Summary Class notes - World ecosystems

- World ecosystems
- A.M Kooijman
- 2019 - 2020
- Universiteit van Amsterdam
- Future Planet Studies
206 Flashcards & Notes
1 Students
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Summary - Class notes - World ecosystems

  • 1572562800 Biodiversity Lecture

  • E.O Wilson is a famous biologist. He is the father of biodiversity, biogeography and sociobiology. He mostly studied ant communities, which is how he got famous.
  • E.O. Wilson (1988) conjoined the words 'biological' and 'diversity' to 'biodiversity'.
  • Ecosystem diversity: number of different ecosystems or habitats within a location. As there are many species in the world, they shape the ecosystems.
  • Species diversity: number of different species within a location.
  • Genetic diversity: different genes or traits within a population.
  • Why is biodiversity important? Many people don't care about it, it might be a monetary value for them. It is, however, important for regulation of our ecosystems (e.g. creating shelter) and services they provide, such as aquaculture. In 2014: global estimation biodiversity worth is $145 trillion annually.
  • Ecosystem services contribute more than 2 times as much to human well being as global GDP.
  • Estimated amount of species in the world is 5-100 million, while only 1.5 million are catalogued (Mora et al. 2011). It is difficult to find new species, for instance in the open ocean. Each year, about 10,000 new species are discovered!
  • To estimate the global amount of insect species, Terry Erwin (1982) used pesticides (fogging) to kill all the Anthropods in tropics and see what came down. Then he said: 1 hectare in Panama contains 41,000 species, thus the earth contains 30 million species of insects. This seems a high over estimation now.
  • Other ways to measure biodiversity: Descriptions follow the Linnaean system of Classification (~250 years ago). In this system there are more specialized groups in lower tiers but they are also the most unknown. Higher taxonomic groups allows us to estimate lower/less well-known groups.
  • Most current estimation of species is 8.7 million. Myers et al. 2000 estimates 25 biodiversity hotspots. These can be found most on the coast lines, islands and around the equator. This is determined by counting 'endemic species': native species only found in localised area.
  • Continuing hot spots: 12% of total land area but 44% of all plants species and 35% of terrestrial vertebrate species can be found in the hotspots. Across all hotspots, 88% of all vegetation has been lost. >20% of global human population lives within hotspots, which means greatest biodiversity loss.
  • Biodiversity has a geographical component: Different areas house different numbers of species / biodiversity. If biodiversity were a contest, tropical rainforests and coral reefs would be winners!
    Tropical rainforests: 7% land area, 50% earth species. Coral reefs: <1% of ocean floor, >25% marine species.
    This also means these areas have the highest levels of extinction rate.
  • The distribution of biodiversity is dependent on: climate, latitude, altitude, soils, presence of other species (including prey, parasites, rivals etc.)
  • Latitudinal (Bio)Diversity Gradient (LDG or LBG): biodiversity is the highest in the tropics and decreases towards the poles. LDG holds true for most contemporary taxa but fails for some groups: e.g. parasites, aquatic flora, marine birds, mammals. This might be partly due to missing data as information is missing about collection / cataloguing animals).
  • Why is there missing data in specific locations? Why would it be there for instance in Venezula (tropics)?
    Lack of funding, measuring equipment, interest. If you are a poor country, it is less likely you will do science.
  • Continuing LDG: Reliable description of any pattern requires us to know where knowledge/data gaps are.
    Marine LDG shows biomodal distribution with lower biodiversity in lower latitudes (sampling bias?).
  • Understanding the causes of LDG are important to explain and predict geographic variation in biodiversity. We know that more species can be found in the tropics and less in the poles, but why is that? 3 hypotheses:
    Ecological: Geographical – more area allows for more species?
    Ecological: Climactic – low seasonality = more species? Higher primary production?
    Evolutionary: Historical – tropics are more stable over time and accumulate more species?
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Ecological: Geographical --> Are the tropics crowded or is it just geometry? Differences in area between the tropics and temperate regions --> tropics have a wider area than the temperate regions and less species fit in a smaller area.
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Ecological: Geographical --> In general: larger areas have higher biodiversity.
    Island Effect: larger have higher diversity, but this is countered by distance to mainland!
    Peninsula Effect: decreasing diversity near the tips of peninsulas
    . Smaller areas could mean higher extinction and isolation or less gene flow. Mountain tops have less species due to precipitation, altitude, air pressure etc.
  • To get a smaller number of species in a specific area, it might also be possible that there are less specie ecosystems. As the tropics are full of species, there is a high amount of specie ecosystems. Data suggests it’s not a linear relationship between the number of species and latititude = tropics are more crowded!
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Ecological: Geographical --> In general: larger areas have higher biodiversity. Mountain tops can act like islands -diversity decreases as elevation increases (or island size decreases). Causes vary for species that might be more build for certain air pressure or temperature or not.
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Ecological: Climatic --> Can low seasonality increase diversity?
    Tropics: little change in temperature = less need for dispersal = little overlap = more species.
    Temperate regions: greater change in temperature = more need for dispersal = more overlap = less species.
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Ecological: Climatic --> Does higher primary production increase diversity?
    The tropics receive more solar radiation = productivity = larger populations =higher plant diversity = support more species.
    Temperature is really important for species, also fluctuations in temperature, precipitation, etc. Primary production is of high influence of specie numbers, for instance solar radiation determines amount of primary production.
  • Hypothesis 1 of why more species in tropics than temperate regions:
    Evolutionary: Historical --> Are the tropics cradles, museums, both, or just a destination? 
    Cradle: Higher rates of speciation in the tropics = more diversity born here.
    Museum: Tropics hold onto more species. Less extinction, maintaining elderly species.
    Destination: Tropics attract more species. Species that originate somewhere else, invade and accumulate.
    The answer most likely: Both cradle and museum --> Higher speciation in the tropics and higher extinction in the temperate zone.
  • Biodiversity patterns --> Still a lack of consensus about what drives biodiversity patterns. What else than LDG?
    Islands: size and distance to the mainland are important. The closer you are to the mainland, the more colonisation / dispersal of species can be found on the islands. If you are a large island and close to the mainland, you will more likely get more species but also more adaptation.
    When endemism is high = lots of unique species.
  • Biodiversity patterns --> Still a lack of consensus about what drives biodiversity patterns. What else than LDG?
    Mountains: act similar to islands, large mountains are more divers with lots of endemic species.
    Reflects high species diversification, biotic interactions, ecological diversity and constant change (movement/erosion).
  • Mountains in biodiversity patterns; reasons for lots of species when there are bigger: 1) Novel high-elevation habitats for species.
    2) Dispersal barrier to low-level species because they cannot go over the higher ranges and go to different areas).
    3) Act as a corridor for dispersal between regions.
    4) Environmental modifier (hydrology and minerology).
    Mountains act as both cradles and museums, both those have different effects on the species.
  • Rocks are also important in specie amounts: geologically and ecologically diverse.
    Mafic rock comes from the ocean floor. Soils formed on these rocks have distinct geochemical properties that require specialized plant metabolism.
    In biodiversity patterns, scale matters. Question to ask: What’s the scale of dispersal and how does this differ between species?
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