Hiroyuki Matsuda in Ecology
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Coevolutionarily Stable Community Structures

Community structure is not randomly constructed. Under the assumptions that predators choose prey species and prey pay anti-predator effort to maximize their own fitness, I try to explain some properties of community structures.

Exploitative Mutualism between Predators

The relationship between predators that share a common prey has been considered to be competition (exploitative competition). However, if a prey has anti-predator effort and if anti-predator effort against one predator is not effective against the other (predator-specific defense), the relationship can be mutualistic. The exploitative mutualism can promotes coexistence of predators and complex community structure.

Should a larger individual have a higher fitness? No!

Suppose that two clones of cellular slime molds aggregate to form a fruiting body. About 2/3 of cells become spores and the remainder becomes stalk which support spores but leave no descendants. Why should a clone make any stalk that support spores of the other clone? I explain this by evolutionarily stable stalk/spore ratio (ESSR). I obtained the condition that ESSR is size invariant. In ESSR, the number of spores produced by each clone can be equalized. I argue that larger individuals do not necessarily enjoy higher fitness than the smaller ones. This is called the law of equalization in net incomes.

Self-extinction due to 'Adaptive' Evolution

Ever since "Selfish Gene" by R. Dawkins, it is well known that selection may decrease the population size. I argue that evolutionary dynamics based on individual selection may make (1) evolutionarily unstable fitness maxima and stable minima and (2) self-extinction of asymmetric competitors or herbivores.
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MATSUDA in Ecology