Ecology PDF

Costs of reproduction Tradeoff: An increase in one life-history trait may result in a decrease in another trait Organisms cannot can't maximize all traits Simultaneously invest associated with fitness Example: brightest male guppies may have high...

Costs of reproduction Tradeoff: An increase in one life-history trait may result in a decrease in another trait Organisms cannot can't maximize all traits Simultaneously invest associated with fitness Example: brightest male guppies may have high - reproductive success, - but are more visible to - predators - Cost ?? - Trinidadian guppies 36  Selection on life histories To be evolutionarily successful, an organism must survive to reproduce, and it must reproduce Natural selection favours genotypes where survival and fecundity result in the highest fitness relative to other genotypes “This is a fundamental component of the meaning of life” 37  r-selection vs K-selection Ways to categorize life histories: r-strategy: emphasis on rate of growth fast reproduction - Ex. squirrel K strategy: emphasis on slower , reach stable maximum survival, resource use Ex sharks. , humans 38  Fast vs slow life histories Ways to categorize life histories: Fast life history: high fecundity, short life, - - lots of offspring young age of maturity - - - Slow life history: low fecundity, long life, old - -- age of maturity - 39  Alternative life histories Bluegill Sunfish Sexually dimorphic F M M sexual selection through competition hidden between males for access to resources 40 41 42 Secretes sperm of the on top eggs M looks after kids 43 keeps Of moving around 44 another male sneaks in quickly produces sperm over top of the eggs Sneaker dead beat dad Father some of ofspring 45  Alternative life histories Life histories can vary within a species: Multiple strategies may be successful FIGURE 8.30 46  Alternative life histories Male Chinook Salmon can be hooknoses or jacks This large hooknose male … but this small matured at 4 or 5 years old… jack matured at 247  Alternative life histories Male dung beetles can be large horned males used (horns for fighting over females), or small hornless males > - SNEAKER 48  Alternative life histories Male ruffs can be territorial or satellite males A third female-like male form is very rare: faeder 49  Alternative life histories Alternative strategies can be maintained by frequency- dependent selection FIGURE 8.31 50  I’ve added more labels to Incidence of parental strategy make it clearer ßCommon Rare à that rarer Fitness of parental strategy Fitness of sneaker strategy strategy has higher fitness Rarer strategy then becomes more common Stable strategy occurs at the intersection, where both strategies have ßRare Commonà similar fitness Incidence of sneaker strategy is off to be a sneaker when Sneaker strategy very rare - fitness pays E of ↑ fitness (I Sneaker - all other males other strategy able to sneak a lot sperm) rie , u common d fitness 51 Sneaker is around enough parental when males common strategy very not FIGURE 8.31 IMPROVED , is strategy 52  Harvest-induced evolution Intensive harvest can result in genetic changes, driving earlier age of maturity and smaller size at maturity Selective hunting of males with large horns has lead to a decline in body size and horn length in Alberta’s bighorn sheep FIGURE 8.33 53  Horn length and body weight of male bighorn sheep have changed in response to hunting FIGURE 8.33 55