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BIOL 359
Jonathan Witt

Kin Selection: Direct Fitness: an individual’s contribution to the next generation directly through reproduction Indirect Fitness: additional reproduction caused by relatives to the species resulting from actions (assistance). The additional reproduction would not have been made without the assistance. Kin Selection: is the selection for and spread of alleles that cause increased indirect fitness Altruism is paradox to Darwin’s theory – it is highly unlikely that a species would undergo an action that would in turn decrease its own fitness for the increase of another individuals fitness.  However selection would favour traits that decrease an individual’s personal fitness if it increased the survival traits and fitness of close relatives Co-efficient of relatedness (r) – the probability that two homologous alleles are identical by decent; involves an allele in the actor and allele in the recipient at the same locus HAMILTONS RULE: the spread of an allele for altruistic behavior will occur if B r – C > 0  The benefit to the recipient minus the cost to the actor is greater than 0  The benefits and costs are measured in terms of surviving offspring Prairie Dogs:  Prairie dogs reside in coteries and were observed to have altruistic behavior  When both males and females spotted prey they would made a call to warn others in the coteries that there was danger although it meant self sacrifice  At first they were unsure whether these calls were selfish (the action was done to increase their own chance of survival or fitness) or whether they were altruistic (although the action reduced their own survival rate and fitness decreased it increased the fitness of the recipient)  Studies showed that the proximity to kin related members affected the ways in which they called  The closer the individual was to relatives, the more likely they were to call White Fronted Bee Eaters  They are responsible for kin selection  It is very hard for all birds to find their own territories, raise offspring etc. so when young birds are of age to rear offspring they will mostly stay in their own nest and assist other members in raising their offspring instead  The birds will choose relatives that have the closest relation to them and help them raise their own offspring (help parents raise siblings etc)  Most of the young birds die of starvation before leaving the nest but they have huge benefits to their kin, by increasing the additional reproduction offspring. Wood Mice  Female wood mice are highly promiscuous and mate with multiple males  The males are in competition for their sperm to reach and fertilize the egg the fastest  Males with large testes is an adaptive trait for sperm competition  The sperm show their competitiveness – they have hooks that hook onto other sperm heads or flagella and form a train of thousands of individual cells that increase the speed of travel in comparison to single sperm  When the sperm reaches the cell they must release from one another via an enzyme and a lot of the sperm are destroyed in this process  This altruistic behavior is a form of kin selection as siblings are helping one another to reach the egg Cannibalistic Tadpoles:  2 forms of tadpoles: omnivorous and cannibalistic  Omnivorous are plant eating however their morphs are capable of eating other tadpoles  Did a study to see whether cannibalistic toads would eat their omniviorous kin and found out that 6/8 times they would not  These tadpoles display kin selection by choosing to eat non kin members over relatives  Did not affect their own fitness levels by eating other non kin members – the cost of missing a meal was less than the benefit Conspecific: individuals belonging to the same species Heterospecific: individuals belonging to different species Congeneric: individuals from different species belonging to the same genus Conspecific Nest Parasitism: Mal Altruistic behavior  Avoid paying the costs on behalf of non-kin individuals  American coots may sometimes place their own eggs in the nests of other coots (conspecific) so that they can rear them  This will decrease the fitness of their own offspring because for every parasitic egg in their nest, their own offspring have less chance of survival  Coots have ways of avoiding mal-altruism through noticing the specific color of their own eggs in comparison to the parasitic one and also counting, they can see if there is an extra egg  The survival of a parasitic egg with increase the fitness of the parasitic kin Kin Selection and Eusociality: Eusociality: individuals that have no direct contribution to the next generation (non reproducing) but instead provide additional reproduction by means of assistance  Involves: cooperative family (brood) care  Individuals who do not reproduce  Overlap of generations between parents and offspring Eusociality and Hymenoptra  Special species of insects that are haplodiploid  The males are haploid but the females are diploid  The genetic code is different and causes a special coefficient of relatedness the sisters are more related to each other than they are to their offspring  Sister – sister = ¾  Sister – brother = ¼  Sister – offspring = ½  The sisters will assist in helping the queen with child rearing rather than making their own offspring  The queen has equal relatedness with both male and female; and wants to keep a 1:1 ratio  But the sisters want to make more sisters 3:1 ratio and will deliberately destroy male eggs  Many males will develop into soldiers to protect the colony and others are reproductive and will mate with the queen  Hamilton’s rule may not be the reason behind eusociality but instead be caused by nesting Parent Offspring Conflict  The more parental care given will increase the fitness of the offspring and their contribution to the next generation  The relation of coefficient between: o the parent and offspring is ½ o Siblings = ½ o Half siblings = ¼ o Yourself = 1  Offspring compete for the most parental care between their siblings  The cost benefit ratio is very low when offspring is small  When they get bigger the weaning conflict begins where parents will try to kick offspring out of nest but they will attack and try to continue parental care  The cost increases because they now use more nutrients and it is expensive  Sublicide also occurs – siblings attack/kill others to fight for more parental care Reciprocal Altruism:  Altruistic behavior that occurs among individuals that are not related may occur if the cost to benefit is equal or low  Those who do not return the favour will be punished  Reciprocal altruism is likely to occur among individuals who spend a lot of time together and constantly see each other; species have good memories  In bats, species will go out at night and prey on mammal blood; however not all of them will get blood  If a bat does not get blood 3 nights in a row then it will starve  Those who INTERACT most with one another will regurgitate their own blood to help the starving bat – reciprocal altruism Species Concepts and Speciation:  Defining a species is hard to do; taxonomists go around assigning organisms to different “kinds” based on certain similarities on characteristics  There are 3 species concepts covered: phylogenetic, biology and morphology Morphological Species Concept:  Type specimen: an individual is used to represent the entire species  Specimens with the same morphological traits are considered to be part of the species type  This method is known as the type method, is very hard because if you look around you can see that there are many different morphologies between people; writing morphologies is very tedious and there are many different variabilities  There must be rules used such as the botanical code and the zoological code Typological/Morphological Species Problems: Cryptic Species: species that cannot be deduced on a morphological basis Phenotypic Plasticity: the same genotype produces different phenotypes due to environmental conditions Biological Species Concept: species can be defined as interbreeding natural populations that are reproductively isolated from other groups  Individuals are “alike” based on gene flow and interbreeding  Evolutionary criterion: reproductively isolated and interbreeding Problems:  Not all species can be tested using this definition o Asexual Taxa: do not interbreed therefore all individuals would be considered as reproductively isolated and their own species o Fossil Taxa: cannot tell whether two species were reproductively isolated or not o Hybridization: species that hybridize are difficult to tell whether they are interbreeding and reproductively isolated  Some species have hybridized so much that they seem to have created their own species because are no longer seen without one another  Hybridization and the splake: they made a hybrid of a speckle trout and a lake trout named a splake which was an example of hybrid inferiority which reduced the fitness of both species  Interspecific Hybridization: hybridization among individuals of different species (ex. Polar bears and grizzly bears)  Intraspecific Hybridization: hybridization among individuals in the same species that are distant from one another (raccoons on the east and west coast) Phylogenetic Species Concept  Species are defined as populations or groups of populations that have the same evolutionary fate through time  These populationare monophyletic (they have all the same known descendants and common ancestor)  The population must have evolved independently for a long enough time to develop diagnostic traits Eurytemora  Bacterial species found around the world- wanted to see if they were all the same species or they were different  Did experiments and took groups from diff parts of the world and tried making them mate : they would not mate and therefore they went against the biological concept (no interbreeding)  However they did DNA testing – and found that on phylogentic basis the populations were species of the same Species De-lineation  There were first thought to be two species of elephants 1.) Africa and 2.) Asia  However when looking at the African group there was a morphological difference between two groups , one that lived in savannas and one in forests  The phylogentic concept (through dna tests) proved that they were actually divided into two species Hyalella Azetca: Cryptic Species  There was thought of to only be one species however it as found all over the world and they cannot be morphologically distinguished from one another; however when you look on a phylogentic basis there are already over 110 different species Problems:  In phylogentic species concept there can be problems with more than one monophyletic group  Some species are more related to other species than to their own lineages  This can occur in rapidly evolving species Biological Species Concept VS Phylogenetic Species Concept  Bio: inbreeding populations that are reproductively isolated from other groups  Cannot be used on asexual taxa, fossil taxa, hybridized species  Phylo: populations/groups of populations that are monophyletic (all known decendants and common ancestor) must have evolved independently for a long enough time that diagnostic traits are show  They can be used on asexual and fossil taxa but there are issues with multiple monopyletic groups where species are more closely related to different lineages (happens in rapidly evolving species) Mechanisms of Speciation  There are 3 steps to speciation o Isolation of the population o Divergence of the population o Evolutionary independence and reproductive isolation  1) Isolation of Population: occurs when the ancestral species is split and isolated into different groups; gene flow is disrupted o Allopatric speciation:  The ancestral species is isolated geographically into independently evolving species  The gene flow stops due to a barrier of the ancestral species  When the species splits- the different habitats may cause different modes of selection and the populations may become quite different from one another. If the barrier is finally removed the populations may become two different species  Geological Isolation Can be caused by: o Divergence: populations diverge and colonize new habitats and eventually become new species Ex. The drosophila of Hawaii – this theory of colonization/divergence involves two rules:  1.) similar species are found on adjacent islands  2.) the sequence of branching event must correspond to the sequence in which the islands were formed o Vicariance: the species are formed due to some form of barrier in the geological habitat which splits the population into two. This can be slow such as formation of mountain, or fast such as lava flow. In both cases the gene flow is disrupted and leads to speciation  Parapatric Speciation: o Speciation can occur in contiguous populations when there are environmental gradients (geographical extremes) o Within the geographic regions there are genotypes that natural selection acts upon that split the population up and can eventually create two different species (ex. Genotypes that prefer hot weather vs. cold weather) o Hybrid zones also occur where both genotypes are favoured and creates hybridization  Sympatric Speciation: o New species evolve within the same environmental range as the ancestral species o This can occur through:  Disruptive selection: two extreme low value phenotypes come together and create an offspring; however selection will most likely eliminate it  Assortative Mating: individuals with similar traits are likely to mate o Polyploidy and Sympatric speciation  Speciation can occur when diploid gametes form tetraploids which are unable to mate with diploids; the species becomes reproductively isolated and forms a new species  2.) Divergence of Population: in order for speciation to continue, after reproductive isolation the populations must diverge from one another via natural selection, genetic drift, mutation and sexual selection  Genetic Drift: in small isolated populations genetic drift can play a large role in diverging populations and creating new species o Bottlenecking and founder effect  Natural Selection: can occur in populations when one or both the populations occupy novel environments o even if there is small number of gene flow, natural selection still stronger on speciation o causes an isolated population to diverge on the basis of competition for food and resources, ecological differences etc  Sexual Selection: o changes in mate selection may cause populations to rapid diverge o sexual selection directly affects gene flow o Example in Drosophilla Het. – females chose to mate with males that win the most combats for leks. The males fight by head butting and have developed a mutation for hooked heads that help them battle o The ancestors did not have hooked heads and fought through grappling, and the female chose the winner of the fights, but an isolated population mutation caused the hooked heads which caused a new way of fighting and the females still chose the winner to mate with. The mutation led to fixa
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