cycles with intermediate and final hosts challenge: how to infect new hosts?2. Higher reproductive potential than host (high fecundity necessary for dispersal)3. Parasites can kill highly infected hosts but typically do not — allow host to live4. Infection produces an overdispersed distribution of parasites among hostsSlide46
Parasite ExamplesAssassin bugs (Triatoma)Chagas’ disease, Malaria, Zika VirusTapeworms (Cestodes)Cholera (Shigella) transmission via dysenteryToilet seats, elevator buttons, shopping carts...Molecular mimicry“eclipsed antigens” resemble host antigens hence do not elicit formation of host antibodiesMajor Histocompatibility Complex (MHC)Trypanosoma shed coats, change antigensFilariasis Elephantiasis (blocked lymph nodes, nematode worms carried by mosquitos)Slide47Slide48
Assassin bugs (Triatoma), contact, blood sucking, Chagas’s DiseaseTriatomaSlide49Slide50
Microbiome, antibiotics, Germs R us, appendix =“bomb shelter”Challenges facing Parasites, hosts as islands, how to infect new ones?Host specificity, high fecundities, exploitation of vectors (mosquitoes)Intermediate and final hosts, host altered behavior (rabies, etc.)Assassin bugs (Triatoma), contact, blood sucking, Chagas’s DiseaseMalaria (Plasmodium), feverTapeworms (Cestodes), Nematodes (roundworms)Cholera (Shigella) transmission via dysentery, water borneToilet seats, elevator buttons, door knobs, shopping carts...etc.Getting into and out of a public restroom safelyMolecular mimicry: “eclipsed antigens” resemble host antigens hence do not elicit formation of host antibodiesMajor Histocompatibility Complex (MHC), identity of self, immune response Trypanosoma shed coats, change antigensFilariasis Elephantiasis (lymph nodes blocked by nematodes carried by mosquitoes)BotfliesDracunculus medinensis, caduceus symbol of medicineSlide51
Evolution of Virulence (benign parasites allow hosts to live)Host altered behaviorRabies virus — rabid animals bite, passes on virus to new hostLancet fluke Trematode Dicrocoelium dentriticumCercaria —> Metacercariae encyst on ant’s brainSheep ingest an ant and get infectedStarlings, Pill bugs, and AcanthocephalansDucks, Amphipods, and AcanthocephalansSTDs ——> increased sexual activity?Ectoparasites (fleas, ticks, lice), endoparasitesSocial parasites (thievery, brood parasitism)Parasitoids: Ichneumonid wasps ————> Microparasites —> macroparasites —> parasitoids —> predator spectrum and many correlates thereof, such as relative sizes, rates of increase, number of parasites per host, virulence, stability, and ability to regulate lower trophic levelSlide52
BotflySlide53
Botfly Botfly larva Slide54Slide55Slide56
Filariasis Elephantiasis (blocked lymph nodes,nematode worms carried by mosquitos)Slide57
Filariasis Elephantiasis (blocked lymph nodes,nematode worms carried by mosquitos)Zika VirusSlide58Slide59
Nematode (Roundworm)Dracunculus medinensisSlide60Slide61Slide62Slide63
Dracunculus medinensisSlide64Slide65Slide66
Nephrurus laevissimusSlide67Slide68
Host Altered Behavior Rabies virus — rabid animals bite Lancet fluke Trematode Dicrocoelium dentriticum Cercaria —> Metacercariae encyst on ant’s brain Sheep ingest an ant and get infected Starlings, Pill bugs, and Acanthocephalans Ducks, Amphipods, and Acanthocephalans STDs —> increased sexual activity?Slide69Slide70
Ebola zaire Ebola restonCrisis in a Hot Zone. CDC Biohazard Level 4 Nancy Jax. Modes of transmission: airborne,waterborne, food, contact, intermediate hosts. Slide71
Ectoparasites, endoparasitesSocial parasites: Brood ParasitismParasite–Predator spectrumMicroparasites: Viruses, BacteriaMacroparasites: “Worms” CestodesParasitoids: Ichneumonid wasps ——> PredatorsMode of transmission & virulence Slide72
__________________________________________________________________ Slide73
Common Pathways For Transmission of Parasites______________________________________________________Food or Water Contamination roundworm, amoebae, cryptosporidium, Giardia ——> Vector Bourne mosquito - canine heartworm, filaria, malaria flea - canine tapeworm housefly - amoebic cysts sand fly - leishmaniasisSexual Contact Trichomonas, Giardia, amoebae, HIVInhalation of Contaminated Dust or Air pinworm, Toxoplasma gondii ———> Skin Penetration rabies, hookworms, schistosomes, strongyloides _____________________________________________________________Slide74
Parasitism > Commensalism > Mutualism(+, –) < (+, 0) < (+, +)Host-Altered BehaviorEvolution of VirulenceBiological ControlSlide75
Robert BuckmanHuman Wildlife: TheLife that Lives on Us.Johns Hopkins Univ.Press100 trillion cells, but only 10 trillionare human cells. Most of the other90 trillion are bacteria, with a fewother parasites, fungi, and othercreatures. Shown here is an eyebrowmite, Demodex folliculorum, whichburrow into eyebrow follicles (thoseare three of their rear ends sticklingout of a human eyebrow follicle).Slide76
1/10th mmDermatophagoides farinae Dust MiteSlide77Slide78
Oryctolagus cunniculus Biological ControlSlide79
Oryctolagus cunniculusSwag manThomas AustinSlide80Slide81Slide82Slide83
Rabbit Proof FenceSlide84Slide85Slide86Slide87Slide88
Rabbit Proof FenceSlide89
Brazilian cottontail rabbit Sylvilagus brasilensiscarried a benign myxoma virus which, wheninjected into an Oryctolagus cunniculus harecaused cancers that quickly killed the rabbits.Released in 1951, epidemic killed 99.9% of bunniesbut, rabbits being rabbits, bred like bunnies, andsoon there were as many as ever. Second epidemiconly killed 70% and the third only 50%. ResistentRabbits evolved, but so did the virus — as it wasspreading through the rabbit population, the virusevolved reduced virulence.Slide90Slide91Slide92
Opuntia Prickly Pear Cactus and Cactoblastis MothSlide93Slide94Slide95Slide96Slide97Slide98
Cane ToadSlide99Slide100Slide101Slide102Slide103Slide104Slide105
CaneToadsSlide106Slide107
Asian Toad, Duttaphrynus melanostictus Slide108
EpidemiologyBasic reproductive rate of infection(does one infection result in one new infection?)Threshold host population sizeSlide109
Sigmoidal time course of an epidemicdI /dt = b ISdS/dt = – b ISSlide110
Darwinian Medicinedon’t just treat symptomsidentify host defensesfever and inflammationiron additivesVitamin C and cancerAntibiotic resistant strainsApplication of an evolutionary approach to medical treatmentSlide111
Methicillin-resistant Staphylococcus aureus (MRSA)Slide112
Darwinian Medicinedon’t treat symptomshost response or parasite manipulation?fever and inflammationiron additivesVitamin C and cancerAntibiotic resistant strainsApplication of an evolutionary approach to medical treatmentR. M. NesseG. C. WilliamsSlide113Slide114
CoevolutionJoint evolution of two (or more) taxa that have close ecological relationships but do not exchange genes, and in which reciprocal selective pressures operate to make the evolution of either taxon partially dependent on the evolution of the otherSlide115
Modes of transmission airborne waterborne food contact intermediate hostsSlide116
EnterobiusPinworms(Parasiteson Primates)Slide117
Parallel phylogeniesBrooks and Glen 1982 Primate hosts Enterobius speciesSlide118
Drosophila pachea and senita cactus.Danaid butterflies use polyuridine alkaloids as chemical precursors for synthesis of pheromones used in attracting mates.An arginine mimic, l-canavavine, present in many legumes,ruins protein structure in most insects.However, a bruchid beetle has evolved metabolic machinerythat enable it to use plants containing canavanine.Slide119
Wild ginger, Asarum caudatum, in western Washington arepolymorphic for growth rate, seed production, and palatabililty toa native slug, (Cates 1975). Where slugs are uncommon, plants allocate more energy togrowth and seed production and less to production of antiherbivorechemicals. In habitats with lots of slugs, less palatable plants have a fitness advantage — even though they grow more slowly, theyLose less photosynthetic tissue to slug herbivory.Slide120
Some of the Suggested Correlates of Plant Apparency ___________________________________________________________________________ Apparent Plants Unapparent Plants ___________________________________________________________________________ Common or conspicuous Rare or ephemeralWoody perennials Herbaceous annuals Paul FeenyLong leaf life span Short-lived leavesSlow growing, competitive species Faster growing, often fugitive speciesLate stages of succession, climax Early stages of succession, second growthBound to be found by herbivores Protected from herbivores by escape in (cannot escape in time and space) time and space (but still encountered by wide-ranging generalized herbivores)Produce more expensive quantitative Produce inexpensive qualitative chemical(broad-based) antiherbivore defenses defenses (poisons or toxins) to discourage(tough leaves, thorns, tannins) generalized herbivoresQuantitative defenses constitute Qualitative defenses may be broken downeffective ecological barriers to her- over evolutionary time by coevolution ofbivores, although perhaps only a weak appropriate detoxification mechanisms inevolutionary barrier unless supple- herbivores (host plant-specific herbivoremented with qualitative defenses species result)___________________________________________________________________________ Slide121
Daniel JanzenSlide122
Pine squirrels (Tamiasciurus) and coniferous food trees (Smith 1970)Squirrels are very effective seed predators, stockpile conesTrees reduce squirrel effectiveness in many different ways:Cones difficult for squirrels to reach, open, or carryPutting fewer seeds in each cone (fake cones without any seeds)Increasing thickness of seed coats (seeds harder to harvest)Putting less energy into each seed (smaller seeds)Shedding seeds from cones early, before young squirrels foragePeriodic cone crop failures decimate squirrel populationsIndividual trees out of synchrony would set fewer seeds and thusbe selected against.