Cryptic diversity in non-geniculate coralline algae: a new genus Roseolithon (Hapalidiales, Rhodophyta) and seven new species from the Western Atlantic

Taxonomic contributions to Hapalidiales (Corallinophycidae, Rhodophyta): Boreolithothamnion gen. nov., Lithothamnion redefined and with three new species and Roseolithon with new combinations

“…Based on a collection of coralline algae made in 2011 along the coast of southern Australia, specimens were obtained and sequenced that, while not L. muelleri, are closely related and belong in the same clade with the generitype of Lithothamnion as shown herein (Figures 11,12,and S3). This clade is clearly distinct from all specimens currently called Lithothamnion and whose type specimens have been sequenced so that the correct application of the names is known as well as from the recently described Roseolithon (Coutinho et al, 2021;Richards et al, 2022). Four species comprise Lithothamnion, L. muelleri, L. kraftii, L. saundersii, and L. woelkerlingii, all from southern Australia, with L. woelkerlingii also found in New Zealand (Table S1).…”

“…Phylogenetic analyses of single gene and/or concatenated genes of plastid encoded psb A, rbc L, and UPA, mitochondrial encoded COI, and nuclear encoded SSU rDNA gene all indicated that Lithothamnion , as currently constituted, is polyphyletic (Coutinho et al, 2021; Jeong et al, 2021; Peña et al, 2014; Richards et al, 2016). Not until Jeong et al (2021), however, was there a DNA sequence ( rbc L) for the generitype of Lithothamnion , L. muelleri (type locality: Western Port Bay, Victoria, Australia), demonstrating that L. muelleri did not belong to a clade with other Lithothamnion species, namely L. lemoineae , L. glaciale , and a specimen from New Zealand called L. crispatum .…”

“…However, rbcL sequences of one of the variable regions within the rbcL gene, amplified by the primer pair F1150 and R1308, yielded sequence divergences of 4.2%-9.3% among these species, indicating that each is distinct. Moreover, the RAxML phylogenetic analysis of the rbcL sequences (Figure 11) placed L. crispatum, L. indicum, and L. superpositum in the recently described genus Roseolithon (Coutinho et al, 2021). In the rbcL Bayesian analysis (Figure . S3), L. crispatum and L. indicum were also resolved in Roseolithon, but L. superpositum was sister to Thalassolithon that was sister to Roseolithon.…”

“…Keats et al (2000) followed by Basso et al (2011) used rosette cells in conspicuous depressions as a species rank character, leading first Keats et al (2000) to place in synonymy Lithothamnion indicum under L. superpositum and then Basso et al (2011) to place both species in synonymy under L. crispatum. Coutinho et al (2021), however, in a phylogenetic analysis of DNA sequences based on specimens from Brazil, recognized this disposition of rosette cells as a distinguishing feature at the generic rank for their new genus, Roseolithon. The rbcL sequences, reported herein, from the type specimens of L. crispatum, L. indicum, and L. superpositum demonstrated that each is a distinct species, confirming that the disposition of rosette cells is a generic rank character and cannot be used to synonymize species.…”

“…The Bayesian analysis of this rbc L sequence placed L. muelleri sister to Synarthrophyton (Jeong et al, 2021, figure 2) and distant from other species of Lithothamnion , namely L. glaciale , L. lemoineae , and L. crispatum (the last likely a misapplied name in New Zealand). The phylogenetic placement of L. muelleri also enabled Coutinho et al (2021) to establish a new genus, Roseolithon , for Brazilian species whose morpho‐anatomical characteristics, namely flared epithallial cells and multiporate tetrasporangial conceptacles, would otherwise have placed them in Lithothamnion .…”