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

Jeong Chan Kang,Myung Sook Kim,Showe-Mei Lin,Kathy Ann Miller

doi:10.3390/plants10112269

Abstract

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.

Highlights

The cosmopolitan genus Acrosorium Zanardini ex Kützing [1] currently comprises 11 species [2]
Two other species have a part in the nomenclatural history of A. ciliolatum: Nitophyllum venulosum Zanardini was described from Zara, Croatia, Adriatic Sea in 1866 [8] and transferred to Acrosorium by Kylin as Acrosorium venulosum (Zanardini) Kylin in 1924 [3]; and Fucus laceratus var. uncinatus Turner 1808 [9] was elevated to species-level and transferred to Acrosorium by Kylin, in 1924 [3]
Wynne [6] proposed that A. venulosum is the correct name for the globally distributed hook-forming Acrosorium species going under the name of A. uncinatum, and authentic A. uncinatum is conspecific with Cryptopleura ramosa (Hudson) L

Summary

Introduction

The cosmopolitan genus Acrosorium Zanardini ex Kützing [1] currently comprises 11 species [2]. Acrosorium ciliolatum (Harvey) Kylin [3], with its distinctive hook-forming branches [4,5,6], is the most widely distributed species, occurring from tropical to subpolar regions in both the southern and northern hemispheres [2]. This species was described by Harvey in 1855 as Nitophyllum ciliolatum on the basis of specimens from King George Sound, Western Australia and Tasmania [7]. The name Acrosorium ciliolatum is applied to species with hook-forming thalli [2,5,11,12,13,14,15,16,17]

Methods

Findings

Discussion

Conclusion