Lecture Four - Community Structure Flashcards
Name the green seaweed that has invaded the Mediterranean sea.
How did it get there?
- Caulerpa taxifolia
- From fishtanks
What has been the effect of the invasive seaweed species in the Mediterranean?
Formed large, overgrown meadows and vastly reduced native fish habitats.
What are species:genus ratios?
Use species:genus ratios as an indicator of competition.
What are neutral models?
- Strong patterns can emerge from random processes / randomly generated communities
- Used to explain lower species:genus ratios on islands compared to mainland.
What do neutral models assume?
That there are no interactions between species. Every species is behaving independently from each other.
Describe some proof for neutral models.
- SAD diagrams with ‘lazy J’ shape can be formed from randomly choosing coloured sweets.
- From this alone, cannot infer that interactions are happening, as the pattern can occur from a random process.
What is the Glaesonian view?
That species go about their business and don’t interact with other species = the null model.
What is Whittaker famous for?
- Mapping world biomes onto moisture and temperature gradients.
- Working on mountains and viewing ecological control by climatic factors (how climate controls appearance of plants)
Describe Whittaker’s experiment on climatic control of plants.
- Walks and transects through mountains
- Counts how many trees of each species there are
What do the following words mean?
a) Mesic
b) Xeric
a) Mesic = wet
b) Xeric = dry
What did Whittaker find in diorite soil?
Distinctive community composed of over 6 trees.
What did Whittaker find in serpentine soil?
Some of previous tree species still there, but three new species.
What is the point of Whittaker’s experiment?
That there is no consistent community to which our focal species actually belong.
What was Whittaker’s main observation of the habitat?
There were no edges, only boundaries for each organisms or species.
Were Whittaker’s results Clemensian or Gleasonian?
Why?
Gleasonian
Because trees drop in and out of habitat without rules about the presence and absence of other tree species.
What does a food web consist of?
Predator-prey interactions
What does an interaction web consist of?
Any ecological interactions! Such as
- Predation
- Competition
- Mutualism
- Parasitism
- Disease
What is the USDA Germplasm Bank?
A place in Washington USA where all seeds are kept in freezers in case a species becomes extinct.
What is a bipartite network?
A network that has two layers, e.g. plants connected to bees, but plants also connected to other plants by cross-pollination by bees.
What is a topological food web?
A web with no indication of interaction strengths.
What is chain length in a food web?
Number of links between a basal species and a top predator.
What is linkage density?
The mean number of links per species
What is connectance?
Number of actual links/possible links.
What is the linkage density hypothesis?
Linkage density is constant, at approximately 2.
Because connectance decreases with the number of species in the food web.
What is the constant connectance hypothesis?
That connectance is constant, but diet breadth is wider in larger webs.
What is Six Degrees of Kevin Bacon?
A game based on the small world phenomenon that assumes any actor can be linked through his or her film roles to Kevin Bacon within six steps.
What is the approximate Bacon number for humans?
6
How many species of mammals in
a) The UK?
b) Ireland?
a) UK = 44 species
b) Ireland = 22 species
Give the equation showing relationship between size of an area and how many species can fit into it.
S(A) = C x A^z
Where
C = species richness of one unit area
A = area of habitat in same units
z = a constant
When do species and area have a linear relationship?
When z = 1
What is the habitat diversity hypothesis?
That habitat diversity increases with area, accommodating different kinds of species.
What is the passive sampling hypothesis?
That larger areas present a larger target for colonising species.
What is the average value of z?
0.3
Give the log equation for species diversity linked to area.
logS = logC + zlogA
