3. Patterns of Biodiversity

Question 1

What is the importance of species definitions? 5

Answer 1

1. species must be defined before we can measure biodiversity 2. definitions aid classification of organisms into discrete groups of similar organisms 3. allow us to understand how discrete groups arise 4. represent products of evolutionary history 5. quantify and explain the variety of organisms that exist

Question 2

Define the different species concepts. 6

Answer 2

1. none work perfectly but some are better than others 2. biological species - groups of actual/potentially interbreeding organisms isolated reproductively from other groups - problematic for plants, microbes and insects - can hybridise 3. evolutionary species - a single lineage of organisms that maintain a separate identity from other organisms/lineages with own evolutionary tendancies and histories 4. phylogenetic species - distinct, irreducable cluster of organisms with common ancestry and descent/the smallest monophyletic group of common ancestry 5. genealogical species - exclusive group of organisms more closely related to each other than organisms outside group 6. recognition species - the most inclusive population of biparental individuals sharing a common fertile system

Question 3

How can we estimate species biodiversity? 5

Answer 3

1. species number/richness 2. species abundance - how many of each species 3. tells of relationship between species 4. heterogeneity (evenness) of species numbers 5. Greater heterogeneity means more diversity, as deaths have less impact

Question 4

What is the Shannon-Wiener diversity measurement.

Answer 4

1. Predicts how difficult it is to predict the species of next individual sampled 2. The easier it is, the lower diversity 3. Range is from 0 to log₂s
2. Comparisons between communities are unadvisable with this
3. Larger value means more uncertainty.

Question 5

What is Simpson’s index of diversity? 5

Answer 5

1. Depends on species richness
2. Can compare communities with some species richness.
3. Finds probability that 2 specimens picked at random are different species
4. More weight given to common species

Question 6

What are the three scales of species biodiversity? 3

Answer 6

1. alpha diversity - diversity within a habitat
2. beta diversity - diversity between habitats/how similar they are
3. gamma diversity - total landscape diversity eg. flora of british isles

Question 7

What are the global terrestrial diversity trends? 3

Answer 7

1. Above ground, diversity increases with decreasing latitude
2. the tropics support higher biodiversity
3. this applies for plants and animals

Question 8

What are the factors contributing to diversity gradients? 8

Answer 8

1. history - more time permits more colonisation and evolution of species
2. habitat heterogeneity - complex habitats mean more niches
3. competition reduces niche size
4. predation prevents competitive exclusion
5. climate - unfavourable tolerated by fewer species
6. climate variability - fewer species adapted for this
7. productivity - more productive supports more species
8. disturbance - moderate disturbance prevents competitive exclusion

Question 9

What are the soil diversity gradients? 7

Answer 9

1. tropic trend not followed
2. overall, common findings in a scottish field are common globally
3. High nematode diversity at tropics but peaks in temperate zones
4. but could be artefact of sampling efforts
5. doesn’t explain all off trends but will contribute
6. overall, still significant peak in tropics for nematodes
7. above ground trends mirror below for some things

Question 10

What is the intermediate disturbance hypothesis? 5

Answer 10

1. Disturbance of succession at midpoint promotes both pioneer and competitive species
2. Particularly in tropical grassland
3. examples of disturbance include fire, tree fall, landslides
4. in soil, disturbance reduces diversity
5. eg. making space in soil by root pushing

Question 11

What is habitat heterogeneity? 1

Answer 11

1. Less heterogeneity means more complex, so more niches, so more species

Question 12

Describe the landscape diversity of soil bacteria. 4

Answer 12

1. countryside survey audits UK land use
2. carried out every few years
3. information on flora, fauna and environmental variables collected
4. last survey included analysis of soil bacterial communities from 1000 cores across the uk

Question 13

Describe the bacterial biogeography of british soils, as described by Griffiths et al., 2007. 8

Answer 13

1. bacterial communities associated with most environmental factors measured
2. broadly follows same patterns as plant communities
3. pH major factor in determining diversity and community structure
4. relationship shanges depending on scale measured
5. positive relationship between alpha and gamma diversity and pH
6. negative relationship between beta diversity and pH
7. more alkaline soils are more similar
8. within site, diversity increases as alkalinity increases

Question 14

What are the seasonal assemblages of arbuscular mycorrhizal fungi, according to dumbell at al., 2011? 6

Answer 14

1. Single site study of arbuscular mycorrhizal fungi on plant roots from a temperate grassland
2. change in communities over time
3. summer and winter communities very different
4. negative relationship between temp. and diversity
5. higher diversity in winter
6. may be due to increased competition for scarce resources

Question 15

How can we measure soil diversity? 3

Answer 15

1. Very difficult
2. need to define what counts as species/individual
3. how do you measure richness and abundance without them?

Question 16

What is arbuscular mycorrhizal fungi? 5

Answer 16

1. very abundant with global distribution
2. form symbiotic associations with most land plants
3. asexual conal lineages - taxonomy defined by clonal isolates
4. ecological characteristics differ between isolates
5. no formal species concept

Question 17

Describe AMF (arbuscular mycorrhizal fungi) species definitions. 4

Answer 17

1. taxonomy can also be based on morphology of resting, asexual spores
2. limited by distinguishing features
3. very few described species but large diversity revealed by molecular approaches
4. diversity within and between isolates

Question 18

What is the significance of the rhizobium leguminosarum bacteria genome? 7

Answer 18

1. One circular chromosome and several large plasmids
2. these are the two main components of the genome
3. core genes are conserved
4. accessory geners more labile
5. different evolutionary histories and trajectories
6. form nitrogen fixing nodules with legumes
7. horizontal gene transmission violates phylogenetic species concept

Question 19

Talk about Sinorhizobium medicae bacteria phylogeny. 2

Answer 19

1. different parts of the genome have different histories
2. isolate position in network changes based on what part of the genome is used

Question 20

How can we measure microbial diversity? 4

Answer 20

1. traditionally used culture techniques
2. count number of distinct colonies
3. only able to culture 0.3% of microbial soil diversity
4. molecular techniques now used

Question 21

How can we separate microbe species with phenotypic analysis? 5

Answer 21

1. Phospholipid fatty acid analysis (PLFA)
2. Phospholipids are in the membranes of all living cells
3. different compounds in different microbial communities
4. measures living component
5. relative abundance of broad taxonomic groups (bacteria not fungi)

Question 22

How can we determine abundance of microbes using genotypic analysis? 6

Answer 22

1. DNA sequences very more among species than within species
2. can use PCR based techniques to look at phylogenetic and functional diversity, community diversity and species composition
3. if 97% similar, isolates classed as same species
4. we do this with denaturant gradient gel electrophoresis, using terminal restriction fragment length polymorphism (T-RFLP)
5. Sequencing technologies used
6. Good for species richness but not abundance

Question 23

Ecology. C. Krebs. 2014.

What are the difficulties in measuring biodiversity? 3

Answer 23

1. finding no species in a community can be difficult because species counts depend on sample size
2. communities have more rare species than common species
3. many communities show some abundance curves

Question 24

Ecology. C. Krebs. 2014.

What are some inconsistencies in diversity gradients? 3

Answer 24

1. some fauna eg. those that are seals/sea lions do not increase in diversity at tropics
2. in USA, many mammals more diverse in temperate zones eg. shrews and pocket gophers
3. Areas of sudden change often include mountains

Question 25

Ecology. C. Krebs. 2014.

What is the evolutionary speed hypothesis? 2

Answer 25

1. older communities have more species richness - particularly non-interrrupted ones
2. more diverse may equal fast evolution and low extinction

Question 26

Ecology. C. Krebs. 2014.

Describe some interspecific interactions. 5

Answer 26

1. competition and predation may be keener in tropics - smaller niches
2. polar/temperature populations more ompacted by environmental factors
3. does not explain alpha diversity of plants - few limiting factors
4. more niche overlap means more species - may apply to tropic
5. important in animals, especially predation

Question 27

Ecology. C. Krebs. 2014.

What is the ambient energy hypothesis? 4

Answer 27

1. Availability of energy is important in maintaining species rich habitats, and creates gradients
2. lots of evidence to support this
3. energy includes light, temperature and water
4. Only explains large gradients, not small ones

Question 28

Ecology. C. Krebs. 2014.

What is the productivity hypothesis? 2

Answer 28

1. thought that greater productivity means greater biodiversity, but no supporting evidence has been found
2. productivity in plants leads to lower local biodiversity

Question 29

Fundamentals of Ecology. Odum and Barrett. 2005.

What are the types of biodiversity? 4

Answer 29

1. larger areas have more diversity
2. pattern diversity - due to zonation, patchiness etc
3. genetic diversity - genetic variability
4. habitat diversity

Question 30

Fundamentals of Ecology. Odum and Barrett. 2005.

What is the relationship between diversity and stability? 3

Answer 30

1. more stable communities are more diverse
2. not necessarily causal
3. in community parts, trophic levels are influential over species diversity