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The major types of organism-organism interactions
1. Competition- Interspecific competition (competition between different species)- Intraspecific competition (competition within the same species)2. Predation- Interspecific predation (predator-prey interactions)- Intraspecific predation (cannibalism, infanticide)3. Cooperation- Interspecific cooperation (mutualism, symbiosis)- Intraspecific cooperation (kin selection, reciprocal altruism)4. Parasitism- Interspecific parasitism (host-parasite interactions, e.g.
ectoparasites, endoparasites, viruses, pathogens)- Intraspecific parasitism (within-species brood parasitism, e.g. egg
dumping, sneaking)
Interspecific parasitism: definitionParasite (pathogen) = organism that obtains its nutrients from one
or a very few host individuals, causing harm* but not causing host death immediately.
Parasitoid = egg to larval organism that obtains its nutrients from a single host individual, causing host death in the end (incl. parasitic Hymenoptera and Diptera insects).
´Host´ Co-species (always benefit) InteractionCost parasite ParasitismNo cost, no benefit commensalist CommensalismBenefit mutualist or symbiont Mutualism or
Symbiosis
Cost and benefits in terms of fitness: life expectancy (age) * reproductive success/age step
* harm = fitness of host is reduced, though perhaps only in appropriate circumstances (e.g. a sufficient number of parasites or when the host is in poor body condition)
Interspecific parasitism 1.
Example of the effect of a parasite on survival, growth and fecundity of a host
Parasitic mite Hydraphantes tenuabilis
Water bug Hydrometra myrae
Interspecific parasitism 3.
The diversity of interspecific parasites
Microparasites = multiply directly within their host (usually within the host cells): bacteria, viruses, protozoa, fungi.
Macroparasites = grow in their host, but multiply by producing infective stages which are released from the host to infect new hosts (or intermediate hosts).
Brood parasites = use resources of the host (e.g. food, shelter), and/or they feed on larvae or eggs. Often mimicry involved (e.g. chemical, tactile, morphological). Special case: slave-making ants.
Trypanosoma brucei (sleeping sickness, Schlafkrankheit)
cestode worms Schistocephalus solidus in stickleback
Interspecific parasitism 4.
Microparasites:1. Directly transmitted from host to host:
a. immediate transfer: e.g. venereal diseases, influenza, measlesb. dormant period: e.g. amoebic dysentry, plant pathogen spores in soil
2. Indirectly transmitted via some other species (vector or intermediate host(s))
Entamoeba histolytica trophozoites (amoebic dysentry, Amüben-Ruhr)
Plasmodium falciparum (malaria)
within red blood cells
Vector: anopheline mosquito
Interspecific parasitism 5.
in liver in bloodThe malaria cycle
in mosquitoPlasmodium vivax, after Vickerman & Cox 1967 Interspecific parasitism 6.
Macroparasites:platyhelminth worms (tapeworms, trematodes)acanthocephalans(intestinal) nematodeslice, fleas, ticks, mites, fungi
1. Directly transmitted from host to host
2. Indirectly transmitted via some other species (vector or intermediate host(s))
Dactylogyridae worm of fish
Interspecific parasitism 7.
Interspecific brood parasites
Brood parasites = use resources of the host (e.g. food, shelter), and/or they feed on larvae or eggs.Many examples in insects, but also some examples in birds and fish. Most important taxon: Hymenoptera, e.g. parasitoid wasps
Cleptoparasite = idem, only uses resources.Example: Parastizopus armaticeps withcleptoparasite Eremostibes opacus(tenebrionid beetles from the Kalahari desert)
Interspecific parasitism 4.
Example brood parasites: Atemeles pubicollisBeetle larvae produce glandular secretion which induces grooming. Larva begs to obtain regurgated food
Staphylinid beetle Atemeles pubicollisenters colony of Formica rufa
Interspecific parasitism 9.
Example brood parasites: ant parasites
Limulodid beetle Paralimulodes wasmanni on Neivamyrmex nigriscens
Nicoletiid silverfish Trichatelura mannion Eciton sp.
Mite Macrocheles rettenmeyeri on Eciton dulcius
Mite Circocylliba sp. on Eciton sp.
Mite Antennequesoma sp.on army ant
Histerid beetle Euxenister carolion Eciton burchelli
Interspecific parasitism 10.
Example brood parasites: slave-making antsSlave-maker ant Epimyrma stumperi enters nest and strangles, kills....
.... Host queen ant Leptothorax tuberum
This slave-maker ant Formica subintegra has a large Dufour´s gland for the production of ´propaganda substances´ that will scatter the slave-ants (also from the genus Formica) during raids.
It is contrasted with the Dufour´s gland of F. subserica, which is an ordinary ant.
Interspecific parasitism 11.
Population dynamics of directly transmitted microparasites
Basic reproductive rate:
R0 = Σ lx * mx
lx = proportion of individuals surviving until age xmx = average number of offspring produced
per individual at age x
For parasites usually Rp is used:
ExamplePhlox drummondii: R0 = 2.41
Rp = average number of new cases of the disease that arise from each infected host
Rp = 1: the transmission thresholdRp < 1: disease will die outRp > 1: disease will spread
Interspecific parasitism 12.
Directly transmitted microparasites:determinants of Rp
Rp = average number of new cases of the disease that arise from each infected host
Rp = β * N * ƒ * LWhere:
β = transmission rate of the disease = frequency of host contact * probability that host contact leads to infection
(0.0 – 1.0)
N = density of (susceptible) hosts (0.0 - ∞)
ƒ = fraction of hosts that survive long enough to become infectious themselves(0.0 – 1.0)
L = average period of time over which the infected host remains infectious (>0 - ∞)
Interspecific parasitism 13.
Directly transmitted microparasites:determinants of Rp
Rp = average number of new cases of the disease that arise from each infected host
Rp = β * N * ƒ * L
Proportion of alive infectious hosts * time alive
Number of new hosts getting infected
Note: in most biotrophic parasites L is the period of the host`s life when it is infectious, but for necrotrophic parasites and some biotrophs, the parasite may remain infectious long after the host has died (and decomposed)
Interspecific parasitism 14.
Directly transmitted microparasites:determinants of Rp
Rp = 1: transmission threshold
⇒ Nt = 1 : density thresholdβ * ƒ * L
So if parasites (diseases) are highly infectious (large β), or are unlikely to kill their host (large ƒ), or give rise to long periods of infectiousness (large L), they will have high Rp values and can persist in small populations (Nt is small).
Hosts acquiring immunity against parasite versus mutant parasites arising or influx of new hosts=> cycles of parasite incidence.
Interspecific parasitism 15.
Vector-transmitted microparasites:determinants of Rp
Both the life cycle of the host h and the vector v has to be taken into account:
Rp = β2 * Nv * ƒv*ƒh * Lv*LhNh
Note: β is squared, because when the vector bites, it both can get infected by the host itself, or pass the infection to a new host when it is already infected itself.
Interspecific parasitism 16.
Vector-transmitted microparasites:determinants of Rp
Rp = 1: transmission threshold
⇒ Nv = 1 : the ratio-of-densities thresholdNh β2 * ƒv * ƒh * Lv * Lh
Hence, disease control measures are usually aimed directly at reducing the numbers of vectors, and only indirectly at the parasite. This reduces the likelihood that the final host (e.g. man) will get infected, so less direct treatments of the parasite in the final host are necessary.
Interspecific parasitism 17.
Directly transmitted macroparasites:determinants of Rp
For macroparasites it is possible to determine the reproductive success and life expectancy of a single individual parasite = the sum of offspring produced that themselves survive to produce offspring.Rp = average number of new cases of the disease that arise from each infected host
Rp = (λ*ƒa*La) * (β*N*ƒi*Li )
adult infective stageReproductive contribution of:
Interspecific parasitism 18.
λ = rate of egg production per adult parasiteƒa = proportion of parasites in the host that attain sexual maturityLa = expected life span of adult parasiteβ = transmission rateN = host densityƒi = proportion of the parasite transmission stage that become infectiveLi = expected life span of the infective stage outside the host
Density-dependence within the host is crucially important for the reproductive rate of macroparasites
Interspecific parasitism 19.
λ = rate of egg production per adult parasiteƒa = proportion of parasites in the host that attain sexual maturityLa = expected life span of adult parasite
Parasitoids
Parasitoid = egg to larval organism that obtains its nutrients from a single host individual, causing host death in the end (incl. parasitic Hymenoptera and Diptera insects).
extremely numerous group of organisms, since an estimated 25% of the world species are parasitoids (since most insect species host at least one parasitoid, and some parasitoids host parasitoids themselves = superparasitism by same parasite species, or hyperparasitism by other parasite species)
Interspecific parasitism 20.
Effects of parasites on behavioural ecology: case study barn swallow
♂♂
♀ ♀
Interspecific parasitism 22.
Brood parasitism
Fish: 2-3 speciesBirds: ~1% of all species (50% of the cuckoos, two genera of
finches, five cowbirds, and a duck)
Interspecific parasitism 26.
Brood parasitism by catfish from Lake
Tanganyika:
Catfish Synodontis multipunctatus
Simochromis babaulti & S. diagramma
Tropheus moorii
Ctenochromis horei
Gnathochromis pfefferi
Pseudosimochromis curvifrons
Mouthbrooding cichlids
Interspecific parasitism 27.
Brood parasitism by catfish Synodontis multipunctatus
Number of broods examined:
% w
ith c
atfis
h
Host´s eggs and offspring are consumed by the catfish offspring....
Interspecific parasitism 28.
Brood parasitism by birds: cuckoo Cuculus canorus
References:N.B. Davies and others (1987-2003)M. & B.Taborsky et al.
Interspecific parasitism 29.
Cuckoo Cuculus canorus: mimicry of host eggshost cuckoo model
Robin (Erithacus rubercula)
Pied wagtail (Motacilla alba)
Dunnock (Prunella modularis)
(Acrocephalus scripaceus)Reed warbler
(Anthus pratensis)Meadow pipit
Great reed warbler (Acrocephalus arundinaceus)
Interspecific parasitism 31.
Cuckoo Cuculus canorus
Individual females specialize on specific host species, e.g.
Reed warbler Acrocephalus scirpaceus
Meadow pipit Anthus pratensisDunnock Prunella modularis
Gibbs et al. 2000. Nature
Cuckoo Cuculus canorus
Hosts-parasite co-evolution 2 (Lotem et al. 1995. Animal Behaviour 49: 1185-1209).
Host strategy Probability of event Payoff to hostAccept p parasitized 0
1-p non-parasitized X
p parasitized 1-e rejects cuckoo X – 1***
Reject e rejects own offspring* 01-p non-parasitized 1-e no error X
e rejects own offspring** X - 1X = number of host offspring
* = mistakingly rejects own offspring instead of cuckoo offspring!** = mistakingly rejects own offspring, despite there is no cuckoo in the nest!!*** = if the host kills own offspring by removing the parasite (e.g. breaks own eggs), term will be X – 2 ..
Cuckoo Cuculus canorus
Hosts-parasite co-evolution 3.
The payoff of an accepter will be equal to that of a rejecter when:
(1-p)X = p(1-e)(X+1) + (1-p)(1-e)X + (1-p)e(X+1)
⇒ Rejection error e = (p-pX)(2p-pX-1)
Natural parasitism level p is ~3%,so low rejection error level of ~7-8% would make payoff accepter = rejecter!
Interspecific parasitism 36.
Intraspecific parasitism: definition
Conspecific individual using the brood care of other individuals, without providing brood care themselves.
Females: egg dumping.Males: extra-pair fertilizations, sneaker spawning.
Intraspecific parasitism 1.
Intraspecific parasitism: sperm competition
Females: egg dumping virtually equivalent with interspecific brood parasitism.
Males: sperm competition plays an important role in the relative success of extra-pair copulations or sneaker spawnings.
Sperm competition = the likelihood that sperm of a particular male will fertilise the ova, depending on the sperm of other male(s) in the reproductive tract of the female
Intraspecific parasitism 1.
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