Who wins in the beginning? Secondary succession space, light, and nutrients are abundantspace, light, and nutrients are abundant classic r-selected species (opportunists)classic r-selected species (opportunists) Primary succession space and light are abundantspace and light are abundant nutrients may not benutrients may not be N-fixing plants are commonN-fixing plants are common convert atmospheric N 2 into NH 4 +convert atmospheric N 2 into NH 4 +

Who wins at the end? Early succession species are eventually replaced by more competitive late succession species Early succession species are eventually replaced by more competitive late succession species Late succession species get established in niches that early succession species can’t use Late succession species get established in niches that early succession species can’t use

How does succession happen? Facilitation early succession species alter conditions to favor the growth of late succession speciesearly succession species alter conditions to favor the growth of late succession species N-fixers make soil richerN-fixers make soil richer dune grass stabilizes sanddune grass stabilizes sandAcceleration late succession species alter conditions to favor their own growth and prevent the growth of early succession specieslate succession species alter conditions to favor their own growth and prevent the growth of early succession species some plants produce toxic littersome plants produce toxic litter

Succession, Disturbance, and Diversity Succession occurs after disturbance Succession occurs after disturbance Over time, many different species live in one area Over time, many different species live in one area Patchy disturbance leads to a “quilt” of different communities across the landscape Patchy disturbance leads to a “quilt” of different communities across the landscape Disturbance increases diversity!

An ecosystem experiencing succession becomes more complex over time An ecosystem experiencing succession becomes more complex over time more niches are filled more niches are filled greater total number of species greater total number of species Disturbance interrupts this process Disturbance interrupts this process Disturbance decreases diversity! Succession, Disturbance, and Diversity

What is the relationship between disturbance and diversity? Disturbance frequency or intensity Diversity

What is the relationship between disturbance and diversity? Disturbance frequency or intensity Diversity a b c

Announcements The invasive species writing assignment is due in lecture on Wednesday, Nov. 10 th The invasive species writing assignment is due in lecture on Wednesday, Nov. 10 th

Summary from Monday Success of different species under: Success of different species under: primary successionprimary succession secondary successionsecondary succession Mechanisms of succession Mechanisms of succession facilitationfacilitation accelerationacceleration Succession, disturbance, and diversity Succession, disturbance, and diversity Intermediate Disturbance HypothesisIntermediate Disturbance Hypothesis

Populations across the landscape Metapopulation: sum of multiple interacting sub-populations sub-population A sub-population B sub-population D sub-population C

Populations across the landscape Genetic diversity is maintained by exchange of genes between the sub-populations sub-population A sub-population B sub-population D sub-population C

Populations across the landscape Most mating occurs within a sub-population sub-population A sub-population B sub-population D sub-population C

Populations across the landscape Some habitat patches are better than others hot and dry most ideal many predators few nesting sites

Populations across the landscape Sub-populations can be source populations or sink populations hot and dry many predators few nesting sites most ideal source sink

Populations across the landscape In source population habitats: living conditions are good, so births meet or exceed deaths living conditions are good, so births meet or exceed deaths competition may be great, forcing some members out competition may be great, forcing some members out hot and dry many predators few nesting sites most ideal source sink

Populations across the landscape locally extinct source of recruits source sink If a sub-population goes extinct, it can be revived by recruits from another sub-population

Population Maintenance Important to preserve both source and sink habitats Important to preserve both source and sink habitats Just because animals are found somewhere doesn’t mean they can reproduce there Just because animals are found somewhere doesn’t mean they can reproduce there

Metapopulations over time How many species will be found in a certain area? Change in # of species over time = Immigration – Local extinction Change in # of species over time = Speciation + Immigration – Extinction On an ecological time scale: On a geological/evolutionary time scale:

Controls on immigration Distance to source population mainland Lots of immigration Little immigration

Controls on immigration Distance to source population mainland Lots of immigration Little immigration Obstacles Mountains Mountains Waterways Waterways mountains hills

How do non-native species arrive? AccidentallyAccidentally seedsseeds parasitesparasites unintended cargounintended cargo DeliberatelyDeliberately foodfood timbertimber biocontrolbiocontrol

Why study invasive species? After habitat loss and fragmentation, the third greatest threat to conservation is invasionAfter habitat loss and fragmentation, the third greatest threat to conservation is invasion economic consequenceseconomic consequences human health consequenceshuman health consequences

Invasive Species Glossary native: an organism that is living in its home environment native: an organism that is living in its home environment exotic exotic non-native originally from a different location non-native originally from a different location foreign/alien foreign/alien naturalized: a non-native that has become a part of its new environment naturalized: a non-native that has become a part of its new environment invasive: a non-native that has spread to become a dominant member of its new environment invasive: a non-native that has spread to become a dominant member of its new environment noxious weed: an invasive species of plant that causes environmental or economic problems noxious weed: an invasive species of plant that causes environmental or economic problems

How many invaders are successful? PlantsPlants 10% of introduced species will naturalize10% of introduced species will naturalize 10% of naturalized species will become weeds10% of naturalized species will become weeds 10% of weeds will become major problems10% of weeds will become major problems AnimalsAnimals How would the proportions be different?How would the proportions be different?

What makes an invader successful? r-strategists r-strategists grow quicklygrow quickly produce many offspringproduce many offspring short generation timeshort generation time good dispersion good dispersion generalists: highly adaptable to new conditions generalists: highly adaptable to new conditions broad geographic range in native environment broad geographic range in native environment broad diet broad diet

What makes a community vulnerable to invasion? human disturbance human disturbance early succession early succession climate similar to native habitat climate similar to native habitat absence of predators or pathogens absence of predators or pathogens wrong ones for the invaderwrong ones for the invader no predators or pathogens at all - islandsno predators or pathogens at all - islands

What do invasive plants do? Change ecosystem structure fire suppression fire suppression grassland  shrublandgrassland  shrubland grow faster than competing species grow faster than competing species woodland  kudzu-dominated landwoodland  kudzu-dominated land use up limiting resources, such as water use up limiting resources, such as water riparian zone  desertriparian zone  desert

What do invasive animals do? *Humans are the most invasive animal* Change foodweb structure hyperpredation hyperpredation drive out native competitors drive out native competitors

A case study: kudzu originally from China and Japan originally from China and Japan introduced to Florida in 1876 as forage introduced to Florida in 1876 as forage grows over everything! grows over everything! competes for light competes for light

A case study: zebra mussels native to Russian lakes native to Russian lakes introduced to North America in 1985 from bilge of a ship introduced to North America in 1985 from bilge of a ship after <1 year, can produce 1,000,000 eggs after <1 year, can produce 1,000,000 eggs large colonies clog pipes large colonies clog pipes very efficient filterers very efficient filterers clear waterclear water eliminate native specieseliminate native species

Zebra mussel range map