Question

• What is a niche? What may happen if two organisms occupy the same fundamental niche in an environment? A set of experiments was run to test for character displacement in two species of humming birds with regards to bill length. They found the following results: 1) When the two species are found together, their bill lengths are more different than when they are found apart. 2) The sympatric populations often have high immigration rates from the corresponding allopatric populations. 3) The presence of the 2nd humming bird species reduces the amount of resources for the 1st humming bird species. What other three pieces of information would you need to know to prove character displacement? And explain the reasoning behind why one of those pieces of information would be needed.

Answer 1

A niche is a role that a species occupies in the community, including the food it eats, the habitat it lives & reproduces in, and the relationship with other species.

If two species of organisms occupy the same fundamental niche in an environment, then they compete with each other for resources. In this while, one species may drive the extinction of other species.

Three pieces of information necessary to prove character displacement in the humming bird species:

• The difference in the bill lengths should be related to the reduction in the interspecific competition.

Reasoning: This can happen due to the variation in the accessibility of the short and long flowers by the long-billed and short billed hummingbirds respectively, for obtaining nectar.

• It needs to be made sure that the resources distribution in both the sympatry and allopatry is same.

Reasoning: This is done to make sure that the character displacement has not happened due to the differences in the resource distribution.The ideal situation is to keep the resources limiting, such that the interspecific competition for these resources acts as a function of character similarity i.e.bill length.

• These Differences in the beak length must be genetically based.

Reasoning: The variations evolved in-situ in this experiment must be genetically transmisable, so that the phenomenon of natural selection through genetic variation is proved. It also helps to rule-out the possibility of other environmental factors due to which the bill length dimorphism could be occuring.