Phylogenetic analysis of the Cladophora coelothrix complex, including the description of the new genus Leliaertia (Cladophorales, Ulvophyceae)

Abstract

ABSTRACT Molecular phylogenetic studies have revealed the polyphyletic nature of Cladophora as traditionally circumscribed, which is separated into four main clades: Cladophoraceae, Siphonocladus, Pithophoraceae and Pseudocladophoraceae. Several taxonomic proposals have recently been made to resolve its polyphyletic nature. The present work focuses on the cryptic diversity of Cladophora coelothrix, within the Siphonocladus clade. Based on new collections from northeastern Brazil and phylogenetic analyses of partial SSU and LSU rDNA sequence alignments, we propose the new genus and species Leliaertia repens to accommodate one of the cryptic species hitherto included in C. coelothrix, occurring in the tropical Atlantic, Indian and Pacific Oceans. Leliaertia repens was recovered in the Siphonocladus clade and is phylogenetic distinct from the genuine Cladophora species in the Cladophoraceae. The new species occurs in marine and estuarine environments and forms conspicuous mats of semi-prostrate filaments. It represents a cryptic species and genus since morphological features, including the diameter and length:diameter ratio of the apical cell, show high levels of overlap with other species, including C. socialis. Our phylogenetic data indicate that L. repens, C. coelothrix and C. socialis represent a complex of cryptic species with at least four lineages, some of which co-occur in tropical seas.