ABSTRACT

Over the last decade, our knowledge of the phylogenetic and taxonomic diversity of coralline algae has greatly progressed thanks to the use of DNA sequence data. Despite this, in some geographic regions the knowledge of coralline diversity is still incomplete, because it is entirely based on traditional morpho-anatomical grounds; Antarctica can certainly be included among these regions. During an investigation of the marine phototrophic biodiversity of the Ross Sea, a crustose coralline alga was collected from two sites in Tethys Bay. The alga formed thin crusts adherent to cobbles at ~20 m depth and showed morpho-anatomical features typical of the order Hapalidiales, family Hapalidiaceae (cell fusions, zonate tetrasporangia produced in multiporate conceptacles, and apical plugs). Molecular phylogenies based on the psbA, rbcL and 18S rRNA genes showed that this alga formed a lineage in the family Hapalidiaceae for which a formal assignment at genus level was not yet available. The only other known member of the lineage was a coralline from the Balleny Islands, named as Hapalidiaceae sp. ASG448A, for which psbA and 18S rRNA sequences were deposited in GenBank without identification at genus and species level. Based on our results, we describe this lineage as the new genus Tethysphytum Sciuto, Moschin & Moro, with the single species Tethysphytum antarcticum Sciuto, Moschin & Moro. At present, morpho-anatomical characters do not allow for the discrimination of Tethysphytum from other similar genera of Hapalidiaceae. The discovery of a new genus suggests that the diversity of coralline algae in Antarctica may have been underestimated and that molecular data will be essential for future taxonomic assessments of this group within this region.

摘要

在过去十年中，由于 DNA 序列数据的使用，我们对珊瑚藻的系统发育和分类多样性的了解取得了很大进展。尽管如此，在一些地理区域，珊瑚多样性的知识仍然不完整，因为它完全基于传统的形态解剖学基础；南极洲当然可以包括在这些地区中。在对罗斯海的海洋光养生物多样性进行调查期间，从特提斯湾的两个地点收集了一种硬壳珊瑚藻。藻类形成了附着在约 20 m 深度的鹅卵石上的薄壳，并显示出典型的 Hapalidiales 目、Hapalidiaceae 科（细胞融合、带状四孢子囊在多孔概念中产生的带状四孢子囊和顶端栓塞）的形态解剖特征。基于psb 的分子系统发育A、rbc L 和 18S rRNA 基因表明该藻类在 Hapalidiaceae 家族中形成了一个谱系，但尚无法在属级水平上对其进行正式分配。该谱系中唯一已知的其他成员是来自巴莱尼群岛的珊瑚，名为 Hapalidiaceae sp。ASG448A，其psb A 和 18S rRNA 序列存放在 GenBank 中，未进行属和种级别的鉴定。根据我们的结果，我们将该谱系描述为新属Tethysphytum Sciuto、Moschin & Moro，以及单一物种Tethysphytum antarcticum Sciuto、Moschin & Moro。目前，形态解剖特征不允许区分Tethysphytum来自 Hapalidiaceae 的其他类似属。一个新属的发现表明南极洲珊瑚藻类的多样性可能被低估了，分子数据对于该地区该类群的未来分类学评估至关重要。