Biodiversity

1. Biodiversity What is it? BCB 705: Biodiversity

2. How do we define ‘biodiversity’? • Biodiversity = biotic diversity = biological diversity • Biodiversity may be defined as the number, variety and variability of living organisms at all levels within a region. Three levels of diversity are highlighted: • Genetic diversity • Species or organismal diversity • Ecosystem or ecological diversity – including functional variety and the variety of interactions. • Some definitions specify landscape diversity as well. • Biodiversity = Speciation – Extinction Section of DNA

3. How do we define ‘biodiversity’?Genetic diversity • Genetic diversity = “heritable variation within and between populations of organisms” (p xiii Groombridge 1992). • Within an organism, the following levels of genetic diversity may be recognised: • Nucleotides • Alleles • Genes • Chromosomes. • The primary source of genetic diversity is mutation. Mutation operates at two levels: • chemical alteration of DNA molecule changing the information; • during replication and/or recombination. Paired Chromosomes

4. How do we define ‘biodiversity’?Species or organismal diversity (1) • The individual organism is “the basic unit of the living world” (p14 Leveque & Mounolou 2001) hence organismal diversity. • “The species is the basic unit of classification” (p9 Heywood & Baste 1995) . • The definition of a species is not clear (especially for microorganisms). • Problem - sibling species. • This lack of clarity suggests that organismal diversity is more viable as a level of biodiversity than species diversity.

5. How do we define ‘biodiversity’?Species or organismal diversity (2) • Biodiversity is usually measured in terms of species. • Species diversity ≠ species richness. • Species diversity ≠ taxonomic diversity. • Thus if all the conditions of the species are the same, two species belonging to the same genus have a lower taxonomic diversity than two species belonging to different families while having the same amount of species diversity.

6. How do we define ‘biodiversity’?Ecosystem or ecological diversity • An ecosystem or ecological system is defined as a functioning unit of interacting organisms (plant, animal and microbe = biocoenosis) and their interactions with their physical and chemical environment (biotope) often linked to an area. • Ecosystem diversity is defined as the variety of ecosystems within a bigger landscape and their variability over time. • Ecological diversity is regarded variously as the variety of ecosystems in an area and their interactions or intra-ecosystem variety. The first definition is better.

7. Elements of biodiversity Table 1.1: Elements of biodiversity slightly modified from Gaston & Spicer (1998)

8. Biodiversity in different contexts • The definition given defines biodiversity as a scientific concept. • Biodiversity may be considered as a social/political construct. • Biodiversity in the context of measurement and quantification.

9. The Social/Political Context of Biodiversity • Term is used in science, the media and parts of the public arena. • Use is linked to the loss of the natural environment and its contents. • In some instances, the word ‘biodiversity’ is regarded as referring not only to the variety of life but also to the value of this life. Biodiversity is perceived as a value or as having a value. This link to conservation raises some issues: • ‘biodiversity crisis’; • high biodiversity as measured by species richness≠ high conservation priority; • How does one judge the success of conservation goals and actions? • Biodiversity may be viewed as a source of useful products.

10. How do we quantify biodiversity? • There cannot be one all-encompassing measure of biodiversity but aspects of biodiversity may be quantified. • The choice of what aspect of biodiversity to measure depends on the purpose the measurement will be used for. • If the chosen aspect of biodiversity is not directly quantifiable, measuring something correlated to the aspect of interest is an option. This is termed a surrogate measure. • Several different ways of looking at biodiversity exist that may be quantified. Measuring Clams

11. Perceptions of biodiversity 1 • Biodiversity may be viewed in the context of evolutionary time. • One could look at the radiation of species or other taxa from a single ancestor. • One could consider the diversity within a selected taxon over time. • One could consider the total number of species that have ever existed. • Biodiversity may be regarded “as a characteristic of natural communities” (p7 Lovejoy 1997).

12. Perceptions of biodiversity 2 • Biodiversity may be considered globally and collectively. • Aproximately 1.4—1.8 million species have been described. • How many species are there in total at present? • How much we know about biodiversity depends on location and taxon. • One may look at where biodiversity is concentrated. • The numbers of species tend to increase as one moves toward the equator. Amazon Rainforest

13. Some examples of measures of parts of biodiversity • Most measures are concerned with either the genetic or species level. • Species richness (the number of species)at different scales is frequently used as a measure of biodiversity . • Usually taxon related and/or limited. • Indices. • Shannon-Wiener Index • Biomass

14. Link to Chapter 2 Chapter 1 Biodiversity: what is it? Chapter 2 … I hope that you found chapter 1 informative and that you will enjoy chapter 2.