Interspecific interaction (異種個体間相互作用)

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)

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

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

Symbiosis (共生) (+, + or +, 0)

Indexces of interspecific interaction

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

(Armas et al. 2004)

RII

B_w: biomass observed by the target plant grown with other plants

B_o: biomass potentially achieved without species interactions
ΔB_F: an increase of biomass produced by facilitation (from 0 to +∞)
ΔB_C: decrease caused by competition

ΔB_FC: observed biomass change = absolute effect of the interaction

-B_o ≤ ΔB_FC ≤ +∞

if only facilitation occurs, ΔB_FC ranges from 0 to 1

if only competition occurs, ΔB_FC 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

= ΔB_FC/(ΔB_FC + 2B_o)
= (B_w - B_o)/(B_w + B_o), RII = [-1, 1]

Habitat segregation (棲み分け)

Closely related species can coexist by avoiding competition through habitat segregation and dietary partitioning

by consuming different prey types, prey sizes and/or foraging in different microhabitats

Natural enemy (天敵)

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

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

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

__(a)_______________(b)_________________(c)

(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)

vs Didinium nasutum, as the predator
1) D. nasutum ate every Paramecium
2) added precipitate tha hid Paramecium from Didinium

⇒ Didinium starved to death without Paramecium extinction

Defense strategy (防衛戦略)

Primary defense (indirect defense)

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

+ combined with secondary defense

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

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

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

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

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

reduces predation (Ex. Batesian, Müllerian mimicry)
increases predatory success (aggressive mimicry)
improves reproductive success (Ex. sexual mimicry)

develping yellow and black stripes for most 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

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

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

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

predator - feed insects excluded by ants

Secondary defense (direct defense)

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

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

(1) developed barricade represented by protective hatch

Ex. neck and head of turtle

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

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)

large terrestrial predator: found a chick or chicks

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

generally developing high self-renewal capacity

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

Group defense

Ex. herd of herbivores, defensive roundness

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

mimicry to ant (and living with the ant)

Interspecific cooperation

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

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

feed on larvae - becoming carnivorous (= parasite)

rove beetle living adjacent to ant nest

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

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

Calliactis on Dardanus and Pagurus

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

symbiosis - initiated by the sea anemone

crab: presence of behavioral order to replace sea anemone

sea anemone on the shell - navigated by the crab

crab without sea anemone → eaten by octopus within 3 days

⇔ Intraspecific competition: competition between members of the same species

Intraspecific competition (種内競争)

Interspecific competition (種間競争)

Gause GF (1910-1986)

Gause's axiom, theorem or law (ガウゼの定理)

≡ competitive exclusion principle (競争排除則)

Exp. Competitive exclusion principle