Dispersal

Diffusion Gradual movement Over several generations

California Sea Otter Thought to be extinct in 1911 Found at Point Sur in 1914 More rapid southern expansion

Jump Dispersal Example: oceanic islands Mostly by volant organisms (flight) ex.: Galapagos Islands Rare, large (distance), and "surprising" events Explains large discontinuous distributions of some organisms Explains taxonomic similarity of distant biotas and populations

Collared Dove Expansion

Dispersal Polymorphism Gymnarrhena micrantha

Philopatry Tendency to disperse near close kin Belding’s Ground Squirrel

Barriers Physical –human introductions indicate how effective barriers can be –overcome resistant propagules –"weeds" are good dispersers (hardy) Physiological – land-water –salinity for aquatic organisms – temperature: both low and high Ecological-Behavioral –predators –strong fliers that won't cross water

U.S. Starling Dispersal 100+ birds added to Central Park in late 1800’s

Gypsy moth Accidental introduction at end of 19th century

River barriers

Acorn dispersal by Jays The more seeds carried, the farther the distance

Neritina dispersal

Dispersal Distance Edge of forest Isolated tree Eucalyptus Longocarpus

Measuring Dispersal Distance Breadth of normal distribution characterized by standard deviation (s) Variance : If mean (release point) is 0, & distance from release site(x i -mean) is d i, then: Distance over time is:

Dispersal vs. range

Birth nest to yearling nesting House wren nesting at distances (1000 ft segments) from nest where hatched

Dispersal for mating Distance from birth site to mating site for the Great Tit

Inbreeding vs. Outbreeding In many bird populations, about 50% of the birds in an area are immigrants. Great Tit study - 22 % of pairings were from resident males & females Inbred nestling mortality = 27.7 % Outbred nestling mortality = 16.2%

Opossum expansion Climate related?

Maple/Hemlock expansion

Large seeds and fruits Long-lived plants Low relative growth rates Strong competitive ability Predator defenses in plants Innate, transient dormancy High decay rates of soil seed populations Flat dispersal curve Stable populations of plants Small seeds Short-lived plants High relative growth rates Weak competitive ability Predator defenses in seeds Enforced dormancy dependent upon burial Low decay rates of soil seed populations Steep dispersal curve Unstable populations of plants Dispersal in SpaceDispersal in Time

Seed Dormancy Innate dormancy - from when seed first produced Induced dormancy - internal, but first induced by environmental factor Enforced dormancy - environmental factors