Tempo and mode in the evolution of morphological disparity in the Neotropical fern genus Pleopeltis

摘要

Species diversity and morphological disparity are two measures to examine the diversity of life. Evidence based on the fossil record suggests a complex relation between these two parameters of biodiversity including frequent decoupling of their assembly through time. However, rather few studies explored the correlation of these two measurements by studying extant plant species. This study was designed to explore the accumulation of morphological disparity of the derived Neotropical fern genus Pleopeltis. To explore the relationship of species diversity and morphological disparity, we employed several approaches including divergence time estimates based on DNA sequence variation, reconstruction of character state changes based on a morphological matrix comprising 41 discrete characters, and exploration of the phylomorphospace. Accumulation of species diversity and morphological disparity was found to be concordant although the assumption of independence was not rejected for the accumulation of genetic and morphological variation. The phylomorphospace reconstruction provided further evidence for clade-specific morphospace expansion that imply developmental pathways and competition among clades as major factors shaping the assembly of morphological disparity over time.