Sexual Selection/Molecular Evolution (W4-L2)

• Advantagous mutations are more common • Molecular evolution will are dominated by selection • No molecular clock

• Pseudogenes evolve very fast • genes that have important functions should evolve slower • synonymous codon positions evolve faster than non-synonymous sites adn should evolve with a constant rate (not always true)

Dead genes that have no function and no fitness effect

concept that the rate of molecular evolution is pretty constant Exceptions: • different protiens have different rates • different domains of the same protein may have different rates • same protein in differnet organisms may have differnet rates

Discovered by Tomoko Ohta Suggests most muation events at the molecular level are slightly deletrious rather than strictly neutral Small populations: drift dominates and slightly deletrious mutations are neutral (fix relativly quickly) Large populations: seletion is more pronounced

Method used to detect postive selection; suitable for between species Ka=nonsynonymous Ks=synonymous Purifying (negative) selction: ka/ks=0 Neutral selection: ka/ks=1 Positive selction: ka/ks > 1

Method used to compare divergence between two species with polymorphism within each species Proved that positive selection exists after acceptence of neutral theory in the 1990s

Selection for traits that increase reproductive output/likelyhood of obtaining a mate Slection in relation to reproduction not survival

Imbalance generatedfrom fundamental differences in investment in gamates Females produce fewer large gamates whereas males produce many ‘cheap’ gamates Causes intra and inter selection Males maximize fitness by reproducing more Females maximize fitness by selecting ‘better’ males

• condition • good at avoiding predation • liklihood to productive attractive offspring • high investment in offspring