Palaeoecology

Question 1

What is palaeoecology?

Answer 1

Palaeoecology is the study of past ecosystem which may or may not exist in the modern world. It is also the study of interactions between past living organisms and their environment.

Question 2

What sort of changes can we reconstruct through palaeoecology?

Answer 2

Flora, Fauna, Climate and the impact of people on the environment. This is limited by the availability of floral and faunal evidence.

Question 3

What are macrofossils?

Answer 3

These are whole skeletons to small fragments of animals or plants, we identify these by eye or magnification. Smaller remains are preserved in larger quantities so we can get a more complete dataset for smaller fossils.

Question 4

What are microfossils?

Answer 4

These are minute remains, e.g. pollen, ostracods, diatoms. We magnify these over 400x to see.

Question 5

Founding assumptions of palaeoecology

Answer 5

• Uniformitarianism: present is the key to the past and to what might be happening in the future.
• We need modern analogues.
• Speed of change is ignored.
• Does not recognise time-transgressive change.
• Controlling environmental factors on the analogue are known.
• Ecological affinities remain constant.
• Assumes populations are/were in equilibrium.
• Assumes modern analogues exist for past species/environment.
• Process of fossilisation is known.
• No contamination or differential preservations.
• Hence palaeoecology is not always spot on.

Question 6

What might reduce the evidence in the fossil record?

Answer 6

• Seasonal migration of organisms.
• Exotic organisms may stray into ecosystem.
• Some corpses are predated after death.
• Decay or erosion may destroy record.
• Only a few organisms remain well-preserved.

Question 7

Faunal Evidence: Vertebrates

Answer 7

Bones of vertebrates tend to be big and easily diagnostic: tusks, teeth.
Hair and horns also preserve well, and coprolites (droppings) give evidence about climate, environment and what the species ate.

Question 8

What characteristics enable good preservation?

Answer 8

Frozen places, e.g. Siberia preserve very well. A baby wooly mammoth was found after 39,000 years.
Dry environments where dessication and drying out preserve fossils and vertebrates.
Amber can also preserve small things such as hair.

Question 9

Limitation of Vertebrate evidence

Answer 9

• Identification can be difficult with small, poorly preserved fossils.
• Remains are rare as preservation is sparse, and will only become more sparse.
• preservation may be unrepresentative, due to sporadic preservation sites. Taar pits in LA upwell fumes that animals fall into.
• Fossils can be transported by predators or erosion.
• Rapid evolution or extinction cause changes in ecological affinities and cause disequilibrium.

Question 10

Advantages of Vertebrate Evidence

Answer 10

• Age easily determined using radiocarbon dating, or uranium-thorium dating.
• Can determine diets through isotopes and minerals in teeth, bones or coprolites.
• DNA detection (Gilbert et al., 2007 on mammoth hair DNA).
• Strong ecological preferences and affinities)
• Size is related to climate (Bergmann’s Rule).

Question 11

What is Bergmann’s Rule?

Answer 11

Body size increases as temperature decreases to help conserve energy.
I.e. volume grows more rapidly than skin area (heat production vs heat dissipation).

Question 12

How can we see differences between interglacial periods through vertebrate evidence?

Answer 12

We know animals migrate to warmer regions during glacial periods, and they move back north when it warms. The spatial distribution of vertebrate evidence can be assessed to identify between glacials and interglacials.

Question 13

Invertebrate forms of Evidence

Answer 13

Terrestrial: molluscs (snails), coleopteran (beetles)

Aquatic: Molluscs (snails/clams), Ostracods (crustaceans), Chronimids (midges), Cladocera (water fleas).

Question 14

What controls the presence and distribution of invertebrates?

Answer 14

Chemical: pH, salinity, dissolved oxygen, trophic nutrient level, solute composition.
Physical: substrate, presence of plants, water movement, temperature, depth.

The low tolerance to change in these properties make invertebrates good for understanding climate changes.
Many of these properties are interdependent.

Question 15

What are foraminifa?

Answer 15

These are microscopic single-celled organisms, that coil in one direction is sea water is above 9 degrees, and the opposite way in colder seas, hence these records can indicate sea temperature.
Forams can be planktonic or benthic, which means they reside at the surface or bottom of the sea respectively.

Question 16

Why are coleoptera a good modern analogue?

Answer 16

Their head capsules preserve well, and cover all sizes and shapes so are easily identifiable.
Beetles are STENOTHERMIC meaning they are ecologically temperature controlled.
Many are STENOTOPIC which means they show a marked preference for particular environments (Lowe & Walker)
They also travel long distances and have a low rate of evolution, making them good for understanding past changes.

Question 17

How do we use a mutual climatic range approach with coleoptera?

Answer 17

If you find three beetle species in an assemblage, you can overlap their climatic ranges to find a tight window in which they all could exist.

Question 18

What is pollen?

Answer 18

Pollen consists of a cell, intone and extine. The waxy extine helps preserve pollen grains.
The pollen of a plant is usually very distinct in shape and colour.

Question 19

How is pollen dispersed?`

Answer 19

By wind (anemophilous), insects, birds and animals (entomophilous/zoophilus). 
Aquatic pollen is dispersed by water and self fertilisation.

Question 20

What features of pollen make it a good evidence source?

Answer 20

The extine is very resistant to decay, its morphology varies between species.
It evolves extremely slowly, a principle of uniformitarianism.
Produced in very high numbers and disperses well, reflecting the natural vegetation of a location.

Question 21

Controlling Factors on Pollen production and dispersion.

Answer 21

• Location of refugia: distance and presence of physical obstacles.
• Rates of migration: method of pollination and/or seed dispersal: trees migrate very slowly, but depends on species.
• Temperature tolerance varies between species.
• Inter-species competition can control species population rather than climate.
• Soil maturity, some soils may not be able to facilitate certain biological processes.

Question 22

Is there a lag time between climate and vegetation?

Answer 22

Yes. They are out of equilibrium by 1-2,000 years. This is likely to be longer during the transition from cold to warm, as trees have to migrate long distances, whereas in a cooling climate trees will hang on.

Question 23

Problems with using Pollen?

Answer 23

• Some uniformitarian assumptions as before.
• Not all plants produce the same amount of pollen. Self-fertilizers don’t produce much so finding 1-2 grains may indicate there was a lot of them.
• The method of dispersal varies, wind can carry pollen grains a great distance away from where it was growing: you can have over and underestimations of the plant population.

Question 24

What plant types ‘break the rules’ in terms of pollen production?

Answer 24

• Culluna Vulgaris (heather) produces lots of pollen although it self-fertilizes.
• Fagus (beech), Quercus (Oak) don’t produce as much pollen as expected.
• Triticum (wheat) is self pollinating but produces reasonable amounts.

An index of relative production has been created to correct for pollen production rates.

Question 25

How far can pollen travel? and what affects the distance travelled?

Answer 25

Most pollen only travels up to 1km, and after a certain distance it is referred to as background pollen.
Dispersal is a function of: grain size, wind direction and speed, precipitation, plant habitat, dispersal mechanism.

Question 26

Problems with pollen preservation?

Answer 26

Pollen prefers to be in acidic conditions for preservation, so carbon rich and alkaline environments don’t preserve pollen well.
Hence extreme chemical physical or bio process can reduce preservation. Also delicate species can become damaged and hard to identify.

Question 27

Problems with pollen interpretation?

Answer 27

Pollen data only shows relative pollen changes, so as one species (taxon) increases, others decrease in %, so understanding populations in a relative sense is not as informative as actual amounts.
Solution: correct data into an absolute pollen diagram by adding a known spike of exotic pollen, to see a ratio of local to exotic to find the local pollen concentration.

Question 28

Trends in Quaternary Flora

Answer 28

Varied insolation through the quaternary has led to a loss of exotic species in the UK.
However, total biomass on Earth has increased and so has species diversity.
There has been sharp decline in European tree diversity, losing trees that couldn’t adapt to frost.

Question 29

What is Palynology?

Answer 29

This is the scientific study of pollen.
It studies vegetation succession through relative chronologies, and correlation of deposits.
It also creates isopollen and palaeovegetation maps through tracking of long term vegetation changes and of regional/global climate.

Question 30

Late Pleistocene Vegetation Change

Answer 30

There has been a significant variation in the extent of the Sahara. IT has covered most area during glacial periods because all the moisture is locked up in ice sheets and unavailable as precip.

Question 31

Applications of Pollen: Vegetation Cycles

Answer 31

Pollen is a huge record that extends back many glacial cycles. Repetition in patterns help in identifying these periods.
we find a lot more diversity in interglacial records, and we can date things to understand things going back in time.

Question 32

Application of Pollen: Vegetation Succession

Answer 32

Iverson (1958) divided glacial-interglacial cycles into five stages, reflecting temperature, vegetation and soils. LOOK UP DIAGRAM LECTURE 6.

Question 33

Palaeovegetation Maps

Answer 33

We can map large datasets to demonstrate vegetation/climate change through time over wide areas. Isopollen maps show a single taxa, and palaeovegetation maps include many to provide a regional overview of vegetation composition, yet we can only make these if there is enough data for a wide range of taxa.

Question 34

What is Arboreal taxa?

Answer 34

All species containing woody tissue, including trees, shrubs, dwarf shrubs or lianas.

Question 35

What is Non-arboreal taxa?

Answer 35

Consists solely of taxa belonging to herbs.

Question 36

What is a pollen assemblage?

Answer 36

A mixture of pollen types within a single horizon of a sample of stratified sediments, such as a lake or peat sequence.