Taxonomic Revision of Hook-Forming Acrosorium (Delesseriaceae, Rhodophyta) from the Northwestern Pacific Based on Morphology and Molecular Data

Cosmopolitan Acrosorium species with hook-forming thalli have been merged under the name of Acrosorium ciliolatum (Harvey) Kylin through a long and complicated nomenclatural history. We examined the specimens of ‘A. ciliolatum’ and related taxa from the northwestern (NW) Pacific, the UK, southern Spain, Australia, New Zealand, and Chile, using morphological and molecular analyses. We confirmed that these specimens are separated into four clades based on rbcL phylogeny, and the absence or presence of terminal hook-like structures represent intraspecific variation. Our results indicated that Acrosorium flabellatum Yamada, Cryptopleura hayamensis Yamada, Cryptopleura membranacea Yamada and the entities known as ‘A. ciliolatum’ in the NW Pacific are conspecific; the name A. flabellatum is the oldest and has priority. This taxon exhibits extreme variations in external blade morphology. We also confirmed that the position of the tetrasporangial sori is a valuable diagnostic characteristic for distinguishing A. flabellatum in the NW Pacific. We also discussed the need for further study of European and southern hemisphere specimens from type localities, as well as the ambiguous position of California specimens.

An updated species inventory of Callithamnion sensu lato Rhodophyta, Callithamniaceae in South Africa with the description of Callithamnion africanum sp. nov.

The species diversity of Callithamnion sensu lato in South Africa is re-visited using existing literature, morphology and DNA. The identity of a putative new species is confirmed as distinct using DNA and is described here as Callithamnion africanum sp. nov. Callithamnion africanum differs molecularly and morphologically from a similar species, C. cordatum with which it shares a similar habitat and distribution range in South Africa. Callithamnion africanum is resolved in the Callithamnion sensu stricto clade and is sister to the type species of the genus, Callithamnion corymbosum. Additionally, Callithamnion stuposum, a species described from South Africa and a common component of the seaweed flora, was recovered in the larger, unresolved Callithamnion sensu lato clade. An updated species inventory of Callithamnion sensu lato in South Africa is provided, and indicates a lack of sequence data for the large majority of species. Furthermore, a global rbcL phylogeny highlights a number of taxonomic concerns regarding the classification of taxa circumscribed to Callithamnion sensu lato and calls for a global revision using DNA, type specimens or material collected from near type localities.

Morphological and molecular systematic investigation of Laurencia karachiana sp. nov. (Ceramiales, Rhodophyta) from Karachi, Pakistan

Laurencia karachiana sp. nov. is described from the Karachi coast of Pakistan, based on rbcL and COI-5P genes sequences. The molecular analyses for both markers positioned L. karachiana within Laurencia sensu stricto and it possesses all vegetative and reproductive structures typical of the genus. Laurencia karachiana grouped with Laurencia sp. from Sri Lanka for both markers. The genetic divergence between these taxa for rbcL was only 0.27%, whereas for COI-5P was much higher, 2.7%. The latter is within ranges of interspecific divergence for Laurencia s.s. The discrepancy of divergence between these markers and the lack of description and illustrations of Laurencia sp. from Sri Lanka for comparison leave the identity of Laurencia sp. as an open question. The rbcL phylogeny resolved L. karachiana and Laurencia sp. as sister to a subclade formed by sequences of Laurencia pumila and L. pumila var. dehoopiensis from South Africa, diverging by 1.7–1.8%. This genetic divergence and also morphological differences observed support the recognition of L. karachiana as a novel species. Our finding shows that this complex from Pakistan requires major revision, because its diversity is likely underestimated.

Implications of rbcL phylogeny for historical biogeography of genus Mercurialis L.: Estimating age and center of origin

The aim of this study was to address questions concerning the historical biogeography of the genus Mercurialis in the subfamily Acalyphoideae. Applying a molecular clock to obtained rbcL phylogeny, we estimated the minimal age of divergence of genus Mercurialis to ~65-66 Ma, placing it at the Cretaceous/Paleogene boundary. We used ancestral area analysis and dispersal-vicariance analysis to infer the center of origin of the genus. Contrary to previous hypothesis, our results show that Mercurialis originated in Indomalaya and migrated westward, while the Mediterranean area was most probably the center of ecological diversification and further speciation. Evolutionary events of vicariance and dispersals were reconstructed in a proposed scenario of divergence of Mercurialis within Acalyphoideae. .