Question

What is life-dinner principle? What are the drawbacks of the life-dinner principle? Under what conditions do and don’t the life-dinner principle hold true?

Answer 1

The hypothesis that attempts to explain why prey is a step ahead of predators in evolutionary arms races; essentially the prey must be one step ahead because their lives depend on it, whereas for the predator only a meal is at stake. If prey is killed, they do not reproduce; if dinner is missed the predator may still reproduce, even if it eventually starves.

The “life-dinner” principle is valid not only in the relationship between a parasite and its host but also in a great many other inter-species and intra-species interactions. This principle was originally identified (and named) in systems of the predator and prey type. Put simply, rabbits run faster than foxes for the simple reason that they are running for their lives, while the fox is only concerned about its supper.

'The rabbit runs faster than the fox because the rabbit is running for his life while the fox is only running for his dinner' (Dawkins 1979, after Aesop). There is a built-in imbalance between predator and prey with respect to the penalty of failure. Mutations that make foxes lose races against rabbits might, therefore, survive in the fox gene pool longer than mutations that cause rabbits to lose races can expect to survive in the rabbit gene pool. A fox may reproduce after losing a race against a rabbit. No rabbit has ever reproduced after losing a race against a fox. Foxes who often fail to catch prey eventually starve to death, but they may get some reproduction in first. The life-dinner principle does not imply that 'rabbits' under strong selection pressure will win in the sense of driving weaker-selected 'foxes' to extinction. The suggestion is more subtle than this. The adaptations of one type, say for running fast, have to be paid for in the form of less perfect adaptations of other types. An illustration of the cost of antipredator adaptations is seen in some kinds of plants which produce chemical defence compounds. Within one species there tends to be a negative relationship between investment in defence chemicals and fecundity (Price 1975 ). If 'foxes' are less strongly selected for running speed than 'rabbits', this means that they can afford to put more resources into other things such as gonads or intraspecific competitive adaptations. We could almost measure the cost of adaptations in 'gonad equivalents'. The life-dinner principle simply implies that all other things being equal, animals under strong selection for speed will pay relatively more 'gonad equivalents' over to developing adaptations for running fast. Animals under weak selection for running speed will correspondingly benefit by being able to deploy relatively more resources in gonads or other adaptations. Parker et al. (I972) used something like the life-dinner principle in discussing the origin of anisogamy. They postulated an ancient arms race between small, mobile 'male' gametes, and large, well-nourished 'female' gametes. Selection favoured female gametes that discriminated against male ones, and simultaneously selection favoured male gametes that broke through the female defences. As Williams (1975) put it: 'This primaeval conflict between the sexes was resolved in favour of the males because of more intense selection for male functions. Once the issue was decided, macrogametes abandoned the attempt to unite with other macrogametes and reject sperm'. The general point here is that where one side in an arms race is under stronger selection pressure than the other, it will tend to have an advantage in that particular arms race. A similar idea was used by Pimentel (e.g. I968) in his 'genetic feedback' theory of population regulation. The life-dinner principle is just one example of a way in which inequalities in rates of evolution may be important in determining the course and outcome of an arms race. A few others are mentioned in the next section.

For more details follow the link.

https://www.jstor.org/stable/pdf/77442.pdf