Biodiversity. I. What is it? Where is it? III. Where did it come from? IV. What is its future?

Transcription

1 Biodiversity I. What is it? II. Where is it? III. Where did it come from? IV. What is its future?

2 What is Biodiversity? Ecosystem Diversity

3 What is Biodiversity? Species Diversity

4 What is Biodiversity? Leaves taken at the same time from different trees of the same species growing in the same place. Genetic Diversity

5 We will be concerned with species diversity today Species Diversity

6 How are species defined? Biological species concept A population whose members are able to interbreed freely and successfully under natural conditions. Morphological species concept A population whose members are grouped together based on morphological similarities (Can lead to classifications above and below the BSC). Phylogenetic species concept A population whose members, because of their relatedness, share at least one morphological or molecular trait that is absent in the next most closely related group (Often leads to classifications at a finer level than the BSC). Understand why we need a species concept and what the pitfalls are with the BSC

7 How are species distributed within broader taxonomic groups? What group is missing here?

8 How is species biomass distributed across groups? (Photosynthesizers)

9 Why does each level of the food pyramid become smaller as you move upwards? A. At higher trophic levels there is more competition among species. B. Energy is lost as you move up the food chain. C. Plants are more successful than animals. D. Because of high insect diversity. At higher trophic level... 14% Energy is lost as you... 84% Plants are more succ... 2% Because of high insec... 0%

10 Where is Biodiversity? Biodiversity is richest near the equator (low latitudes, tropics) - aka Latitudinal Species Diversity Gradient GLOBAL DIVERSITY OF MAMMAL SPECIES GLOBAL DIVERSITY OF PLANT SPECIES Source: IUCN

11 Also true for Coral, Mangroves, Seagrass and Pelagic Fish Open Ocean Fish diversity tuna and billfish diversity from Longline fishing Worm at al. 2005

12 Biodiversity is not always evenly distributed within latitude - Climate, altitude, soils & the presence of other species are determinants

13 Two ways of thinking about species richness: Each colored line represents a separate species (10 species on each graph). Pop. Density A Distance (m) If you are not used to reading graphs, or if you simply found the point of these graphs confusing, here is a little help. (Don t feel bad about being confused). B Distance (m) These graphs are theoretical models designed to demonstrate two concepts about the distribution of biodiversity. They are not based on actual data, but it is hypothetically possible that they could represent someone s actual data. If it helps you, think of it as actual data. The first things to look at on a graph are the axes. What do the axes represent? What are the units? In these two graphs, researchers laid down a 500m transect across two hypothetical landscapes (X axis). At every point along the transect, they surveyed what species were present, and how densely populated each species was (Y axis). Each colored line represents a different species. A different color signifies a different species. So, to summarize, these graphs show the location and density of species along a hypothetical geographical transect. Note, a transect is a fixed line along which a scientist records data about the environment at standardized intervals.

14 Two ways of thinking about species richness: Each colored line represents a separate species (10 species on each graph). Pop. Density A Distance (m) B Distance (m) So, with this information in mind (see previous slide), you can now make some sense of these graphs. In Graph A at point 0, the first measurement on the transect, there were 10 species present, although the dark green one was at a density of almost 0. On Graph B, at point 0, there were only 2 species present, with the pink one being at very low density. On Graph B it is impossible to find a point along the X axis where there are more than 4 species present, whereas on Graph A, in most places there at least 9 species present at a time. Also note that the species on Graph A are much more wide ranging than the species in Graph B. All of the species in B have restricted ranges. None are found along more than 200 m of the transect, whereas in A most exist along the whole 500 m transect, even if their densities fluctuate slightly. You should now be able to answer the questions posed in class (next slide).

15 Two ways of thinking about species richness: High Sympatric Richness aka Alpha or point sample richness High Allopatric richness aka Beta or turnover richness Each colored line represents a separate species (10 species on each graph). Pop. Density A Distance (m) B Distance (m) Why does it matter at what scale you choose to measure diversity?for example, on graph B would you miss some diversity on that landscape if your transect was only 100m long? What about a 100m transect on the landscape shown in Graph A? Do you find it interesting that species densities change along the transect? A longer transect may be necessary to see that change. Which landscape has higher species coexistence at any given point? Landscape A has more species coexisting together at any given point than does landscape B. Why? There are many potential reasons and we cannot answer that without more data. A possibility: Competition among species may have driven them to use the the landscape slightly differently, thus allowing coexistence. One could argue equally that competition may have driven the species on landscape B to occupy different parts of the landscape and not coexist. This is why it s a tricky question. Either way, species avoid direct competition for resources by occupying different niches. This gets at an age old dilemma: Is a niche a characteristic of the species or a characteristic of the environment. You don t have to worry about this. Take ecology if you want to know more. On which landscape will your conservation dollars go the furthest per unit area? Is there an argument to be made for conserving landscape B over A? There is no right answer here and it is difficult to come up with an argument. But assuming you have the money, there could be an argument for conserving landscape B, at least equally to A. There is something special about the environment in landscape B that leads to many restricted range species. Each segment along that transect, captures some unique species that are found nowhere else along the transect. There is also something special about this environment in that it is generating and maintaining unique species. Perhaps it should be preserved for its evolutionary potential in a worl with changing climate?

16 Washington 466 bird species (2.65 species per 1000 sq. km) Ecuador 1600 bird species (5.65 species per 1000 sq km) Sympatric (Alpha) - point sample (10km x 10km point) Low Alpha Pop. Density Alpha richness Distance (m) Beta richness Distance (m) Allopatric (Beta) turnover Low Beta High Alpha = high point coexistence Apha and beta diversity for finch species Figures courtesy of Paul Martin High Beta = high turnover across landscape (why is it high only in western S. America?) The climate changes dramatically across the Andes and species composition changes drastically with it.

17 Where does biodiversity come from? Why is it concentrated at low (tropical) latitudes?

18 Where does biodiversity come from? Example: Allopatric speciation Stage 1. isolation Stage 2. selection New habitat! Stage 3. secondary contact Time Note: Stage 3 is not essential, but it is essential to prove that the populations are good species under the BSC.

19 Why is biodiversity concentrated in the tropical latitudes? Some hypotheses: High speciation rates? High immigration rates? Low emigration rates? Low extinction rates? Why should these things differ by latitude? - Climatic stability

20 Recall how species are formed: Isolation and time, coupled with: Natural selection And/or Sexual selection And/or Genetic drift How does climatic stability contribute to isolation?

21 Seasonality increases with latitude Organisms living here must deal with wide ranges of temperatures. Sometimes they move around to avoid get away from hot or cold or theymove by accident, and it s not a big deal because they re used to dealing with different temperatures. Annual temperature range in ºC Temperature Month Organisms living here deal with only with very minor temperature variation throughout the year. They are adapted to one specific temperature and have no reason to move. In fact, if they did move, they might find themselves in a temperature zone where they are severely mal-adapted. Note opossum on shoulder! Janzen 1967

22 So, in the tropics: Low seasonality means Low climate variability Low climate variability means: Low rates of dispersal (you can stay in one place because it s comfortable year round) Low rates of dispersal means: Greater adaptation to the local environment (you get comfortable where you are) Greater local adaptation means: -- Greater genetic isolation over shorter geographic distances (you breed only with those around you so genepool is more and more specialize for that place). Greater genetic isolation over shorter distances means: -- Greater speciation rates in the tropics (your little population becomes so specialized and so different from the neighboring population that you can no long interbreed with them). Areas of high beta diversity may indicate areas of high rates speciation. Is this the only explanation for high biodiversity at low latitudes? No, but it has some implications for conservation which we ll explore later.

23 Great Natural Extinction Events Great Extinctions have been large determinants of the composition & diversity of life on earth about 97% of species that have ever existed are extinct. How does extinction aid new bouts of speciation? 2 75% if species extinct 1 1. End Permian Event (251 MYA): ~70% of terrestrial species and >90% of marine species went extinct 2. End-Cretaceous Event: 75% of all species went extinct

24 Ehrlich and Pringle argue all of these except 1. The next 2 b people will have more impact that the previous 2 b people 2. Biodiversity loss will increase the debt b/c of lower park fees and endowments 3. Biodiversity loss will lead to lower future evolutionary potential 4. Climate change stems from a special case of toxification

25 Which recommendation is not discussed by Ehrlich/Pringle? 1. Put conservation on the cultural radar screen 2. Conserve biodiversity in human-dominated landscapes 3. Create a stronger United Nations environmental conservation program 4. Increase financial endowments for conservation

26 Contours of the 6 th Great Extinction Species are being lost at an alarming rate Current extinction rate is 1,000 to 10,000 times the natural rate 2 out of 5 recognized species on the planet faces the risk extinction Global homogenization and simplification of biodiversity is occurring at all three levels (genes, species, ecosystems) Why? You probably know why, but we will explore this, and its consequences, in more detail another time. Chapin et al, 2000

27 Supplemental slides in case you want more information:

28 Biodiversity hotspots recognized by E.O. Wilson and others as having not only with high alpha diversity, but high uniqueness

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32 The Age of the Anthropocene It is thought that the influence of human behavior on the Earth in recent centuries as so significant as to constitute a new geological era We are modifying physical, chemical, and biological systems in new ways, at faster rates, and over larger spatial scales than ever recorded on earth. Jane Luchenco, current NOAA Administrator The biosphere itself, at all levels from genetic to the landscape, is increasingly a human product. Braden Allenby, ASU Professor NASA 2010 Daniel Beltra