Lecture 25 Flashcards
What is an ecological community?
a group of potentially interacting species that occur together in space and time
- can think of continental scale + microscopic scales
Particular species?
- many species are very common across ecological communities - across hills, coasts, and plains
- relative abundance of species is important
What ecological processes affect communities?
- selection
- drift
- speciation (diversification)
- dispersal
analogous to the EVOLUTIONARY processes that affect populations
What evolutionary processes affect population?
- selection
- genetic drift
- mutation
- gene flow
Traits
things that drive their response to environment
Selection
changes in community structure caused by non-random (Deterministic) fitness differences between taxa
sites vary w respect to temp, rainfall, soil, fire regime
Features of selection pressures
- varies over space / time
- constant
- density-dependent
Drift
random changes in the relative abundances of different taxa within the community through time
neutral processes
doesn’t favour 1 species over another
Diversification
the evolution of new lineages (including new genotypes, forms, varieties, sub-species and species) from existing lineages
Dispersal
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)
What is a metacommunity?
a group of local communities occupying a set of habitat patches that are linked by the dispersal of multiple, potentially interacting species
Distinguish bw ecological and evolutionary processes.
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
Xeromorphic traits
structural adaptations that reduce water loss
Pyrophytic traits
adaptations that allow plants to deal with fires
Which ecological processes help to explain the current diversity of Australian plant communities?
- 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
What was Gondwana?
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.
What is alpha diversity?
the composition of a local ecological community with respect to its RICHNESS (number of species), EVENNESS (Distribution of abundances of the species), or both
Issues with describing ecological communities
- 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
- 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
ABUNDANCE CAN BE HARD TO MEASURE
– we can measure species richness (Sum of the species present)
but NOT species evenness bc the abundance actually can’t be determined
