BIO120H1 Lecture Notes - Lecture 5: Predator Satiation, Mecha, Thomas Robert Malthus
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Allee effects are small pop phenomenon where pgr is reduced by undercrowding. At low density, population growth of populations subject to allee is reduced. Darwin observed that large pop size important to stop extinctions when there are predators, but, it maltusian printiple + logistic model for pg was accepted. Malthusian principle: intra-specific comp doesn"t decrease with pop size. Pg = limited by undercrowding, not competition. Ex) aggregation had (+) effects on survival of land isopods that decreased fast when isolated. These benefits contradict malth + log model. An allee effect it (+) relationship between aai fitness + pop size over some infinite interval (+) relationship might give rise to a critical pop size. Mechs that cause it: mechs that affect r + s. Ex) mate limitation = under crowding in species that reproduce sexually, it reduces r when plants of animals can"t release gametes/find each other (plants + animals)
