[Paolo Piccinelli]

Pesce a parte... è molto interessante la discussione sul numero minimo di riproduttori per mantenere inalterato il patrimonio genetico di una colonia/popolazione:

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While this is all generalizations, here’s some interesting talking points: •A minimal captive population size of 50, in equal sex ratios, randomly mating, will keep inbreeding at roughly 1%. At this population size, the total population will lose 1/4 of it’s genetic variations in 20 to 30 generations. •An interesting aside to the first point, the number of individuals in a small population (let’s say 25) is roughly equivalent to the number of generations that population can exist while maintaining a reasonable level of “fitness” (so 25 generations if the total population is limited to 25 individuals in each generation, as well as the other stipulations of equal sex ratios and random matings). •It is argued that 500 individuals is the minimum necessary to maintain a long term captive population that loses variations to genetic drift at a rate compensated for by new variations gained through mutation. •The most interesting one I’ll quote verbatim – “the number of founders in a colony, so long as it is greater than about five individuals, is not nearly as important as the long-term maintenance size of the colony (Nei et al., 1975; Denniston, 1978). That is, a single bottleneck event followed by rapid growth to a large size, say 2Ne greater than 500, does relatively little damage, compared, that is, to a chronically small Ne.”. Or to try to paraphrase – a captive population started with only 5 individuals can still be enough (in a fish) to potentially establish a stable captive population, so long as that population is brought up to at least 500 breeding individuals in short order. So what does that all mean? Well, for starters, it means that even with only 8 founding individuals, the captive population of Amphiprion mccullochi could be very stable and with us for a long time so long as the fish is actively bred by many people and it’s done in as few generations as possible.