Midterm 1 Flashcards
What does community ecology focus on?
focuses on interactions between different communities; understanding the structures of communities
What’s the definition of a community?
the group of species that occupy a given area, interacting either directly or indirectly
What’s the definition of biogeography?
focuses on the spatial distribution of organisms
What does ecosystem ecology focus on?
focuses on the nutrient flow in different parts of an ecosystem and between ecosystems, as well as energy flux
What does population ecology focus on?
Focuses on one or two population(s)’s dynamics
What is facilitation?
One species needs another species in order to thrive; it occurs when one species positively impacts the fitness of another species
true or false: community structure is a spatial concept?
TRUE
What are the 4 components of the structure of ecological communities?
1) species richness
2) Abundance
3) Evenness
4) Composition
What is species richness?
of species in the community
What is abundance?
the total # of individuals in the community
What is evenness?
The spread of individuals among species
What is composition?
A comparison of the identity of species between 2 or more communities
True or false: it’s impossible to define a community
TRUE: because it’s impossible, we often have to standardize the amount of area being studied
What are the 3 reasons as to why ecologists care about the structure of ecological communities?
1) Understand the processes that enable the maintenance, and govern the distribution, of biological diversity
2) Biodiversity has intrinsic value for many of us, and provide services to humans
3) Better understanding how biodiversity is maintained through time and distribution in space is essential foe effective conservation efforts
Where do the prairies reside and how were they created in the US/CANADA?
They extend from Alberta to Midwestern states and they follow the Rockies and they were created by the Rain Shadow effect due to the Rockies
What % of prairies remain intact?
less than 1% remain intact, mostly in small isolated patches so vegetation in prairies became scarce
What are 2 reasons that the 1960s efforts to reverse prairie loss were met w/ failure?
1) Small pops were too distant from other patches, preventing pollination
2) A lack of understanding of the role of natural disturbance (ex: fire) - they prevented fires which some species rely on in order for seeds to grow. A certain level of disturbance is required to maintain biodiversity
The success in community restoration today is the product of what?
product of a better understanding of community dynamics
What is relative abundance?
Represents the % of individuals (ni) each species contributes to the total # of individuals (N) in a community. Something we assign to a given species and it’s used to quantify evenness
What’s the formula for relative abundance?
P = (individuals of one species/total # of individuals) x 100%
Why is it better to use the scientific name of a species in science? (2 reasons)
1) 2 different species could have the same common name
2) the same species could have multiple common names
What is the simplest measure of diversity?
Species richness
True or False: When estimating richness within a single community, we have to count every single type of species?
FALSE: we usually rely on an estimate rather than an absolute # (except for plants which don’t move)
What do we need to do to estimate the # of species?
we need to delineate a sampling area
What do we use accumulation curves for?
used to assess the completeness of the sampling effort, and therefore our level of confidence in the estimation of (S)
In accumulation curves, what’s on the y-axis?
cumulative species richness (S) meaning if you have 4 species in sample 1, the cumulative richness for sample 2 will be all new species plus # of species found in sample 1
In accumulation curves, what’s on the x-axis?
of samples
What can we conclude if a plateau is not reached on an accumulation curve?
If no plateau is reached, we CANNOT be confident in our estimation of S and the sampling is incomplete and our species estimation is inaccurate
What should the accumulation curve do as less and less new species are being found?
it should reach a plateau due to the asymptote
What 2 things can you do if your accumulation curve isn’t reaching a plateau?
1) Increase the number samples so that less and less new species will be discovered
2) Ensure you’re covering all areas because species can change with light cover, etc.
What are rank abundance curves used for?
used to compare the species richness visually to see which community is more even
What part of the rank abundance curve demonstrates evenness?
The slope will be flatter
What part of rank abundance curves demonstrates species richness?
Number of dots
True or false: Understory dominant species are the same as a canopy dominant species?
FALSE: Dominant species are usually defined for different taxonmoci or functional groups of organisms within the community
True or false: a community with a high level of dominance also exhibits high evenness?
FALSE: a community with a high level of dominance exhibits low evenness
What can dominance be reflected by?
can be reflected by # of individuals, size of individuals (biomass), or some combination of both characteristics
Why are some species Dominant?
Because under the conditions of the community, those species are performing well in terms of growth, survival, etc.
What do diversity indices provide?
they provide a way to quantify the relationship between species richness and relative abundance
What are 2 examples of species diversity indices?
1) Shannon-Wiener diversity index
2) Simpson’s diversity index
How is species composition quantified?
It can ONLY be quantified in relation to another community
What do multivariate statistical methods such as ordination allow for?
They allow for more sophisticated comparisons of community structure based on species composition
What does Ordination graph look like?
The axes act as a form of similarity between 2 points
In ordination graphs, what does the distance between two dots mean?
When dots/communities are right next to each other, they’re very similar in the species they have (similar species composition)
What is an ordination graph used to show?
Shows the similarity in composition between different communities
In the example of ant communities (Ground, Shrub, and Tree), what was the conclusion that was derived from the ordination graph?
Ants that you find on the ground, on shrubs and on trees are different from each other. There’s clustering of the points/communities. These differences between groups of ants on different substrate types is likely due to the adaptations each group has developed based on their environment
What dictates species composition?
Adaptations
What does ecological biogeography study?
It’s the study of the spatial or geographical distribution of organisms, both past and present
What does biogeography work to describe and understand?
works to describe and understand the process responsible for patterns in the spatial distribution of species, species diversity, and species composition
What are 3 approaches used to map spatial patterns of community composition?
1) Biomes
2) Ecoregions
3) Biogeographic regions
What are biomes?
Large-scale regions describing spatial variation in plant growth forms and climate; divides the planet into areas depending on the type of plant forms
What are the 3 main forms of plants that are described in biomes?
1) Grass
2) Shrubs
3) Trees
What plant form occurs in boreal forests?
Conifers because boreal forests are prone to insect outbreaks so the trees need to be adapted to surviving this. Conifers have needles that make them impenetrable and their sap acts as a barrier
What are ecoregions?
Small-scale regions describing spatial variation in plant growth forms and climate. Can take biomes and dissect them into mini-ecoregions
What are Biogeographic regions?
Large-scale regions describing spatial variation in species composition (of animals, plants, microbes, etc.). Only use data on species composition and they use the data to delineate the world into different large-scale communities
Who first noted that biome types differ in response to a distinctive pattern?
First noted by R. Whittaker (Cornell University)
What 3 things influence the occurrence of a biome in a location?
1) Topography
2) Soil type
3) Disturbance
What is topography the study of?
It’s the study of the forms and features of land surfaces.
What are the patterns of temperature across the planet?
Mean annual temp decreases form the equator to the poles, while seasonal variation in temp increases
What are the patterns of precipitation across the planet?
Mean annual precipitation (generally) declines with decreasing mean annual temp
Why is precipitation more complicated to predict than temp?
Oceanic currents and mountains can change precipitation patterns
What decreases as one moves from the tropics to the temperate and arctic regions?
Moisture availability decreases as you move from the tropics to colder regions
What key trait influences the distribution of trees and leafy plants?
Leaf longevity
What is the leaf longevity for deciduous trees?
Leaves live for only a single year or growing season
What is the leaf longevity for Evergreen trees?
Leaves live beyond a year; includes the lineage of broadleaf conifers in the tropics (evolved twice)
How many times have broadleaf conifers evolved?
Twice
Plant life and leaf type are distributed relative to what?
Their distributed relative to climate (precipitation and temp)
Where are broadleaf evergreen trees found?
tropical or subtropical forests
Where are winter-deciduous trees found?
temperate forests
Where are needle-leaf evergreen trees found?
conifer forest or taiga (boreal)
Where are trees no longer supported?
past the tree line, giving rise to tundra
True or false: the evolution of certain key traits will allow survival in certain environments which may explain distribution?
TRUE
What trees dominate tropical forests?
dominated by broadleaf evergreen plants (always green and don’t shed)
What regions are rain forests located?
they’re restricted to the equatorial zone between 10N and 10S
What is the mean temp of a tropical rain forest?
18C
What is the minimum monthly amount of precipitation in tropical forests?
> 60mm
What is the blue bar represent and which y-axis is it?
blue bar = average temp; y-axis on the left
What is the red bar and which y-axis is it?
The red bar = precipitation; y-axis on right side
**TRICK = RED = RIGHT
What is denoted on top in metres?
Elevation
Where are tropical savannahs found?
almost always next to rainforest
What kinds of vegetation occur in tropical savannahs?
characterized by a ground cover of grasses with scattered trees or shrubs
What’s the difference between grasslands and savannahs?
Grasslands = temperate and Savannahs = subtropic (near equator)
How many vertical layers doe savannahs have?
have 2 layer vertical structure: 1) grasses and 2) trees or shrubs
What are 2 characteristics of savannahs?
1) occur on land surfaces of little relief
2) fire-adapted vegetation
What is the climate like in savannahs?
they’re very warm, but have rainfall based on season; total precipitation per year falls between medium to high
What controls the distribution of savannah vegetation?
water availability: rainfall seasonality, AND soil texture, structure and water-holding capacity
What’s the difference in the soils of savannahs and grasslands?
Grasslands = clay particles which are much smaller and they pack tighter, thus retaining a lot of water and will get flooded.
Savannahs = sand particles which don’t retain water because they’re much larger
What are grasslands?
areas where the vegetation is dominated by grasses and are one of the largest biomes on earth
True or false: grasslands are one of the smallest biomes on earth?
FALSE: they’re one of the largest biomes on earth, covering 31-43% of the Earth’s land area
What % of area do grasslands cover?
31-43% of earth’s land area
Why have grasslands shrank and by how much?
Natural grasslands have shrunk to less than 12% of their original size because we used the majority of grasslands for agriculture
Where do grasslands occur?
occur in mid-latitudes in mid-continental regions where annual precipitation is reduced
What does the climate look like in grasslands?
low levels of precipitation as well as cold winters and hot summers
In comparison to the mountains such as the rockies, where are the grasslands?
On the east side there’s always grasslands because of the “rain shadow effect”
Why are Grasslands are characterized by many ecoregions?
because depending on the type of clay = change in type of grasses
Where do temperate deserts lie?
in the rain shadow of mountain barriers or are located far inland
What % of the Earth’s landmass are occupied by deserts?
25 to 35%
What is the distinctive characteristic of all deserts?
lack of precipitation
In deserts, what does the temperature look like?
The difference in temperature throughout the day is one of the most extreme because it gets extremely cold at night
What’s the name of the largest desert?
The Sahara Desert
How long ago did deserts appear
250-300 mya
What is the dominant or co-dominant plant form in shrublands?
shrubs = plant with multiple woody, persistent stems and a height from 4.5-8m
What is the definition of a shrub?
a plant with multiple woody, persistent stems and a height from 4.5-8m
What does the climate look like in shrublands?
Either a dip in precipitation around july with increase in temp or an increase in precipitation with decrease in temp.
Highest rain: 200 mm
What does the climate look like in temperate deciduous forests?
The temperature varies widely from season to season with cold winters and hot, wet summers. The average yearly temperature is about 10°C.
What type of vegetation dominates temperate deciduous forests?
dominated by broadleaf deciduous trees
Why have most deciduous forests disappeared?
cleared for agriculture
What does the climate look like in coniferous forests?
Low temps since they’re primarily found in a broad circumpolar belt across the Northern Hemisphere on mountain ranges
What type of vegetation dominates coniferous forests?
dominated by needle-leaf evergreen trees
Where are temperate coniferous forests found?
Found along the treeline and in Canada these forests are known as Boreal Forests
What is the treeline?
the geographic limit beyond which forest does not grow. It essentially delineates the transition zone between the coniferous forest and the tundra
What does the treeline separate (acts as a transition zone between 2 areas)?
delineates the transition zone between the coniferous forest and the tundra
What does the climate look like in the tundra?
General increase in temps during summers with highs of 10-15C. Precipitation increase in summer.
What type of vegetation dominates the tundra where tree growth is hindered by low temps and short growing seasons?
vegetation is composed of dwarf shrubs, sedges, grasses, mosses and lichens
What is permafrost and where is it found?
Found in the tundra biome, it is the perennially frozen subsurface that develops where the ground temps remain below 0C. Layer of ice under the soil surface that releases carbon as it melts
True or false: Permafrost is impervious to water so it forces all the water to remain and move above it, thus keeping ground soggy even when precipitation is low?
TRUE
Why is permafrost melting and what does it do to houses built on it?
Melting as a result to rapid climate change, releasing Carbon dioxide and causing infrastructure to collapse in northern villages
True or false: if there’s anywhere in the world where climate change is having the strongest effect, it’s boreal forests?
FALSE: strongest effect of climate chnage in the tundra because temperatures are rising the fastest in these delicate regions
Why is climate change having the most effect in the tundra?
temps are rising the fastest in these delicate regions
What are peat bogs?
They’re shallow lakes covered in peat made of sphagnum mosses (bryophytes)
What’s happening to the peat bogs in the north?
There’s a layer of permafrost below the peat bogs, but with increase in temps, the peat is collapsing into the lakes. They generally are important for sequestering carbon since they release less carbon in cold temps, but with increase in temps, decomposition is increasing and peat bogs are releasing a lot of carbon
What are 3 approaches used to map spatial patterns of community composition?
1) Biomes
2) Ecoregions
3) Biogeographic regions
What are biomes based on?
Climates and plants
What are ecoregions based on?
more delineated by plant cover at a small scale
Why are ecoregions useful?
they’re useful for identifying unique ecosystems and priority areas for conservation since by splitting the world into ecoregions, we can see them as different unique plant-based ecoregions and at least a chunk of each can be preserved
What are biogeographic regions based on?
based on taxonomic groupings
Who was the first person to draw a map of the biogeographic regions?
Alfred R. Wallace
What was Wallace’s approach to biogeographic regions (4 different steps)?
He showed the zoogeographic regions (mammals only):
1) 6 regions each divided into 4 sub-regions
2) different regions tend to have different families and/or genera
3) different sub-regions may only differ in species composition
4) taxonomic hierarchical approach
True or false: based on Wallace’s approach to biogeographic regions, sub-regions will have similar families and genera?
TRUE
What was Wallace’s approach to biogeographic regions?
taxonomic hierarchical approach
How do you map the world by biogeographic regions?
world is divided into grid cells and assigned each of the grid cells into regions. Coloured polygons show the range of a hypothetical species; where colours overlap is where those species exist (species richness)
What is clustering analysis in regards to mapping the world in biogeographic regions?
An algorithm that goes through each grid cell and compares their similarities in order to create clusters of grid cells; different clusters have different similarities
What was Kreft and Jetz 2010’s approach to mapping the world?
clustering of beta diversity; mammals. They got 6 distinct clusters with however many sub-clusters where symbols = species and colours = phylogenetic membership
How did Holt et al. (2013) define their zoogeographic regions?
by using phylogenetics and global distributions of terrestrial vertebrates, thus rendering it more accurate and descriptive
Based on Holt et al. (2013)’s approach, why is Australia an extremely different colour compared to other regioons?
different colour is due to the many different lineages that are found there such as Marsupials and Monotremes
What do zoogeographic regions look at?
Spatial patterns of animal species composition
What do phytogeographic regions look at?
spatial patterns of plant species composition
How many species have been identified and named by the end of the 20th century?
nearly 1.4 million species
How many species did E.O. Wilson suggest there are?
closer to 10 million species exist
A more recent estimate was made on the total # of species by Mora et al. 2011, PloS Biology, how mnay species did they suggest?
8.7 million
How many species of arthropods have been described on the planet?
1.2 million arthropods described on the planet out of 2 million arthropods
What are the spatial patterns of diversity, globally?
Globally, species diversity declines as you move northward and southward from the equator
Why is the latitudinal gradient of diversity called “The Holy Grail of Ecology”?
because it’s been fascinating ecologists for centuries
Why are hypotheses for global patterns of diversity more accurate now?
The hypotheses are now more accurate because ecologists are working with evolutionary biologists
What’s the difference between evolution and ecology?
They both try to understand how organisms interact with each other and how they interact with their environment, but on different time scales; ecology fuels rapid evolution
What is the global pattern of vertebrate species richness?
clear pattern for biodiversity to peak along the equator
Where in the world (specifically) has the highest amounts of diversity?
Tropical mountains; the Andes, Himalayas, Eastern Arc of Africa = 70-80% of all biodiversity
What’s the Holy Grail of Ecology?
Why are there more species in the tropics than in temperate regions
What are the 4 hypotheses to explain why there are more species in the tropics?
1) Evolutionary time
2) Historical Climatic Stability (Biodiversity Preservation)
3) Productivity (Maintaining Biodiversity)
4) Heterogeneity (scale by which we generate richness)
What is the Evolutionary time hypothesis to explain why the tropics are more diverse?
tropics are older so more time to accumulate species; this is explained by the “Tropical Niche Conservatism” Hypothesis by John Wiens (2004).
What is the “Tropical Niche Conservatism” Hypothesis by John Wiens (2004)?
States that Tropical Niche Conservatism is responsible for the species gradient:
i) World = all tropical up to about 40 million years ago; all species were adapted to tropical environments until continents began to move towards poles and planet started to cool = new biomes
ii) Most extant (still in existence) lineages have evolved in and adapted to tropical conditions millions of years ago
iii) Lineages have had more time to accumulate (diversify) in the tropics since temperate biomes appeared more recently; only had 30 million years to create new species adapted to the new biomes
iv) due to evolutionary constraints (i.e. conservatism = hard to diverge from your ancestors) most lineages were not able to diversify in temperate climates when they appeared
What’s the issue with the tropical niche conservatism hypothesis?
It doesn’t give an explanation for a buildup for the # of species
The dynamics of the evolutionary time/tropical niche conservatism hypothesis spans how long?
The dynamics of this hypothesis spans about 100 million years
What is the historical climatic stability (biodiversity preservation) hypothesis?
climate more stable in tropics (tropical mountains) = less extinctions meaning endemic species remaining there come from older lineages (half old, half new). Over last 2 million years there were multiple glaciations which didn’t affect the planet equally = along equator was stable and most stable were tropical mountains
The dynamics of the historical climatic stability (biodiversity preservation) hypothesis spans how long?
2 million years
Why are tropical mountains the most stable in climate and the best place to be during glaciations?
Walls of mountain trap warm humid air coming from tropics and reduce the amount of wind, creating an oasis of perfectly suitable climate (cloud forest) = Endemic species. Numerous endemic species in tropics causing increase in diversity compared to other areas
What study done by who showed that mountain act as cradles for biodiversity?
Sonne et al. (2022). Biodiversity cradles and museums segregating within hotspots of endemism.
Which species are more likely to go extinct with climate change?
Small # of populations with few individuals within them = prone to extinction
What is a species wide extinction?
All pops = 0
What is another word for local extinction and what does it mean?
Extirpation: population of species goes extinct in an area, but there are other populations elsewhere
What did Sandel et al. 2011’s study (The influence of late Quaternary climate-change velocity on species endemism) show?
a) The speed (velocity) at which climate changed over last 2 million years is lower in tropics than in temperate regions
b) Less climate fluctuations reduce rates of extinctions and promote survival of small-ranged (endemic) species (specialists)
c) Endemic species represent the ‘bulk’ of global biodiversity, so understanding where they persist the most gives insight into the latitudinal gradient
What is the productivity (maintaining biodiversity) hypothesis?
more resources, more individuals, more species. More light and nutrients which can sustain more species. The tropics have lots of energy which can support larger populations so ecological drift will be less likely to drive these pops to extinction
What does ecological drift do?
Causes species abundances to fluctuate randomly
What did David J. Currie and V. Paquin find based on the productivity (maintaining biodiversity) hypothesis?
Tree species richness increases with increasing annual evapotranspiration
What is AET?
the flux of water from terrestrial surface to the atmosphere through evaporation and transpiration. It’s often used as a “proxy” for energy availability
What is often used as a “Proxy” for energy availability?
AET
What’s a better hypothesis than David J. Currie and V. Paquin’s one?
Fluctuations in abundance in pops. Tropical ecosystems have larger pops because there’s more energy and resources to support larger pops. Therefore, since tropical regions have larger pops, they’re less likely to go extinct due to random chance, so you’re more likely to maintain biodiversity through time
What is the Heterogeneity (scale by which we generate richness) hypothesis?
more environmental heterogeneity in the tropics = greater diversity in habitats/ecological niches due to lots of big mountains. It’s defined as the difference or diversity in kind or arrangement of component elements or constituents. Mountainous regions, bc of their topography and steep environmental gradients, generally support more species. Tropical mountain = squishing 3-4 biomes within one grid cell, thus creating different environments for plants and animals to diversify/adapt to
Who published the heterogeneity hypothesis?
Rahbek et al., Science 2019
True or false: mountains are much larger when they’ve been recently formed because over time they erode, so younger mountains create multiple different layers of conditions for species to adapt to?
TRUE
What mountain has the highest diversity of salamanders on the planet? WHY?
Appalachians; when glaciations occur, pops get small and their genes mix (no speciation), but when it gets warm again, pops increase and individuals and pops will go back up the mountain and become isolated, thus creating new species (speciation)
Out of the 4 hypotheses, which fit under the historical and evolutionary category and which fit under the contemporary hypotheses?
1) Historical and evolutionary Hypotheses = Niche Conservatism and Climate Stability
2) Contemporary Hypotheses = Productivity/Energy and Environmental Heterogeneity
What is the definition of dynamics?
Processes explaining the pattern
Why is the structure of any given community dynamic?
Shifting of species’ dominance, composition and richness through time
What’s determinism?
there’s something you can predict; in 100 years, an old field can bounce back and support trees.
What are stochastic processes?
a collection of random variables indexed by time
Is succession stochastic or deterministic?
Deterministic
What is succession?
Change in communities over time; changes in dominance, abundance and richness
What is crucial to succession?
disturbance is crucial otherwise it would only occur once since it’s like a reset in communities following a major disturbance
What is primary succession?
Occurs when there’s only rock to grow on (sites that never supported a community) and there isn’t any organic material present such as a seedbank
What is secondary succession?
occurs on organic material and is often aided by a seedbank
What are the 7 steps to primary succession?
1) Lichen (fungus + algae) pioneer species; grows directly on rocks and tendrils enter the cracks of rocks to extract minerals and then they release nutrients
2) Nutrients released by lichens can be used by bryophytes such as mosses and when they die, they create organic matter/layer of soil
3) With soil under the moss, grasses and weeds can grow and die and soil continues to buildup
4) Shrubs
5) Young forest (Tulip poplar)
6) Mature forest (white oak and hickory)
7) Climax forest: beech, sugar maple, and red maple
What are r-strategists?
early successional or pioneer species that are usually characterized by high growth rates, high degree of dispersal, and high rates of per capita pop growth. When they stop growing around medium height, K-strategists can grow and r-strategists get stuck in shade and die
What are 2 examples of r-strategists?
Cherry trees and birch
What are k-strategists
late successional species that have lower rates of dispersal and colonization, slower per capita growth rate, and they’re larger and longer living. Have Bigger seeds so they’re less efficient in spreading that’s why they’re less likely to come up right after disturbance
What part of succession is deterministic and what part is stochastic?
Deterministic: deterministic steps that happen through time and lead to climax forest
Stochastic: knowing the abundance and spatial distribution of these climax species, as well as the dominance within the community and how it will change
What did the Hubbard Brook Experiment show about succession, and what was its initial idea?
Clear cutting one side of the watershed/mountain. Initial idea was to look at nutrient fluxes when you disturb a forest, however, after clear-cutting, secondary succession was triggered. Initially, the climax forest was dominated by Beech and sugar maple and then replaced by raspberry thickets and seedlings of sun-adapted, fast-growing species.
What approach is used to document succession for long-lived systems?
“space-for-time” = chronosequence?
What is chronosequence used for and how is it used?
Used to document succession and a chronosequence is when you compare ecosystems of different ages that are located in different places in space. It’s used to monitor temporal change in forest stands using “similar” adjacent sites; assumes similar substrates and site history
What’s an example of primary succession?
The glacier Bay fjord complex in Alaska, showing ice retreat since 1760: On sites that were uncovered 50 years ago: cottonwood and alder are dominating which are characterized as pioneer species. Looking at sites that are 500 years old you can see that they’re dominated by Hemlock and Spruce which are climax species (have large seeds)
What 3 other traits in addition to composition of species changes during succession?
1) Community structure: Biomass and total organic matter increase; more nutrients stored in organic form
2) Food Chains: Food chains grow in length and complexity; plants first then eventually it can support consumers
3) Species richness: Species richness often increases from early to mid-succession then declines (less predictable)
How does succession also occur in heterotrophic communities (heterotrophic succession)?
- As succession proceeds the animals present during early succession and climax will be different due to resources available. Early succession will attract birds with smaller beaks due to small seeds. They’ll be more exposed to predators as well, so the behaviour of prey must be adapted to escaping/hiding
- Changes in animal and fungal species that are dependent on vegetation
- The decomposition of fallen trees, animal carcasses, and droppings by fungi and invertebrates recycle nutrients and alter the substrate
What is Paleoecology?
The study of the distribution and abundance of ancient organisms and their relationship to the environment. It involves the extraction of soil cores which are then sliced carefully and dated to get the age of each section reconstructing a whole history of succession
What is the name for the max of the last glaciation and when did it occur?
Wisconsinan glaciation and it occurred 18,000 years ago
What does the reconstruction of plant distribution after the last glacial maximum (Laurentian ice sheet) of the Pleistocene look like and show?
Shows that it was once was a boreal forest/climate and then the glacier happened and pushed the climate downward and the boreal climate and forest was pushed down as well
The northern migration of 4 tree species following the retreat of the Laurentian ice sheet has been reconstructed and what does it show?
You can see 10,000 years ago, spruce were already back in Canada (further north) compared to Oak which were around the New England region. Spruce are dominated by pine and balsam fir which are a part of boreal forest species.
What’s the outdated succession term and what has it been replaced by?
The mechanism by which multiple species colonize a previously inhabited area = secondary succession. However, it’s been replaced by models of community assembly
What is the theory of community assembly which has replaced succession?
Theory addresses the rules governing how communities are assembled from a regional species pool. The process of how communities are put together through time.
Why is community assembly better than succession?
Succession implies that community assembly is deterministic, that’s why community assembly is more accurate since it doesn’t assume that it’s deterministic
What is a species pool?
The set of species that could potentially colonize the local community you’re looking at/studying. OR: All the species that can disperse and establish in a local community. Difficult to determine the exact species pool; not all the species in the species pool will end up in the community you’re looking at
What determines the composition of species in a community?
1) To predict, you must know the regional species pool, and to predict the number of species in the local communities. These are the species that can live in the same kind of conditions and can disperse into the community
2) Dispersal, environmental filtering and biotic interactions will determine what species from the regional species pool will be found in the local community
What can tell us if community assembly was deterministic or stochastic?
The magnitude in the difference of the species pool: different species = stochastic and same species = deterministic
Is dispersal large scale or small scale and is it deterministic or stochastic?
Large scale and knowing which species will colonize first = stochastic
Is environmental filtering large scale or small scale and is it deterministic or stochastic?
Medium scale and only some species can get into the local community because only some are adapted to the environmental conditions of the local community = deterministic since you know the characteristics of the species in the species pool (Ex: sun exposure; intolerant or tolerant)
Are biotic interactions large scale or small scale and is it deterministic or stochastic?
Small scale and if species are too similar, one will be able to occupy the niche in the local community, and the other will be excluded = deterministic because you know the traits of the competing species
Who came up with the monoclimax hypothesis?
Clements
What is the monoclimax hypothesis by Clements?
the community is a highly integrated superorganism; every step is predictable: The process of succession represents the gradual and progressive development of the community to the climax stage.
Is the Monoclimax theory deterministic or stochastic?
This hypothesis represents a deterministic view of community assembly
How did Gleason see community assembly?
Saw the community as an arbitrary concept and stated that each species responds independently to the underlying features of the environment; Individualistic or continuum concept
What’s the issue with the approach of predicting community assembly using species pool?
If you see that the traits you predicted aren’t in the local community it’s possible that this is due to not properly considering all traits, or it’s just a stochastic process
What’s the difference between Gleason and Clements’ concepts on community?
1) Clements: viewed the community as a quasi-organism made up of interdependent species; superorganism concept, seen as deterministic assembly where abiotic and biotic filters play a crucial role.
2) Gleason: saw the community as an arbitrary concept and stated that each species responds independently to the underlying features of the environment; Individualistic or continuum concept = stochastic
When did the term metapopulations become popular and why?
Became popular in the 90s as humans caused fragmentation which caused pops to basically live on islands
What is a metapopulation?
A population consisting of many local populations - a population of populations; collection of small pops connected by dispersal
What’s an example of a metapopulation using brook trout?
Brook trout in boreal forest lakes are isolated by the surrounding forest, however, during floods in the spring, the lakes become connected (water enters and water leaves - not both ways)
What’s a more realistic idea of a metapopulation?
The dynamics in which local pops interact via immigration and emigration
Who suggested that there are 4 necessary conditions for “metapopulation” to be applicable to a system of local populations?
Ilka Hanski (university of Helsinki)
What are the 4 necessary criteria for a system of local pops to be considered a metapopulation?
1) Suitable habitat occurs in discrete patches that may be occupied by local breeding pops
2) Even the largest populations have a substantial risk of extinction
3) Habitat patches must not be too isolated to prevent recolonization after local extinction (connectivity)
4) Dynamics of the local pops aren’t synchronized; different ups and downs -> or else they’re same pop
Metapopulations are governed by 2 sets of processes that operate at 2 distinctive spatial scales, what are the 2 scales?
1) Local: at the local or within-patch scaled, individuals interact with one another; pop growth/regulation governed by demographic processes (birth and death)
2) Regional: at the metapopulation or regional-scaled, population dynamics are governed by local pop interactions = dispersal, colonization, and extinction (extirpation)
What is colonization?
involves the movements of individuals into a patch
What is metapopulation persistence?
a dynamic balance between the extinction of a local population and colonization of empty habitat patches by new individuals
How do source pops and sink pops work together?
Dispersal from source pops in high-quality habitat may permit sink pops to exist in inferior habitats
Who developed the idea of source and sink pops?
R. Pulliam (university of Georgia)
Define source population?
maintain a positive growth rate (r>0); generally larger pops leading to overcrowding so they’ll often donate/send-off individs which can end up in sink pops
Define sink populations?
has a tendency for collapse and therefore, cannot support positive pop growth (r<0) and are more likely to experience extirpation
Which 2 people studied the impact of habitat patch location and size on metapopulation dynamics of the bush cricket?
O. Kinvall and I. Ahlen
What did O. Kinvall and I. Ahlen find when studying bush crickets and grasshoppers?
Chances of recolonization decreased when patches were farther apart and the risk of local extinction increases with decreasing patch size
What is the rescue effect?
The increase in pop size that occurs w/ an increasing rate of immigration
Who developed the idea of the rescue effect?
J. Brown and A. KodricBrown
When does the rescue effect usually occur?
occurs in response to a decline in local population size (abundance) in a local patch; big patch (source) can rescue small patch (sink)
What are corridors?
Strips of suitable habitat enabling or facilitating movement on individuals b/w suitable habitat patches, which can help crossing the unsuitable habitat matrix
What 2 things do corridors promote?
1) Promotes rescue effect and helps reestablish species in habitats that have experienced local extinction
2) Can also facilitate gene flow between sub-pops (genetic rescue); they can prevent low gene diversity, thus also preventing local extinction
What kind of corridors are used along the rockies where there are roads?
vegetated bridges were created for animals to criss highwats
True or false: human-origin corridors play a positive role in conservation of mammal habitat?
TRUE
Who studied the efficiency of corridors by installing infrared cameras to document mammal crossings?
Jochen A. G. Jaeger, PhD; Associate Professor, Geography, Planning and Environment
What is a meta-community?
Sub-communities within a larger community = same thing as species pool, connected through dispersal; if you take one community within the meta-community, the remaining communities act as a species pool for that one community
How is the meta-community concept and species pool related?
if you take one community within the meta-community, the remaining communities act as a species pool for that one community
What can metapopulation models be used to predict?
incidence of a species in a given habitat patch
What can metacommunity models be used to predict?
used to predict the expected # of species
How did Andy Gonzalez from McGill try to help establish the meta-community concept?
He created a small-scale system and designed his own landscape by cutting patches of moss of rocks and creating fragmentation between them
What did Andy’s result conclude?
His results showed that the abundance of most species was higher in patches connected by corridors than those with pseudo-corridors bc species can disperse more easily
True or false: stochastic extinction is more likely to occur in large populations?
FALSE: stochastic extinction more likely in small pops
Why is it when you go from a completely connected patch to a lesser connected patch (pseudo-corridors), you get a decrease in abundance?
Fragmentation can make it difficult for individuals that die to be replaced; the lack of flow of new individuals coming in has caused their population to crash -> prevents rescue effect
What is a major issue with Andy’s experiement?
Small scale experiment = hard to apply to real life so results could be inaccurate
Who was sceptical about Andy’s results and created a large scale experiment to test Andy’s hypothesis?
Nick Haddad
What were Nick Haddad’s predictions?
Higher richness in connected patches and lower richness in isolated patches, and the larger rectangular patch (control) likely expected to show the largest richness
What were Nick Haddad’s results to his large scale experiment?
The unconnected patch through time, always had lower plant species richness, and connected patches through time had higher richness and the differences between the connected and unconnected patches increased over time
What did Nick Haddad’s and Andy’s experiment both demonstrate?
Both experiments demonstrated that fragmentation reduces population size and decreases richness
Why on an island are there more than 1 species?
Coexistence promoting diversity
Why are many species able to coexist?
Many species can coexist because there are many niches that multiple species can occupy and thus coexist = Niche partitioning
What is niche partitioning?
the process by which natural selection drives competing species into different patterns of resource use or different niches
Why is it impossible for one species to dominate over all species?
Traits can act as trade-offs for other characteristics; ex: if a bird needs a large beak then it needs a large head and then a large body to hold the head, this can lead to a trade-off which reduces dexterity and/or speed
What is a neutral theory of coexistence?
Not a niche-based theory
What did early explorers note about larger islands and species?
large islands hold more species than do small islands: larger area = more likely to have environmental heterogeneity, thus more niches and potentially more species
What did P. Darlington show about islands and species richness?
Through studying bird species richness in regards to island area, they found that on islands, a tenfold increase in land area leads to a doubling of the # of species
What did D. Simberloff compare islands to?
islands can behave/act the same way as discrete ecological patches
What does the eqm theory of island biogeography posit?
It posits that the # of species established on an island represents a dynamic eqm b/w the immigration of new colonizing species and the extinction of previously established ones
Who developed the eqm theory of island biogeography and when?
R. MacArthur (Princeton University) and E.O. Wilson (Harvard University) developed this theory in 1967
Based on the eqm theory of island biogeography, when is an eqm species richness (S) achieved?
An eqm species richness (S) is achieved when immigration rate = extinction rate
Based on the eqm theory of island biogeography, when will the immigration rate decline?
immigration rate will decline as the # of species on the island increases -> fewer new species from the mainland left to colonize (potential source pool = depleted)
Based on the eqm theory of island biogeography, when will the immigration rate be zero?
immigration rate will be zero when all mainland species exist on the island
Based on the eqm theory of island biogeography, when will the rate of species extinction on an island increase?
rate of species extinction on an island will increase with increasing species richness; based purely on chance. This is because later immigrants will have less access to habitats and resources = depletion of resources and competition will increase
Based on the eqm theory of island biogeography, what 2 things is eqm species richness (S) affected by?
1) The distance of the island from the mainland: the rate of immigration is lower on islands that are farther from mainland due to dispersal limitations
2) Size of the island: the rate of extinction is higher on small islands than on larger ones due to ecological drift and competition intensity
Why is the rate of immigration lower on islands further from the mainland compared to those that are closer?
Dispersal limitations
Why is the rate of extinction on smaller islands higher than on larger ones?
Ecological drift and competition intensity = Smaller island = less resources (more competition) = all pops are smaller = more prone to extinction or ecological drift
Who performed the first experimental test on the theory of island biogeography?
Performed by E.O, Wilson’s PhD student: Daniel Simberloff
True or false: The island biogeography theory is largely derived from meta-community concepts whereby species disperse randomly from mainland to islands and therefore dispersal (immigration) is one of the main processes governing coexistence?
TRUE
What is one of the main processes that governs coexistence?
dispersal/immigration
What are the 2 main processes that govern coexistence?
1) Dispersal (immigration)
2) Stochastic extinction
Is the island biogeography theory considered a stochastic or deterministic theory?
Stochastic
Why is the island biogeography theory stochastic?
It’s because dispersal and extinction are not driven by niche differences between species
What are the 3 caveats in the island biogeography theory?
1) Theory disregards differences in species autecology (i.e. species are neutral); maybe some species are better dispersers than others and maybe some species are better competitors
2) It assumes that they new arrivals affect the risk of competition exclusion. This assumption would not work if the new species was a facultative mutualist
3) It ignores the role of speciation, which clearly plays a role when considering isolated oceanic islands and archipelagos; at larger scales you need to start considering speciation
Out of all the caveats for the island biogeography theory, which is the most pertinent according to Lessard?
3) It ignores the role of speciation, which clearly plays a role when considering isolated oceanic islands and archipelagos because isolation can lead to new species
Based on Valente et al. (2020)’s research paper, what were the predictions based on islands and speciation?
Predicting more speciation on larger islands -> so they also have higher species richness due to higher rates of speciation: larger area = higher colonization + lower colonization when island is further from mainland
Why would larger islands have higher rates of colonization?
If you have 1 large bin and 1 small bin and you throw a ball into the air, the ball is more likely to fall into the larger bin just by random chance -> same goes for islands (animals more likely to find larger islands just by chance)
True or false: The theory of island Biogeography explains species coexistence based on stochastic processes
TRUE
True or false: many ecologists accept the view that coexistence can be explained without considering niche differences
FALSE: few ecologists can accept the view that coexistence can be explained without considering niche differences
What is the broad definition of a niche of a species?
species responses to the total of all abiotic and biotic factors in its environment
Who came up with the theory that the niche is described as an n-dimensional hypervolume and when was it created?
G.E. Hutchinson in 1957
Explain G.E. Hutchinson’s Niche concept
A species-defined “space” where it can survive, grow and/or reproduce, is in response to n-dimensional environmental factors. Where n shows that we don’t know how many factors we need to consider in order to define a niche for a species and niche dimensions include resources and conditions.
Hutchinson’s “niche” concept is often depicted as a three-dimensional volume, what are the 3 dimensions?
1) size
2) relative importance of niche axes (represents conditions or requirements necessary for the growth of individuals and populations of a given species) -> humidity and food size
What’s the limitation of Hutchinson’s concept?
the # of niche dimensions is theoretically limitless = difficult to define or quantify the niche in real life
Based on Hutchinson’s concept, when can species coexist?
Species can only coexist if there is minimal overlapping in their niche dimensions because there’s less competition for resources: if there’s more area of not overlapping compared to the amount of area overlapping = can still coexist
What is niche breadth of a species?
Niche breadth of a species is defined as the tolerance range of environmental conditions (e.g. n-niche volume)
Is the niche breadth for a generalist wide or narrow?
Wide
Is the niche breadth of a specialist wide or narrow?
narrow
True or false: species can have both a wide and narrow niche breadth
True: Jack pine have wide niche breath for substrate requirements (bare rock, sandy soil, and boggy sites), but narrow in terms of light requirements (shade intolerant) and disturbance regime (adapted to frequent fires)
What are the 2 types of niches?
1) fundamental
2) Realized
What is the fundamental niche of a species?
full range of conditions and resources under which it can survive and reproduce; in the wild, most species don’t experience their fundamental niche and they only actually exploit a portion of their fundamental niche (realized niche)
What is the realized niche of a species?
The portion of the fundamental niche that a species exploits
What are the 2 factors that create the differences between a realized and fundamental niche?
1) competition -> competitors will compress you into your realized niche
2) Dispersal limitations -> prevents species from colonizing a part of the niche due to barriers (ex: river, mountain wall, ect.)
What is an example that demonstrates a realized vs. fundamental niche?
2 cattail species: 1) dominates shallow waters and 2) dominates deeper water. When grown alone, the fundamental niche of both species is similar since they can both survive in shallow water. BUT when grown together cattail 1 outcompetes cattail 2 in shallow water
Who introduced an alternative definition to the niche (different compared to Hutchinson’s) and what is it?
Charles Elton introduced an alternative definition of the niche; he emphasized that specues-environment interactions are 2 sided: A species has an effect ON its environment as much or more than its response TO its environment
What is Charles Elton’s definition of the niche?
- He emphasized that species-environment interactions are 2 sided: A species has an effect ON its environment as much or more than its response TO its environment
- Elton’s definition of the niche emphasizes the effect
What is niche differentiation?
differences in the range and type of resources used, or in environmental tolerances
How similar can 2 species be in their resource requirements and still coexist?
Coexistence of competitors is often associated with some degree of niche differentiation
Who came up with the limiting similarity idea and when?
G.E. Hutchinson in 1959
What is the limiting similarity idea by G.E. Hutchinson?
ecologically similar species coexist only if they have evolved sufficient differences in morphological traits to allow niche separation
What does too much ecological similarity possibly lead to?
competitive exclusion
How do similar species coexist?
by partitioning available resources (resource partitioning)
define resource partitioning?
the division of limited resources by species to help avoid competition in an ecological niche
What are 2 examples of resource partitioning?
1) Foraging in different areas; Robert MacArthur’s Warbler
2) Feeding at different times = Albretch and Gotelli 2001: different ant species feed at different times
What’s another example of resource partitioning with 3 plant species growing in prairie soil = vertically partitioned soil resources (water)?
One year after disturbance, 3 plant species regrow roots: Bristly has a fibrous, shallow root system, Indian mallow has a sparse, branched taproot, and Smartweed has moderately branched taproot that develops further below the rooting zone of the other 2 species
What’s another example of resource partitioning demonstrated by T. Dayan?
He examined resource partitioning in a group of wild cat species of the Middle East. There was even spacing in teeth size and a positive relationship b/w teeth size and prey size
What do the contemporary effects (ecological effects) assume for the coexistence theory?
This view assumes that species are adapted to certain resources and conditions, which determines what they eat, where they occur and who their neighbours can or can’t be
Who came up with the idea of the “Ghost of competition past”?
J. Connell
What is an example of the idea of the “ghost of competition past”?
2 bell shaped curves for both species depicts consumption frequency (based on seed size). The area of overlap = intense competition, tails of both curves = individuals that consume either small or large seeds. These individuals will have higher fitness, resulting in divergence and character displacement
What is an example of an evolutionary effect which could explain the coexistence theory?
character displacement
What is character displacement?
An evolutionary effect that explains the coexistence theory: it involves a shift in feeding niche that subsequently affects a species’ morphology, behaviour, or physiology
Character displacement involves a shift in feeding niche that subsequently affects a species’….?
1) Morphology
2) Behaviour
3) Physiology
Who first documented character displacement?
Rosemary and Peter Grants
How did P. and R. Grant document character displacement?
They studied the medium and small finches that feed on an overlapping array of seed sizes: Where finch species coexist, beak size distribution for each species doesn’t overlap = divergence in phenotypes (beak sizes) allows for each species to access resources. On islands where the species live separately (allopatric), populations possess intermediate and overlapping distributions of beak sizes
What is an adaptive radiation?
In an adaptive radiation, multiple species that are phylogenetically related (same clade) rapidly evolve into different ecological types
True or false: Character displacement is often involved in an adaptive radiation?
TRUE: Character displacement can lead to “ecological speciation” in sympatry
What is ecological speciation?
reproductive isolation that occurs due to an ecological factor that reduces or eliminates gene flow between two pops of a species = sympatric speciation
What is speciation in allopatry?
Dispersal limitation between populations reduces gene flow and leads to reproductive isolation = Resulting species tends to share similar traits or niches (Conservatism)
What is speciation in sympatry?
Competition for resources leads to character displacement and eventually leads to reproductive isolation = ecological speciation. Resulting species tend to have different traits or niches (Convergence)
