GGR Week 3

Fogged some trees in an area and put sheets in the ground to collect tree beetles. He used this number to extrapolate how many species he thinks live on earth.

We can see a pattern of species which are found around the world to have richer distributions the closer to the equator than away. It looks like a normal distribution turned horizontal.

If there are more plants and primary producers, it allows for more secondary consumers. But how did the primary consumers get there in the first place?

There is more land on the equator, so there is more room to roam and co-habitate. However, boreal forests exist in the equator and do not have representative species richness.

Because the equator has never been subject to crazy ice ages or things like that, it has allowed species richness to increase unabated.

While the equator has not been subject to massive earrth-changing events, climate fluctuations are plenty, and could cause enough of a reason for new species to emerge.

There is ample water and sunlight in the equator, which allows primary producers to thrive. In turn this allows for more secondary consumers to thrive as well. Furthermore, a lot of species near the equator have fast metabolisms and reproduce much faster. Natural selection happens at an increased rate here, and this increases species richness.

The change from one set of species to another over a span of time.

• 1st colonization of previously lifeless surface.
• Example is the island off Iceland where a volcano created a new island.

• Colonization and change after a disturbance.
• Say a forest fire comes through. First we would expect to see 
• Annuals (1 year)
• Perennials (10 years)
• Shrubs(40 years)
• Young Forest (100 years)
• Mature Forest (>100 years)

• Many small, wind-dispersed seeds.
• Ability to handle variety of climate conditions (harsh winds, etc...)

• Longer life span.
• Shade tolerant.
• Larger non wind-borne seeds.

• A sequence (sere) of plant communities (seral stages) characterized by increasing complexity of the lifeforms, with the end stage being the climax vegetation. Works through facilitation.
• However, this ignores impact of herbivores, disturbance, and the seral stages are not well-defined. Also, most land is undergoing secondary succession (modified seed bank).

• Tolerance Model - Fastest growing dominate in short term, slower growers eventually out compete
• Inhibition Model - Early colonizers ensure other species cannot establish themselves
• Random - No facilitation or inhibition occurs

A species that is widely distributed around the world. An example is bats (chiroptera)

• Endemic: found only in one restricted area and no where else
• Paleoendemic: old endemic that once had a larger distribution
• Neoendemic: evolved through isolation, not yet had time to spread out

• Disjunct - Taxa found in two or more areas that are widely separated
• Evolutionary relics: once had very broad distribution but no longer (Magnilia grandiflora)
• Climactic relics: widely distributed, but now only located in a few “islands” which remained climatically favourable (Tetracanthella arctica)

• Travel to new area
• Withstand (unfavourable) conditions along the way
• Establish viable population upon arrival

• Jump dispersal: long distance movement by individuals
• Diffusion: gradual spreading at margins of geographic distribution
• Secular migration: hundred of generation, with species evolving along route

• Corridors: Routes that allow most taxa to move from one region to another. Does not discriminate.
• Filter: More restrictive than corridor, with select subset of species able to pass through
• Sweepstakes Routes: Chance dispersal by individuals.
• Colonization by individuals.
• Colonization of isolated islands by flying or floating