Variation: Variation is present within individuals among individuals within populations among populations.

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Presentation transcript:

Variation: Variation is present within individuals among individuals within populations among populations

metapopulations - networks of populations that have some degree of gene flow among geographically separate populations - regular extinction and recolonization events

Populations that are spatially isolated will tend to diverge genetically each population is representative of the species, but may not contain all of the species’ variation many populations may disappear before the species is endangered

endangered Glanville fritillary butterfly (Finland) – occupies meadows 1600 meadows, of which were occupied in approx 200 extinctions and 114 colonizations per year Alan Barnes Metapopulations

Populations that are spatially isolated will tend to diverge genetically how many subpopulations can we afford to lose? which ones do we choose to save? how many? how many do we have habitat for? how different is different enough to warrant isolation/preservation?

Populations that are spatially isolated will tend to diverge genetically how many subpopulations can we afford to lose? which ones do we choose to save? how many? how many do we have habitat for? how different is different enough to warrant isolation/preservation? how well can we describe differences among populations?

: genetic distance (D) Measurement of genetic differentiation among populations : genetic distance (D) Quantitative measure of genetic divergence between two sequences, individuals, or taxa Relative estimate of the time that has passed since two populations existed as a single, panmictic population

Three most commonly used distance measures Nei’s genetic distance (Nei, 1972) Cavalli-Sforza chord measure (Cavalli-Sforza and Edwards, 1967) Reynolds, Weir, and Cockerham’s genetic distance (1983) Nei’s assumes that differences arise due to mutation and genetic drift, C-S and RWC assume genetic drift only

Genetic distance Nei’s genetic distance surveyed over wide variety of taxa: geographic populations subspecies species genera Avise and Smith 1977, Davis 1983

Genetic distance (D) Dendrogram of genetic distances: (clustered using UPGMA, Unweighted Pair-Group Method with Arithmetic Mean: each new unit has a distance to the cluster = average of the distance from unit to each species in the cluster )

Lampsilis cardium (pocketbook mussel) Lampsilis ovata (pocketbook mussel)

WV L. ovata IL L. cardium WV L. cardium VT L. “ovata” MO L. cardium WV L. fasciola Nei’s genetic distance Lampsilis cardium (pocketbook mussel) Lampsilis ovata (pocketbook mussel)

Genetic distance (D)

Tuatara – New Zealand

dusky seaside sparrow Habitat loss (mosquito control) Spraying for mosquitoes added pesticides to food web Reserve established; highway constructed through it (to connect Kennedy Space Center w. Disney World) Marsh drained Last 7 males cross-bred with related sub-species – unsuccessful Last sparrow died in 1987

Tuatara – New Zealand dusky seaside sparrow