Lec Flashcards Population Ecology Midterm 2

How does elephant seal pop show a bottleneck effect ?

• north elephant seal was hunted to near extinction for oil→ then became protected and population grew again

• Reproducing female numbers dropped below 100 reproducing individuals→ this causes loss of genetic diversity, also can cause different gene frequencies if surviving individuals have a unique combo of genes

• For brief period where population is small genetic drift is going to be acting

• Traits will make it through bottle neck in different frequencies than older population exhibited

• The odds the offspring have genetic diversity puts them at greater risk for disease and parasites

• If population drops that means losing individual carrying specific alleles→ after several generations heterozygosity will drop

Founder effect

• a new suitable habitat opens up and a subset of the original population moves and colonizes it

• The subset could represent the parent population allele frequencies but also by random chance there will be a new combination of alleles

Principle of Allocation

• an organism only has so much energy

• In juveniles that energy will go into growth in adults it could go into maintenance, reproduction, hormones & organs, or growth of fetus

• A species is going to have to allocate for one thing or another→ won’t be a conscious choice is selected for

What are some allocation trade offs in reproductive strategies of plants?

Seed size by dispersal strategy: a trade-off btw making less but bigger seeds or producing thousands of seeds that are smaller and have low energy reserves

Unassisted seed dispersal: drop down & put down roots, won’t even compete w/parents bc they are annual plants

Wind dispersal- seeds can’t be heavy need to be small to be carried by wind

Animal dispersal- adhesive seeds will stick to animal and fall off in new habitat, still need to be light but being bigger could be benefical

Animal seed dispersa specific example

• ants collect a to of seeds, some will have a chance to germinate before they get eaten,

• Some seeds can be bigger bc the animals can carry them→ birds will eat fruit and then drop the seeds with fertilizer (poop)

• Scatter hoarding- collect a lot of seeds and cache them, seeds need to be big enough to be enticing but trade off is that less seeds can be made

Energy Allocation in birds that are in temperate zones

• if you have a larger clutch you will have to make more feeding trips and will die more likely, mortality rate goes up for the parents

• Provisioning per offspring, as clutch size goes up less food to spread between all of them

• Temperate birds make much more offspring but can’t put as much energy into them

• Tropical birds wil have smaller clutches but can incest more in them

How do guppies use the principle of allocation

• if predation is high guppies will produce more offspring in that area as quickly as possible

• Trade off is smaller embryo size

• In high predation zones parents put way more energy into reproduction, in areas with less predators they will survive longer to have more chances to reproduce

• Size of maturity for male fish under high predation will be smaller, a larger male would be a better competitive mate but probably won’t survive long enough to grow that much→ give up potential competitive edge bc predation is a bigger selection pressure

Iteroparity

An organism can reproduce multiple times over lifespan

Semelparity

Individual can reproduce only once in their life and then die→ extremely risky need a specific set of conditions for this to be worth it

• agave- put all energy into growing huge flower stalk to produce many seeds as possible which can overwhelm predation pressures

• Salmon- swim upstream, modify physiology to swim in freshwater to get to best possible place to spawn eggs and then die

• Northern quoll- only males semelparous, will put so much energy into reproduction that their immune system shuts down and they die

What conditions lead to Semelparity?

• high mortality rate

• Seasonally harsh conditions→ if they have a short lifespan want to put everything into that reproductive event because probably won’t get another

• For pants they will only reproduce if the conditions are very good→ store up energy, wait until conditions are right, put all energy into reproducing because they don’t know when the best conditions will happen again

Optimal reproductive effort

Putting enough energy into producing a lot of offspring in the present but not enough to harm reproduction in the future

Asexual Reproduction Benefits

• low cost

• 100% gene transfer

• Quick and efficent

Binary Fission

• circular chromosome→gets replicated→segregation of DNA→cell splits into to

• Really fast

• Is really good for disease and parasites to rapidly reproduce before immune system takes notice

Vegetative Reproduction

• parent plant puts out shoot and runner plant

• Stays attached to parent plant and puts down roots when it touches ground

• Strawberry plants do this and they also spread seeds

• Hydra (animal)- have bud polyps that come out of parent, and eventually fall off→ if any of the buds reproduce its like the parent reproducing

Parthenogenesis

• if the parent happens to be haploid→ can’t undergo mitosis, only meiosis to produce one locate and haploid zygote

• In diploid if eggs are produced by mitosis, end up with diploid egg→ doesn’t need to be fertilized

• In some cases can produce egg through meiosis→ produce locate, 2 haploid locates can come together to fertilize each other

• Has only been seen in kayuga the mouse who was manipulated to produce

Costs of Sexual Reproduction

• only 50% of genes are passed on

• Takes a lot of energy

• Must find a mate

• Slow growth rate

Coral Spawning and Salmon

• gamete bundles are released→ disintegrate in water column→ eggs and sperm mix

• Broadcast spawning

• Female salmon will lay eggs and male will swim over and release sperm

Barnacle Mating

Anchored in place, but use internal fertilization

• have largest penis relative to body own body size

• Are hermaphroditic

• Have at least some amount of mate choice with internal fertilization

• If an organism is producing shelled eggs need internal fertilization

Red Queen Hypothesis

• parasites evolve quickly, high reproductive rates

• If hosts don’t evolve fast enough parasite will wipe out hose

• Only way to combat this is to maximize genetic diversity

• The cost of being parasitized is so high it is worth the cost of sexual reproduction

Red queen hypothesis in snails

• snail that is parasitized by flatworm

• Infection by the worms sterilizes the snail so they are evolutionary dead

• Rage selective pressure for snail to not get parasitized

• The snails can reproduce sexually and asexually

• In shallow water where worm dropped through bird feces can find way more males which indicates sexual reproduction taking place

• More females found in deeper water, less parasites, asexual reproduction through parthenogenesis more common bc don’t need as high genetic diversity to combat parasitism

Protogynous

Born female (safer reproductive strategy) when they are bigger turn into male where they can take risk of completions but payoff more fertilization

How do we end up with sexual dimorphism

By having a choosy and non choosy sex

Mate Gaurding

Preventing partner from mating with other individuals

• behavior of excluding other mates of a chosen mate

• Males will attach to body of female so no other males can mate w/female

• Mating pug- after mating with female insert plug so no other males sperm can get to her eggs first

Why has extra pair copulation evolved

• for a male extremely beneficial- sperm is cheap and can fertilize as many female eggs as possible, also can reduce potential completion with other males because they all of young spread out in different nests so they don’t want to harm a potential offspring

• For females it maximizes genetic variation of offspring

• A good parent who invest energy into offspring not necessarily the same individual who has the best genes

Benefits of Group Living

• protection- way to physically defend each other

• Predator dilution- odds of individuals getting preyed upon is a lot over w/many individuals present

• Increase access to mates for the male that remains

• Shared resources through cooperation- babysitting, shared parental care, care among each other

Costs of Group living

• if you exceed carrying capacity not enough resources

• Social interaction comes at an energy cost

• Competition for mates

• Compete for resources- even if enough it is helpful to be selfish

• Disease spread

• Predator specialization- specialize in eating large clumped group of prey

Wolfpack territories

• each pack of wolves has very defined region where they are the only ones allowed to hunt

• Only a group of wolves could hold that size of a territory which allows them to have access to all those resources

• If cost of excluding predators is less than cost of competing with them→ territories develop

Case Study of Florida Panthers

• current range is small area in southern tip in Everglades-endemic

• Can predict presence of finding them based on habitat parameters→ fragmentation w/in their range due to too much water

• Epilation needs to protect this range along with buffer zones if they move

• Had very low abundance

• Stepped in with genetic breeding w/Texas panthers- can’t do a census bc of the natural behaviors of the panthers

How can we estimate population sizes?

• species per unit area- works well if species evenly distributed

• Capture and tag- reproduction/death

• Camera traps- get a sense of how many panthers are in a given area

• Fur traps- sticky stamping when they walk by can distinguish DNA and create a database

• Mark and recapture method

Mark and recapture method

• catch as many animas as possible and take them so you can re-id later

• Then sample again→ some will be tagged some wont

• If half the individuals in the sample are tagged it can be assumed you’ve tagged half the population

• Problems: can affect survivability, mark can also affect recapture likeliness if it makes the individual more visible

• If a species is territorial or has uneven distribution can also not make it ideal

Density

number of individuals per unit area or volume

Dispersion

How individuals are spatially arranged in a given area

Dispersal

How they spread out from their place of origin

• in marine life→ planktonic larval dispersal through currents

• In panthers females travel max 20 km, males 70km, vulnerable period while they are traveling

• Toads- as tadpoles in water to adult habitats

• A lot get killed in collisions- set up tunnels but have to set up nets to guide them to the tunnels

• To do this have to know exactly when dispersal period is (duration)

Subpopulations

• patches of individuals separated by habitats that are part of a larger population

• Subpops will have some interconnectedness

How do we determine subpopulations?

• how often they interact

• Fragmentation- how far are the patches from each other

• Can use different mathematical models to determine

Metapopulation

Loosely connected subpopulations

• a set of islands w/habitat patches, is harder for individual to move btw islands

• Non equilibrium status- highly isolated pops are very cunerable

• Can look at size of patches→ small and large

Why is it important to understand connections btw subpopulations?

• disease spread

• Landscape connectivity

• Understand gene flow

• Conservation implications

• Can mode two different starting habitats for butterfly based on optimal habitat→ can start w/lots of patches and then less

• After climatic event can see change in quality of habitat and disappearance of butterflies in certain habitats

Study on Orangutans population

• threatened by palm oil plantations in Indonesia

• Palm plantations are horrible habitat→ no understory, no branches for movement

• Orangutans only live in forest, rarely leave tree cover

• Patches in middle will probably be cut down

• Found that in females unless they’re very close together wont use the patches in the middle, males will use them to move farther to find other females

• Get a sense of maximum crossing distance for males, the fragments are necessary for maintaining connectivity or the connectivity btw populations will be lost

How do source sink models work?

• sources are we here young are coming from that move to other zones in the meta population

• Sinks- where populations move to but there is not reproduction, like adult toads moving to forests but they won’t reproduce there

• In marine ecosystems larvae disperse with current, southern pops will be source and northern will be sink bc it won’t contribute larvae back to the Metapopulation as a whole

• If there is a disaster at the sink population it will recover and repopulate from the source but the same will not happen if something happens to the source- important to think about for allocating conservation resources

Population growth

No restriction to an organisms reproduction- no predation, competition (rare in stable habitats but can be found in new habitats)

Population growth equation

P=P0xe^rt

Population size at a given time = starting population x X x constant to the percent growth rate x time in hours or years

• under absence of competition

To maximize P can have a larger starting pop, increase reproduction rate, increase amount of time

Age structure diagram

• need a lot of ages to do this

• Population w/wide base→ lots of young individuals

• Triangle concave- fast growing pop with lots of young

• More linear triangle- still producing a lot of juveniles but they are replacing the adults so growth is slower

• Half circle- stable pop

• Half circle bottom concave in- declining pop

• Can predict how individuals will age up in a few years- in humans this is easy to do bc of records

Net Reproduction Rate

Number off female offspring we expect a female to produce over her life span

R0=sum(Lx*Bx)

Net reproduction rate= sum of (survivorship * birth rate)