- These unique traits and behaviours are only seen in one sex

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1 Coyne chapter 6 how sex drives evolution for lec 6 and 7 - Peacock with its blue tail violates every aspect of Darwin because the traits that make him beautiful is making him maladaptive for survival because the tail produces a problem in it not being able to fly to escape predators especially when their tail so wet it s hard to drag. The sparkling colours also make it attract praetors especially compared to the females who are short tailed and camolfauged to have a more drab greenish colour and a lot of the energy is gone into to the male s tail which must be re-grown each year - How could the peacocks feathers be an adaptation when it is a barrier? Also if the males evolved by natural selection why the females aren t as bright as the males are? - These unique traits and behaviours are only seen in one sex - Another example would be the frog of central America where the male sing at night time to attract the attention of the females but also in doing so they are attracting predators like flies that prey on these frogs and get their attention more than the intended no calling females they are after - These examples shows us that just as Darwin thought these traits do reduce survival - Let s take a look at the red colored widowbird who have long talk feathers longer than their bodies and so a university group captured them as they would see them flying in struggle so what they did was cut an inch in one group and another 4 inch in another and recapturing them in the breeding season they found that: longer tailed males lost more weight than shorter ones making te longer tailed ones a disability for them - Another example would be the footlong lizard where the males and females look different meaning the males are bright colours having yellow head while the females were grayish colour and lightly spotted. An experiment was done to test a hypothesis to see that the males bright colours attracts more predators and after the experiment the male models showed bite marks by birds and snakes while none were on the female models - Sexual dimorphisms traits that differ between males and females of a species such as colour, and songs - biologists have found that sexual dimorphic traits that are found in males seem to violate the evolutionary theory because they waste time and energy and reduce survival look at the colours of the species in males we have seen in experiments that they are eaten more than the plain females - If selection is responsible for these traits we need to explain how? - Before Darwin sexual dimorphism was a mystery that not even creationist could explain how one sex should produce features that are harmful for their survival

2 - Darwin finally noted an explanation- if traits he said differed between males and females such as their behaviours, ornaments, or structures only being done to the males these costly traits have evolved for a reason and it is not for survival - selection we have to remember is not only for survival but it is also for successful reproduction and by having fancy tail or singing doesn t help you to survive but it does enhance your chances to have offspring s which answers why these traits have Rosen - Darwin was the first to recognize this trade off and said that this type of selection responsible for sexually dimorphic features are called sexual selection - Sexual selection- it s a selection that increases an individual s chance of getting a mate which is a division of natural selection but has a unique way of operating and is also nonadaptive adaptation that it produces - Sexually selected traits evolve more when there is a increase in reproduction like the widowbird noted before have long tails because the females prefer the longer tailed males as mates even though it is hard for the males to run from predators or look at deers with big antlers where they too might struggle with a burden but the win contests more to create more offspring s - Sexual selection comes in 2 forms: - 1)direct competition between males for access to females (huge antlers) - 2) female choiceness widowbird long tail among possible mates - Male-male completion is the easiest to understand with almost all animals between the males for the possession of the female and when the males battle directly it is usually clashing antlers of the deer, the stabbing horns of stag beetle, head butting of stalk eyed flies - Selection will favour any trait that promotes victories so getting more mates for pffsprings producing armaments- stronger weapons, larger body size or anything that helps the male win physical contest - Whereas bright colours, ornaments are more for mate choice - To female eyes not all males are the same because they find that some male traits and - behaviours more attractive so genes that produce those favourites are accumulated in the population - Another indirect completion among males is that they have the loudest voice, brightest colours and then the winner is decided by the female in contrast to the male- male competition

3 - Why is it that in sexual selection males competes for females and not the other way around? Because of the differences in sizes of the sperm and the egg - Is this theory true though those males who are winners have the best displays because if they do not the whole sexual selection theory fails!! - Don t worry evidences support the theory - Sexual selection promotes the evolution for large, fierce males because the bigger males pass on their genes to the next generation where the smaller ones don t - Females who do not have to fight are close to their original weight for reproduction - So sexual dimophorims of body size even in our own may be due to competition between males for access to females - Male birds compete for estate as well to attract females by controlling a patch of land one with good vegetation that is goof for nesting and when the males have it they defend it with vocal sounds to keep other males away - look at elephant seals who are polygynous with the males having more than 15 females nesting in their territory - many other males are called floaters (players) trying to invade territories so that they can copulate with females - beside the males protecting their turf they also they sing complex songs and making threats with their ornaments which is a bright red epaulet on the shoulder and when a experiment was done colouring it black 70% males lost their territories and so it is not to attract females but to warn males away to say this territory is occupied - we can tell how selections are done are by going in the fields to instead of labs - sexual selection doesn t end after sex because males can still compete even after mating because females mate with more than one male in a short period of time so a male has to protect his paternity by post mating competition by the male hanging around after mating guarding his female against other suitors just like a dragon fly attached its the male guarding the female - chemicals also do this job for them- like snakes when they have ejaculated they release a chemical that temporarily plug up a females reproductive tract after mating or fruit flies where the male injects the female with a chemical called antiaphrodisiac a chemical in his semen making her unwilling to remate for several days

4 - some males use devious weapons such as getting rid of a sperm from a previously mating male and replace it with their own called the penis scoop using backward pointing spines on his penis to scoop put the sperm or earlier male and after its ridden he dispenses his own (DROsophila) - we know less about mate choice because it is less obvious than antlers - peacocks in mate choice: work done by marion petrie and did observational study the more eyespot in the male the more number of mating like a male with 160 eyespots in tail had 36 % sex showing detailed tails are more preferred by females but doesn t prove it because to might be the males way of displaying its feathers but with experiments done it showed that females like males whose ornaments that have not been reduced - another experiment with widowbird showed that males have tails 20 inches longer than females with 3 inches and cutting them the experiment showed that males with short tails had fewer females nesting compared to normal males but males with artificially long tails had a enormous increase in mating attracting twice as much as females than normal ones - Who wouldn t the birds have evolved such longer tails in the first place? Not known but it would be that this would reduce their longevity more than getting mates so 20 inches is the max it should be - biologists have focused more on birds because they are easier to study mate choice in them because they are active in the day and easy to observe - malte Anderson has showed that there is a variety of male traits correlated with mating success involving female choice and therefore female choice has driven the evolution of many sexual dimorphisms therefore DARWIN WAS RIGHT - WHY DO FEMALES CHOOSE? OR WHY HAVE SEX AT ALL????? - REPRODUCING sexually giving 50 % of genetic contribution to the next generation compared to asexual - Suppose a mutant in a female human enabled her to reproduce parthnogenetically- by producing eggs that develop without needing fertilization, and some animals do reproduce this way like aphids, fish and lizards - The first mutant wiman would only have daughters who then would produce more daughters but sexually reproduction needs males to produce half sons and half daughters - The population of mutant woman would rise above 50 % as pools of woman would be increased in producing only daughters making males disappear - The asexual gene would produce twice as much copies of itself calling it the 2 fold cost of sex

5 - In sexual reproduction you have random shuffling of genes producing new combination of genes in the offspring by bringing in several good genes in one individual sex might promote faster evolution to deal with then environment that is constantly changing like parasites that evolve to counter our own evolving defences - Or sex can put bad genes from a specie by recombining it together into one bad disadvantaged individual called a genetic scapegoat - Natural selection will favour changing ancestral in which one sex makes a lot of small gametes (sperm or pollen, eggs) - The evolutionary difference is the between males and females is differential investment- investment in expensive eggs vs cheap sperm for female more investment in the nourinshing of the egg and time - Selection favours males that are sluts with any female but females are picky because of egg investment by choosing the best father to fertilize their limited eggs - Thats why males look for females and females are coy - All females will find mates since males are competing for them so distribution of their mating will be even more even - Variance in mating success is higher in males leaving more offspring s - Male and females potential number of offspring s drives the evolution for male male competition and female choice - Evolution can favour monogamy by males halping with their children if they produce a lot because if not a lot they abandon going to seek to mate for more - But monogamous species aren t common in the wild like the birds where one goes to forage and other incubates the egg only 2% of all mammals have this mating system - In fruit flies females are larger because they need to produce large eggs and costly eggs - Females in monogamous bonds are more to cheat - 90% of bird species are monogamous - Less sexual diamorphism means they should be monogamous but if they don t cheat and stay with one another there is no sexual competition and then no sexual slection - Penguins, pigeons, parrots are monogamous

6 - In some species its the male that gets pregnant than the female its the same process but the male has a pouch on his belly or tail and carries them until they hatch and males invest more in child rearing then females and also there are more females with eggs than males to accept them because they do it one at a time its the female here who compete for rare non pregnant males like fishes and seashores and in this situation its the females here who are bright coloured while males are dab - Or another example is the birds male phalaropes they take care of their chick while female move around to mate and then they are coloured bright like seashores, pipefish, and phalaropes which are reverse - Darwin was closer than Wallace meaning yes females do choose to explain sexual dimorphism but does not make sense that their preference is on the outer appearance, but now we have evidence that female preference are adaptive preferring certaintyoes of males helping females spread their genes - Preference isn t always random inborn taste that Darwin said but may have evolved by selection because by a female choosing a particular type she has 2 things to gain : - Directly- picking a male producing a healthier baby during act of childcare and second - Indirectly- choosing a male who has better genes - Either way evolution of female preference is favoured by natural selection - When they choose indirect they pick males that are resistant to diseases and giving babies having that disease resitance and also giving them a preference to to choose the males of the same kind - Female finches like males that are brighter because they feed their children showing that colour is a sign of overall health because they are better fed giving direct benefits - 3 types of gene indications- trait showing he has good genes, gene that makes female prefer that trait, and good genes that are a indicator - Peackos with more eyes produce babies that grow faster but survive better even though the fathers donr take care of them - Sexual dimorphism by sensory bias- sexual diamophism exist by pre-existing biases in females nervous system liking bigger males to stimulate their nervous system so this is important even if Darwin is partky correct.