Lecture 17 - BIO220

Genetics dominates after takes time to accumulate

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Unformatted text preview: ore, genetics or demographics ? • Genetics DOMINATES AFTER (takes time to accumulate) • Potential for allee effects is enhanced – The influence of population decline on Ne and its consequences should predominate in leading to extinction – Reproductive rate depends positively on density – At low densities, low reproductive rates – Likely in colonial breeders Warder Clyde Allee • Demography DOMINATES FIRST • Increased risk of demographic stochasticity – The effects of demographic stochasticity should predominate and lead to extinction before the effects of genetics can manifest (Lande 1988) – Random differences among individuals in survivorship and reproduction create variability in population growth rate – Happens even if individuals have the same average survival and reproduction – Most important in small populations Russell Lande, photo by Spencer Barrett 7 Image from wikipedia Demographic Stochasticity: E.g. A random lightning strike can kill off a ll the females in a population if the population is small -In a larger population, there is a larger chance that some females will s ur vive and will be able to replenish the population • Importance of alternative world views: alternative management actions for rare, endangered, and declining species 8 -Our plan of action depends on which factor is more i mportant Case study #1: Cheetahs Early view • Historical bottleneck lowered Ne • Acinonyx jubatus • Genetically depauperate • Inbreedi...
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