Phylogenetic Signal Detection in the Taxa Experienced A Slowdown of Diversification Rate: Verification onPedicularissp. (Orobanchaceae)

Abstract

Presence of phylogenetic signal implies that phylogenetically-informed methods provide a better fit to the data under analysis than traditional methods. Recent simulation work indicates that an early burst in diversification followed by deceleration can result in increased phylogenetic signal. Thus, phylogenetic signal would be determined by the role the trait played as a key innovation. Phylogenetic signal is also hypothesized to be determined by the lability of the trait, which may in turn be determined by the variability in selective pressures upon the trait, or the genetic architecture underlying the trait. In this work, we examine the genus Pedicularis to verify that strong phylogenetic signal is easily detected in the taxa that has a diversification rate decreasing over time. Our results show that a recent slowdown in diversification rates is confirmed. The K analysis indicated that half of morphological variables are not obviously influenced by the phylogeny, and other variables have lower phylogenetic signal than expected under Brownian motion. Thus significant phylogenetic signal or not is decided by a lot of factors, we cannot infer its presence or absence from a single factor.