BIOSCI 109: Lecture 26 - Biogeography of New Zealand

Biogeography

The study of the temporal and spatial distribution of species. Asking how a species got there, when, as well as why.

Understanding biogeography allows us to better inform conservation strategies, leading to more environmental and economical stability.

Principles of Biogeography

The four principles are:

• Colonisation

• Evolution

• Geoenvironmental Conditions

• Extinction

Colonisation

The act of a species travelling, ending up in a new area, and settling an established population there.

Evolution

The population adapting to the new environment and conditions, as well as filling up any available niches and roles and interacting with the native ecosystem.

Geoenvironmental Conditions

The environmental change that occurs over time that can put stressors onto and tests the limits of existing and new population

Extinction

The loss of species, making more space for resources, available niches, and so on for existing and new species to use.

Dispersal

When a group of individuals migrates and crosses a geographic barrier to colobise and settle in a new isolated area.

Vicariance

When a group of individuals are slowly isolated from the main population due to a growing geographic barrier that divides them.

Rates of Colonisation

Are faster when the new island is closer to the main island as it is easier to cross to.

Are slow when there are already a lot of different species present on the new island.

Rates of Extinction

Are faster on smaller islands due to how they aren’t as abundant in resources and may have more competition.

Are slower when there are a small number of species on the island.

Aotearoa’s Unique Biogeography

Aotearoa has unique biogeography due to the historical geological events it experienced.

• New Zealand is actually the tip of a larger sunken continent called Zealandia

• Zealandia was once part of Pangea that split of into Laurasia and Gondwana

• It then slowly split of and drifted away from Gondwana where it experienced partial drowning.

• Then, tectonic events and volcanic activity over time caused varying topologies and unique habitats.

All of which makes it so that Aotearoa has a few very ancient lineages that surpass the drowning as well as newer dispersed linneages that came recently.

Gut Microbiome & Biogeography

We can also apply the principles of biogeogeaphy onto our gut microbiome.

Each region of the gut has distinct conditjons (pH, temperature, oxygen, and so on).

• This means that varying microbes can colonise specific areas depending on their suitable conditions.

Between regions are barriers that can prevent movement of microbes within or between regions.

• These are things such as mucus layers, portrusions/topology of gut, antimicrobial peptides, gut motility, and so on.

• These barriers can isolate microbiomes to specjfic regions where they then have local adaptations with their local crypts/mucus.

The mucus also serves as the living space for the bacteria. The more mucus there is, the more resources there are. This then may mean more microbes and more competition.