Population and Community Ecology Flashcards
What is this a definition for?
Predicts how natural selection should shape the way organisms parcel their resources into making babies
Life history (theory)
Organism reproduces in one event
Semelparity
Organism reproduces throughout their life
Iteroparity
Life history can be p——– (seasonal) or c——— (but may fluctuate)
Pulsed, continuous
Each organism has a limited amount of energy that can allocate for maintenance, survival, growth and reproduction - L—-, 196-
Principle of allocation (Levon 1968)
There are i— individuals and i— generational trade-offs
Intra, inter
Give some examples of intra-individual trade-offs - 6 examples
Reproduction vs survival, reproduction vs growth, current reproduction vs future reproduction, no. of offspring vs size of offspring, no. of offspring vs survival of offspring, reproduction vs conditions
Give some examples of inter-generational trade-offs
Parental survival vs the number of offspring. Parental survival vs offspring condition.
Give an example for each of these survivorship curves:
Type 1
Type 2
Type 3
Humans, Birds, Trees (respectively)
Net reproductive rate = Survivorship * F——- (Look at equations in lecture 1)
Fertility
T/F R0 tells you how fast a population is growing
False (just tells you if it is growing or shrinking)
What is the equation for population growth rate?
= R0^1/T
If a population growth rate was 0.98, then a population would be growing / declining by -% each year
Declining, 2
The fundamental equation for an unstructured population size makes these assumptions:
1. U——- population
2. C—– population
3. Time-i—– around reproduction and survival
4. S——– breeding (birth pulse reproduction)
5. Pre——— census
unstructured, closed, invariant, seasonal, breeding
BIRTHS depends on per-capita f——- rate and offspring s—— rate from one year to the next
fertility, survival
The number of individuals n— year depends on the number of individuals THIS year multiplied by the probability they s—— and the b—- contribution
Survive, birth
Population growth rate is dictated by the symbol l—–
Lambda (review this lecture though. Lecture 2. It’s a big one)
What is the main difference between a structured and a unstructured population model?
- in a structured one,ndividuals starting b—— at a certain age
- Their survival & fertility is considered to be c—— once they reach that age
- The other unstructured assumptions remain
breeding, constant
The l—- in life-cycle diagrams just show us that an individual is staying in that class (ie. that age class)
loops
The structured population model not only tells us the total numner of individuals, but also the p——– of individuals in each class (ie. age / sex/ size / state)
proportion
Z— are included in the matrix projection models to NULLIFY irrelevant values, such as fertility when an individual is not old enough to breed
Zeros
In an MPM, does the state vector or the projection matrix give you the transitions amongst the different states
The projection matrix
In an MPM, what does the state vector give you?
It gives you the abundance of individual in each state
Together, the state vector and the projection matrix give you the p——- g—- r—
population growth rate (PGR)
In the column vector model, you f— the far right column and m—— everything in the column it then fulls in. The zeros do not count so they do not matter
flip, multiply
A growth model has 2 phases. What are they?
- The initial ‘transient’ phase
- The long term constant phase
T/F initial conditions affect long term behaviour
FALSE (they only affect short term behaviour. )
Each age / demographic class eventually settles down to a constant value,. This is known as the S—- P—— S——-
Stable population structure
T/F a computer can calculate stable population behaviour for us
True (we just need the projection matrix)
Do matrix projection models (MPMs) account for population strucure?
Yes
An MPM for stage-strucutre populations (which life stage an organism is in) will generally include:
1. ——-
2. ——
3. ——- rates amongst the states
Fertility, survival, transition
To build a MPM, you must consider:
1. When r——– happens
2. When we c—– the population
reproduction, census
Why are pre-breeding census more common?
May be due to logistical reasons, such as when species have offspring they may hide away more leading to underestimation, and knowing adult populations BEFORE breeding season could help to estimate the number of individuals entering the breeding season
In a post-breeding census, the youngest individuals are - years old, an individual which is j—— but matures next year contributes o——- and we have to discount additions through reproduction by the adult survival rate
juvenile, offspring
In a pre-breeding census, we have to DISCOUNT additions through reproduction by the n——- survival rate
newborn
T/F pre-breeding and post-breeding census have different long-term population growth rates
FALSE (they are THE SAME, only age classes are defined differently)
P——– A—— can use MPMs to produce simulations of how some aspect of demography changing may effect population growth
Pertubation Analysis
Pertibation analysis can be classified by:
i) the type of p——– we are interested in such as population growth
ii) the type of p——- such as a change in survival
property, pertubation
In pertubation analysis, we calculate the g—— of the line at the point on the graph we are interested in. We create a tangent. This gives us the rate of change of l—-
Gradient, lambda / population growth
When we calculate sensisivities we need:
1. The h— level matrix elements (just the elements with the numbers)
2. The l– level matrix parameters which give the ‘formulae’ or relevant parts i guess
- These are displayed in 2 different matrixes. Review lecture 3.
high, low
Definition: Gives you how much a dependent variable will change (ie. population growth) when we alter the independent variable (ie.survival) by a small amount
Sensitivity Analysis
When calculating a paremeter sensitivity which relies on two seperate paramaters (ie. survival and reproduction), we must calculate rates of c—– for both of these parameters and then m—— the effects and s– them to get their total ‘net’ effect.
- See lecture 3.
change, multiply, sum
Calculating parameter sensistivity can hep us deal with many drivers of c—-
Change. Such as climactic variable, species traits and anything to do with demography
Elasticities are needed because different parameters in s———- are on different s—- so cannot be used to show p——— changes in parameters or matrix elements
sensitivities, scales, proportional
Sensitivities only show a—– changes in parameters wheras elasticities show p—— changes which can be compared
- Lecture 3
absolute, proportional
Sensitivity analysis can resolve m—— pathways of effect when more than one thing effects population size
Multiple
Elasticity analysis gives better s——–
sensitivities
CASE STUDY: The desert tortoise is CRITICALLY endangerous due to r——— diseases, pet attacks, h—— loss and competition with livestock for f—.
Take 15 to – years to reproduce.
Respiratory, habitat, food, 20
CASE STUDY: Built an MPM on desert tortoises based around s—, considering survival, r——– and also growth. Used m—-c——-r—— to get data.
size, reproduction, mark-capture-recapture
CASE STUDY: Desert Tortoise. Conclusion was that the survival of —– individuals was the most important.
large
An intervention can help population growth by:
1. Affecting rates with l—- elasticities by a s—- amount.
2. Affecting rates with m——- elasticities by a —– amount
large, small, medium, large
CASE STUDY: Comparing mammal species. Used a t——- (triangular) plot to do this. Works like the Soil Triangle if u know u know xx. Found that f—— was best for ‘faster’ lived species
Ternary, fertility
CASE SUDY: Black-browed albatross.
Live in southern ocean. L—- concern, live for – years, mature at -to 9 years.
Least, 70, 7
CASE STUDY: Black-browed albatross. Considered a– and when they first reproduced and became ‘experienced breeders’. SST was most important c—— variable and transitions (f——) was the most important functional trait but not by much
age, climate, foraging
Problems with how phylogenies used to be derived:
1. Based on h—— and not rigorous scientific analysis
2. Too much reliance on s———- distribution of fossils from where the fossils were in rock and how old the rock does. This doesn’t necessarily make one thing the ancestor of another.
hunches, stratigraphic
What is this a definition of?
A table that lists terminal taxa as rows and the characters (presence of certain features) as columns. Each cell in the matrix is then coded with the character state applicable for each taxon-character combination. Used to calculate cladistic relationships by seeing what features organisms SHAREQ
Character Matrix
Give an example of analaguous characteristics
Wing shape in insects vs birds
Define homoplasy
The independent acquisition of the same trait in unrelated lineages
What is Cole’s paradox?
The fact that iteroparity abounds in nature despite the theoretical prediction that it would be easier to be semelparous as all you’d need to do is increase your offspring number by one.
Are most perennials itero or semelparous
Most perrenials are iteroparous.
When calculating a demographic model for a perennial species, you must consider the individuals which are —- ——- as well as those which have just produced seeds (lecture 5 see equations)
Still around
Why doesn’t Cole’s paradox actually work in reality?
1. Seed s—— CONSTANTLY assumed to be 1.
2. P——– surivival also CONSANTLY assumed to be 1
3. Populations are NOT limited by d—— d——– etc.
survival, perennial, density dependence.
The good news is analysis can account for these things
How must an iteroparous species ‘win’ against a semelparous one?
It’s fertility (seed production) per average lifespan must be HIGHER than the total lifetime seed production for the semeloarous ine.
Perennial production per lifespan must be higher than annual per year production (even though a year is essentially an annuals lifespan)
- See equation in lecture 5
Iteroparity is FAVOURED when:
1. Average adult s——- is high (longevity is good)
2. T——— variation in adult s—— is low (ie. s—— is ALWAYS high)
survival, temporal, survival
What kind of environment are r-selected species expected to evolve in?
A low-density, low competition environment (opposite is true of K-selected species)
Lecture 5:
The L—– g—– model shows us that r is favoured at Low densities (in that period of exponential growth - low N) and K at high densities when a pop is near / at it’s carrying capacity (high N)
logistic growth
What are the characteristics of a K and an r selective species?
R:
Many small offspring
Early reproduction
Small size
Short lived
K:
Few large offspring
Delayed reproduction
Large size
Long-lived
What is the problem with r / K selection theory?
We DO see these kind of species in nature, but selection would have to act on a POPULATION LEVEL
Generation time is hard to calcilate when rates of s——- and r——– VARY with age / a class
selection, reproduction.
Generation time is the average time between a birth of an i—— and their o——. Must be weighted by a–. Survivorship * fertility * age of an individual (lxmx) gives you this weight.
individual, offspring
It is harder to calculate gen time when the class is NOT a– and is something like s— instead. This is as:
1. Individuals can be in multiple s—- throughout their life.
2. Individuals in the SAME state may still have different t——— in life.
MPMs can calciulate this for us
states, trajectories
MPMs can give us:
- G——– time
- Average time of f—- reproduction
- L— expectancy
- S———– curves
generation, first, life, survivorship
What is levin’s principle of allocation?
Each individual has a finite quantity of resources which is can use for all necessary processes.
Understanding how life-histories are structured can help us understand:
1. E——-
2. A——– of a species
3. D———– of a species
evolution, abundance, distribution
The c——— d——— case study took many plant life histories to see if any charecteristics correlated. Ended up with 2 axis:
1. Fast-s— continuum (fast growth & short lived vs slow growth and long lived)
2. R———- strategy (highly reproductive & itero vs poorly & semel)
comparative demographic, slow, reproductive.
- Results showed patterns, such as if you were slow-growing you were unlikely to be short-lived. Can be used to predict life-histories of certain species with insufficient data.
What is r?
r is the intrinsix EXPONENTIAL population growth. It is calculated by subtracting deaths from births
dN/dt = bN-dN = r. What is N in this?
N is the population size. b & d are given in terms of per-capita. dN/dt is the change per unit time
When populations start at a relatively large / small size, they demonstrate exponential growth
small
What is the normal shape for population growth?
The logisitc growth model. Big events can have an impact on populations but nonetheless these populations tend to bounce back.
What is the most common determinant of K?
Energy & Resource limitation.
K is when b ? d
When b = d
What does the equation dN/dt = bN-dN become when you account for the logsitic growth model?
It becomes dN/dt = rN-rN^2 / K. rN would just be exponentual, where as rN SQUARED means that per capita growth DECLINES with density
In early competition experiments, it was found to be hard/ easy to predict the outcomes between species
hard. The Lotka Volterra model can help us tounderstand when competitive exclusion may occur however.
In early experiments on competition, they included r——- u– to show how competition reduced it’s availability
Resource use.
The L— V——- model shows i——– competition wheras the l——- g—– model shows i——– competition. In the LV model, N1 shows species one and N2 shows species 2.
Lotka Volterra, interspecific, logistic growth, intraspecific
What does alpha 12 model and what does alpha 21 model.
Alpha 12 models the impact of species 2 on species 1. Alpha21 modles the impact of species 1 on species 2. The larger the value, the bigger the effect (look up equation!! Lecture 7)
Alphaij can be described to measure ecological equivalence. What does this mean?
It shows how many memeber of one species are equivalent to another. In terms of resource use it shows how much an individual of one spcies consumes of a resource in comparison to another.
If aij = 2 then species j would consume twice as much as species i.
Competition coeffiecients (aij) is higher when the niche overlap is lower/higher and there is therefore more/less competition
higher, more
When we change model parameters in the Lotka Volterra model, we assume that - and - are the same.
K and r for both species. These models can then be used to give an alpha value and see if coexistence is possible at varying levels of competition
Can density of a species affect the impact of competition outcomes?
Yes. For example, at a medium density competion may be possible, but at lower or higher ones, this may not be the case.
To solve the competition equation and examine the outcomes (lecture 7) we must find the conditions wherein dN1/dt = –2/–
= DN2/dt = 0 (an equilibrium)
Under these equations we eventually get to see under which value of alpha co-existence can occur (really look at this lecture again lily)
Which equation shows interspecific competition being stronger and which shoes INTRA specific competition being stronger.
1. a12 <1 and a21 <1
2. a12 >1 and a21 > 1a
- Intra is stronger. Stable co-existence possible
- Inter is stronger. Unstable co-existence possible
aij<1 and aji <1 means that c——- co——— can occur, as when the density of species i increases past a certain amount, the effect on itself pushes it back to an e——-. They can/cannot coexist no matter the starting densities
competitive co-existence, equilibirum, can
What does aij>1 and aji>1 result in?
UNSTABLE competitive co-existence. The species may coexist but interspecific comp is more important than intra, so they can only exist at some starting densities. May depend on which species has entered a habitat first. Unlikely to happen in reality as dependent on a stable habitat like tropical rainforest
Ecologists have been troubled as to how in h——- communities, there can be enough n—- for every specoes
hyperdiverse, niches
A limitation of the Lotka Volterra Model is that it assumes species live in a c—— environment
constant
What is equilibrium theory?
Dictates that the balance between losses & gains in a community maintain specie richeness at an overall constant. Implied processes balance diversity.
What is non-equilibirum theory?
States that disturbance and stochastic events prevent an equilibrium from being reached, hence delaying competitive exclusion
What is the intermediate disturbance hypothesis?
States intuitively that too much disturbance will reduce species diversity by destroying communities entirely. Supported my Molino & Sabatier 2001 and Bongers et al. 2009
Does disturbance prevent competitive exclusion?
No, it only delays it in time
What is the neutral theory?
This is a model for diversity wherin all species are identical, so competition takes longer to rin it’s cause. When randomness is added in, species can co-exist for a very long time before just 1 species ‘wins’.
Neutral theory does NOT explain diversity. Why?
- ignores species specific traits
- neglects ecological interactions like predation, mutualism etc.
- ignored evolutionary processes
- does not consider habitat heterogeneity
What two communities does Hubbell’s Neutral Theory involve?
The local community at the specific sites, and then the wider meta-community
In Hubbell’s Neutral theory, the letter J refers to what?
The number of trees (or other individuals) in a community
G– D—— described gap formation and competition to fill that gap left
gap dynamics
We assume there are / are not empty spaces in Hubbell’s Neutral Theory
Are NOT. Every gap left is immediatelly filled.
In the Hubbell theory, what occupies a vacant site is r—– and all species essentially are e—— identical and the same in b—– and d—–.
!!! What is the problem with this??
random, ecologically, births, deaths
- Normally these assumptions are not correct
In Hubbell Theory, species can be —– from a population just by chance
lost
What number of species will you eventually end up with under Hubbell’s Theory?
1 (although they will persist for a long time before this)
In Hubbell’s model, including a metacommunity allows for m——– and s——– so extinction from the local one is NOT permenant. The more immigration the more species.
migration, speciation
What are some pros of Hubbell’s Neutral theory?(5)
Can compare data with it
- a useful and simple startpoint for more complex models
- a null hypothesis for other theories
- shows community dynamics n turnover overtime
- recognizes.role of stochastic processes on communities
- recognizes role of a wider metacommunity in diversity
For what 2 reasons can density dependence occur?
- Intraspecific competition
- Predation rate increasing with prey density
P— death function is believed to equal p—— growth function
prey, predator
What is the FUNCTIONAL response in predator/prey theory?
How mortality rate of prey and consumption rate of predators vary with one another.
Define each functional response:
Type 1
Type 2 (most common)
Type 3
Type 1 - Mortality rate does NOT vary and consumption increases constants. Density independent mortality
Type 2 Inverse density dependence as predator gets full. Mortality thus decreases with density
Type 3 - Inverse density dependence where mortality increases then decreases with density. This is predator induced density dependence. ONLY Stabilizing PNE
What does the numerical response describe in the predator prey models?
How predator density varies as a function of prey, meaning how much eaten prey fgets converted to predator babies.
Predator growth = - (energy conversion rate) * F——- response * predator number
E, functional
Lecture 11. What do all the letters in this equation stand for?
Prey/time = r * Prey - a * Prey * predator
r* Prey gives you prey growth
a*prey (a is the constant for type 1/2/3) gives you the functional response
Lecture 11: What do all the letters in this equation stand for?
Predator/time = e * a * Prey * predator - d * predator
e * a * Prey gives you the numerical response. Remember that e is the energy conversion rate and a is the constant)
* Predator - d * Predator
d* Predator = Predator death
Which equation is for prey equilibrium and which is for predator equilibrium?
- P* = r/a
- N* = d/ea
P* gives you the prey equilibriium as defined by the number of predators (P)
N gives tyou the predator equilibirum as defined bu the abundance of prey (N*)
These are both CONSTANTS and produce straight line zero net growth isoclines when you use the type 1 functional growth model
Using type 1 functional growth and our predator death / prey growth function, you end up with c—–. These do / do not appear often in nature as this makes assumptions of
1. E—— growth
2. Constant m—–
3. Constant predator d—- rate
Thus there is no density dependent negative feedback
cycle, do NOT, exponential, mortality, death
If you use LOGISTIC growth and TYPE 2 functional responses in predator/prwey modelling, what can you get?
A stable system. Predators decline after the inflection point (where prey numbers stop increasing) and rise up again, creating a natural cycle.
It is important to remeber that MODELS make a———
assumptions
When are predators inefficient?
When they are close to the carrying capacity of their prey.
Predators AND prey are in decline when their numbers are above/below their lines on the graph
ABOVE
Do predators allow co-existence when they are efficient or when they are inefficient?
When they are inefficient. They need a lot of prey to sustain them.
In efficient predators, how near is their zingy to prey K? Does this create a stable or an unstable population?
They are NEAR K. Population is UNSTABLE
What is the paradox of enrichment? What type of equilibrium does this create?
Adding enrichment to lower trophic levels creates an UNSTABLE equilibirum, as prey number increase whilst the ‘zingy’ for predators stays in the same place. Thus predators can go from inefficient to very efficient
RECAP: How do predators…
1. Decrease biodiversity
2. Increase biodiversity
- By eating the weakest competitor (mosquito larvae eating protists)
- By eating the dominant competitor (starfish eating muscles or rabbits eating grass)
RECAP: Predators can alter R— of competitors and R—— A—— without affecting biodiverisity (no. of species)
Rank, relative abundance.
Shown in the study of newts and tadpoles.
RECAP: Predators can c— competitive domiunance depending on the community: Periwinkles and ephemerals / perennials. This is an example of c—– d——, in this example the context being habitat type.
CHANGE, context dependency
RECAP: G—– and K—– predation can lower biodiversity. K—– predation can also increase biodiversity
Generalist, Keystone, Keystone
How did sea otters increase genetic diversity in eel grass?
They broke up the eelgrasses rhizomes with otter pits and left spaces into which seeds could grow. More sexual reproduction led to more genetic diversity, better for environmental change
Burian et al. 2022.
Predation was necessary to increase diversity of prey species. The community composition of prey species made them better at aerating the water and processing waste. Predation had a positive effect in DILUITED communities, where there was less of an encounter rate between predator and prey
What is the dilution effect hypothesis?
Biodiversity DECREASES disease risk. It is controversial but recently we have seen infectious disease rise globally as we hit a biodiversity crisis.
What is intraguild predation?
A predator eating prey AND the preys parasites. Damsels and dragonflies eating tadpoles and their free living parasites.
What is non-intraguild predation?
A predator JUST eating the freeliving parasites of a prey species OR just eating the prey
What were the findings of the R— et al. 2015 study into the effects of damsel and dragonflies on parasitism in tadpoles.
Rohr et al. 2015:
That non-intraguild species REDUCED infection and intraguild species INCREASED infection by INCREASING the exposure to parasites of the surviving tadpoles.
This DOES make sense as non-intraguild predators just consume the parasite
At K, what is PGR?
It is 0, which makes sense as the population is no longer growing
At what fraction of K is the PGR at it’s highest?
PGR is at it’s highest at half of K . This is the INFLECTION point
At what fraction of K should we harvest a population in a sustainable system?
At 1/2 of K (where PGR is highest). In THEORY
A population takes a shorter/longer time to hit K when r is higher
A SHORTER time
Where on that funny spiral graph is a joint equilibrium for predators and prey? And why is it there?
At the centre of the spiral, as the numbers of predators and prey are the same for both populations
Ecosystem functions can be split into r— (eg. productivity) or a——- (eg. biomass). They can also be split into plants, animals and a— processes.
rates, amounts, abiotic
Which of these allows for more species in an ecosystem?
1. A larger / smaller R (resources)
2. A larger / smaller n (niche space)
3. A larger / smaller o
- A larger R - more resources
- A smaller n - more specialized
- A larger o - more overlap
Define the complementarity hypothesis
Adding more species with DIFFERENT niches thus increasing species richness. Each species has a unique function
Define the redundancy hypothesis
Increasing species richness by increasing overlap. Each species has less than 1 unique function.
In the redundancy hypothesis community function eventually p—–. This does NOT happen with the complementarity hypothesis
plateaus
In the complementarity AND k—– hypothesis, community function would increase e———- with new species. One species has a d—– effect
keystone, exponentially, disproportionate
In the redundancy and k—– hypothesis, community function increases then plateus but again one species has a d——– impact
keystone, disproportionate
What were the main findings from all the many studies on the humpbacked biodiversity curve?
- Only a trend over MANY ecosystems / just anthropogenic ones.
- Varies ecosystem by ecosystem - sometimes positive sometimes negative
- Problematically use many different units as a proxy for this.
- The more functions you consider the more likely species are to have apositive effect
- More studies should focus on trophic levels above plants
What is an example of ordered species loss?
The more rare species being lost first. Such as your oven.
A—– and r— can show the same processes to an extent.
Amounts, rates.
T/F Species richness is a good indicator of functional diversity
False. It hides a lot depending on what the species is.
T/F Describing ecosystems in terms of productivity and species richness is an effective way of measuring functional diversity
False. It misses a lot
The Biodepth data showed a very v——- loss of species richness per biomass, indicating that species i—– is VERY IMPORTANT in causing varying levels of effect on ecosystems.
variable, identity
What is grimes mass ration hypothesis?
What was the date?
States that species identity is IMPORTANT and that controls on ecosystem function are proportional to the BIOMASS or productivity of that species.
Eg. the most common species contributes the most and subordinate / transient species the least
The date was 1998
What were the findings from the study on german biomass about community composition and groundwater.
Showed a NEGATIVE relationship with plant species and functional group richness but legumes contributed DISPROPORTIONATELY.
Communities with less n—– and or more s—— ecological roles to one another have LESS functional diversity
niches, similar
What does multivariate analysis do to show functional diversity?
Places more dissimilar species FURTHER away from one another to show how much functional diversity there is in a commmunity.
! Still holds the problem as to WHICH FUNCTION is important to functional diversity (eg. what is measured)
What did the study by —- et al. 2013 (https://www.nature.com/articles/nature12529) reveal about fish species density vs functional diversity?
Functional diversity did NOT show the same hotspots as species diversity showing many species REDUNDANT in ecosystem function. Also showed that the gradient between species diversity and functional diversity can vary greatly across the world, supporting the redundancy hypothesis over the complementarity hypothesis.
Diversity at different trophic levels can show d—— correlations and g—– when functional diversity and biomass plotted together.
Different, gradients.
! This makes things COMPLICATED to asses functional diversity, but computers can help !
Give the main conclusion to be drawn from the S—p et al. 200- paper on adaptive divergence and phytoplankton in sea.
Stomp et al. 2004:
The variability in their pigment colours allowed them to show niche partitioning and reduce competition as there was less niche overlap allowing for coexistence. Also demonstrated the adaptive significance of divergent pigmemtn compositions in phototrophic microorganisms
How did stomp et al. 2004 test their hypotheses?
Saw which plankton won in green light and which in red light. Green won in red and vice versa. Only co-existed in white
Carrying capacities are increased/reduced during co-existence
REDUCED
Symbiosis was first defined by Simon Schwendener in 18– using a—-, but wasn’t given a term until A—- F— came along in 1877
1869, algae, Albert Frank
In 19–, Heinrich Anton de Barry applied symbiosis to a whole s—- of living interactions
1979, spectrum
What are the four main types of Symbiosis?
1. M——- (++)
2. C——- (+0)
3. Amensalism (-0)
4. Parasitism (+0)
Mutualism, commensalism, amensalism, parasitism.
Give 2 examples of mutualism
- Mycorrhiza, wherin trees provide carbon and fungi provide access to nutrients
- Lichens, wherin fungi procides structure and algae / bacteria provide food
Spribille et al. 2016 discovered a 3rd symbiotic partner in algae. This was y—. These may help maintain the shape of the algae
Yeast
Give 2 examples of commensalism.
- Barnacles on whales - Kim et al. 2020
- Epiphytes on trees such as vanilla orchid
Give an example of amensalism using walnut trees.
Allelopathy in plants. Walunuts produce toxin julgone which inhibits growth & reproduction of other plants. Reduces competition with them.
Kocace & Terzi 2001
Give an example of parasitism
Mistletoe. Is a hemiparasite. Roots penetrate plant for nutrients and water, spread by bird droppings.
Define hemiparasite
An organism which depends on it’s host for some, but not ALL of it’s needs.
In reality parasitism is more of a g——. This is evidenced in the adders tongue fern, wherin it swithced from being a—— above ground, to a g——- below ground, which takes advantage of fungi beneath it
gradient, autotrophic, gametophyte
3 Main mechanisms for Symbiosisi:
1. C——- - (bees and flowers)
2. H—– t—-
3. E——- (mitochondria & chloroplasts)
co-evolution
horizontal transfer
endosymbiosis
Give some examples of co-evolution - 2
Humminbird hawkmoth and pollinatorsin general
Orchid flower resembling a fly pollinating those flies
How does agrobacerium tumefaciens utilize Horizontal gene transfer?
Infects plants causing crown gall via uncontrolled cell division. Transfers a piece of DNA which is integrated into the plants genome.
Why are walnut trees an example of ammensalism?
Their leaves poison surrounding plants but their real and main intention is to put off herbivores. Thus effect by killing competitors is pretty neutral.
What do ants AND plants get from ant-plant mutualisms?
Ants get food and shelter (shelter primarily as nest sites limited in canopy)
Trees get protection from herbivores & parasites and some food from their dead bodies.
What is a Myremecophyte?
A plant with an adaped structure to shelter ants.
What is a domatium?
Word originated from the latin ‘domus’ meaning home. It is a little ant home that a plant has made.
What does the ant Philidris nagasae do?
Plants and fertilized exclusively the seeds of the species of tree which gives them shelter
T/F Mycorrhizas are the MAIN organ of nutrient transport for most plants
True!!
What are the differences between arbuscular and ectomycorrhiza?
ECTO has cell walls and stays primarily on OUTSIDE of plant roots. Moves AROUND cell walls but not THROUGH them. Has a hartig net instead
ARBUSCULAR has no cear cell walls and penetrates into cells
By what mechanism do AMF help the plant?
Can access much greater area of soil than root alone.
AMF are o—— biotrophs meaning they need their plant host for organic c—– compounds. This has been shown via i—— tracing of c—–
obligate, carbon, isotope, carbon
T/F K—- et al.2017 showed that AMF may rely on the transfer of fatty acids and lipids more so than glucose from their plant host.
Keymar, TRUEE
What evidence did T— 2011 find for the reciprocal reward hypothesis?
Toby et al., Cooperative fungi got more C from the plant
Cooperative plants got more P from the fungi
What is a holoparasite?
One which obtains ALL nutrients and carbon from host. CANNOT photosynthesus.
How did the holoparasite Rhinanthus give back to it’s community?
Despite praying on grassses, it was shown to INCREASE the total biomass of plant communities with it’s nutrient-rich litter fall, basically restoring all the plants it had parasitized.
Most parasitic plants are h——
hemiparasites
How do Shannon’s and Simpson’s indexes aim to improve on species richness?
Aim to account for species EVENESS (relative abundance in a community)
Shannon’s and Simpson’s index have the highest / lowest value when communities are even
HIGHEST
The Simpson’s index gives us the p——- that 2 species taken at r—— in a dataset represent the s— species
probability, random, same
—- diversity gives us species turnover, ie. the number of species UNIQUE between sites
Beta
—- diversity gives us the number of species in ONE population
alpha
—- diversity gives us the number of species in ONE population
alpha
—– diversity gives the number of species in a COLLECTION of different populations across sites
Gamma
Productivity correlates with…..what?
Diversity
Thinking in terms of productivity can help us think about what?
Ways to manage ecosystems and their functions
Thinking in terms of biodiversity can help us think about what?
How to find conservation hotspots
What did Tilman’s park grass experiments do? What relationships did they find?
- Grew grass in different fertilizer / nutrient conditions
- Found negative correlation between no. plant species & nutrients AND hump-backed relationships
Give some key takeaways from all these European grassland experiments / experiments on productivity in general:
- Many d—— relationships in data
- Many d—— measures for p——-
- Species r—— POOR metric of diversity
- Sometimes there’s not enough s—– to reveal patterns, eg. the hump-backed curve
different, different, productivity, richness, sampling
In a meta-analysis, A—- et al. 200- concluded that productivity is a —- predictor of plant species richness. Hump-backed, U-shaped, positive AND negative relationships ALL exist
Adler, 2004, poor
In what type of habitat are POSITIVE biodiversity-productivity relationships found? What does this infer for monocultures?
In major forests, especially tropical
- Liang et al. 2016
Mixed-species forests are much better than monocultures for forestry praxtices.
Across the different taxa, which biodiversity-productivity relationship appears to prevail?
The hump-backed relatiopnship
We can put many different —- through s—— analysis to see which ones show the ——- correlations with species richness / productivity
factors / measurements / things, statistical, strongest.
Strong correlations include soil fertility, richness and climate with productivity, and biomass and climate with richness
Definition: An ecological system which is capable of returning to a state of equilibrium after a pertubation.
Stability
A stable ecosystem is one which can be described in terms of r——, r———, v—— and e——–.
resilient - it comes back fast after perturbation
resistant - can be moved away (to a certain extent) from it’s initial state.
variability
Equilibirum
Why do we care about stability?
It is important in terms of climate change, biodiversity and biological, economic and social resistance to these changes.
What is ecosystem connectivity / complexity?
The number of links between species
What is the calculation for connectivity / complexity?
The number of links between species / the number of species^2*
C = Links / S^2
Species are squared to account for them eating other members of their own species (cannibals)
Connectivity can be described in terms of c—— and r—–
consumers, resource
Connectivity / Complexity is the number of different i——— between c——— and their resources (other s—–)
interactions, consumer, species
Complexity diagrams can show us g——, s—— and v——–
generalism (big no. of other species consumed), specialism (small), vulnerability (consumed by most other species)
Complexity diagrams can aklso show us species r—–, diet b—–, t—- levels and c—— in ecosystems
richness, breadth, trophic, compartments (position in ecosystems)
Can also see trophic cascades
History of complexity & stability:
E—– (1958) argued that simple communities were more vulnerable to disruption and invasion based on his observations of t—— ecosystem.
Mac—– also observed this in A—— ecosystems.
M– challeneged these ideas using r—– communities and found these to be l— stable
Y—– looked at REAL f—- web data and found them generally to be more stable than the random ones.
Elton, terrestrial
Macarthur, American
May, random, less
Yodzis, food
May’s random modelling for stable communities did NOT account for:
- P——
- C——-
- M——-
Allesina and T— found that in natural systems species DO have well-defined interactions and p—-p— relationships ESPECIALLY generated stability
Predation, competition, mutualisms.
Tang, predator-prey
A—— and Tang:
V—— structure leads to more p——- communities (more predator-prey interactions)
Allesina, vertical, persistent
Sh—– et al. 2016:
Compares bees feeding in closeby areas on 2 different food sources. What are the food sources?
What are the pros and cons of each food source?
- Two food sources were fruit juices from guava and nectar
- Fruit juice caused more weight gain and was less energetically expensive to consume, but nectar had a higher sugar concentration
S—— et al. 20–:
Compares bees feeding in closeby areas on 2 different food sources.
Which food source did they prefer?
How does this support optimal foraging theory?
Shackletone et al. 2016
- Bees preferred nectar despite it being less abundant than fruit juice
- Supports optimal foraging as the bees are prepared to spend more time and effort obtaining nectar as it is a HIGHER QUALITY food source for them.
What did Beckerman (1—) discover about trophic cascades?
1. Can be b—– m—— - landscapes of f—
2. Predators - levels away from a process can still have an effect on it
Beckerman 1997, behaviour mediated, landscapes of fear,
4 levels away
Beckerman 1997 - Spiders especially effected processes such as N m——- and ANPP (what does this stand for?)
N mineralization, Annual Net Primary Productivity
B—— 1997 - Sit and wait vs a—- predators had d—— effects on ecosystem processes
active, different
Beckerman 1997 - what did grasshoppers do in response to spider predation? Did this change species richness or species evenness?
Were active at different times of day and moved to more woody and less herbaceous plants, where they would be more camouflaged. This changes species EVENNESS
Beckerman tested if his experiment showed RISK of predation only by having a c—– (inanimate object) and a s—- (fake spider)
control, sham
T/F organisms in marine ecosystems also show trophic cascades
TRUE - Seals & cod & cod food for example
to test t—- c—–, studies hae played sounds of large carnivore to mesocarnivores (racoons) to demonstrate how l—– of f—- operate.
trophic cascades, landscapes of fear
What did the E—- et al. 2—- paper tell us about trophic downgrading?
Estes et al. 2021 - Loss of many apex predators could be our worst impact on ecosystems
- Can lead to loss of entire ecological interactions
- Paper studies top-down degradation on ecosystems
Give some examples the E—- et al. 20– paper gave of processes which could be affected.
- Estes et al. 2011
- Disease
- Wildfires
- Carbon sequestration
- Invasive species
- Biogeochemical cycles
What is the healthy herd hypothesis?
Suggests that predators may GET RID of disease in herds, benefitting their fitness
Give some direct effects of predators on prey ~ 3 (Estes et al. 2011)
- Allow more herbivores to co-exist by being generalists
- Change diet of herbivores
- Change prey growth rate
Give some indirect effects of predators on ecosystems
- Allow other herbivores to compete.
- Allow lower trophic levels to grow.
- Change species evenness of lower prey / primary producers.
- Change functional group composition.
- Change other species growth rates.
- Change shape of landscape - wolves and rivers / coral reef shape.
- Can change ecosystem functioning like decomposition, mineralization and such. Eutrophication.
T/F Trophic downgrading is very different between aquatic and terrestrial ecosystems.
FALSE, all based around the same fundamental processes
Give some things which make communities complex and hard to predict (7)
- Structure
- Complexity
- Traits
- Direct and indirect interactions
- Stability
- Biodiversity
- Function
What model did William & Martinez (2000) come up with? What did they use for their model’s parameters? BODY SIZE relates to the diet-breadth model instead
They created a statistica model which predicted the strucutre of ecosystem in a more accurate way than previous models using only species number and connectance as their parameters.
- More accurate than previous models when tested on freshwater ecosystems.
What are some slight problems with William & Martinez (2)
- Hard to figure out C, ie. what species eats what.
- Prey choice is NOT random - remember that species will choose the most PROFITABLE prey items.
What 3 parameters does the contingency model for optimal foraging use?
E - energy
h- Handling times
lambda - encounter / attack rates
How is diet breadth calculated for the contingency model?
1. Define ——- of species
2. Define -, - and l—– for each species
3. Rank the p—— of each consumers resources.
4. Apply the contingency model
number
E, h, lambda
profitability
What was the advantage of the contingency model over the niche model (William & Martinez)?
The contingency model just needed to know the SIZE of an organism not it’s C.
Body size data has been proved to produce quite accurate predation matrixes.
In consumer / resource matrixes, there is often an u—— t—— pattern
upper triangular
The c—— m—– also applies to prey / lower trophic levels but l— accurately.
It works best on a—– ecosystems, as predators tend to engulf their prey here, and LESS well on organisms only consuming part of their prey
contingency model, less, aquatic
Foraging Biology (used in the contingency model) predicts food web c——- and s——–
complexity and structure
The GENERAL problem with ecosystem modelling (contingency / niche) is what?
The models need to encounter for MULTIPLE factors and COMPLEX ecosystems when facing the threats our planet encounters today. They generally may not
If ecosystem modelling is GOOD, it can make inferences for the f—– from past (paleo deep-time) and present (Lake Windermere) ecosystems.
future
With aij / aji, the larger/smaller the value, the greater the effect of i——- competition
larger, interspecific. aij = 1 is the value for intraspecific competition
Does a higher growth rate stop a species from being outcompeted?
No, in the long run it still leads to competitive exclusion
Under what value of alpha (for 2 species) can competitive co-existence occur?
Which of thesae never really happens in reality due to stochasicity and stuff? Where may it occasionally occur?
Both have an alpha HIGHER than 1.
Both have an alpha SMALLER than 1
1 RARELY happens in reality APART from in remarkably stable ecosystems such as tropical rainforests
Why does stochasicity not increase the likelihood of 2 species coexisting?
Species could just be randomly killed and not come back :(
What does the concept of limiting similarity describe?
It means that species CAN co-exist but must be DIFFERENT enough from one another to do so. Have different niches.
Janzen & Connel both tried to explain H——-
hyperdiversity
J & C noticed there was lots of h—– / fungal infections in tropical forests and that these may play a role maintaining d—– in h——— systems
herbivory, diversity, hyperdiverse
DEFINITION: One tree dying leaving another to fill it’s place. Plays a big role in species turnover in tropical forest.
Gap dynamics
Give some of J & C’s key obersvations
All plants attacked by natural enemies
Many natural enemies specialists
Specialists aggregate on high densities on their hosts.
If a species becomes very common, it will attract high numbers of enemies
Rare species will thus attract fewer enemies
Thus rare species should increase, and common species become rarer.
Explain each of these principles of J & C:
1. Dispersal shadows
2. Aggregation of hosts
3. Local density-dependence
Dispersal shadows: Seed density steeply declines as it gets further away from the parent tree.
Aggregation of hosts: Seedlings aggregate in a small space.
Local density-dependence: Probability of dying INCREASES with seedling density as natural enemies will also accumulate in these areas.
In J&C’s theory, the number of survivors increases/ decreases with distance from parent tree
INCREASES
In J&C, seedling survivorship is best AWAY from the host (where there is lot of h—–) but not REALLY far away (where there just arent many s—-)
herbivory, seeds
How does the J&C model differ from the neutral model for diversity?
Means when one tree dies, it is UNLIKELY that the same species will replace it. Thus common species are LESS LIKELY to win this ‘lottery’
The J&C model means that r— species can have an advantage due to f—— dependence and there is d—– dependence due to density dependence upon the saplings
rare, frequency, distance
J-C model includes local AND global density dependence. What does this mean?
Local = seedling density
Glocal = rare vs common species
In the J-C model, the generation of strong density dependence means that i——– effects are always weaker on species, allowing co-existence
interspecific
What did the Pimm et al. 2023 paper tell us about co-existence?
Supports LIMITING SIMILARITY. Found in pigeon species in new guinea, co-existing species would show MORE variety in size, thus reside in different niches
What is the name of the model which uses body size, handling time, encounter rate and metabolism, and could be applied to multiple stressors?
The Bioenergetic Food Web Model
Why may it be hard to be observe competition? What paper supports this?
It occurred in the geological past and niches may already have been partitioned.
Connell 1980 - “Ghost of Competition Past”
How did Bagchi et al. 2010 show that there WAS overcompensating DD in the presence of natural enemies?
Used fungicide to remove natural predators and see if they played a role.
Is the J-C model right that there are enough natural enemies which are specialists to cause hyperdiversity?
Yes. Analysis of real ecosystems showed correlation between specialist enemies and diversity. J-C model predictions only made slightly higher diversity value.
There IS a relationship between evolutionary d—- and h—– (Bagchi et al. 2009)
distance, herbivory
Density dependence shown to produce higher d——- in the J-C model than the n—– model.
Insects / fungi found to generate the most diversity
diversity, neutral. Fungi
Modern co-existence theory is based on
1. E—– mechanisms which minimize the difference between species allowing co-existence (neutral model)
2. S——- mechanisms which PROMOT co-existence by increasing intra-specific DD (J-C Model)
COMBINES the 2 models
equalizing, stabilizing
Allesina and tang recognised the importance of PAIRWISE interactions, such as…
Predator prey, mutualism, competition and neutral
Loggerhead turtles
Crouse et al. 1987
Phytoplankton
Stomp et al. 2004
