<P> In reality, this still leaves the question of how much differentiation is needed for coexistence (Hutchinson 1959). A vague answer to this question is that the more similar two species are, the more finely balanced the suitability of their environment must be in order to allow coexistence . There are limits to the amount of niche differentiation required for coexistence, and this can vary with the type of resource, the nature of the environment, and the amount of variation both within and between the species . </P> <P> To answer questions about niche differentiation, it is necessary for ecologists to be able to detect, measure, and quantify the niches of different coexisting and competing species . This is often done through a combination of detailed natural history studies, controlled experiments (to determine the strength of competition), and mathematical models (Strong 1982, Leibold 1995). To understand the mechanisms of niche differentiation and competition, much data must be gathered on how the two species interact, how they use their resources, and the type of ecosystem in which they exist, among other factors . In addition, several mathematical models exist to quantify niche breadth, competition, and coexistence (Bastolla et al. 2005). However, regardless of methods used, niches and competition can be distinctly difficult to measure quantitatively, and this makes detection and demonstration of niche differentiation difficult and complex . </P> <P> Over time, two competing species can either coexist, through niche differentiation or other means, or compete until one species becomes locally extinct . Several theories exist for how niche differentiation arises or evolves given these two possible outcomes . </P> <P> Niche differentiation can arise from current competition . For instance, species X has a fundamental niche of the entire slope of a hillside, but its realized niche is only the top portion of the slope because species Y, which is a better competitor but cannot survive on the top portion of the slope, has excluded it from the lower portion of the slope . With this scenario, competition will continue indefinitely in the middle of the slope between these two species . Because of this, detection of the presence of niche differentiation (through competition) will be relatively easy . It is also important to remember that there is no evolutionary change of the individual species in this case; rather this is an ecological effect of species Y out - competing species X within the bounds of species Y's fundamental niche . </P>

Explain briefly how niche differentiation may cause the formation of a new species