Darwin drew from Malthus about ideas of struggle of existence Reasons for

Darwin drew from malthus about ideas of struggle of

This preview shows page 3 - 5 out of 25 pages.

distributions of species. Darwin drew from Malthus about ideas of struggle of existence. Reasons for populations reaching carrying capacity, source of density from intraspecific competition. Intra influences abundance of organisms. High density population does poorly and decreases and low density population does good and increases. Plant hopper in high densities. Test whether intraspecific occurs. Took plotted plants, put a cage around them and put diff. densities of plant hoppers in them. If intraspecific competition occurs, then fitness should decrease as density increases. As density increases, survivorship would decline. First graph. Development time tends to increase with population density suggests that as resources become scarce plant hopers take longer to reach reproductive maturity. Second graph. End up maturing to smaller body size. Affects not only survivorship and how long they take to develop from egg to adult and how big they will grow. Affected by intra. Tansley’s Bedstraw. Interspecific (Tansley’s). First study of interspecific competition. Studied 2 plant species known as bed straws. Called like that because that’s what they were used for. Noticed interesting pattern. Sylvestre (forest dwelling species live on basic hillsides) saxatile (low elevations and acidic bog). Interesting distribution pattern here. Asked simple question. Are abiotic conditions determining their distribution or competitive interactions. Common garden experiment. Go on field dig up plants, grow them in standard soil in common environment. Brought them back into lab, both species in basic and acidic soils. If it was abiotic, sylvestre would only grow on basic. Grew them alone in different soil types. Basic soils sylevestre has high germination rate. Saxatile seems to do ok as well and can germinate and germinated seeds survive and produce flowers. Both species by themselves in acidic soils, they both germinate and both survive. Rejects that abiotic environment influences their survivorship. Then both species together in pot in different soils and allowed them to compete with one another for available nutrients. In both cases, he found that tin basic soils Sylvester always was the one that survived to the end of the study. When he grew both plants in acidic, only saxatile was there at the end of seasons. Other species died out. Species from native soils are only ones that survived. Study by Tansley’s was important to field of ecology because it told us important things. Suggests that species present or absent in area due to interspecific competition. Environmental conditions can determine outcome of competition. In basic soils, sylevester was winner for competition and acidic was saxotile. Environmental conditions can dictate who winner of competition is. Study suggests that current distributional patterns of species could be result of competition that took place in past. Ghost of competition past. Plants can tolerate both conditions. Don’t co-occur with each other, because one of species would go extinct. Interspecific could be important in determining distribution of species.
Image of page 3
Interspecific competition is important. Gause published influential paper which
Image of page 4
Image of page 5

You've reached the end of your free preview.

Want to read all 25 pages?

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture