BIOL 370 Part II Flashcards
percent of population persisting vs time
-populations less than 100 have low probability of persisting >50 years
negative density dependence
- population growth is negatively effected by its density
- examples: crowding, predators and competition
sources of variation in population growth
- environmental stochasticity
- demographic stochasticity
stochasticity
- model in which parameters vary unpredictably with time
- random, chance events in nature
environmental stochasticity
- unpredictable environmental changes
- NOT: predictable ∆ like seasons; env’t trends
geometric mean
(π λ_i) ^ 1/n
incorporating stochasticity into population growth model implication
- makes pop growth slower than expected form constant growth
- variance in N_t increases w/ time
- variance in N_t proportional to both mean, variance of r
Extinction from environmental stochasticity likely if
var(r) >2r
var(r) is greater than 2r
what does a per capita birth rate of 0.2 mean
- for every z individuals we expect 0.2z new offspring in a year
- eg. 20 in a pop of 100
P_birth
= b/(b+d)
populations with high b and d
much higher demographic stochasticity than ones w/ low rates, even for same r
what changes in demographic stochasticity
only b and d, r stays same
P_death
= d/ (b+d)
P_extinction
= (d/b)^No
density dependence
birth and death rates are affected by density
the simplest model of density dependence
logistic growth
logistic growth assumptions
- linear density dependence in vital rates (b, d)
- decline in per-capita growth as density increases (negative dd)
exponential growth
dn/dt = rN_t
intrinsic rate of population increase r
r = per capita births b’ - per capita deaths d’
exponential growth with intrinsic pop growth
dN/dt = (b’-d’)N_t
exponential vs logistic growth, N vs t
exp: exponentially increasing
log: S-shape, increase to asymptote
exponential vs. logistic, dN/Ndt vs N
exp: linear (flat)
log: linear decreasing
logistic growth
dN/dt = rN_t (1 - (N_t / K)
theta logistic population growth
dN/dt = rN(1-(N/K) ^ θ)
θ = 1
- linear effects of density on pop growth rate
- logistic growth
θ > 1
- convex relationship
- density dependence stronger at high density
deterministic factors
- intrinsic (eg. density dependence)
- extrinsic (eg. seasonal ∆ in envt, long-term trends, species interaction)
sample variance
- sampling error
- adds undesired variability in pop. growth beyond true variation
recovery plans and population size
less than 50% of record plans include estimate of current pop size, N
why estimating population size is challenging
- expensive
- time consuming
- biological challenges
biological challenges to estimating pop size
- detectability
- mobility
- wide ranges
- non-uniform distribution
managing fisheries is like
managing a forest of invisible trees that move around
θ less than 1
- concave relationship
- density dependence stronger at low density
all animals are counted
census
-perfect detectability
number of individuals
abundance
abundance estimate
actual estimate, often accounting for detectability
index
some measure assumed to be proportional to abundance or density (relative abundance)
random sampling
- unbiased
- representative
- can be inaccessible
abundance per unit area
density
common wildlife abundance indices
- track count
- scat
- vocalizations
- # captured/observed per day
difficulties with abundance indices
- only reliable if standardized and w/o confounding variables
- index changes: temporal, spatial, technological, observer
abundance indices temporal changes
-diurnal vs nocturnal
-seasonal
temporal ∆ doesn’t necessarily mean a pop. ∆
abundance indices spatial changes
- schooling
- depth
- range contraction
estimating abundance w/ detectability
^N= c/ ^p c = observed count ^p = estimated detectability
common abundance estimation techniques
- distance sampling
- double sampling
- multiple observers
- mark-recapture
Lincoln-Peterson
mark-recapture methods N = ms/r m = number marked r = # w/ markings on 2nd sampling s = total # captured on 2nd sampling
marking individuals
radio telemetry, PIT tag, banding, elastomer, photography, genotyping
capturing individuals
physical or non-invasive (genetic hair/scat, photography)
Lincoln-Peterson assumptions
- closed population
- all individuals have equal opportunity of being caught
- no effect of marking on recapture or survival
- complete mixing of marked/unmarked
- marks not lost
sources of variation in population abundance estimates
- deterministic factors
- process error
- observation/ measurement error
process error
stochasticity
sensitivity
how much lambda changes/ change in given vital rate; absolute change
problem w/ sensitivity
survival and fecundity are on different scales
elasticity
proportional λ∆ in a given vital rate
-how a small, proportional change in rate will affect overall pop growth
sensitivity and elasticity, importance of survival
- survival more important than fecundity
- survival relatively more important in longer-lived organisms
adult survival in long-lived organisms
- highest elasticity
- lowest variability
relative strength of forces driving African cheetah population
inside protected areas:
- lower cub survival due to lion, hyena
- higher adult survival less human conflict
- adult survival key for pop. growth
a large increase in a vital rate (eg. 10%) with low elasticity
can outweigh a small change in a vital rate w/ high elasticity
viability
probability of extinction
PVA
population viability analysis
population viability analysis
quantitative assessment of probability a pop. will become extinct or quasi-extinct w/i specified time frame
Types of PVA
- count-based
- demographic
- metapopulatin
- spatially-explicit (powerful, but dada hungry)
- individual-based (computationally intensive)
count-based PVA
- unstructured population
- uses time-series of abundance or density
demographic PVA
- structure population
- uses matrix-models, sensitivity analysis, etc.
quasi-extinction
or pseudo-extinction
- easier to estimate than extinction probability
- chance that pop. will hit some critical minimum threshold
- can be used to reflect management options
example of quasi-extinction use
-species are listed on SARA if pop. drops below threshold of 50 individuals
PVA goals
- Assess extinction risk (probabilities of single pop., relative risk of multiple pops.)
- guide management (ID key life stages as management target)
PVA tools
population models
simplicity vs realism trade-off
simplicity: low data demand, few assumptions, broadly applicable, unrealistic, limited biological insight
realism: high data, many assump., narrowly applicable, realistic, biologically detailed
what can we learn from Number of individuals (N_t) vs time (t), simple unstructured PVA
- range of values pop. is likely to take
- estimated probability of extinction (or pseudo-extinction)
usefulness of PVAs dependent on
- data quality
- assumption that future pop. dynamics will be similar to present
Demographic PVA
- incorporates age/stage structure and age/stage specific vital rates
- may also include: sex-specific rate, variance/covariance in vital rate, dd, inbreeding depression, allee effects, env’t/demo stochasticity, animal behaviour
Key PVA points
- remain aware of data quantity, quality
- always show CIs around variability estimate
- view viability metrics as relative not absolute
- shorter predictions more realistic
- keep simple, but be aware of what is left out
- consider multiple models
- consider PVAs as work in progress
PVA simple model example
breeding pairs owls vs year
-count individuals over time
-estimate trend
project forward
PVA demographic structure example
- add life stages: fledgling, juvenile, sub-adult, adult
- add competition from other species, barred owl
- spatial structure: potentially suitable owl habitat
Sumatran orangutan demographic PVA
-add year-to-year stochasticity, rare catastrophic events
what can be learned from orangutan PVA
- complexity can always be added (dd, competition, allee, spatial complexity)
- if there are data it can be modelled
questions to ask about habitat fragmentation
- how many protected areas
- what configuration
- how big should each be
- what shape should each be
landscape ecology
-study of how spatial patterning of landscapes affects behaviour, populations, diversity of organisms, as well as the functioning of ecosystems
IBT equilibrium theory
equilibrium where colonization = extinction
which type of islands will have greatest equilibrium number of species under IBT
large, near source population
why IBT is important for designing protected areas
-extinction rate increases for small fragments isolated from source pop.
faunal relaxation
reduction in diversity following a reduction in habitat area or creation of habitat island within formerly continuous habitat
faunal relaxation in national parks
extinctions after park establishment vs area of park
- larger parks = less extinctions
- most parks are not large enough to support MVP
SLOSS
- single large or several small
- depends on overlap
nested diversity
-collection of species found in a given small area overlaps extensively w/ other areas and large areas contain these species plus more
edge effects
- more light, wind
- could result in dessication
habitat lost to edge effect, shape and size
- too small and all of core habitat is lost
- shapes that maximize SA:V minimize core habitat, i.e. long slender rectangle
metapopulation
- set of spatially isolated pop.’s of same species that interact on some level
- small subpops w/i fragments
- prone to local extinction
- connected by dispersal
metapopulation regional persistence
extinctions must be balanced by colonizations
Theoretical spatial ecology
- homogenous space
- focus on population dynamics
metapopulation spatial ecology
- habitat is suitable on a patch basis
- consider only patch sub populations
landscape spatial ecology
- landscapes is a complex mosaic varying in suitability, area, isolation, shape
- less emphasis on modelling pop dynamics
example of meta population with regional persistence
- Glanville fritillary, butterfly
- small populations of specialists
- high local extinction and colonization
habitat suitability
- not all patches are equal
- source-sink metapopulations
source-sink metapopulations
maintained only by dispersal from elsewhere
turnover of patch occupancy
- some habitat patches newly colonized, some extinctions, emmigration, immigration
- fraction colonized changing
key metapopulation concepts
- unoccupied, suitable habitat can be very important
- reduced dispersal success can result in extinction
- critical threshold for habitat destruction
- patch arrangement and connectivity just as important as absolute #
- local events depend on regional context
critical threshold for habitat destruction
-metapop can become extinct long before all habitat patches are destroyed
aiding patch colonization
dispersal corridors
eg. wildlife overpass
corridor experiment results
corridor increased SR in native species but not exotics
potential problems with corridors
- straight edge effect (long thin rectangle)
- increased exposure, predation
SLOSS Hawaii, Galapagos
- rank islands from smallest-largest and largest-smallest
- plot cumulative species vs. cumulative area
- find more species for less area in both s-l lines
- lots of small patches probably better
conservation genetics can
- ID unique evolutionary lineages
- monitor dispersal, movements
- estimate pop. size
- trace genetic changes through t
evolutionary change in population is a function of
amount of genetic diversity available
genetic issues in conservational biology
- deleterious effects of inbreeding
- loss of genetic div. and ability to evolve
- fragmentation, reduction in gene flow
- genetic drift overriding natural selection
- accumulation of deleterious mutations
- adaptation to captivity
- resolving taxonomic uncertainties
- defining management issues
- outbreeding depression
problems with genetic adaptation to captavity
adverse effects on reintroduction success
primary level of biodiversity
diversity measured at the level of genes, or quantitative genetic traits
reduced genetic diversity causes
lower ability to withstand extremes
genetic variation depends on
- the species/population
- genome/ chrmosome region
- part of the gene
- whether sequence/ nucleotide codes for anything
Theodosius Dobzhansky
Nothing in biology makes sense except in the light of evolution
adaptive radiation
- morphological and genetic diversity from founder species (ancestor)
- diversification of a group of organisms into forms filling different ecological niches
types of genetic markers
- allozymes
- microsatellite DNA
- single nucleotide polymorphisms
- direct DNA sequencing
allonymes
- protein variants
- grind up organism, liberate DNA, gel electrophoresis, compare protein differences
- indirect way of looking at DNA changes w/o examining DNA
microsatellite DNA
- genetic variants in a section of b.p.’s
- short repeated sequences = microsatellite
- examine size of microsatellite w/ PCR
single nucleotide polymorphisms
- SNPs
- single bp change
- many thousands per individual
- used for individual-tailored medical treatments
DNA sequencing improvements
- large scale high throughput
- lower cost/b.p.
- lower cost/genome
- single molecule sequencing
- portable sequencer
cost of getting genome sequenced
ca. $1000 US
Hardy-Weinberg assumptions
- diploid organism
- sexual reproduction
- nonoverlapping generations
- identical allele frequencies in both sexes
- random mating
- large pop
- no migration, mutation, selection
frequency of heterozygotes
2pq
frequency of homozygotes
q^2
or
p^2
frequency of heterozygotes maximum when
p = q = 1/2
forces that effect allele frequencies
- migration
- mutation
- drift
- selection
raw material of diversity and evolution
mutations
vast majority of mutations
deleterious
germ cell vs somatic cell
- gametes arise from germ cells
- somatic cells are all other cells besides reproductive
polymorphism rate
- much lower in nature than we expect
- mutations are rare
fate of a mutation
- die out or persist, quickly or slowly
- depends on factors that enhance or downgrade mutation effect (drift, mutation, selection, etc)
- depends on effect on fitness, genome neighbours
natural selection requirements
- must be phenotypic variation in pop.
- variation must result in fitness differences
- variation must be heritable
types of selection
purifying selection
positive selection - directional, balancing
purifying selection
removes deleterious mutations
random genetic drift
- chance/ random event allele frequency fluctuation
- drift direction unpredictable (especially in small pop.)
- reduces variation w/i pop.
- causes populations to diverge from one another
how does random genetic drift reduce population variability
- causes lost off alleles
- increase homozygosity
- decreases heterozygosity
random genetic drift example
x # marbles in a jar
- some fraction passed on at random
- unique combinations for each sample repitition
- smaller sample = higher chance of misrepresenting true pop.
favours beneficial mutations
positive selection
fixation of a beneficial mutation
directional selection
genetic bottlenecks
- relatively large pop is reduced to very small # by catastrophic event
- non-natural selection related
- bottleneck survivors likely have low level of genetic diversity and usually carry non-representative collection of source pop. alleles
founder effect
small # individuals form a pop. with low diversity
- may be positive, negative, or all new
- rare alleles present more often due to bottleneck effect
inbreeding coefficient
probability that alleles in an individual are identical by descent, homozygosity
number of eggs that fail to hatch vs inbreeding coefficient
increasing exponentially as inbreeding increases
inbredding coefficient vs generations for N=i
- for i = low population increase exponentially until completely inbred
- for i = 500 linear increase
balancing selection
maintains polymorphisms
MVP
- minimum viable population
- smallest population that will not exacerbate inbreeding effects
% homozygosity vs # generations of inbreeding
smaller pop. increases to complete homozygosity exponentially
F = 1/4
brother-sister matings
Effective population size
N_e
- N_census > N_e
- not everyone in pop. contributes to reproduction
- fluctuation of N_e influences genetic drift
- difficult to measure
N_e : N_c
- generally 0.1 - 0.2
- i.e. for every 5-10 indiv. only 1 breeding individual
fixation index
- a measure of the difference in the allele
- increased in small populations
F statistics
-useful to summarize reduction in heterozygosity at different scales and due to different processes
F = 1/16
means children of first cousins
reduction in heterozygosity due to
- bottlenecks
- founder effects
- population structure
- inbreeding
barrier to migrations
- subdivide populations
- decrease heterozygosity
isolated population
- can see reduced gene flow
- in real life we can not
without barriers to migration we expect to see
HW ratios of homozygosity : heterozygosity
Sewall Wright’s F statistic
- reduction in heterozygosity at one level of of pop. hierarchy relative to another level
- popular, useful measure of pop. differentiation
F_ST levels
0-0.05 = little structure 0.05 - 0.15 = moderate 0.15 - 0.25 = high >0.25 = very high 1 = full homozygosity, no breeding
no gene flow =
genetic divergence among subpopulations
F_ST =
1/(4Nm + 1)
N_e*m = number of migrants
N = drift
m = migration
Equilibrium fixation index F^ vs number of migrants per generation (Nm)
- negative exponential
- high F = very great divergence
- low F = little divergence
migration
- reduces pop. structure
- can balance drift
Ne*m =~
(1 - F_ST)/ 4F_ST
F_ST = (H_T - H_s) / H_T
H_s = average heterozygosity of sub pop.
H_T = average allele frequency
the 50/500 rule
- N_e should be at least 50 to avoid inbreeding depression (loss of fitness)
- N_e should be at least 500 to avoid eroding evolutionary potential (evolve and adapt to env’t ∆)
revised 50/500 rule
- not good enough
- Ne >100 required to limit inbreeding depression to 10% over 5 generations
- Ne >1000 required to retain evolutionary potential
phylogeny
history of descent of a group of taxa from their common ancestors
-includes order of branching, absolute ages of divergence
cladogram
- only shows branching points, divergences
- no distances implied by length of lines
reconstructing phylogeny
- ID, score taxa for phylogenetically informative characters
- model how evolution might have given rise to the states we see
- ID tree most compatible w/ data
homoplasy
character shared by a set of species but not present in their common ancestor
homology
existence of shared ancestry between a pair of structures, or genes, in different taxa
molecular clock
how fast DNA sequences change over time
why gene tree doesn’t always = species tree
- horizontal gene transfer and hybridization
- incomplete lineage sorting
- different rates of evolution
red panda most closely related to
other weasels, raccoons, skunks
Levin model
-assume a large set of identical habitat patches with ‘global’ dispersal
-df/dt = C - E
df/dt = are of change in fraction of occupied suitable patches
-c = colonization rate
-e = extinction rate
E (extinction rate) =
p_e * f
p_e = probability a pop. in an occupied patch becomes locally extinct
patch occupancy
- determined by a balance between colonization and extinction (independent events)
- colonization rate increases until few patches left to colonize
- extinction rate increases as colonization increases
- equilibrium where the two cross
how does additional habitat destruction affect population viability, Levin’s model
- lowers colonization curve = equilibrium shift left
- if colonization is lowered too much, p_e>c, f = 0, entire meta population extinct
key implications of Levin’s Model
- empty habitat patches are not dispensable (new colonizations)
- there are critical thresholds (habitat destruction, dispersal barriers) below which entire metaphor. doomed to extinction
same total habitat but smaller patches, Levin’s model
colonization curve = same
extinction line = steeper
same patch size, fewer patches, Levin’s model
colonization curve decreased
extinction line same
key concepts from meta population theory
- unoccupied suitable habitat important
- reduced dispersal success can cause extinction
- critical thresholds for habitat destruction
- arrangement and connectivity of patches can be just as important as absolute habitat
- local effects depend on regional context
demographic matrix model
- structured population
- start with life cycle diagram
- convert to demographic matrix model
demographic matrix model M =
b1 b2 b3 ... p2,1 0 0.... 0 p3,2 0.... births across top survival on diagonal px, y = prob of surviving from age y to x y = column x= row by = # offspring produced by individual of age y that survive to enter next age class
number of births =
% of females that give birth x % of births that are female
practice of making conservation decisions based on evidence accumulated from similar studies
Evidence-based conservation
fewer patches, smaller patches, Levin’s model
colonization curve decreased, extinction line increases, complete extinction
meta-analysis
quantitative s summary of the size of the treatment effect
levels of science
- government
- academic
- environmental/ NGOs
the top threats to at-risk species
- habitat loss/ degradation
- intrinsic factors
- harvesting
- pollution
- invasives
manipulative experiments can help determine
most significant threat and most effective management
experiments must be
- random
- replicated
- control for confounding variables
sea turtles
7 species, all endangered or threatened
- long-lived
- nest on beach
- disturbance to nest sites and bycatch
loggerhead turtle sensitivity analyses
- lambda much more sensitive to survivorship of stages 2-4
- traditional conservation focuses on wrong age class
- critical importance of increasing juvenile survivorship not obvious w/o modeling
TEDs
- turtle excluder device
- lets turtle escape fishing net
Spring/Summer Chinook Salmon, biggest threat?
- dams most obvious
- others: CC, water use/pollution, fishing, hatchery issues
- brook trout?
ESU
evolutionary significant unit
-demographically and genetically independent, significant pop. of the species
calculating birth in the demographic matrix model
bpµ
b = fecundity (number of eggs produced)
p = survival from age 0-1
µ = adult survival
SRSS chinook salmon and brook trout
- 12% higher survival when brook trout absent
- but correlation does not equal causation
- confounding variables in study (habitat quality, brook trout habitat may have different favourability)
Types of studies utilized to determine threats to SRSS chinooks
- demographic matrix model
- control impact studies
- regression approaches
- before-after-control-impact analyses
BACI
before after control impact analyses
- examines if impacted sites do worse after the impact relative to the control site
- combination of before/after and control/impact studies
conservation assessment most effective if
-hypotheses can be rigorously tested through well-designed manipulative experiments
When experiments are not feasible
- careful observations/ monitoring
- modeling approaches (matrix, control-impact, BACI, regression)
adaptive management
- scientific approach to conservation
- projects are designed, managed, and monitored to maximize opportunities to learn from actions, test assumptions, and adapt future management in response to findings
reactive management
- managers deal w/ events as they arise or as new info becomes available
- do not systematically attempt to build learning into project design and implementation
Passive management
- course of action remains constant w/ no opportunity for new info to influence future actions
- usually no monitoring
are grey seals inhibiting recovery of Atlantic cod
- 20 years later cod have not recovered
- cull the seals and call it an experiment?
- can’t control any of the other variables
- no evidence to support the hypothesis that killing seals will help
why so important to monitor?
spending conservation $ w/o rigorous evidence is ineffective and wasteful
when randomization is not possible
perform a quasi-experiment
confounding variable
variable besides hypothesized predictor, response variables that might lead to incorrect conclusions
hardest adaptive management decision
when to give up
protected areas
now typically intensively managed areas w/ some restrictions on human activities
IUCN categories of protected areas
strict nature reserves, wilderness areas, national parks, natural monuments, habitat/species management areas, protected landscapes, protected areas w/ sustainable use of natural resources
IUCN definition of protected area
clearly defined geographical space, recognized, dedicated and managed, through legal or other effective means, to achieve long-term conservation of nature w/ associated ecosystem services and cultural values
goal of protected lands
10%
-surpassed goal
global growth of protected areas
-levelling off
around 70k areas
-around 18 million km^2
why are protected lands not increasing
- people weren’t compensated for their lands
- governments backing away from earlier commitments
why do protected areas typically require intensive management
- too small to maintain MVP
- overpopulation of some species
- invasive species
- enforcement against illegal logging and poaching
protected area costs
- monitoring
- science
- enforcement
- assessing quality
- removing non-native spp.
how to increase effectiveness of protected areas
- design them strategically
- enhance enforcement
- buy-in from local communities
- research and review goals
how to get support from locals
- compensate for their land/resources
- education
- involve them
conservation on privately owned lands
- 60% of at-risk species only on private lands
- purchase and protect lands (land trust)
- engage private land owners in voluntary contracts or legal agreements
paper park
protected areas existing on paper only, no enforcement
natural vegetation inside and outside of protected areas
significantly lower outside of protected area
GDP and change in forest volume
- no nation w/ per capita GDP > $4600 had shrinking volume of harvestable trees
- poor countries lowing forests, rich gaining (kuznets?)
habitat destruction often greatest
- in areas of highest biodiversity
- more to lose?
- more human dominated?
mountain logging
- on steep slopes = erosion, mudslides
- drain into tributaries
Is habitat loss reversible from logging
- structure, function, recreational value - Yes
- biodiversity- Maybe?
is habitat loss reversible from desertification
No
other impacts to forests
-road building = edge effects
FAO definition of forests
too broad
- overestimate global land area forested
- underestimate deforestation
FAO
Food and Agricultural Organizations of the United Nations
forest ecosystem services
- food
- timber
- fuel
- carbon storage
- nutrient cycling
- water/air purification
- social and cultural benefits
Introduced species
- non-native, non indigenous, alien, exotic
- species that have been moved through human activities beyond their natural range
naturalized
- an introduced species that establishes
- self-perpetuating
Invasive species
-introduced species that thrives, spreads, harms native species, ecosystems, and/or ecosystem services
The invasion process
uptake from native range –> transfer via vector –> release in new region –> establishment –> population increase and range expansion
Pathways of invasion
- intentional introductions
- unintentional introductions
Intentional introductions
- European colonization
- Agriculture, horticulture, aquaculture
- Pet trade
- Biocontrol agents
Unintentional introductions
- stowaways: ship ballast, water, grain shipments, commercial freight, individual travellers
- escape from aquaculture facilities
- unregulated e-commerce
Southwest BC aliens
- eastern grey squirrel
- Japanese knotweed
- English Ivy
- House sparrow
- Scotch broom
- Himalayan blackberry
- European green crab
The tens rule
- 10% of imported species escape control/cultivation (eg. 100 out of 1000)
- 10% of these establish (eg. 10 out of 100)
- 10% of these become invasive (eg. 1 out of 10)
key points of tens rule
- not literal/exact
- only a small proportion of introduced species actually become invasive
predictors of invasion success
- reproductive rate
- trophic level
- # times introduced
- habitat generalist
- diet generalist
most consistent predictor of success
propagule pressure
community invasibility
- susceptibility of a community to invasion
- measured as presence, success, # invasives
what controls community invasibility
- disturbance
- diversity
- natural enemy release
- ecosystem health
community invasibility, disturbance
- frees resource and/or harms native species
- habitat destruction, pollution create high levels of disturbance (reduced diversity, increased invasion)
community invasibility, diversity
-higher native diversity = lower risk of invasion
community invisibility, community health
- degraded ecosystem more prone to invasion
- overexploitation removes competitors/ predators (low biotic resistance)
Biotic resistance hypothesis
- community w/ more species more resistant to invasion
- more species = higher proportion of utilized available resources = less available for invaders
The Natural Enemy Release hypothesis
-degree of enemy release predicts invasiveness
ecological consequences of invasive species
- extinction
- dilution of native biodiversity (local, regional)
- biotic homogenization
- modify env’t, alter ecosystem processes
direct mechanisms of invasive species consequences
- outcompete
- exclude
- predation
- disease
alines and extinctions
- > 50% of documented animal extinctions
biotic homogenization
- the anthropogenic blender
- establishment of exotics, loss of natives reduces regional differences
alteration of ecosystem processes and services by invasives, examples
- C4 grasses (eg. cheatgrass) increase fire frequency
- nonnative N fixers change soil nutrients, facilitate other invasions
of invaders vs trophic level
producers - highest
consumers - lower
predators - lowest
-however predators can cause highest damage
economic consequences of invasive species
- reduce agricultural/ pasture productivity
- forest damage
- clog water intakes
- choke waterways
- health costs
what aliens cause forest damagae
insect pests
what alines clog water intakes
zebra mussesls
cost of aliens
- > 100billion/yr in US
- $840,000 million/yr
strategies for dealing w/ introduced species
Prevention: uptake and transfer stages
Eradication: release and establishment stages
Control: population increase and range expansion stages
prevention of invasives
- public education
- inspection (border control)
- regulation (empty ballast water)
eradication of invasives
- possible on islands and/or if species is easily removed, restricted in range, small pop., easily accessible habitat
- extremely difficult on mainland
invasive species controls
- biological
- restoration
- acceptance
what aliens have health costs
introduced diseases
Biological invasive control
- introduction of natural enemies (consumer, pathogen)
- difficult
- backfires
restoration control of invasives
-restore natives to minimize reinvasion
what aliens choke waterways
aquatic plants
lionfish
- from Indo-Pacific –> invading Caribbean, Atlantic
- largest magnitude marine invasion
- harming already stressed corals
- voracious, ambush predators
- well camoflouged
- 65% reduction in prey biomass over 2 yrs
- very low predator abundance
historical views of the ocean
- hostile, barrier
- mysterious, we don’t occupy it
- bountiful, food source
current views of the ocean
- fun
- cute
- delicious
- endangered
Marine ecosystem services
- provisioning: seafood, timber, fiber, parhmaceuticals
- regulating: water quality, climate regulation
- cultural services: tourism, recreation, aesthetic, spiritual
- supporting services: nurseries
world fisheries value
- $240 billion
- $10 billion in tuna alone
island nations
- 90% of ppl who derive livelihood from fishing live in developing nations
- 1 billion ppl in developing countries depend on fish for primary source of protein
types of fisheries
- recreational
- artisanal /subsistence
- industrial
artisanal fisheries
- communities w/ few resources
- nearshore, limited by fuel costs
- multi-species
artisanal fishery tools
- cast net
- seine net
- line
- spear
- trap: passive, non-selective
selectivity in fisheries
- more selective = better ecological impacts and management
- more selective = lower by-catch
Industrial fisheries
- far ranging
- on-board processing
- onboard technology: GPS, fish-finder
Industrial gear
- purse seines: circle net, close like purse
- trawls: shrimp, groundfish
- longline: surface, pelagic, demersal; >2500 hooks, miles long
overfishing
fishing rate that exceeds maximum sustainable yield
MSY
- largest yield that can be taken over an indefinite period
- maintain high growth rates by reducing #s
- maintain stocks below carrying capacity
Effectiveness of MSY
- should be able to avoid overfishing if fish below MSY
- ecosystems are complicated and we can’t always predict what will happen
Problems w/ MSY
- hard to estimate: uncertain data
- stochasticity
- multispecies interactions difficult
tragedy of the commons
- everyone competing for common resource, only concerned about personal needs
- overuse and exploit
Who owns the ocean
historically everyone
- EEZs governed by nations ( 200 nautical miles offshore) – 42% of the ocean
- high seas governed by UNCLOS
UNCLOS
UN Convention on the Law of the SEa
fishing subsidies
- US: $92 million/yr for boat construction, fishery development, tax exemption, fuel subsidy
- Globally: tens of billions /yr
Types of fisheries data
- catch data
- Stock assessments
catches vs time
catch is all increasing - more fish?
-no, just more effort, better technology
status of stocks vs time
1950s: 85% developing, 15% fully exploited
2000s: 40% collapsed, 30% over-exploited, 30% fully exploited
state of fisheries projection
global collapse of all taxa currently fished by 2048
human predation
- unsustainable super predators
- prey on adults
catch data
- landings, CPUE catch per unit effort
- variable quality
- widely available
stock assessments
- model output: biomass, harvest rate
- high quality
- rare
- difficult to find
- no single database
why don’t we see overfishing
- effort displacement, supermarket problem
- shifting baselines
The supermarket problem
- overstocking
- makes it look like sea is inexhaustable
effort displacement
when local populations become overexploited move to new ones, expand to underdeveloped regions
shifting baselines
our perception of what is normal changes across generations
mean fish size 1956 - 2007
1956 mean: 19.9kg
2007 mean: 2.3kg
why does overfishing happen
MSY often used as benchmark but difficult to estimate and regulate
how common is overfishing?
- difficult to know
- 63% of assessed estimated to be overfished
coral holobiont
diverse community of organisms including endosymbiotic algae, protists, fungi, bacteria, Archaea, and viruses living w/i and on the coral
zooxanthellae genus
Symbiodinium
symbiosis benefit to coral
- productivity
- O2
- nutrient recycling
symbiosis benefits to zooxanthellae
- predator protection
- environmental regulation
- nutrients
- CO2
parrotfish
indirectly have positive impact on coral recruitment
2015-2016 weather
biggest El Niño on record + warm water anomaly
NOAA coral reef watch
- detect possible bleaching events based on SST
- 7-day bleaching alert in Nov 2015
videophillia
the new human tendency to focus on sedentary activities involving electronic media
stochasticity
randomness, uncertainty, hard to predict the outcome, increases probability of extinction
demographic stochasticity
chance variation in ratio of sexes, reproductive success, etc.
to make conservation decisions must know
- # of individuals in population
- trend in pop. size
- estimated risk
less than 1/2 species on endangered species act have
known population size
only 40% have trend in pop size
census especially difficult to obtain for
aquatic, subterranean, cryptic, highly mobile species
environmental stochasticity
fluctuations in env’t conditions that affect reproduction/survival
relative abundance
of individuals sampled per unit effort
to estimate sample/pop of sessile/ sedentary species
quadrat sample
large sample size =
lower sampling error
random sample to
reduce/avoid bias
transects ideal for
vegetation, slow animals, gradients
Lincoln-Peterson method
capture, mark, release m = # marked allow time to remix sample, s = #sampled record # marked, r = recaptured total pop N = ms/r
mark-recapture assumptions
- no effect of marking on individual
- no effect of marking on recapture
- mixing of marked/unmarked is complete
- captured indiv. represent whole pop.
- closed, stable pop.
- marks not lost/removed
mark-recapture assumption, no effect of marking on survival
- no more obvious to predator
- no increase chance of parasite/disease
- no increase to hunting
non-invasive sampling techniques
- photography (especially for dangerous or hard to sample species (tigers, whales)
- DNA (fecal, hair)
- aerial survey (open habitat)
- vocalization
- nests, burrows
- records, journals, fossils, pollen
discrete population change
N_t+1 = lambda * N_t
-births, deaths occur in one big pulse per yr
population growth rate
λ = N_t+1 / N
λ > 1 growth
λ less than 1 = pop decline
Discrete model assumptions
- density indepen. pop ∆ - shrinks/grows at constant rate
- deterministic pop dynamics
- homogeneous individuals
- closed population
implications of density independent population ∆
- resources unlimited no matter how large
- no carrying capacity
- no trouble finding mates/resources for small pop. (allee)
implications of deterministic population dynamics
- no ‘good’ years and ‘bad’ years
- no stochasticity
- constant environment
implications of homogeneous individuals
- same reproductive success
- same probability of survival, growth, behaviours
PVA
population viability analysis
-combine current pop size, trend, estimated yr-yr variability, quantify prob of extinction w/i specified time frame
essential simple PVA info
- estimate of current pop size, N
- estimated pop trend, λ
- info about fluctuations in λ with time
MVP
min # of indiv. having a 95% prob. persisting over 50-100yrs
Threat analysis
- assess factors that cause pop decline
- manipulative experiment, observational study, models
key elements to manipulative experiment
- confounding variables
- replication
- random
randomization important for
reducing bias
replication important for
discerning the signal from the noise
observational study
more realistic
- harder to discern cause and effect
- harder to control variables
sea turtles and conservation actions
- protect nesting sites, captive rearing, reduce mortality in open ocean
- increase prob. of juvenile survival to 1.0 – find no change to pop decline
- increase large juvenile survival – may reverse decline
- efforts should be focused on large juveniles, contrary to what was thought
sensitivity analysis
- systematically vary model inputs (survival, growth, fecundity)
- determine impact of each parameter to the system
- ID where conservation efforts most effective
dam impact
- survival of 1 yr old
- survival/health of reproductively mature adults
determining conservation action of spring/summer chinook salmon
-demo matrix model: set survival of 1yr old, adult to 100%, pop still declines - dams not the biggest/only threat
landscape ecology
study of how spatial patterns of landscapes affects organisms and ecosystems (fragmentation, connectiveness, etc)
Equilibrium theory of island biogeography
- larger islands tend to harbour more species
- # species is a balance btw colonization and extinction
- low # species = large colonization potential, low extinction potential, pop tends to increase
faunal relaxation
reduction in diversity following reduction in habitat area
extinction debt
difference btw large # of species doomed to extinction from habitat loss/fragmentation, and the relatively smaller # that have already occurred
SLOSS, nested
single large
-contains same species of the small patches, plus others
collection of spatially isolated subpopulations of the same species
metapopulation
rate of change of fraction of patches occupied
df/dt = C - E = colonization - extinction E = p_e * f C = C*f (1 - f) p_e = prob. sub pop becomes locally extinct f = fraction of patches occupied
land trust
non-profit organization dedicated to land protection
IUCN categories of protected land
1a. Strict nature reserve- human visitation/ activity strictly limited
1b. wilderness area - human habitation prohibited
II. National park - rec permitted, protect large-scale ecological processes
III. Natural Monuments- protect geological/living features
IV. Habitat/species management area- protect particular species/habitat
V. Protected landscape/seascape - preserve distinctive character produced by human/nature interaction
VI. Protected areas w/ sustainable use of natural resources
PADDD
protected area downgrading, downsizing, degazettement
Degazettement
loss of legal protection for entire national park or protected area
SLOSS, unnested
SS, patches contain unique species
Debt-for-nature swap
NGO pays some portion of nations debt and nation commits to conservation
management that utilizes learning by doing
monitor projects and allow for adaptations
if an action has a possibility of causing harm it should be avoided
precautionary principle
prioritizing species and ecosystem based on severity and likelihood of recovery
conservation triage
coral reef coverage
- cover less than 0.1% of Earth’s surface
- 20% lost, 24% under imminent threat, 26% in danger
- support 1-9 million species
problems with reef loss
- reduced storm surge protection
- job losses
- impacts to religion/tourism
- reduced diversity
threats to coral
- overfishing or pollution
- overfishing -decreased herbivores -increased algae (top-down)
- pollution –nutrients –algae increase (bottom-up)
- more important to focus on water quality or fishing regulation
- find herbivores to be more important control
manipulative experiment trade-off
- ability to control, replicate, randomly assign treatments, reduce chance and confounding variables
- small spatial scales, controlled environments, not entirely realistic
positive deviance approach
- seek out samples of unusual or rare success
- determine what these rare cases have that is lacking from other unsuccessful cases
how to use positive deviance research in corals
-determine what makes some species of corals thrive in warmer waters –> particular symbiont species –> focus conservation on species that contain them
anthropogenic mercury emissions
- smoke from burning coal
- cometics, pharmaceuticals, dental products
nearly half of the world lives
within 200km of the coast
overharvest
harvest that exceeds productive capacity of a species and causes the pop, and consequently the yield, to decline over time
stock
single harvested species in a limited geographical area corresponding to jurisdictional boundaries
yield vs stock size and MSY
below MSY yield increasing, past MSY yield decreasing (less steeply than it increased)
sequential depletion
deplete one marine organism until it becomes unprofitable then move on to the next
collapse of all fisheries by 2048?
- discredited
- declined in catch could have been due to fisheries management restricting harvest
validity of CPUE as standardization
-as pop declines, takes greater effort to capture quota
overcapacity
- ramping up of technological efficiency and effort beyond sustainable levels
- as stocks decrease greater effort is required which causes further depression
stock assessment models
use all available data to predict whether fish pop is shrinking or growing and how pop will respond to different levels/types of harvest
countries that utilize stock assessment models
- 36%, the other 64% lack data and resources required
- less than 350 regularly assessed w/ robust scientific methods
- largely upper-income countries
stock assessment in poor countries
- teach fisherman to collect simple data measures that can be used for basic calculations like spawning potential
- eg. size of fish caught, reproductive status
- may also gain local support and belief by having the fisherman collect the data
bycatch
- includes juveniles therefore reducing future harvests
- ca. 1.5kg of bycatch per 1kg of shrimp landed (includes turtles, seabirds, mammals)
- ca. 500,000 individuals/yr
- strongly influenced by type of gear used and location of fishing
most indiscriminate fishing gear
- trawl nets
- gillnets
- longlines
reducing bycatch
- TED
- trailing streamers behind boat to deter seabird
- close fishery when mammals are abundant
- acoustic alarms deter marine mammals
bycatch is primary threat to
- vaquita
- Hector’s dolphin
- Mediterranean monk seal
- North Atlantic right whale
fishing down the food web
- collapse of predator populations followed by a shift toward smaller fish and invert. pops of lower trophic level
- fisheries then shift their attention to the lower trophic level species causing a subsequent shift to lower trophic level pops
- sequential depletion hypothesis
sequential depletion hypothesis
- catch of top predators will decline as mean trophic level of catch declines
- suggests that over harvest is severe and widespread
- sustainability requires immediate and drastic reduction of harvest
sequential addition hypothesis
- top predator catch does not need to decline, could grow as mean trophic level of catch declines
- e.g. if dietary choices or fishing gear change
- suggests top predators have not been severely depleted, rather diversity of species targets is expanding and shifting
sequential depletion or addition?
- appears to be sequential addition
- except in N Atl where cod collapsed
solutions to the tragedy of the commons
- transform commons into privately owned areas
- establish strong regulations with severe penalties and fines
species that have been moved through human activity beyond their natural range
introduced
intentionally introducing consumer or pathogen species to control or eliminate organisms interfering with human activity
biological control
biological control backfire example
- cane toads native to central, south America
- brought to Australia for sugarcane insect pest control
- became very abundant, >2000 indiv./ha
- secrete toxins in skin harmful to dogs, snakes
reducing backfire in biological control
make sure predator is specialized
propagule pressure
- frequency of introductions and quantity of organisms introduced to a site
- has to be relatively high for most introduced species to take hold
- eg. Starlings introduced at least 8 times unsuccessfully before taking hold
only a tiny fraction of introduced species exhibit the high rates of pop growth required to produce severe biological impacts
the tens rule
why the tens rule may provide false comfort
- the volume of introductions is enormous, even 10% can be quite large
- long time lags are common between import and establishment
- 10% may be too low
species that establish as self-perpetuating populations in their non-natural habitat
naturalized
species traits associated w/ invasion success
- high dispersal rate
- high rate of pop growth
- small seed size, longer viability of seed in soil
natural enemy release hypothesis
-absence of natural enemies give introduced species advantage over competing native species, promoting large pop size and rapid growth
Naturalization hypothesis
- Darwin, 1859
- introduced species are less likely to become established if other congeners are native to the recipient community
- natural competitors
- likely to have shared predators
species that become so abundant in their non-native habitat that they threaten habitats, ES, or native species
invasive
biotic resistance hypothesis
-highly diverse, undisturbed communities have lower invisibility than disturbed, low species ones
congener
species of the same genus
biotic acceptance hypothesis
- conditions good for native species also good for nonnative species
- eg. nonnative reptiles most abundant where reptiles are most abundant
- means that biodiversity hotspots might be in danger
important nonnative species
- crops
- livestock
- pets
- pollinators
nonnative species benefits
- substantial increases in PP
- increased nutrients
- facilitate growth by adapting previously harsh environments (ex. nitrogen fixers, primary succession plants after fire)
feral cats
- 33 extinctions (bird, reptile, mammal)
- 1.3-4 billion bird deaths/yr
- 6.3 - 22.3 billion mammals/yr
- greatest source of anthropogenic mortality of US birds and mammals
invasion hotspots
- areas where nonnatives are >25% of the species
- correlated w/ high human pop. and economic activity
how to determine very rare species presence, especially in waterways
eDNA - environmental DNA
Species to focus invasion control on
predators - have much higher impact than invasive herbivores are plants
Improving companies environmental reputation
- report debt to nature
- carbon/water neutral
- sustainability
- partner w/ env’t groups
biophilia
humans have an innate need for intimate association w/ nature, especially its living biota, and that this need is deeply rooted in the evolutionary history of our species
Video games have largely replaced the outdoor activities of many adolescents
videophilia
environmentalism and generation
millennials ca. 10% less likely to self-identify as environmentalists - due to less contact w/ nature?