Lecture 25

Question 1

What is an ecological community?

Answer 1

a group of potentially interacting species that occur together in space and time

• can think of continental scale + microscopic scales

Question 2

Particular species?

Answer 2

• many species are very common across ecological communities - across hills, coasts, and plains
• relative abundance of species is important

Question 3

What ecological processes affect communities?

Answer 3

• selection
• drift
• speciation (diversification)
• dispersal

analogous to the EVOLUTIONARY processes that affect populations

Question 4

What evolutionary processes affect population?

Answer 4

• selection
• genetic drift
• mutation
• gene flow

Question 5

Traits

Answer 5

things that drive their response to environment

Question 6

Selection

Answer 6

changes in community structure caused by non-random (Deterministic) fitness differences between taxa

sites vary w respect to temp, rainfall, soil, fire regime

Question 7

Features of selection pressures

Answer 7

• varies over space / time
• constant
• density-dependent

Question 8

Drift

Answer 8

random changes in the relative abundances of different taxa within the community through time

neutral processes
doesn’t favour 1 species over another

Question 9

Diversification

Answer 9

the evolution of new lineages (including new genotypes, forms, varieties, sub-species and species) from existing lineages

Question 10

Dispersal

Answer 10

the movement of individuals from one place to another as propagules (seeds and spores), larvae, juveniles, or adults

• immigration / emigration
• source / receiver
• can be one-way (large to small)

Question 11

What is a metacommunity?

Answer 11

a group of local communities occupying a set of habitat patches that are linked by the dispersal of multiple, potentially interacting species

Question 12

Distinguish bw ecological and evolutionary processes.

Answer 12

ecological - processes that lead to changes in the species composition of a community

evolutionary - processes that lead to changes in the genetic composition of a population

Question 13

Xeromorphic traits

Answer 13

structural adaptations that reduce water loss

Question 14

Pyrophytic traits

Answer 14

adaptations that allow plants to deal with fires

Question 15

Which ecological processes help to explain the current diversity of Australian plant communities?

Answer 15

• persistence of rainforest species that evolved prior to the breakup of Gondwana
• Persistence of species that evolved after the breakup of Gondwana in response to a trend of drying of the continent and increased frequency of fire
• dispersal of rainforest species from SE Asia into Australia

Question 16

What was Gondwana?

Answer 16

one of the two ancient supercontinents produced by the first split of the even larger supercontinent Pangaea about 200 million years ago, comprising chiefly what are now Africa, South America, Australia, Antarctica, and the Indian subcontinent.

Question 17

What is alpha diversity?

Answer 17

the composition of a local ecological community with respect to its RICHNESS (number of species), EVENNESS (Distribution of abundances of the species), or both

Question 18

Issues with describing ecological communities

Answer 18

1. detectability of species
   - we need to actually be sure that we can determine the presence / absence of species

e.g. measuring mushrooms is hard bc the vast majority of them are underground in soil and only appear above ground in specific seasons

2. taxonomy
   - we don’t have a full description of ALL the species that are present
   - for some taxonomic groups, we only know a tiny fraction of them w names

Question 19

ABUNDANCE CAN BE HARD TO MEASURE

Answer 19

– we can measure species richness (Sum of the species present)
but NOT species evenness bc the abundance actually can’t be determined