Finish Population Dynamics (Ch. 10)

Fecundity Schedule for Phlox drummondii Age (days) nxnx lxlx m x l x m x xl x m x m x = Age-specific fecundity: Average number seeds produced by individual in age category. n x = number survivorsl x = survivorship

Fecundity Schedule for Phlox drummondii Age (days) nxnx lxlx m x l x m x xl x m x m x = Age-specific fecundity: Average number seeds produced by individual in age category. i.e. plants 300 days old produce on average seeds

Fecundity Schedule for Phlox drummondii Age (days) nxnx lxlx m x l x m x xl x m x R o =  l x m x x = age interval l x = proportion pop. surviving to age x m x = Age-specific fecundity: Average number seeds produced by individual in age category. Sum these!

Annual Plant Phlox drummondii (hermaphrodite) –R o = Net reproductive rate; Average number seeds produced by individual during life –If > 1, population increasing –If = 1, population stable –If < 1, population declining

Annual Plant Is pop. stable, increasing, decreasing?

Annual Plant Non-overlapping generations: can estimate growth rate (per unit time). Geometric Rate of Increase, lambda ( ):

Annual Plant Non-overlapping generations: can estimate growth rate. Geometric Rate of Increase, lambda ( ): – = N t+1 / N t –N t+1 = Size population future time –N t = Size population earlier time

Annual Plant Geometric Rate of Increase, lambda ( ): –Start 996 plants: seeds/individual (Table 10.1) –996 x = 2,408 seeds start next year – = N t+1 / N t – = 2,408 / 996 – = 2.41 – = R o for annual plant (generations do not overlap & reproduction not continuous)

Estimating Rates when Generations Overlap Who am I? Hermaphrodite?

Estimating Rates when Generations Overlap Common Mud Turtle (Kinosternon subrubrum) Data: –survivorship in age class (years) –reproductive info for each age class

How can a turtle reproduce? Need Females! Population mix males & females Not all reproduce Clutch Size: # eggs laid by female/nest How many nests/year (or time period)? m x = (% fem) x (% reproducing) x (clutch size) x (# nests)

Table 10.2 –Trick: Pop. has males & females, so calculate production females by females

Sum col. 4 in Table 10.2 (l x m x ), R 0 = Stable, increasing, decreasing?

Other population parameters Common Mud Turtle –Average generation time (T): Average time from egg to egg between generations

Fecundity Schedule for Kinosternon subrubrum Age (yrs) nxnx lxlx m x l x m x xl x m x = 1 x = 2 x T=  xl x m x /R o x = age interval l x = proportion pop. surviving to age x m x = Age-specific fecundity: Average number eggs/seeds produced by individual in age category. Sum these!

Table 10.2: T = 6.4 / = 10.6 years T =  xl x m x / R o

Other population parameters Common Mud Turtle Per Capita Rate of Increase (r) r = rate population change per individual per unit time r = (ln R o ) / T –ln = natural log Also: r is births per individual per unit time (b) minus deaths per individual per unit time (d) r = b - d

Estimating Rates when Generations Overlap Common Mud Turtle r = (ln R o ) / T r = ln (0.601) / 10.6 r = –rate population change per individual per unit time If r > 0, population increasing If r = 0, population stable If r < 0, population declining Makes sense: r = b - d

Organism Size and Population Density A search for patterns………….(recall size vs. density) body size population density (log) hi lo

Organism Size and Population Density A search for patterns………….(recall size vs. density) Generation time vs. size? –Also log-log scale Gen time (T) Size

Generation time vs. size Positive slope Log-log scale

Use of population dynamics info Control invasive species (who am I?) 2008 map

Use of population dynamics info Prevent extinction rare species (who are we?) 200 or fewer individuals in wild

Use of population dynamics info Managing harvested species Ex, orange roughy Slimehead family! New Zealand Fishery areas

Use of population dynamics info Long lived (150 years) –Breed when yr old Harvest only large fish (allow some to breed)?

Population Density Immigration Emigration

Dispersal Important to population dynamics Immigration: add individuals Emigration: lose individuals

Dispersal Hard to study: 1) tracking movements adults 2) dispersal phase may be small wolf Bee!

Dispersal Africanized Honeybees –Killer bees...

Dispersal Africanized Honeybees –Honeybees (Apis mellifera) subspecies Africanized disperse faster than European honeybees.

Dispersal Africanized Honeybees

They are Here!! First in Mobile AL, Aug 2004! 28 US fatalities 2010 near Albany GA Aug 2004, first

Most species don’t disperse fast....

When Do Organisms Disperse? Eggs/ Sperm/ Seed (e.g. pollen, soft corals, burrs) Larvae/Juveniles (e.g. Corals, Fish, spiders) Adults (e.g. Cats, Butterflies, birds) Immobile adults must disperse as Juveniles, Zygotes or Gametes!

Dispersal & Climate Change Organisms spread northward 16,000 years ago (retreat of glaciers) –Evidence: preserved pollen in sediments.

Changes in Response to Climate Change –Tree species: Movement slow m/yr. Fig. 10.6

–Climate envelope: area with appropriate climate conditions American Pika (Ochotona princeps)

Climate Change –Climate envelope: area with appropriate climate conditions –Will envelopes move too fast? –Assisted migration: human help to prevent extinctions Torreya taxifolia

Dispersal in Response to Changing Food Supply Holling: numerical responses to increased prey –Increased prey density led to increased predator density This figure from Ch. 7 showed functional responses

Dispersal in Response to Changing Food Supply Numerical response: dispersal + increased reproduction Vole Kestrel Owl

Dispersal in Response to Changing Food Supply Predators moved to areas of more dense prey Fig. 10.7

Dispersal in Rivers and Streams

Current (flow of water) causes drift (movement downstream) Adaptations to maintain position: –1) Streamlined bodies/strong swimmers Jumping salmon

Dispersal in Rivers and Streams Adaptations to maintain position: –2) Bottom-dwelling: avoid current –3) Adhesion: hang on! Alabama hogsucker Etowah darter

Dispersal in Rivers and Streams Still get washed downstream in flash floods (spates). James River VA, 1985

Dispersal in Rivers and Streams Colonization cycle: interplay downstream & upstream dispersal

Dispersal in Rivers and Streams Cool story: Costa Rican river snail moves upstream in migratory wave (to 1/2 million snails!)