1 1 population dynamics chapter 10 honeybees pollinate one-third of the fruits, nuts and vegetables...
TRANSCRIPT
11
Population DynamicsChapter 10
Honeybees pollinate one-third of the fruits, nuts and vegetables that end up in our homey kitchen baskets. Fall 2006- the nation’s beekeepers watched in horror as more than a quarter of their 2.4 million colonies collapsed, killing billions of nature’s little fertilizers.
22
Outline
• Dispersal– In Response to Climate Change– In Response to Changing Food Supply– In Rivers and Streams
• Metapopulations• Estimating Patterns of Survival• Survivorship Curves• Age Distribution• Rates of Population Change
– Overlapping Generations
55
Dispersal
• Africanized Honeybees– Honeybees (Apis melifera) evolved in Africa
and Europe and have since differentiated into many locally adapted subspecies.
• Africanized honeybees disperse much faster than European honeybees.
– Within 30 years they occupied most of South America, Mexico, and all of Central America.
88
Collared Doves
• Collared Doves, Streptopelia decaocto, spread from Turkey into Europe after 1900.– Dispersal began suddenly.
• Not influenced by humans.• Took place in small jumps.
– 45 km/yr
Mourning Dove (left) with Eurasian Collared-Dove (right). Photo by Marie Weinstein, Alabaster, AL.
1010
Rapid Changes in Response to Climate Change
• Organisms began to spread northward about 16,000 years ago following retreat of glaciers and warming climate.– Evidence found in preserved pollen in lake
sediments.– Movement rate 100 - 400 m/yr.
1414
Dispersal in Response to Changing Food Supply
• Holling observed numerical responses to increased prey availability.– Increased prey density led to increased
density of predators.• Individuals move into new areas in response to
higher prey densities.
1616
Dispersal in Rivers and Streams
• Stream dwellers have mechanisms to allow them to maintain their stream position.– Streamlined bodies– Bottom-dwelling– Adhesion to surfaces
• Tend to get washed downstream in spates.– Muller hypothesized populations maintained via
dynamic interplay between downstream and upstream dispersal.
• Colonization cycle
2020
Metapopulations
• A metapopulation is made up of a group of subpopulations living on patches of habitat connected by an exchange of individuals.– Alpine Butterfly - Roland et.al.– Lesser Kestrels - Serrano and Tella.
2323
Estimating Patterns of Survival
• Three main methods of estimation:– Cohort life table
• Identify individuals born at same time and keep records from birth.
– Static life table• Record age at death of individuals.
– Age distribution• Calculate difference in proportion of individuals in
each age class.• Assumes differences from mortality.
2424
High Survival Among the Young
• Murie collected Dall Sheep skulls, Ovis dalli.– Major Assumption: Proportion of skulls in
each age class represented typical proportion of individuals dying at that age.
• Reasonable given sample size of 608.
– Constructed survivorship curve.• Discovered bi-modal mortality.
– <1 yr.– 9-13 yrs.
2727
Survivorship Curves
• Type I: Majority of mortality occurs among older individuals. – Dall Sheep
• Type II: Constant rate of survival throughout lifetime.– American Robins
• Type III: High mortality among young, followed by high survivorship.– Sea Turtles
2929
Age Distribution
• Age distribution of a population reflects its history of survival, reproduction, and growth potential.
• Miller published data on age distribution of white oak (Quercus alba).– Determined relationship between age and
trunk diameter.– Age distribution biased towards young trees.
• Sufficient reproduction for replacement.– Stable population
3131
Age Distribution
• Rio Grande Cottonwood populations (Populus deltoides wislizenii) are declining.– Old trees not being replaced.– Reproduction depends on seasonal floods.
• Prepare seed bed.• Keep nursery areas moist.
– Because floods are absent, there are now fewer germination areas.
3333
Dynamic Population in a Variable Climate
• Grant and Grant studied Galapagos Finches.– Drought in 1977 resulted in no recruitment.
• Gap in age distribution.• Additional droughts in 1984 and 1985.• Reproductive output driven by exceptional year in
1983.– Responsiveness of population age structure to environmental
variation.
3737
Rates of Population Change
• Birth Rate: Number of young born per female.
• Fecundity Schedule: Tabulation of birth rates for females of different ages.
3838
Estimating Rates for an Annual Plant• P. drummondii
– Ro = Net reproductive rate; Average number of seeds produced by an individual in a population during its lifetime.
– Ro= Σ lxmx
• X= Age interval in days.
• lx = % pop. surviving to each age (x).
• mx= Average number seeds produced by each individual in each age category.
3939
Estimating Rates for an Annual Plant
• Because P. drummondii has non-overlapping generations, can estimate growth rate.– Geometric Rate of Increase (λ):
• λ=N t+1 / Nt
• N t+1 = Size of population at future time.
• Nt = Size of population at some earlier time.
4040
Estimating Rates when Generations Overlap
• Common Mud Turtle (K. subrubrum)– About half turtles nest each year.– Average generation time:
T = Σ xlxmx / Ro
– X= Age in years – Per Capita Rate of Increase:
r = ln Ro / T
– ln = Base natural logarithms
4141
Review• Dispersal
– In Response to Climate Change– In Response to Changing Food Supply– In Rivers and Streams
• Metapopulations• Estimating Patterns of Survival• Survivorship Curves• Age Distribution• Rates of Population Change
– Overlapping Generations