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Lecture 18, 22 Oct 2009PVA, Populations, Protection

Conservation BiologyECOL 406R/506R

University of ArizonaFall 2009

Kevin BonineMary Jane Epps

Lab Friday 23 October BICYCLE (1pm northwest corner BSE)

506 meet in BSE1299am Wed (04 Nov)

Krista C.

ReadingsPrimack parts of Ch 5 & 6Marmontel et al. 1997 (PVA Manatee)Gilpin 1996 (PVA commentary)

Lab Thanks- Don Swann - Cascabel Crew

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Q5 Genetic tools have made it much easier to ask questions about gene flow among and between populations and even among and between species. Please find a case study from the literature that illustrates a different understanding of movement of individuals among and between populations as a result of application of genetic tools as compared to biologists’understanding before the use of modern molecular techniques. Describe the differences in understanding pre and post molecular techniques and comment on the pros and cons of our increased understanding of population ecology (in the context of conservation biology) from using these techniques. (Due by 6am Monday 02 November as .DOC attachment to MJ (mycota@gmail.com) via email.)

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men women

Social Justice?Environmental Justice?

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Populations &

PVA (population viability analysis)

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1. Exponential growthdensity-independent, deterministic

In a closed population (no immigration or emigration),population growth is a function of birth and death rates dN

dtRing-necked pheasant

on Protection Island

= (b-d)N

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dNdt

= rN K-NK( ) intraspecific competition

stabilizes population sizebirth rates go down and/or death rates go up with increasing population size

2. Logistic growthdensity-dependent, deterministic

carryingcapacity (K)

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The two categories of models we have considered thus far assume that

- all individuals in a population have thesame birth and death rates

(no genetic, developmental, or physiological differences among individuals)

under some circumstances, this might cause us to inaccurately predictpopulation size

What would Darwin & Wallace say?

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This is the type of model most often used in population viability analysis

What is meant by “structure”?A population is unstructured if all individuals have the same rates of survival and fertility.

A population is structured if differences among individuals in age, developmental stage, or size cause them to have different survival or fertility rates.

3. Structured population modelsdensity-independent, deterministic

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Life Table, Demography

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Life Table

n = numberd = number dying in intervall = proportion of original cohort aliveq = mortality rate during intervale = life expectancy of indivs in interval

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3. Density-independent, deterministic, structured population growth

What else can structured population models tell us?Sensitivity

The sensitivity of to each matrix element describes how much will be affected by a change in that transition probability

Would it be better to focus conservation efforts on improving the survival of hatchlings or large juveniles or adults???

(Lambda = population growth rate)

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When lambda is greater than 1 the population increases in size

When lambda is less than 1 the population decreases in size

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Millenium Ecosystem Assessment 8-35% species extinct by 2050 depending on biome and geography(= more than 35 species/day!)

Primack Ch 5, Extinctions

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Van Dyke p. 178

“Four Horsemen of the Extinction Apocalypse:”

1. Genetic Stochasticity

2. Environmental Stochasticity

3. Demographic Stochasticity

4. Natural Catastrophes

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Small Populations-reduced gene flow-inbreeding depression-drift-stochasticity-effective population size (Ne)

(Vs. Declining Populations)

Genetic Diversityand

Population Size

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Effective Population Size

Ne averages 11% of N

-Variation in reproductive contribution-Unequal sex ratio-Population fluctuations & Bottlenecks

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Effective Population Size(unequal Sex Ratio example)

• Ne = 4NmNf / (Nm+Nf)

• Eg: a population of seals with 6 males and 150 females?

• Ne = (4*6*150)/(6+150) = ~23

(Number vs. Breeders)

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Van Dyke 2003

Inbreeding Coefficient, F(2 alleles identical by descent)

1% Rule (Frankel and Soule)Natural selection for survival and reproduction can balance inbreeding depression if the change in inbreeding coefficient is no more than 1%/generation.

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Quickly lose rare alleles in bottlenecks

Cheetah Major Histocompatibility

Complex

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What is the founder effect?Implications for adaptability?

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Genetic Drift

When populations number less than a few hundred individuals random events become more important to genetic structure of population

than natural selection

3,000-10,000 breeding adults?

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Cyprinodon maculariusDesert Pupfish

Photograph Courtesy of John Rinne

Desert pupfish declined due to the introduction and spread of exotic predatory and competitive fishes, water impoundment and diversion, water pollution, groundwater pumping, stream channelization, and habitat modification.

Healthy population of almost 10,000 fish inhabits this oasis. This last refuge of a unique fish is being actively managed.

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Population Extinction Vortex(problems with small populations)

F Vortex: inbreeding depression, lethal equivalents(homozygous recessives)

A Vortex: genetic drift and loss of variation(can’t adapt)

R Vortex: r = spontaneous rate of increase(coupled with environmental stochasticity)

D Vortex: discontinuity (isolation)

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F

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Hardy Weinbergand Heterozygosity

two alleles: p, q

(p + q)2 = p2 +2pq + q2

Under Hardy Weinberg EquilibriumHe = 2pq

Ho can be calculated

If p=0.6, q=0.4, then 2pq = 0.48 = He

Inbreeding, if Ho < He

Outbreeding, if Ho> He

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Equilibrium Heterozygosity (ΔH = 0)

H* = 2Nm

H = heterozygosityN = population sizem = mutation rate

Therefore, smaller populations have lower equilibrium heterozygosity

Assumption: reduced genetic variation in a population correlated

with reduced ability to adapt to changing environmental conditions.

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Minimum Viable Population (MVP)(Frankel, Soule, Franklin, Shaffer)

50/500/+ Rule

Short term

Mid term

Long Term

PVA…

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Population Viability Analysis

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PVA Florida ManateeMarmontel et al. 1997

44% likelihood persist 1000 years

10% increase in mortality OR10% decrease in birth rate

10% decrease in mortality = lambda >1

= lambda <1

Boat-Manatee Collisions!

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How to drive manatees extinct.