Small-time sampling behavior of a Fleming-Viot process

The Fleming-Viot process with parent-independent mutation process is one particular neutral population genetic model. As time goes by, some initial species are replaced by mutated ones gradually. Once the population mutation rate is high, mutated species will elbow out all the initial species very quickly. Small-time behavior in this case seems to be the key to understand this fast transition. The small-time asymptotic results related to time scale tθ and a(θ)t, where lim_θ→∞θa(θ) = 0, are obtained by Dawson and Shui (1998, 2001), Shui and Xiong (2002), and Xiang and Zhang (2005), respectively. Only the behavior under the scale t(θ), where lim_θ→∞t(θ) = 0 and lim_θ→∞θt(θ) = ∞, was left untouched. In this paper, the weak limits under various small-time scales are obtained. Of particular interest is the large deviations for the small-time transient sampling distributions, which reveal interesting phase transition. Interestingly, such a phase transition is uniquely determined by some species diversity indices.