Uneven distribution of progeny Uneven distribution of progeny Red - PDF document

Uneven distribution of progeny Uneven distribution of progeny Red Drum (redfish) N e = 4 N c − 2 σ 2 N c N e σ 2 + 2 0 100 199 Family Sciaenidae, DRUMS Sciaenops ocellatus 1 100 133 σ 2 variance of family size Description: chin without barbels; copper bronze body, lighter shade in clear waters; one N e = 1854 to many spots at base of tail (rarely no spots); mouth horizontal and openng downward; scales large. N c = 3 , 400 , 000 Similar Fish: black drum, Pogonias cromis . 2 100 100 Where found: juveniles are an INSHORE fish, migrating out of the estuaries at about 30 inches (4 years) and joining the spawning population OFFSHORE. N c census size Size: one of 27 inches weighs about 8 pounds. 5 100 57 *Florida Record: 51 lbs., 8 ozs. Turner, T. F. , J.P. Wares, and J.R. Gold. 2002. Genetic Remarks: red drum are an INSHORE species until they attain roughly 30 inches (4 Effective Size is Three Orders of Magnitude lower than years), then they migrate to join the NEARSHORE population; spawning occurs from Adult Census Size in an Abundant, Estuarine Dependent August to November in NEARSHORE waters; sudden cold snaps may kill red drum in shallow, INSHORE waters; feeds on crustaceans, fish and mollusks; longevity to 20 years Marine Fish (Sciaenops ocellatus). Genetics 10 100 33 or more. σ 2 random mating = 2(1 − 1 /N c ) Genetic drift and mutation balance Small populations 1 With mutations a random mating population of diploids has ∆ H = µ − the chance to acquire 2N � new alleles every generation. 2 N e 1 A population looses variability at a rate of Small population loose alleles faster than they arrive in by 2 N e mutation Small population are not at mutation-drift → equilibrium. Heterozygosity H will decrease over time 1 ∆ H = µ − 2 N e loss rate mutation rate Relationship between Founder effect Heterozygosity and Population size When only few individuals from a large population colonize an island (or other isolated habitat), only a small number of alleles will be present in the new population. Expected Locality Heterozygosity Heterozygosity 8 Selçuk 0.114 0.132 13 Samos 0.097 0.119 13 Red-cockaded woodpecker 14 Ikaria 0.042 0.050

Reduction of population size Inbreeding Breeding with close relatives Genetic drift (loss of alleles is larger than gain of alleles) Founder effects Bottlenecks Inbreeding Disease susceptibility in California sea lion Inbreeding depression Breeding with close relatives Reduced heterozygosity and increased mortality of offspring caused by mating of close relatives Experiment showing inbreeding in a cricket Figure 2 Internal relatedness in sea lions and the incidence of different disease classes. Carcinoma, n = 13; helminth infection, n = 72; nonspecific, n = 51; bacterial infection, n = 98; algal toxin, n = 101; trauma (control), n = 36. Values are means s.e. The mean internal relatedness value of trauma animals (-0.004) is indistinguishable from zero, as would be expected for individuals born to randomly mated parents 5 .

Measuring inbreeding Causes of inbreeding depression Reduced heterozygosity Dad Mom Increased exposure of recessive deleterious alleles in homozygotes AB CD Recessive deleterious alleles are common in large populations. These alleles are at low frequencies and typically occur mainly in heterozygotes and are therefore not purged from the populations because there is no Daughter associated penalty for the heterozygotes. In small populations, just by chance, they might get fixed Measuring inbreeding Measuring inbreeding Dad Mom AB CD AB CD p(A)=0.5 Daughter p(AA) = 0.5 * 0.5 * 0.5 = 0.125 What is the probability that the Son p(A)=0.5 p(A)=0.5 son got two copies of the same allele from his dad? = inbreeding coefficient F Measuring inbreeding Measuring inbreeding for population we use the heterozygosity as a proxy F = H Expected − H observed AB CD H Expected p(B)=0.5 p(A)=0.5 F measures the deviation from a random mating population p(AA) = 0.5 * 0.5 * 0.5 = 0.125 p(B)=0.5 p(B)=0.5 p(A)=0.5 p(A)=0.5 p(BB) = 0.5 * 0.5 * 0.5 = 0.125 using Hardy-Weinberg proportions and H Expected = 2 pq F = p(AA) + p(BB) = 0.125 + 0.125 = 0.25 two alleles

Measuring inbreeding Connection to population size t = number of generations 1 F = H e − H o ) t F = 1 − (1 − 2 N e H e Homozygosity if Hois zero, F is maximal and 1 Probability that variability is maintained over t generations Inbreeding coefficient if Ho is equal to He, F is 0 Connection to population size N e = 100 F 1 ) t F = 1 − (1 − 2 N e N e = 1000 N e = 10 , 000 F N e N e = 100 , 000 Time t F t Connection to population size Extinction vortex EXTINCTION The frequency of matings between close relative rises INBREEDING 1 Population ) t F = 1 − (1 − becomes smaller 2 N e “the worse it gets, Heterozygosity is reduced in offspring, reducing the ability to the worse it gets.” respond to environmental change Caughley 1994 F N e As a result of this expression, fecundity is reduced and Semilethal recessive alleles are mortality is increased F t expressed in homozygous (inbreeding depression) conditions

Predicting inbreeding depression Clarkia – a naturally self-pollinating plant that does not show inbreeding depression Hedrick, P . W. 2001. Conservation Genetics: where are we now? Trends in Ecology and Evolution 16:629-636 What is the chance of suffering Scenario Genetic load “Inbreeding depression” when mating with close relatives High Large population Low (large number of rare semilethal alleles) Intermediate Intermediate Recently small (purged some detrimentals of (fixed some detrimentals with population large effect) small effect) Low High Long-term small (purged detrimentals of (fixed many detrimentals with population medium or large effect) small effect) Genetic load = Reduction of the mean fitness resulting from detrimental variation for a population compared to a population without lowered fitness. Predicting inbreeding depression Colonial naked mole rats do not show much inbreeding Hedrick, P . W. 2001. Conservation Genetics: where are we now? Trends in Ecology and Evolution 16:629-636 What is the chance of suffering “Inbreeding depression” when Scenario Genetic load mating with close relatives High Large population Low (large number of rare semilethal alleles) Intermediate Intermediate Recently small (purged some detrimentals of (fixed some detrimentals with population large effect) small effect) Low High Long-term small (purged detrimentals of (fixed many detrimentals with population medium or large effect) small effect) Genetic load = Reduction of the mean fitness resulting from detrimental variation for a population compared to a population without lowered fitness. Larkspur Inbreeding avoidance Delphinium nuttallianum Plants Self-incompatiblity Male and female parts flower at different times Distance between Overall fitness Heterostyly (females and male parts are far from each parents (m) other) 0.30 a 1 Male and females are different plants 0.42 b 3 Animals Mate choice (mice smell whether they belong to the same 0.65 b 10 MHC type or not) 0.08 a 30 Migration behavior (Young lions get driven from their pack)

Outbreeding depression Hybrids and Admixture (=lower fitness due to breeding with unrelated individuals) Two separated populations Individual of two come together different species have Local adaptation : differences in alleles frequencies due to different selection pressures in different places offspring (sometimes fertile) Coadapted gene complexes : group of traits that have high fitness when they occur together, but low fitness when occurring with other traits. Populations that are separated a long time were selected for different combinations, bringing them together might be problematic: Largemouth bass Hybrids Hybrid Zone Bombina variegata Bombina bombina Foto from Website of Beate Nürnberger, Edinburgh Hybridization, Admixture Florida panther has a cowlick and a kinked tail because of inbreeding Hedrick, P . W. 2001. Conservation Genetics: where are we now? Trends in Ecology and Evolution 16:629-636