Part A

  1. Differences in seed size preference might result in stabilizing difference versus # of seeds required to produce offspring might result in a fitness difference. ~ Species that eat different seed sizes have low competition and are more likely to coexist. Species that eat the same seeds may compete and ultimately result in evolutionary change or exclusion.

  2. Box 1 interactions exclusion, all survive

    Outcome of Each Box

    box1

    box2

    box3

    box4

    DA, DC

    BC, BA

    DB

    AC

    Differing seed size promotes stabilization, while differing seed count promotes competition. Finches D and B may have both seed size and seed count variations.

  3. Using resources at different efficiencies is considered a fitness difference, which limits coexistence. Whereas, using different resources promotes coexistence.

  4. True, the Beverton-Holt model is density-dependent. The model will plateau after reaching carrying capacity and the population size at the next time step is calculated using the previous population size.

Table 5
Simulation aii aij ajj aji li lj Can.i.invade Can.j.invade Can.they.coexist Box.from.fig.1
1 1 1.0 1 1.0 10 10 yes yes yes box 4
2 1 1.0 1 1.0 10 20 no yes no box 2
3 1 1.3 1 1.3 10 10 no no no box 5
4 1 0.3 1 0.3 10 10 yes yes yes box 1
5 1 0.3 1 0.3 20 10 yes yes yes box 3

  1. The main difference is that one species was more efficient in sim 3, preventing coexistence. Whereas both species exhibited high interspecific competition in sim 4.

  2. In a priority effect, interspecific competition is too strong for either species to invade. We see no species can invade in simulation 3.

  3. Interspecific competition must be greater than intraspecific competition in order for priority effect to be generated.

  4. It can be considered neutral as the relative abundance of the two species at the point of invasion is kept throughout the simulation. Since the inter and intraspecific competitions are equal, chance events that decrease a population will prevent regrowth if an invasion is successful.