interspecific competition pt 4 (niche differentiation->hidden treatment effect)

niche differentiation

differences in the range of resources used

the coexistence of competitors is associated with some degree of what?

niche differentiation + environmental tolerances

resource partitioning

similar species coexisting by partitioning available resources

what are some examples of resource partitioning?

1) different kinds/sizes of food

2) feed at different times

3) forage in different areas

4) exploit the portion of resources unavailable to others

how does natural selection influence resource partitioning?

past evolutions of natural selection adapts species that are better-able to resource partition in the present

why is it difficult to prove the relationship between resource partitioning due to competition and adaptations?

differences among species have evolved over a long period of time

→ we have limited information about the resources and potential competitors that may have influenced natural selection

what is a major example that proves the relationship between resource partitioning due to competition and adaptations?

when finch species coexist, beak size distribution for each species does NOT overlap

→ the divergence in their phenotypes allows for each species to access specific resources

→ on islands where they lived separately, populations possess intermediate + overlapping distributions of beak size

allopatric

species living separately

what is being illustrated?

relationship between resource partitioning + evolutionary adaptations

→ finches have beak size overlap on SEPARATE islands

→ finches have beak size divergence on the SAME island

character displacement

shift in feeding niche that subsequently affects a species’ morphology, behavior, or physiology

→ finches !!

why is it difficult to show competition under natural conditions?

1) little control over the environment

2) difficult to know if the populations are at or below carrying capacity

3) lack of knowledge on the life history requirements or the subtle differences between species

removal experiments

where one of the potential competitors is removed and the response of the remaining species is monitored

what effect do removal experiments have on the environment?

can have a direct/indirect effect on the environment that are unintended or misunderstood → these effects are called “hidden treatment effects”

hidden treatment effect

unintended or misunderstood effects on an environment due to removal experiments