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Interspecific interaction (種間相互作用)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

Interspecific interaction (異種個体間相互作用)

Interrelationships between populations

predation (捕食) (+/-)
competition (競争) (-/-)
cooperation (+/+, +/0, +/-)

mutualism (双利共生) (+/+), commensalism (片利共生) (+/0)

+ natural selection

Antagonism (拮抗作用)

Parasitism (寄生)
[+ parasite, – host]

Adelphoparasite (同種寄生): a parasite that is closely related to its host (e.g., both placed in the same family)

Ectoparasite [+, -], external paratisism (外部寄生): a parasite living on the outside of its host

haustorium (pl. -a, 吸器): that protion of a parasite that penetrates host cells and absorbs nutrients

Endoparasite [+, -], internal paratisism (内部寄生): a parasite living within the host

Indexces of interspecific interaction

  • RII (relative interaction intensity)
  • RCI (relative competition index)
  • RNE (relative neighbor effect)
  • lnRR (log response ratio)

(Armas et al. 2004)

Bw = Bo + ΔBF - ΔBC

Bw: biomass observed by the target plant grown with other plants
Bo: biomass potentially achieved without species interactions
ΔBF: an increase of biomass produced by facilitation (from 0 to +∞)
ΔBC: decrease caused by competition


ΔBFC: observed biomass change = absolute effect of the interaction

Bw - Bo = ΔBFC

-Bo ≤ ΔBFC ≤ +∞


if only facilitation occurs, ΔBFC ranges from 0 to 1

BFC| ≤ |ΔBFC + Bo|

if only competition occurs, ΔBFC is negative but the above equation may not be true, as the index has an unlimited range [-∞ 0]
Facilitation and comopetition would not be comparable using these equations. Therefore, new index, RII, is proposed

RII = (ΔBF - ΔBC))/((ΔBF + Bo) + (-ΔBC + Bo))

= ΔBFC/(ΔBFC + 2Bo)
= (Bw - Bo)/(Bw + Bo), RII = [-1, 1]

Predation (捕食)

Natural enemy (天敵)

k(N): ratre of predation - number of preys ingested by a predator in a given time
N: population density of prey

1. k(N) = kN: Lotka-Volterra
2. k(N) = kN/(1 + N) saturation
3. k(N) = kN2/(1 + N2) switching

what equation (1-3) is apporpriate is determined by the prey-predator interaction


number of predators: Y = constant
1. dN/dt = r(1 – N/k)nk(N)Y___(k(N) = kN same with capturing)

A: assuming that the number of individuals follows logistic growth
B: speed of prays fed by the predator

2. dN/dt = r[1 – N/kp/(1 + n)]n___(p = kY/N)

p > p*: extinction
at this time, Y* = r(1 + k)2/(4nK)

3. dN/dt = r[1 – n/Kpn/(1 + n2)]n


(a) two stable systems exist
(b) sudden decrease at p* but will not be extinct
(c) increasing number of preys explosively

Predator-prey interactions (食う-食われる関係)

Defense strategy (防衛戦略)

1974 Edmunds: classifed primary and secondary defenses
Primary defense (indirect defense)
before a predator attacks its prey or defense with or without its predator
= preventing detection or identification
seclusion (隠遁) Ex. earthworm, nocturnal insects during daytime

disadvantages: decrease in the chances of reproduction and feeding
→ specific feeding habits, group living or external fertilization

+ combined with secondary defense

camouflage (模倣) making animals or objects hard to see
1904 di Cesnola AP: Mantis religiosa - cryptic coloration

mantis plant green brown    18 day later (survived/prepared)
green           20/20   0/25         ☛ industrial melanism
brown            0/45  20/20
disadvantages: slow move → reduced foraging time

1970 Tinbergen: Corvus corone

9 ggs buried at 50 cm intervals (3 replications) - 24/27 eaten by crow
                       800 cm intervals                          -  5/27
⇒ density ∝ searching image ⇒ the density of prey should be low
∴ Predator: learning searching image (探索像) ☛ armes race

→ adjustment of population density

warning Ex. aposematism

predator must learn the unfavorable preys

learning and conditioning of predtor +
empathy and observation (including immitation) +
innate (or genetic) characteristics

Ex. Plant: Foxglove = glaring flower + poison

1921 Carpenter GDH: feed the monkeys various insects (lab-experiment)

220 glaring species - fed 20% vs 155 discreet species - 73%

1972 Benson: Heliconius erato (red postman)

developing unpalatability and protective coloration
experimentally hide the coloration - increased feeding

Def. Müllerian mimicry (ミューラー型擬態): a form of mimicry in which two or more harmful or unpalatable animals develop similar appearances as a shared protective device
Ex. Vespa (hornets) and Vespula (wasps)

develping yellow and black stripes for most species

Batesian mimicry (ベーツ型擬態): a harmless species is protected from predators by its resemblance to a harmful or inedible species

prerequisite: present harmful or inedible species (model)

mimics is extinct when the model is extinct

upper limit: mimics can not be dominant - predator will learn
sexual dimorphism is present for a few species - handicap theory

1952 De Ruiter, L: Garrulus glandarius (predator)

not distinguish Ennomos alniaria (prey) and branches
after learning, G. glandarius easily found out the preys

Brower, Lincoln Pierson (1931-2018, USA), entomologist
1969 (and others): Danaus plexippus - infraspecific mimicry

becoming bad taste when moths eat Asclepias humistrata and A. curassavica, due to cardenolides in Asclepias
→ various tastes - benefits for palatable moth individuals
→ perfect mimicry, because of within-species mimicry

Hölldobler, Berthold Karl (1936-, German), zoology, sociobiology
1971 beetle (prey) - morphologically similar with ants

predator (bird) - avoid feeding preys (beetles) when ants are together

predator - feed insects excluded by ants

collective defense (sometimes secondary defense)
alliance defense (sometimes secondary defense)
Secondary defense (direct defense)
after a predator attacks its prey
= chemical and morphological defenses, protect prey when attacked by predators

passive secondary defense - usual
positive secondary defense - extended primary defense

withdraw to retreat (退却)

running away to a hideout
carrying retreat equipage Ex. hermit crab or pagurian
morphological equipage Ex. hedgehog, armadillo, pill bug

disadvantage (1): not escaped from the hideout, (2) wasted time while hiding even if the target is not predator

(1) developed barricade represented by protective hatch

Ex. neck and head of turtle

flight (flying behavior) (逃走): enhanced by two behaviors shown below,

protean: running in an uncertain and unpredictable way
flash: running for a short distance and suddenly stops and freezes

deimatic displays or startle display (威嚇): bluffing behavior that

lacks strong defences Ex. motion, stance, alarm signals
often deimatic displays appear after seclusion or warning
eyespot (眼状紋)

intimidation hypothesis: the preys intimidate predator by their own enemy which gives them time to flee away
deflection hypothesis: eyespots are evolved to divert the attack of predators to non-vital organs

death feigning (擬死)

deflection/diversion (陽動)
1952 Simomns: Charadrius alexandrinus (Kentish plover)

large terrestrial predator: found a chick or chicks

→ parent: quietly leaves → parent: ostentatious behavior
→ predator: move towards the parent = save the chick

autotomy (自切): shedding or discarding its own appendages

generally developing high self-renewal capacity

aggressive defense (counterattack)

poison, tusk, etc.
some organs are used for intraspecific competition and aggressive defense Ex. deer antlers
+ specific organs + chemical defense

Group defense
mobbing: preys mob a predator by cooperative attack or harassing

Ex. herd of herbivores, defensive roundness

heterogenous-species group, formed for the cooperation of preys

Ex. ant - prey(s): the prays need to make collaboration with the ants

mimicry to ant (and living with the ant)

Interspecific cooperation
with ant
1963 Way: aphid-ant interaction to avoid the predator(s)

Ex. Aphis favae - foraging more accompanied by ants (Lasius)

the aphid forages even without the ant - facultative dependence

Ex. Protrama - Saissetia zanzibarensis (coccid)

honeydew removed by ant (die if not) - obligatory depencence

1945 Ford EB: Phengaris (Maculinea) arion

first-thrd instar larva - herbivorous
fourth instar larva - carried to the nests of ants

feed on larvae - becoming carnivorous (= parasite)

1971 Hölldobler: Dinandra (rove beetle) - Formica sanguinea

rove beetle living adjacent to ant nest

with echinoderm: evacuation site for preys
1969 Dix TG: Evechinus chloroticus - Dellichthys morelandi
with coelenterata: cnida used for cooperative defense
1966 Rees WJ: Gadus merlangus (cod)

facultative symbiosis with Cyanea lamarcki (jellyfish)
umbrella of jellyfish - evaculation site

1969 Gott: Physalia pelagica (Portuguese man o' war)

Nomeus gronovii (man-of-war fish) - mimicry (opligatory dependent)

symbiosis Ex. symbiosis between sea anemone and hermit crab

Calliactis on Dardanus and Pagurus

Sea anemone: moved with crab - getting food
Hermit crab: protected by sea anemone

1961 Ross DM, Satton L: C. parasitica - P. bernhardus

symbiosis - initiated by the sea anemone

1969 Manardi, Rossi: Adamsia palliata - P. prideauxi

crab: presence of behavioral order to replace sea anemone

1970 Ross: C. polypus always on D. gemmatus

sea anemone on the shell - navigated by the crab

1971 Ross: crab - sea anemone - octopus (predator) (lab-experiment)

crab without sea anemone → eaten by octopus within 3 days

Interspecific competition (種間競争)

Def. competition in which individuals of different species compete for the same resources in an ecosystem

⇔ Intraspecific competition: competition between members of the same species