Genetic Diversity

Factors that make populations vulnerable to extinction Environmental fluctuations Catastrophes Demographic uncertainties Genetic problems Habitat fragmentation

Heath Hen – Extinction Vortex

Minimum Viable Population Size Another definition - often defined as 95% probability of 100 year survival, but can also plan for longer survival (500 or 1000 years) MVP is usually determined by modeling

Forces which may cause extinction 1) deterministic - something essential is removed (habitat loss) or something lethal is added (pollutant, disease, introduced species) - presumably we can act to minimize these risks

Forces which may cause extinction 2) stochastic (random) - environmental, catastrophic, demographic and genetic - this is what we need to worry about and what is hardest to prevent environmental randomness effects resources and conditions and we can't do much about it catastrophic randomness - floods, fires, hurricanes, volcanoes - can't really prevent but can spread individuals around to minimize the impact demographic - just natural random variation in birth and death rates can lead to extinction genetic - lack of genetic variability can lead to problems of inbreeding and poor response to diseases and environmental change

Bighorn Sheep and MVP

Grizzly Bear and 50/500 Rule

MVP – 50/500 Rule?

Reductions in Polymorphism Reductions in population size can lead to losses of genetic polymorphism Two special cases of reductions in population size are: 1.A few individuals move to a new area and start a new population that is isolated from other populations – founder effect 2.We can also experience a population bottleneck where a formerly large population is drastically reduced in size

Founder Effect – Galapagos Tortoise

Founder effect – Amish and Polydactyly

Population Bottleneck – Northern Elephant Seal

Reductions to Polymorphism Genetic drift - random changes in gene frequency in a population – nondirectional evolutionary change which occurs due to sampling errors in mating and mortality - can result in a loss of polymorphism

Effective Population Size Effective population size - the number of reproductive individuals within a population taking into account unequal representation of the sexes in reproduction or unequal representation of generations over time

Sewall Wright at University of Chicago In 1928

Sewall Wright in 1980’s

Effective Population Size in the Social Tuco-Tuco

Using a pedigree chain to calculate inbreeding

Inbreeding in European Royalty

Gene Flow The movement of alleles from one population to another

Rates of Gene Flow – Ne (effective population size) = 120

Gene Flow in Conifers

Gene Flow in Kingsnakes

Figure caption for Kingsnakes a, b, The venomous eastern coral snake (Micrurus fulvius; a) and its non-venomous mimic, the scarlet kingsnake (Lampropeltis triangulum elapsoides; b). c, Geographical distributions of model (yellow) and mimic (yellow, green). For simplicity, sampling locations for genetic analyses are shown for allopatry only (open circles, western allopatry; filled circles, eastern allopatry). d, e, Gene flow among L. t. elapsoides (number of migrants per generation, Nm, shown as means 95% confidence interval) from sympatry into each of two allopatric recipient populations (eastern (d) and western allopatry (e)), as measured in mitochondrial (mtDNA) and nuclear (nucDNA) genomes (the three estimates in each population and genome reflect three runs of MIGRATE-n). Asterisks indicate estimates significantly greater than 0.

Value of genetic diversity Why are genes valuable? Or What kind of value do genes have?

Value of genetic diversity Genes have instrumental value – they are valuable for what they do

Grassy Stunt Virus in Rice

Oryza nivara

Native habitat of O. nivara in Uttara Kannada, India and Distribution