S3: W12 (Prof. Kelsey) Flashcards
Biogeographic components of Southern Africa attributes? (3)
• 2 components in the pre-Gondwana habitat.
• Present South African biota has had input from the north.
• Also appears to be an “Arid” biogeographic entity for some groups.
2 components in the pre-Gondwana habitat?
• Tropical.
• Temperate.
Tropical attributes? (4)
• Warm.
• Moist.
• High rainfall.
• High temperatures.
Temperate?
Pre-Gondwana temperate component is more than that of tropical.
Attributes on the components of the pre-Gondwana habitat? (2)
• Involve elevation & latitude.
• High elevation, high latitude, increased temperature conditions.
Explain what you mean that present South African biota has had input from the north? (2)
● Species in Europe & South Africa are related.
● Afro-eurasian groups that have come into existence since the time Gondwana was intact.
Egs of where present South African biota has had input from the north? (2)
• Helichrysum found in Cape Floristic region & Mediterranean.
• Many vertebrates & invertebrates.
Palaeoclimate kinds that we talk about? (2)
• Glacial periods.
• Interglacial periods.
Palaeoclimate attributes? (10)
● Before rifting, Gondwana was a stable, very ancient series of plains ringed by mountains.
● Vast regions were deserts/semi-desert, as would be expected in the interior of a super-continent.
● After rifting, Africa became more moist, i.e., from dry to moist (was ~15°S of its previous position).
● Drying commenced as Africa formed connections with the northern landmasses, which affected ocean currents & air circulation.
● This, combined with global cooling, cycles of uplifting & warping in the African continent, brought about complex environmental changes (in turn affects species diversity & distribution).
● Cooling started again ~40mya as the Earth went into glacial cycles.
● Fluctuations became more extreme during the Pleristocene (~1.8mya).
● Last glacial maximum was ~20 000 years ago.
● Last inter-glacial climaxed 800 years ago.
● These extremes have left a huge impression on the present biogeographical features of southern Africa.
Glacial?
= cooling.
Inter-glacial?
= warming.
Glacial period attributes? (5)
• Summer rainfall area became cooler, smaller & received less rainfall than current.
• Winter rainfall area expanded & received more rain, extended over the Free State plateau.
• Involves cooling, ice sheets & less water.
• Change in summer & winter rainfall had a significant impact on plants.
• More water was locked in the ice sheets (=drop in sea level).
Why were the vast regions of Africa desert/semi-desert in the interior of the super-continent?
It’s because of the mountains surrounding the super-continent, which experience conventional rain (explain).
How did the drying that came about when Africa commenced with the northern landmasses affect ocean currents & air circulation?
It changed how moist or dry an area of the continent was.
Explain the drop in sea level through ice sheets? (2)
● In the last glacial period the sea level dropped to about 130m below present.
● This resulted in an increase of land along the Agulhas bank.
Egs of Glacial periods? (2)
• Podocarpus forest spread in the SW Cape.
• Southern Cape coastland became grassveld.
Inter-glacial period attributes? (5)
• The area of summer rainfall expanded & received more rainfall.
• Winter rainfall became restricted to the SW Cape & rainfall reduced.
• Involves climate tracking.
• Generally wetter in the summer rainfall areas.
• Fits world trend: maximum glaciation results in the desert belt north & south of the tropics getting more rainfall, while the tropics received reduced rain.
Eg of Inter-glacial period?
Drier in the Karoo & Free State.
Thing to think about when talking about Glacial & Inter-glacial periods?
Think about how parts of Africa change during the Glacial & Inter-glacial periods.
Climate tracking?
= when a species moves from one habitat to the other to keep staying in good environmental conditions.
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Climate tracking attributes? (2)
• Move according to the environment.
• Can happen vertically (N<=>S) & horizontally (E<=>W).
Current biogeographic patterns in South Africa/Current patterns of distribution attributes? (6)
• South Africa has 3 main biogeographic units with centers that are not all in southern Africa.
• Geographic centre is not equal to biogeographic centre.
• RTZ is found between the margins of all units.
• Map of biogeographic units could be a consequence of refugia.
• Transitional species.
• Time frames have an impact on the biogeographic unit size (via rainfall & temperature).
List of the biogeographic units found in South Africa? (3)
• Tropical.
• Temperate.
• Arid.
Biogeographic centre found in the temperate biogeographic unit?
In the SW Cape (for nearly every major tax on group).
Biogeographic centre found in the tropical biogeographic unit?
In East Africa with ranges extending into southern Africa.
Biogeographic centre found in the arid biogeographic unit?
In the Arid west of southern Africa.
Biogeographic centre found in the arid biogeographic unit?
In the Arid west of southern Africa.
Why are geographic centers not equal to biogeographic centres?
It’s because biogeographic centers are strongholds that remain during climate fluctuations (source populations are at the centre of biogeographic region to maintain species diversity/biodiversity).
Biogeographic centre attributes? (4)
• Level varies from a sub-region to a region.
• Larger biogeographic regions can be divided into sub-regions based on plants.
• Think about climate tracking.
• Think about species distributions.
Thing to note about the Cape Floristic Region?
It can be a tropical region, temperate region & arid region.
RTZ stands for?
Replacement Transition Zone.
RTZ attributes? (3)
• Where speciation occurs.
• Where there’s overlap.
• High biodiversity & diversification (isolated populations are formed/can occur).
What to look at/look for when looking at the maps with colours? (2)
● There are multiple species showing the same bigger pattern.
● Temperate, tropical, species distribution, elevation & latitude.
Explain Tropical biogeographic unit on map?
Explain Temperate biogeographic unit on map?
Explain Arid biogeographic unit on map?
Why would temperate regions expand?
It’s because of an increase in elevation.
Why would temperate zones contract/shrink? (2)
• Movement back towards source populations (centre).
• Isolated populations coincide with mountains (because you have similar habitats on mountains to that of source populations).
Result of temperate biogeographic unit?
Diversification or speciation.
Eg of temperate biogeographic unit?
Berg adders.
Current patterns of distribution attributes? (4)
• General pattern holds for amphibians, snakes, birds, mammals, some groups of invertebrates & some plants.
• Lizards appear to not fit the pattern as closely.
• Selection pressures drive biodiversity/diversification.
• Substrate restricts species distribution.
Why do lizards appear to not fit the general pattern as closely as other taxons/groups? (3)
● Deviate because most of the species (80%) appear to be limited by substrate/rock type.
● Biological traits (lizards & locomotion).
● Driven by substrate & not climate and geography (may appear to fit into the transitional fauna).
Egs of where species are restricted/limited to their substrate? (2)
• Legless lizards.
• Mimmulus.
Explain Legless lizards? (2)
● Move through sand.
● Limited biogeographic area due to substrate that they need.
Explain Mimmulus? (2)
● Serpentine soils limit where plants can & cannot live.
● Few species can survive in serpentine soils.
Global hotspots of biodiversity map attributes?
• Biodiversity is similar in Mediterranean climate.
• 2 hypotheses under previous point.
Hypotheses to explain why biodiversity is similar in Mediterranean climate? (2)
• Hypothesis 1.
• Hypothesis 2.
Hypothesis 1 to explain similar biodiversity in Mediterranean climate?
= all taxa were alive in Gondwana before the split.
Hypothesis 2 to explain similar biodiversity in Mediterranean climate?
= LJD via biogeographic corridors.
Eg of biodiversity being similar in Mediterranean climate?
Similar biodiversity in California & Cape.
Explain similar biodiversity in California & the Cape? (2)
● Due to same climate.
● Is an eg of convergent evolution.
Biogeographic corridors attributes? (4)
● Allows distribution of species to expand from one biogeographic unit into another.
● During glacial times, decreased temperature caused expansion of temperate habitat on the mountains of the Rift making habitat islands more connected (elevation = latitude).
● During glacial times, low rainfall in the summer rainfall areas formed an arid corridor, linking the arid western Africa with arid areas on the eastern horn of Africa.
● Can “close” or “disappear”.
What were the results of low temperatures during glacial times? (2)
● Many “Mediterranean” species, island shopping along the rift.
● Organisms speciated en-route (always some fragmentation).
List of the Biogeographic corridors? (2)
• Isthmus of Panama.
• Arid corridor.
Isthmus of Panama location?
Between the Caribbean Sea & the Pacific Ocean, linking North & South America.
Arid corridor location?
Between East Africa & SW Africa.
Refugium?
= a geographic space where climate remains the same as glacial & inter-glacial cycles change.
Refugia attributes? (3)
• Species remain in these regions.
• Mountains are often refugia.
• Mountains at equator are similar to temperate latitudes.
Results of low rainfall during glacial times? (3)
● Allowed arid species exchange between the two areas.
● When corridor closed, caused vicariance & speciation.
● Climate changes caused the vicariance (precipitation pattern changed).
What 2 processes lead to the same biogeographic pattern?
• Sea level.
• Precipitation.
Explain Sea level attributes? (2)
• N/S America.
• Isthmus of Panama.
Explain Precipitation attributes? (2)
• East Africa/SW Africa.
• Arid corridor.
Results of a closed biogeographic corridor? (2)
● Gene flow is decreased.
● Speciation/divergence (eventually).
Egs of organisms in relation to biogeographic corridors? (2)
• Gemsbok & Oryx.
• Pygmy falcon.
Explain Gemsbok & Oryx? (2)
● Diverged due to corridor closing after movement (neither could move back to either side of the biogeographic corridor).
● Corridor closing g resulted in diversification as organism in different regions (now isolated & separate) experienced different selection pressures.
Explain Pygmy falcon?
Rift valleys attributes? (3)
• Form at diverging plate boundaries.
• How the Mid-Atlantic bridge started & then formed a valley, which became flooded.
• Rift valleys on land are often the failed arm of a triple junction (TJ).
Eg of a Rift valley?
African rift valley (ARV).
African rift valley attributes? ()
• One of the most recent developments in Gondwana plate tectonics (~30mya).
• Hotspot under continental crust resulted in the formation of a TJ (Afar TJ).
• Red sea, Gulf of Aden & the Africa rift.
• The rift is the most ••••••
