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DST-NRF CENTRE OF EXCELLENCE FOR INVASION BIOLOGY Ecology and Biodiversity Energy and Food webs What is biodiversity The biodiversity crisis The Convention for Biological Diversity How to measure biodiversity Links WHAT IS ENERGY? Energy is the property of a system that enables it to do work Several forms of energy: kinetic, potential, heat, chemical, nuclear and radiant energy. Common measures of energy: joules (SI Unit), calories and kilowatt-hours SOURCES OF ENERGY Sun: primary source of energy on earth Fossil fuels: coal, oil Nuclear energy LAWS OF ENERGY 1st law of energy: Energy cannot be created or destroyed but can be transferred from one form to another 2nd law of energy: When one form of energy is transferred into another form, some useful energy is always lost as heat, therefore, energy cannot be recycled. In nature systems go from order to chaos - Entropy is the amount of disorder in a physical system Closed system: entropy remains constant or increases In an open system: entropy can decrease, at a local scale - by using energy, this tendency can be “reversed” - Think of a teenager’s bedroom FLOW OF ENERGY Solar energy herbivores carnivores top carnivores HEAT ENERGY RETURNED TO THE ATMOSPHERE death and decay plants ENERGY & NUTRIENT FLOW IN A FOOD CHAIN Solar energy Plants Inorganic nutrient pool Energy Nutrients Consumers (herbivores and carnivores) Decomposers MARINE FOOD CHAIN TERRESTRIAL FOOD CHAIN EXAMPLES OF A FOOD CHAIN EXAMPLE OF A FOOD WEB Definition of Biodiversity “Biological Diversity or BiodiversityThe variety of life in all its forms, levels and combinations. Includes ecosystem diversity, species diversity, and genetic diversity.” Ecosystems River, forest, high alpine, … Species Fir, spruce, oak, … Genetic diversity Different alleles in a population More Definitions Visualise the Earth as being made up of building blocks We start with an INDIVIDUAL An organism is an individual from any kingdom A group of individuals from the same species together in an area is known as a POPULATION More Definitions Populations of different species are usually found living together making up a COMMUNITY The grouping of both living communities and their non-living surroundings form an ECOSYSTEM River, forest, high alpine, … More Definitions A BIOME consists of many different ecosystems together Map taken from: http://www.environment.gov.za/enviroinfo/nat/biome.htm Species diversity Chordates incl. vertebrates Plants Insects After Purvis & Hector 2000 Nature 405: 212-219 Many studies have focused on a few groups of organisms; mostly plants and vertebrates. Ecologists should also investigate the effects of environmental change on invertebrates. Biodiversity in South Africa South Africa is home to an unique selection of species. This even includes the worlds smallest floral kingdom. South Africa is a signatory to the Convention for Biological Diversity that aims to reduce the loss of biodiversity. Capensis The Cape Floral Kingdom The smallest of the six floral kingdoms (the Western Cape province). With a very rich flora including many endemic plant families. Like Australis, Capensis is regarded as a segregated remnant of an ancient Antarctic Floral Kingdom (Gondwana). Fynbos traditionally thought to be less rich in insects than other habitats. Seeds of many fynbos plants are ant – dispersed (myrmechory) Cape Floristic Biodiversity Hotspot One of the world's five Mediterranean hotspots Characterised by evergreen fire-dependent shrublands The greatest non-tropical concentration of higher plant species in the world The only hotspot that encompasses an entire floral kingdom, 5 of South Africa’s 12 endemic plant families and 160 endemic genera. The Succulent Karoo Biodiversity Hotspot Richest succulent flora on earth 69% of plants are endemic Reptiles show relatively high levels of endemism One of only two entirely arid ecosystems to earn hotspot status Home to the mysterious tree-like succulent, the “halfmens”, as well as many unique species of lizards, tortoises and scorpions Threats: Grazing, agriculture and mining, especially for diamonds and heavy metals Maputaland-Pondoland-Albany Biodiversity Hotspot Highest tree richness of any temperate forest on the planet (nearly 600 tree species) Important centre of plant endemism The celebrated, bird-of-paradise flower is a distinctive hotspot endemic Rescue of the white rhino from extinction (took place in this hotspot) one of the best-known success stories in African conservation Threats: industrial and local farming and the expansion of grazing lands Why should we care about biodiversity? Why we should worry about biodiversity is debated Intrinsic value Ethical value (e.g. god’s creation) Economic value (e.g. medicines) Ecosystem services (one of the most important reasons from a scientific perspective) The Earth’s organisms and ecosystems maintain our planet’s life support system ■ Increased stability ■ Increased adaptability ■ Increased productivity Recreation But … Man only uses a small number of species directly for food, medicines, building materials, recreation, … (90% of human food sourced from plants comes from just 30 species) Many species seem to fulfil similar functions. Some monocultures are more productive than diverse systems (under ideal conditions). However, healthy functioning ecosystems are vital to ensure that there essential resources (e.g. air and water) for life on Earth What determines local biodiversity Area Connectivity Productivity Disturbance History … Species-area relationship Larger areas harbour more species. (MacArthur & Wilson 1967 Theory of Island Biogeography, Princeton Univ. Press) ■ less extinctions ■ more immigrations ■ more diverse habitats ■ etc. Same book also explain why more isolated areas are less diverse. Diversity-productivity relationship Overall areas with higher productivity seem to have larger diversity as well. However, some monocultures seem to be very productive (under ideal conditions). Highly productive systems may have reduced diversity through increased competition. The diversity-productivity relationship is scale-dependent. Intermediate disturbance Under stable conditions some species will outcompete others. Disturbance creates free space for establishment by removing strong competitors. Thus disturbance creates a more patchy environment with different successional stages coexisting. However, in strongly disturbed habitats only a few specialists can survive. Disturbance events can vary in frequency and severity. Cattle: cow pads, grazing, trampling Tractor: opening of bare Ground, aeration, … Fire: ash, removal of litter INDICATORS OF BIODIVERSITY Assumption: indicator is correlated with overall biodiversity. Indicators can be taxa or abiotic variables Cost effective Time savings Easy and accurate to measure Biodiversity Indices Problem how to decide what is a diverse site/ which site has a higher diversity Simplest method: Species richness Other Indices contain more information about the species composition than just richness Equitability or evenness Evenness Site dominated by one species If you select an individual at random it is likely to be a grasshopper Site with even species distribution If you select an individual at random it is equally likely to be any of the four species # Individuals 30 25 Site dominated by single species Site with more even species distribution 20 15 10 5 0 Species Biodiversity Indices Shannon-Wiener Diversity: H Shannon-Wiener Equitability: EH Simpson’s Diversity: D Simpson’s Equitability: ED S total number of species in the community (richness) Useful for questions like: pi proportion of S made up of the ith species “Which site is the most diverse?” “Are school grounds impoverished?” Biodiversity Indices Renkonen index Sørensen index p1i = Frequency of species i in site 1 p2i = Frequency of species i in site 2 a = Number of shared species b = Number of species only in site 1 c = Number of species only in site 2 Useful for questions like: “Is ant species composition within a habitat type (e.g. fynbos) more similar than ant species composition between sites from different habitats?” “Are school grounds more similar to each other than nature reserves are to other nature reserves?” Links (Biodiversity) Convention on Biological Diversity Handbook (the 3rd Edition) http://www.biodiv.org/handbook/defa ult.asp IUCN Red lists http://www.redlist.org/ Biodiversity Hotspots http://www.biodiversityhotspots.or g/Pages/default.aspx Links (General) Air photograps http://earth.google.com/ can be linked with antbase http://www.antweb.org/google_earth.jsp Control sites: South Africa National Parks http://www.sanparks.org/ Cape Nature Conservation managed reserves http://www.capenature.org.za