11 Population Dynamics Chapter 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

22 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.

33 Africanized Honeybees =e7fUXw-5T2Q

44 Collared Doves

55 Rapid Changes in Response to…

66 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 m/yr.

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88 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.

99 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

10 Dispersal in Rivers and Streams

11 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.

12 Patterns of Survival Three main methods of estimation: – Identify individuals born at same time and keep records from birth. – Record age at death of individuals. – Calculate difference in proportion of individuals in each age class. Assumes differences from mortality.

13 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 _________________________. Discovered bi-modal mortality. – <1 yr. – 9-13 yrs.

14 Survivorship Curves : Majority of mortality occurs among older individuals. – Dall Sheep : Constant rate of survival throughout lifetime. – American Robins : High mortality among young, followed by high survivorship. – Sea Turtles

15 Survivorship Curves

16 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

17 Age Distribution

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19 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.

20 Rates of Population Change : Number of young born per female. : Tabulation of birth rates for females of different ages.

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22 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 Reproductive output driven by exceptional year in – Responsiveness of population age structure to environmental variation.

23 Estimating Rates for an Annual Plant P. drummondii – R o = Net reproductive rate; Average number of seeds produced by an individual in a population during its lifetime. – R o = Σ l x m x X= Age interval in days. l x = % pop. surviving to each age (x). m x = Average number seeds produced by each individual in each age category.

24 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 / N t N t+1 = Size of population at future time. N t = Size of population at some earlier time.

25 Estimating Rates when Generations Overlap Common Mud Turtle (K. subrubrum) – About half turtles nest each year. – Average generation time: T = Σ xl x m x / R o – X= Age in years – Per Capita Rate of Increase: r = ln R o / T – ln = Base natural logarithms

26 Collared Doves Collared Doves, Streptopelia decaocto, spread from Turkey into Europe after – Dispersal began suddenly. Not influenced by humans. Took place in small jumps. – 45 km/yr