Conservation Bio Exam 2

Common problems with small populations

Population viability, genetic issues, and Allee effects

Allee effects

a decrease in population growth rate in a small population

Types of Allee Effects

Mate limitation

cooperative defense

cooperative feeding

habitat amelioration

Allee Effects: Mate limitation

mating can be initiated by the size of a group (Passenger pigeon)

r-selected species

species that rely on high growth rate, opportunists, pioneer species

• many offspring

• mature quickly

• inhabit lower trophic levels

• high growth rate

• less parental care

• smaller

• most energy investment in reproduction

K selected species

stronger competitors live near carrying capacity, equilibrium species

MVP

Minimum Viable Population

minimum number of individuals required for a population to remain extant over a period of time

• must define goal % chance of extinction and period of time

• must take randomized variability into account (Stochasticity)

Types of random demographic fluctuations

birth/death rates

immigration/emigration

sex ratio

Random environmental fluctuation

predation

competition

disease

food supply

weather

natural catastrophes

PVA

Population Viability Analysis

computer models to simulate pops

calculates probability of extinction

requires estimate of current pop size, pop trend, and amount of variability

pseudoextinction

assumed doomed at some threshold

5 uses of genetics in conservation and WL management

1. Identifying a species

2. Identifying genetic differences between pops

3. Identification of hybridization

4. Identification of individuals or population origin

5. Working with Genetic problems in small populations

Problems with hybridization

can lose genetic info or be sterile

not as well adapted or can be ultra-competitive

General definition of genetic diversity

variety within a species that is heritable measured by polymorphism and heterozygosity

Importance of genetic diversity

1. species: ability to adapt and evolve to changing world

2. Individual: Health/fitness → avoid inbreeding

results of natural selection

1. individuals vary within a population

2. some variation among individuals can be passed on

3. populations produce more offspring than will survive

4. survival and reproduction aren’t random

adaptations

traits that increase an individual’s fitness in a particular environment

chromosome

section of DNA

Gene

section of DNA that codes for a protein

Allele

variations of a gene (maxes out at 2 for diploids)

locus

specific spot-on chromosome for a gene

genotype

combination of alleles you have

Phenotype

trait expressed from a gene

Heterozygous

2 different alleles

homozygous

2 alleles are the same

dominant

masks expression of the recessive allele

recessive

allele that is typically masked by dominant allele

polymorphism

more than one allele at a gene within a population (leads to heterozygosity)

In humans, a gene is polymorphic if the rarest allele occurs in at least 1% of the population

• 25-30% of human genes are polymorphic

heterozygosity

individual; allele at a given gene is present

3 levels of measured genetic diversity

1. variation within an individual

2. variation among individuals (within a population)

3. variation among populations (species level)

Importance of Individual heterozygosity

inbreeding decreases heterozygosity at individual level and affects health

Hardy Weinberg equilibrium

Predicts heterozygosity if:

• organism is diploid

• organisms sexually reproduce

• mating is random

• population size is large

• no natural selection

• no gene flow

p²+2pq+q²=1

more evenness and alleles increase frequency

If Observed heterozygosity doesn’t equal expected

natural selection could be occurring

gene flow from outside population

small population shifting genetic info (genetic drift)

non-random mating

gene flow

individuals transfer genes from one population to another

inbreeding depression

mating between close relatives which reduces fitness i.e. purebred dogs

generally, due to deleterious alleles that are mostly recessive, so they don’t get weeded out

only expressed with homozygosity

increases probability of homozygosity of rare alleles

2 mechanisms that increase genetic diversity that aren’t natural selection

mutations and gene flow

Founder Effect

alleles in new populations are limited to those of the founding members (reduces genetic diversity)

population bottle neck

population becomes smaller and then recovers with a more limited number of individuals

takes 100+ generations to regenerate diversity at ONE locus

genetic drift

change in allele frequency due to random chance

rarely leads to adaptation in a population

reduces genetic variation

effects are greater in smaller populations

gene flow

migration of individuals from other populations

new alleles introduced

increased genetic variation in population but collectively, all populations become more similar

be careful of outbreeding depression

mutation

creation of new alleles

makes a population more diverse

typically recessive but more common in small populations

cannot rely on mutations to restore genetic diversity

Outbreeding:

breeding between unrelated groups

• unrelated individuals are less likely to have same related deleterious effects

• masks effects

Outbreeding Depression

reductions in fitness of hybrids or outcrossed genotype

genetic swamping of locally adapted alleles (hybrids aren’t well adapted)

breakdown of coadapted gene complexes

mutation rate

very slow (10^-4 10^-6/ locus/ generation)

single species approach

focus on one species at a time

• keystone species

• umbrella species

• flagship species

• indicator species

can protect many species by protecting one species which is easier to monitor

needs of other species are sometimes ignored

popular species are not always the most important

multi-species approach

focus on multiple species at a time

Lambeck’s focal species approach

Research triangle of NC

ecosystem and habitat-based approach

focus on entire ecosystem or habitat and not a specific species

initial approach until 1960s/70s

Used when budgets and information is limited

focus on most threatened habitats depending on how well the ecosystem is represented in protected area network, number of endemic species, cost, and likelihood of success

Primary reasons we should find good conservation methods

1. ecosystem management gets fuzzy with general public

2. species data is easier to collect

3. conservation groups often end up directing efforts to a single species anyway

keystone species

removal would cause damage to the ecosystem, has a large impact and disproportionate effect on its ecosystem (size/activity)

i.e. bison, wolves and otters

Umbrella species

species with demanding habitat and area requirements ensuring their viability will protect the needs of many more. Generally large, wide-ranging predators

examples: grizzly bears in N. America, Tigers in India, Spotted Owls

Flagship Species

human chosen for strategic value, ability to raise public awareness and financial support

Charismatic (really adorable)

examples: koala, panda, polar bear, gorilla and red-eyed tree frog

should be a locally supported species

some ecosystems don’t have a flagship species

Indicator species

represent community composition or will reflect environmental change

examples: brook trout

Lambeck’s Focal Species Approach

identify main threats to an area’s biodiversity and choose species most sensitive to each

Example of Lambeck’s: Research Triangle of NC

region is developing rapidly; colleges developed a list of vulnerable species and ranked each in vulnerability to 4 major population limiting factors

• area: insufficient habitat/components

• dispersal: inability to move between habitats

• Resources: food shortages

• Processes: changes due to development/management of habitat

Chose 4 species that were most vulnerable to all

• bobcat

• River otter

• Eastern box turtle

• Pileated woodpecker