Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Notes towards Biodiversity Chapter 1 Introductory/Title Slide (1) Welcome to the Biodiversity Course of the National Information Society Learnership Ecological Informatics. We will start this course by looking at what ‘biodiversity’ is. My name is Gwen Raitt. I will be presenting this chapter. I hope you enjoy the course. Please let me know about any problems or issues that you have with this course. The email address is available from the side bar. How do we define ‘biodiversity’? Biodiversity is a synonym for biotic or biological diversity. Biodiversity may be defined as the number, variety and variability of living organisms at all levels within a region (Groombridge 1992, Dobson 1996, Yeld 1997, Anderson 1999, Wikipedia Contributors 2006a). Three levels of diversity are highlighted: genetic diversity, species or organismal diversity and ecosystem or ecological diversity – including functional variety and the variety of interactions (Yeld 1997, Gaston and Spicer 1998, Anderson 1999, Wikipedia Contributors 2006a). Some definitions specify landscape diversity as well (see Gaston 1996a and Gaston and Spicer 1998). Biodiversity equals the difference between speciation and extinction (Miller 2002). Speciation refers to the evolutionary development of new species while extinction refers to the loss of existing species (Wikipedia Contributors 2006c, g). This definition considers biodiversity from the perspective of organismal diversity. How do we define ‘biodiversity’? Genetic diversity Genetic diversity may be described as the heritable variation within and between populations of organisms (Groombridge 1992). Within an organism, the following levels of genetic diversity may be recognized: nucleotides (the building blocks of DNA and RNA), alleles (variations within a gene), genes (codes for other molecules) and chromosomes (macromolecules containing genes in eukaryotic cells (Groombridge 1992, Wikipedia Contributors 2006b)) (Groombridge 1992, Gaston and Spicer 1998). The primary source of genetic diversity is mutation (Lévêque and Mounolou 2001). Mutation operates at two levels. The first is chemical alteration of the DNA molecule changing the information. Cells have repair systems that catch most of these changes and correct them (Groombridge 1992, Lévêque and Mounolou 2001, Wikipedia Contributors 2006f). The second level is during replication and/or recombination during mitosis or meiosis (Groombridge 1992, Lévêque and Mounolou 2001). Recombination results in new combinations of genes (Groombridge 1992) and is thus a secondary source of genetic diversity. How do we define ‘biodiversity’? Species or organismal diversity (1) The individual organism is “the basic unit of the living world” (p14 Lévêque and Mounolou 2001) hence organismal diversity. “The species is the basic unit of classification” (p9 Heywood and Baste 1995). The definition of a species is not clear (particularly with regard to microorganisms (Pietra 2002)) and is therefore debated (Groombridge 1992, Bisby 1995, Heywood and Baste 1995, Wikipedia Contributors 2006h). Further problems recognizing species are presented by sibling species (Pietra 2002). Sibling species cannot be distinguished morphologically (Clark and Charest 1987) but show significant differences at a molecular level (Stork 1997). This lack of clarity suggests that organismal diversity is more viable as a level of biodiversity than species diversity. The pictures show South African examples of species. The beetle is a toktokkie (Genus Psammodes), the spider is a horned baboon spider (Family Theraphosidae) and the plant is blombos, Metalasia muricata. How do we define ‘biodiversity’? Species or organismal diversity (2) Biodiversity is usually measured in terms of species (Groombridge 1992). Species diversity ≠ species richness. Species diversity may be defined as the variety (number) of species and their relative abundance and distribution in a region (World Resources Institute 1989) where species richness only considers the variety of species in a region (Biosociety 2006). Species diversity ≠ taxonomic diversity. Taxonomic or taxic (Bisby 1995) diversity refers to the diversity of taxa higher in the hierarchy than the species (Groombridge 1992, Pietra 2002). 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. The pictures show some more South African examples of species. The frog is known as the clicking stream frog (Strongylopus grayii), the bird is a black eagle (Aquila verreauxii) and the antelope is a klipspringer (Oreotragus oreotragus). 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) (Wikipedia Contributors 2006e) often linked to an area (Mooney et al. 1995). Ecosystem diversity is defined as the variety of ecosystems within a bigger landscape and their variability over time (Lévêque and Mounolou 2001, FAO 2004). Ecological diversity is regarded variously as the variety of ecosystems in an area and their interactions (Lévêque and Mounolou 2001, LEAF Program 2006, Draper 2002) or intra-ecosystem variety (SustainableAg.net 2001). The first definition is better. Elements of biodiversity This table shows the elements of biodiversity linked to the highlighted categories of biodiversity. Biodiversity in different contexts (Gaston 1996a) The definition given earlier defines biodiversity as a scientific concept. Biodiversity may be considered as a social/political construct or in the context of measurement and quantification (Gaston 1996a). The Social/Political Context of Biodiversity The term biodiversity is used in science, the media and parts of the public arena (Gaston 1996a). Use of the term is linked to the loss of the natural environment and its contents (Gaston 1996a). 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 (Gaston 1996a). This link to conservation raises some issues: ‘Biodiversity crisis’ The present loss of biodiversity is considered a crisis or extinction crisis (Groombridge 1992, Gaston and Spicer 1998). Some say that we are facing or in the midst of the sixth mass extinction caused by humanity (Groombridge 1992, Eldredge 2001, Miller 2002, Wikipedia Contributors 2006d). High biodiversity as measured by species richness ≠ high conservation priority. Other considerations such as level of threat, origins of species (a high biodiversity may result from the introduction of alien species) and contribution to a broad conservation goal need to be taken into account when determining conservation priority (Gaston 1996a). How does one judge the success of conservation goals and actions? What aspects of biodiversity should conservation concentrate on? What is the purpose of conservation (Gaston 1996a)? Biodiversity may be viewed as a source of useful products. This view has been useful in promoting conservation of biodiversity (Lévêque and Mounolou 2001, Pietra 2002) and is considered as part of Chapter 3. How do we quantify biodiversity? There cannot be one all-encompassing measure of biodiversity but aspects of biodiversity may be quantified (Gaston 1996a, Gaston and Spicer 1998, Wikipedia Contributors 2006a). The complexity of the concept of biodiversity is irreducible (Gaston 1996a). The choice of what aspect of biodiversity to measure depends on the purpose the measurement will be used for (Gaston 1996a, Lévêque and Mounolou 2001, Wikipedia Contributors 2006a). 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 (Gaston and Spicer 1998). An example of a surrogate measure is the use of fossil family diversity as a surrogate for fossil species diversity. Species richness may be a surrogate measure (Gaston and Spicer 1998). Several different ways of looking at biodiversity exist that may be quantified. Perceptions of biodiversity 1 Biodiversity may be viewed in the context of evolutionary time (Lovejoy 1997). One could look at the radiation of species or other taxa from a single ancestor (Lovejoy 1997). One could consider the diversity within a selected taxon over time (Anderson 1999). One could consider the total number of species that have ever existed. It is estimated that 90—99.9% of species that have ever existed are extinct (Gaston and Spicer 1998, Miller 2002). Biodiversity may be regarded “as a characteristic of natural communities” (p7 Lovejoy 1997). This usually looks at categories of species not the total biodiversity, e.g. the number of plant species in a community. Perceptions of biodiversity 2 Biodiversity may be considered globally and collectively (Lovejoy 1997). Approximately 1.4—1.8 million species have been described (Dobson 1996, Lovejoy 1997). How many species are there in total at present? Estimates of the total number of species on this planet go up to 111,5 million species (Gaston and Spicer 1998). Working estimates range from 12.5—14 million species (Groombridge 1992, Bisby 1995). How much we know about biodiversity depends on location and taxon. For example, more is known about the insect fauna in Britain than in Australia. In Australia, vertebrates are better known than insects (Lovejoy 1997). One may look at where biodiversity is concentrated – the ‘hotspots’ (Lovejoy 1997). The numbers of species tend to increase as one moves toward the equator (Lovejoy 1997). Some examples of measures of parts of biodiversity Most measures are concerned with either the genetic or species level (Gaston 1996a). Species richness (the number of species) in an area is a frequently used measure of biodiversity (Gaston 1996b, Lévêque and Mounolou 2001). This is usually taxon related and/or limited, e.g. the number of plant and/or animal species without considering microbes. Indices may be based on models of diversity. The Shannon-Wiener Index is a commonly used diversity index (Wikipedia Contributors 2006a). Shannon-Wiener Index = Shannon Index = Shannon-Weaver Index The Shannon Index is a non-parametric index of species diversity used to compare the biodiversity of different areas (Southwood and Henderson 2000, Wikipedia Contributors 2006a. Biomass measures productivity. In plants, it may be limited to above ground biomass (Chapman 1976). Last slide I hope that you found chapter 1 informative and that you will enjoy chapter 2.