Phylogeny of extant genera in the family Characeae (Charales, Charophyceae) based on <i>rbc</i>L, sequences and morphology

Abstract

Extant genera of Characeae have been assigned to two tribes: Chareae ( Chara, Lamprothamnium, Nitellopsis , and Lychnothamnus ) and Nitelleae ( Nitella and Tolypella ), based on morphology of the thallus and reproductive structures. Character analysis of fossil and extant oogonia suggest that Tolypella is polyphyletic, the genus comprising two sections, one in each of the two tribes. Eleven morphological characters and sequence data for the Rubisco large subunit ( rbc L) were used to reconstruct the phylogeny of genera, including the two sections of Tolypella. Parsimony analysis of the rbc L data, with all positions and changes weighted equally, strongly supports the monophyly of the Characeae. The two Tolypella sections form a robust monophyletic group basal to the family. Transversion weighting yielded the same tree but with a paraphyletic Tolypella. The rbc L data strongly support monophyly of tribe Chareae but tribe Nitelleae is paraphyletic. Parsimony analysis of morphological data produced one unrooted tree consistent with monophyly of the two tribes; on this tree the Tolypella sections were paraphyletic. Combining morphological with rbc L data did not change the results derived from rbc L sequences alone. The rbc L data support the monophyly of the Characeae and Coleochaete , which together form a monophyletic sister group to embryophytes.