Population Differentiation and Phylogeography

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Degree Evolutionary Biology of Animals Flashcards on Population Differentiation and Phylogeography, created by katy.lynock on 22/05/2013.
katy.lynock
Flashcards by katy.lynock, updated more than 1 year ago
katy.lynock
Created by katy.lynock over 11 years ago
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Endosymbionts Erigone atra 2 More likely to ballon if not infected with Richettsia Longlivety/reproductive success not effected
Population Differentiation and Gene Flow 2 Individuals of species may be subdivided - spatially distinct populations that differ Mating random in each pop but not between
Panmicitc 2 No subdivision inpopulation population that can freely mix and breed with another to make hybrids Very rare
Linyphilid Spiders 2 Endosymbionts - spiders infected with maternally inherited intracellular bacteria Alter bacteria of host to favour own transmission
Models of Genetic Exchange Between Populations 3 Mediated by movement of individuals Nat. sel. and random genetic drift = contribution the migrating individual makes to gene pool
Models of Genetic Exchange Between Populations Assumptions 5 UNTRUTHFUL All populations are created equal, with N individuals and equal contributions to migrant pool All populations equally close to other populations No selection or mutation Have to assume equally successful movement/breeding/finding of resources
Metapopulation Structure 3 Series of subdivided populations Connected by different migration rates Physical barriers may affect migration also
Endosymbionts Acraea Butterflies 3 Riokettsia bacteria Kills off males off = lack of males = females lekking as reserved competition
Selective Sweeps 5 Loci not always inherited independly Co-inherited traits/genes 'swept' to high frequency with ones under selection = reduced genetic diversity Can be caused by maternally acquired endosymbionts Bacteria promotes own transmission by increasing of infected females 1st females alleles swept to high frequency
Endosymbionts Tetranychus Spider Mites 3 Wolabachia infect females Aggregate offspring Promote sibling mating
Endosymbionts Gryllus Crickets 2 Closely related species, normally reproductivelly isoloated from each other Curing of Wolbachia infection = viable hybrids
Population Structure and Heterozygosity 6 Individual population may/may not in Hardy-Weinberg equilibrium Structured population - overall number of heterozygotes can be fewer than expected Population structure unknown - Difficult to distinguish between TRUE heterozygotic deficiency and APPARENT heterozygotic deficiency Use markers to tell level of population subdivision
Metapopulation Structure and Gene Flow 3 Amount of genetic exchange on strength of selection No selection = migration very strong force for equalising gene frequency between populations Selection = genetic differentiation maintained despite migration
Patterns From the Past 5 Geographical distribution reflect primarily colonisation history 3 migration routes through Europe following last glaciation = hybrid zones Grasshoppers up mountain sounds different to below Couldn't outcompete each other = sound diff. to mate Overlap/hybrid zones for Ensatina species complx (salamanders)
Effective Population Size 1 Determined by number of individuals contributing to next generation
Factors that Influence Population Size Including Fluctuations 4 Effective population size (Ne) closer to small mean population size Never re-coup what previously lost Lowest number used = disproportionate effect Eh Soay sheep population change in size in cyclical manner
Effective Population Size (Ne) Unequal Sex Ratios 3 Sex biased population = More closely related generations = Less genetic types
Effective Population Size (Ne) Unequal sex ratios Example 6 Eg Racer Spider - Pityohphantes phyrygianus Female biased population Manipulating bacterium? Females genetically determine sex ratio? Sperm has more X chormosomes? Adapt particular position to determine sex of offspring?
Endosymbionts Tribolum confusum (Flour Beetles) 2 Uninfected females produce no offspring if mating with an infected male Infect male more fertile than uninfected male
Ne Variation in Reproductive Success Between Individuals 2 Influences sexually dimorphic population sizes Eg Seals and the beachmasters
Ne Population Subdivision 2 Separate Ne for each of the populations Ne influenced by migration rates between populations and chance of extinction for any particular population
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