Lecture 3: Geographies of biodiversity 5

Question 1

Life History Characteristics

Answer 1

There is an energy trade-off between growth and reproduction, and as such species will exhibit different life history strategies

Question 2

Life History Characteristics- R species

Answer 2

• ‘r’ selected species

• found in transitory environments that are unpredictable
• concerned with maximising population growth rates (reproduction over growth)

Question 3

Life History Characteristics- K species

Answer 3

K’ selected species

• found in more stable environments
• intraspecific competition for resources is high, consequently large investment in growth to compete, and fewer offspring that have resources to compete effectively

Question 4

CSR Strategy triangle

Answer 4

Plant life history strategy related to adaptations to disturbance frequency and resource levels

Three basic plant strategies: competitor, stress-tolerator and ruderal
• Strategies equal patterns of abundance:
- competitor = always abundant but depressed under low resource conditions
- stress-tolerator = always rare, displaced spatially to low-resource sites
- ruderal = temporarily abundant, displaced in time by more competitive species

Question 5

Succession on Krakatau

Answer 5

Key example the recolonisation of the Krakatau islands – eruption on 27th August 1883 left several remnant islands devoid of life – two thirds of the main island suffered caldera collapse. Global repercussions.

• Volcanic activity continued, and Anak Krakatau (‘child of Krakatou’) emerged from the sea (pyroclastic flow) in 1930 – it is now a substantial island (60-80 m ash deposits)
• Originally covered in rainforest, and slowly the successional process has led to the rainforest re-establishing on the islands – this was a key natural experiment in island colonisation and extinction, and succession

Question 6

More on succession on Krakatau

Answer 6

No surviving plant or animal life found in the area three months after eruption – first thing recorded was a spider. In September 1884 (one year later), the first grass observed

Coastal communities first to develop – by 1897 already similar to many other sites in the area

• Interior forests are still atypical today
• Recolonisation from Java and Sumatra – by 1935 a tropical rain forest was developing
• Measures of bird diversity found that the number of bird species increased rapidly until 1920 but then the number of species remained relatively constant.