科研之友
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摘要
Semple and Steel (2002) showed that if T is a phylogenetic X-tree and C is a collection of r-state characters that defines T, then vertical bar C vertical bar >= inverted right perpendicular(n -3)/(r -1)inverted left perpendicular, where n = vertical bar X vertical bar. In this paper, we show that, provided n is sufficiently large, this lower bound is sharp. Furthermore, we show that, for all n >= 13, there exists a collection of 4-state characters of size inverted right perpendicular(n -3)/3inverted left perpendicular that defines T, but there is a phylogenetic X-tree with n = 12 which is not defined by any set of 3 characters.
- 出版日期2015
