Quantifying relative effects of Quantifying relative effects of - - PDF document

Quantifying relative effects of protecting different stages

ELASTICITY = proportional change in as a results

• f proportional change in a particular stage (ri). It is a

proportional measure of sensitivity to change.

Eri =

λnew−λoriginal λoriginal ri,new−ri,original ri,original

Quantifying relative effects of protecting different stages

ELASTICITY = proportional change in as a results

• f proportional change in a particular stage (ri).

Eri =

λnew−λoriginal λoriginal ri,new−ri,original ri,original

=

∆λ λoriginal ∆ri ri,original

Size this year 1 2 3 4 5 1 2 3 4 5 Size next year

      4.665 61.896 0.675 0.703 0.047 0.657 0.019 0.682 0.061 0.8091      

1.00

Elasticity

0.675 NEW OLD

EG1 =

0.023 0.952 1−0.675 0.675

= 0.049

Size this year 1 2 3 4 5 1 2 3 4 5 Size next year

      4.665 61.896 0.675 0.703 0.047 0.657 0.019 0.682 0.061 0.8091      

0.812

Elasticity

0.657 NEW OLD

ES3 =

0.041 0.952 0.821−0.657 0.657

= 0.171

Effect of management

Improvement Elasticity Effect Hatchling survival 0.05 small Large juvenile survival (stay in stage class) 0.17 large Large juvenile survival (grow to subadults) 0.05 small

Conservation outcome of this PVA

1987 TED required offshore May-August 1988-89 Court challenges, delay 1990 TEDs implemented seasonally 1993 Year-round TEDs offshore 1994 Year-round TEDs offshore and inshore

Assumptions of structured PVA

(as discussed)

All individuals in a stage class are the same No density dependence does not change Only one population

Density dependent survival Density dependent fecundity Density and growth rate

Nt = λNt−1

Time Number of individuals

Density and Growth

Density with independent discrete growth Independent continuous growth

Nt = λNt−1 dN dt = rN

Density and Growth

Density with independent discrete growth Independent continuous growth Density-dependent continuous growth

Nt = λNt−1 dN dt = rN dN dt = rN(1 − N K )

Carrying capacity K

Carrying capacity K is the maximum stable population size

dN dt = rN(1 − N K )

Density and carrying capacity

20 40 60 80 100 20 40 60 80 100

Time Population size Carrying capacity K

Assumptions and remedies for PVAs

Individuals are not the same !"use structured model No density dependence !"add density dependence never change !"add stochasticity to model Only one population !"use meta-population model Stochasticity will add variability, for example environmental variability induces changes in vital rates

Invasive species

Basics Predicting invasions Managing invasions

Invasive species

Basics How big is the problem? Definitions How do invasives move/spread? Effects of invasives Predicting invasions Managing invasions

How big is the problem?

Second largest cause of extinction: 4500 exotic species in the USA (exotic=non-native) [OTA 1993] More than 25% of all plants in Florida are non-native

A few exotics in Florida

Hydrilla (Hydrilla verticillata), from Sri Lanka Water hyacinth (Eichhornia crassipes) Australian paperbark tree (Melaleuca quinqueneria) Brazilian pepper (Shinus terebinthifolius) Chinese tallow (Sapium sebiferum)

Hydrilla Water hyacinth Brazilian pepper tree Paper bark tree Chinese tallow

Definitions

Introduced (exotic) species = a species living outside its native range Invasive species = introduced species with dramatically expanding populations

How invasives move/spread

Stow-aways

How invasives move/spread

Stow-aways Commerce/Curiosity

Gypsy moth

introduced 1868/1869 Rana ridibunda (lake frogs) were accidentally introduced at several places in Switzerland and France

Specialty food Academic education

How invasives move/spread

Stow-aways Commerce/Curiosity Recreation Excerpts from a website about the Smoky Mountains National Park: The wild hog, Sus scrofa, is native to Europe, Asia, Northern Africa, Japan, and the Malayan Islands. In 1912, a shipment of European wild boar from Poland or Germany was transported to a private game preserve on Hoopers Bald in western North

• Carolina. Hoopers Bald is only 15 miles

southwest of the park boundary in what is now the Nantahala National Forest.

How invasives move/spread

Stow-aways Commerce/Curiosity Recreation Aesthetics

European Starling

The European starling was first introduced to the United States in New York City, in 1890. Inspired by William Shakespeare's plays, Eugene Scheffland let loose one hundred starlings in Central Park.