Myron lectures: 24-31

Question 1

what is ecology?

Answer 1

> the study of the interactions that determine the distribution and abundance of organisms

Question 2

what is ecological theory?

Answer 2

> explanations or ideas that attempt to account for species abundance and distribution (a and d) - these are in effect ‘models’
predict changes in a and d under different conditions

Question 3

what are some theories surrounding regulating populations?

Answer 3

> predation
- top down model
- parasitoids, predators, parasites, pathogens all control the subject organism
resource limitations
- bottom up model
- plants and other food sources regulate the subject animal
Competition
- side to side model
- other organisms control the subject organism
the ecological theatre
- physical factors and climate all effect the habitat of the organism and therefore effect its a and d

Question 4

what factors control all types of interactions?

Answer 4

> the climate influences all controlling mechanisms

Question 5

why is ecology complex?

Answer 5

> the number of species that exist in a given location, the changing environment, makes ecology a difficult discipline
complexity means most ecological data analysis requires statistical approaches

Question 6

what sort of questions do ecologsts ask?

Answer 6

> where organisms are found? - fluctuates
> when the species may occur
> how many occur
> change in numbers
> WHY??

Question 7

how do you go about answering the important questions in ecology?

Answer 7

> natural history 
 - observation
 - describe
> quantitative natural history
- count and measure
> experiments involving manipulations of animals, plants or habitats
> comparative approach: test by comparing 'ecology' of a large number of species
> models and modelling
 - predictions

Question 8

why do we use models in ecology?

Answer 8

> to identify what may happen
to identify key processes that need to be studied and data that need to be collected
to bridge the scale gap between experiments and problems
because management requires models

Question 9

what are some uses for models in ecology?

Answer 9

> population management for conservation or exploitation
invasions
pest management
predictions

Question 10

what determines large scale fluctuations in plant feeding insect abundance?

Answer 10

CLIMATE
> affects resources (K)
> affects reproduction and survival (lambda)
> will have a strong influence on seasonal and year to year abundance and distribution

Question 11

what is a population?

Answer 11

> all individuals of a specified species in a given area
OR
the group of potentially interbreeding individuals at a given locality
OR
all members of a local populations that share a single gene pool

Question 12

what defines an area or locality?

Answer 12

> area such that two individuals have equal probability of mating
the behavior of mating is important

Question 13

how can some populations be defined?

Answer 13

> if there is regular exchange of individuals
can tell this via mark and recapture
if there is some sort of barrier to movement between populations
in practise or operationally for research purposes a population is what a researcher chooses to call a population. IE we define the boundaries
must measure the flux across these boundaries

Question 14

what is a metapopulation?

Answer 14

> a population of population with little movement between them

Question 15

what are two key points about populations?

Answer 15

> individuals that make up a population are unique (variable even though one species)
movement and gene flow define the population boundary

Question 16

how can it be hard to define individuals?

Answer 16

> for clonal organisms such as fungi and corals and some plants it is often not possible to clearly define individuals
biomass or size are used instead of individuals

Question 17

what is scale?

Answer 17

> populations can be defined on very different scales
what defines a population is gene flow
plants: pollen flow and seed dispersal
animals: movement-habitat interaction

Question 18

what are habitat patches?

Answer 18

> the vary in:
size or area
shape
location and suitability

Question 19

what are some properties of populations that can be measured?

Answer 19

> size or number, density
> age structure
> sex ratio
> changes in these
> the contributing processed 
 - B,D,E,I
> with this knowledge over time we can estimate population growth

Question 20

what are important factors for population growth?

Answer 20

> r - intrinsic rate of increase
Ro - net reproductive rate
lambda - multiplication rate

Question 21

what are population and habitat units?

Answer 21

> sources 
- b>d
- I classical populations
 - B=D
 - I=E
> sinks
- BE
- if I--> 0 then population goes extinct 
> potential sinks B empty habitats 
- B>D
- I=0

Question 22

what is a habitat?

Answer 22

> often treated as synonymous with vegetation category or biome, ecosystem type, community, spatial mosaic and foraging patch
places where a species normally lives, often described in terms of physical factors
the resources and conditions present in an area that enable occupancy - including survival and reproduction - by a given organism.
habitat is organism specific. it is the sum of specific resources that are needed by organisms
a place where a species can complete its life cycle

Question 23

how do you measure habitat?

Answer 23

> mapping
physiological ecological approach
observational
experimental

Question 24

what is a species niche model?

Answer 24

> > species niche distribution models the realised niche. they do this by describing the environment in which the species is found - generally in terms of the bioclim variables, and sometimes including non-climatic variables.

Question 25

what is climax?

Answer 25

> describes how the species population responds to environmental variables. SDMs describe the environment, where CLIMAX describes the species.

Question 26

why are empty habitats important?

Answer 26

> if 'suitable accessible habitat' s empty then species are limited by other species, either predation and/or inter-specific competition, or > if all habitats are full, the intra-specific competition is likely important > but how suitable are empty habitats

Question 27

how do you determine if an empty habitat is suitable?

Answer 27

> do a transplant experiment. > if transplant successful - habitat is suitable. Distribution limtied because of access or species fails to recognise area as suitable > transplant not successful - habitat not suitable either due to other species or due to some other requirement (chemical or physical) not being met

Question 28

why are species absent?

Answer 28

``` > dispersal? - area inaccessible > Behaviour? - habitat selection > Other species - predation, competition > physical and chemical factors? - temp, light , moisture, fire, salinity , pH, nutrients ```

Question 29

what is a resource?

Answer 29

> resource life expectancy goes down and the organism using its life expectancy goes up > they are important for habitats because resources combine to give habitats by intersection and union or equivalence and equality

Question 30

what are the different types of habitat/resource boundaries?

Answer 30

> contiguous union and disjointed union via movement >disjointed non-union linked by seasonal movement - count both habitats - migration needs to be taken into consideration > metapopulation of to habitat patches linked by random movement

Question 31

what do individuals vary in?

Answer 31

> age, stage, size, location etc > contributes to likelihood of survival, reproduction and movement > need to be able to get a handle on this to estimate contribution to potential population change - estimate demographics > interested in life-history evolution

Question 32

decribe development

Answer 32

> organisms have to grow, develop and survive to the reproduction stage and reproduce for a population to persist in a location

Question 33

unitary vs. modular organisms

Answer 33

> most animals are unitary - develop from a zygote through a set of irreversible changes; form is determinate > most plants are modular - growth and differentiation occurs at meristems along roots and shoots. plants are thus repetitive modules. timing and form are complex but predictable. colonial animals also modular

Question 34

what do age and module structure d?

Answer 34

> influence potential population change and growth of individual

Question 35

what is the best to measure for demographics? age, stage or size?

Answer 35

> age - usual for mammals and birds - individuals of the same age are similar - assumes you can age individuals - computationally simple - time step and age step are the same > stage - life history stage: egg, larva, pupa, imago - time step and stage duration differ > size - useful if individuals of same age can be very different - need to define size classes - describe growth rate to estimate size class transitions

Question 36

what are the different types of life cycles graphs?

Answer 36

``` > age structured models > stage structured models - can stay in same age class per time step > messy life histories: coral colonies - can fragment and o back to a smaller class ```

Question 37

what is important about temperature and development?

Answer 37

> for 'poikilthermic' (not warm blooded) organisms (insects, plants, frogs etc) development is a function of temperature > how rapidly they progress through their development stages depends on how warm/cool it is

Question 38

what are degree days?

Answer 38

> the amount of heat needed by an organism to progress to the next life stage. temp x time

Question 39

what happens to populations that exist in different habitats? (same species?

Answer 39

> in a cold environment, only have three generations in the time that a hot environment has 7. > these two populations will have very differnt future potential growth rates, PGR. you can estimate PGR using life tables.

Question 40

what are life tables?

Answer 40

> age-specifc summary of the mortality rates operating on a 'population' > can include reproduction > to construct life tables we need to estimate the number in each age class

Question 41

what is a census?

Answer 41

> complete count of all individuals in population > sometimes possible for small, closed populations of very observable 'things' - trees in a small patch of forest - birds on a small island - koalas in a forest remnant > usually impossible - bad!!

Question 42

what is the sub-sampling methods?

Answer 42

``` > quadrats and transects - try to census population in a sub-sample of total area > design issues - how many sub-samples? - what shape should they be? - how should you select them? ```

Question 43

what is the sampling theory?

Answer 43

> how many are there? estimating p > known area, A? known density D, then P=DxA > take n small areas each of area "a", count or census the number xi in each and estimate density D, D=Exi/n

Question 44

what is the number entering stage?

Answer 44

>area under population curve divided by stage duration | > mortality estimates only as good as individual population sample estimates!

Question 45

what are cohort life tables for species with discrete generations?

Answer 45

> apply mostly to annual species or species with short lived adults > a cohort life table follows a single cohort of individuals (those born at the same time) from birth to death of the last one

Question 46

cohort tables with life histories that have overlapping generations

Answer 46

> many birds corals and trees, mammals > hard to get data as it is difficult to recognise cohorts and follow fates of individuals > easier for sessile organisms

Question 47

how do you quantify life histories?

Answer 47

> life tables - mortality and survival with age > fecundity schedules - show how patterns of fecundity change with age > realised versus potential fecundity > problematic in the field

Question 48

what are the columns in life tables?

Answer 48

1) stage or age interval, x 2) number of individuals in the 'population' at start of each stage or age interval (Nx or ax) 3) Lx: proportion of original cohort alive at start of each stage (lx = Nx/No) 4) dx: proportion or number dying during each stage (x = Nx-Nx+1) 5) qx: stage-specific mortality rate (qx =dx/lx or =dx/Nx) is a measure of the probablility of an individual dying during the stage 6) kx: or killing power reflects the intensity or rate of mortality; can be summed and compared across studies (kx=lnNx+1 - lnNx)

Question 49

what is a fecundity table?

Answer 49

> Fx: total number of eggs (offspring) produced during each stage (realised) > mx: the individual fecundity or birth rate per female; mx = Fx/Nx > lxmx: eggs produced per original individual in each stage

Question 50

what is Ro?

Answer 50

> basic or net reproduction rate > the mean number of offspring produced per original individual by the death of the last member of cohort > either sum of Fx divided by No (total number of offspring produced by the cohort per original number of individuals) or as the sum of the lxmx (sum of offspring produced per original individual during each stage) adjusted for sex ratio > Ro indicates to what extent a population can increase or decrease.

Question 51

how do you estimate Ro and lambda?

Answer 51

> Ro fundamental net per capita rate of increase or NET Reproductive rate > lambda is the multiplication rate per generation > if a population doubles every time interval then lambda = 2 > lambda = Nt+1/Nt

Question 52

how do you estimate r?

Answer 52

> r=lnRo/T, > the rate at which the population increases in size (changes in population size) per individual per unit time > and T is generation time > for discrete population T=1 and Ro = lambda > or r=ln lambda for organisms with discrete generations (univoltine) - one generation per year. > in populations with overlapping generations r is the intrinsic rate of increase that the population has the potential to achieve IFF lx and mx are stable over time > if this occurs then age structure becomes stable, and the population grows exponentially >rare

Question 53

what happens to population projections on a spreadsheet

Answer 53

> for given mortality and fecundity schedules, population settles down to exponential growth > but initial behaviour depends on starting conditions > e.g., starting with juveniles or with reproductive adults

Question 54

what are leslie matrixes?

Answer 54

> results (eventually) in exponential growth or decline > reaches a stable age distribution (fixed proportion of individuals in each age class) > can be generalised to stages of differing length (lefkowitz matrix) - individuals can remain in stages, jump stages and drop to previous stages.

Question 55

what is population dynamics?

Answer 55

> change in the abundance and distribution of a species over time > animal and plant populations show a wide range of dynamic 'behaviours' in both time and space > important for measuring outbreaks

Question 56

compare fluctuations in Ni

Answer 56

> N1,N2...,Ni.....Nt > log range (LR) = ln(max(N1,Nt))-ln(min(N1,Nt)) > Ri = Ni+1/Ni = the multiplication rate or some similar measure of growth rate > and the variances > growth rate determines how quickly a population changes

Question 57

is there a pattern of spatial variation in abundance over a species geographic range?

Answer 57

> most dense in the middle of the climatic range, then gets thinner to the edges of the habitat, but this can change with changing climate.

Question 58

what is regulation?

Answer 58

> regulation or a regulator that speeds up or slows down with population size around an equilibrium (often equated with k, or carrying capacity) > since K varies (note this may be a different concept for k) we get regulation that reduces the range of population fluctuations (i.e., the variance in N)

Question 59

what is the regulation belief based on?

Answer 59

> crude evidence, impressions or short data sets that suggest population levels change little from year to year. (this evidence is little more than a mean level of abundance which is often confused with k. is the variance bounded?) > logic, given the potential for species to increase 'something' must prevent them from: a) increasing indefinitely and/ or b) over exploiting their habitat and/ or c) going so low as to go extinct. >HOWEVER populations do go extinct and they do over exploit habitats during outbreaks, and the potential for increase does not have to be realised, which may or may not have anything to do with population density

Question 60

how do we interpret changes in abundance?

Answer 60

> either fluctuations in Nt are around some characteristic level, that is extinctions and outbreaks are rare? OR > do populations persist? with outbreaks and localised extinctions from time to time?

Question 61

what happens if we accept populations are regulated around equilibrium?

Answer 61

> what could achieve this? which biotic factors could have a density dependent effect on: > Death and Emigration > Birth and Immigration > regulation is almost always believed to be due to intra-specific competition and or natural enemies > Death (four ps) > Births (size 'competition) > if this is the general model for a species population ecology then it ha many implications for population dynamics, life history strategies and even speciation (r and k selection?)

Question 62

what views do populations that hold regulation follow?

Answer 62

1) population size determined by equilibrium level which is set at or below the carrying capacity, k 2) density dependence (DD) acts on all population densities, to varying degrees 3) DD factors are intra-specific competition and natural enemies (four Ps) 4) resource limitations infrequent 5) extinctions are rare

Question 63

what is the evidence for no DD?

Answer 63

> real populations appear to exist without DD > extinctions do occur > resource limitations also occurs > BUT apparently life tables are too crude to detect DD which must be present! data too short and subject to perturbation and stochastic effects

Question 64

what are the problems with regulation emphasis?

Answer 64

> density dependence is infrequent > rare species and local extinctions? > many other ecological factors are important > no common ecological influence across species > ignores specific relationships and biology

Question 65

what are some alernatives to regulation

Answer 65

> That population density of insects 'regulated' primarily by effects of weather or climate - so called density independent factor > approach population dynamics by looking at all the components of the environment that affects survival and reproduction of individuals - in fact the reject the notion of regulation > spatial heterogenity - difficulty in finding resources > intraspecifc competiton > abiotic factors limit herbivore numbers > different shade of green (N, Toxins etc.) > carrying capacity is expressed as the capacity of resources available, not the mean density of the pop.

Question 66

what is the resource limitation model?

Answer 66

1) ultimate population size determined by a ceiling set by L (=resources, not N) 2) density dependence, only sometime in some populations and only at narrow high range densities 3) density dependence is by intraspecific competition 4) resource limitation frequent, at least locally 5) extinction frequent, at least locally

Question 67

what is the general model for resource limitation

Answer 67

> to include all factors that affect deaths and births, both quantity and quality of resources (e.g., nitrogen) and weather > envisage many independent factors each with a positive or negative effect on b and or b > as we increase the number of factors from 1 to k then variance of Ni stabilises because r will be 0!