Molecular confirmation and morphological reassessment of Udotea geppiorum (Bryopsidales, Chlorophyta) with ecological observations of mesophotic meadows in the Main Hawaiian Islands

Udotea geppiorum is reported to form meadows in deep-water, soft sediment habitats in the Main Hawaiian Islands. The identification of the species, initially published as U. argentea in the archipelago, is revised and confirmed based on morphological assessment and comparative DNA sequencing with western Pacific specimens. Udotea geppiorum is fully corticated and newly shown to display discrete concentric segments arranged in a ‘tongue and groove’ manner, which are connected by medullary siphons running along the entire segment interface. Udotea geppiorum is phylogenetically nested among a cluster of Udotea spp. recently circumscribed within Udotea sensu stricto. This cluster of species is separate from the remainder of the family Udoteaceae, which includes several genera and Udotea spp. sensu lato that lack or exhibit incomplete cortication. Based on field observations conducted in O‘ahu and Maui, U. geppiorum can be found from 20 m to > 90 m depth with a peak in abundance at mesophotic depths of 60–85 m, where it forms extensive meadows that support associated diversity.

据报道，格氏伞藻（Udotea geppiorum）在夏威夷主群岛的深水软沉积生境中形成大面积藻床。该物种最初在该群岛被鉴定为银伞藻（U. argentea），后经形态学评估与西太平洋标本的DNA序列比对分析，其分类地位得到修订与确认。格氏伞藻完全被皮层覆盖，新研究显示其具有以“榫卯”方式排列的离散同心段，这些结构由沿整个段界面延伸的髓质管体相互连接。格氏伞藻在系统发育上嵌套于近期被界定为狭义伞藻属（Udotea sensu stricto）的伞藻物种种群中。该物种种群与伞藻科（Udoteaceae）的其余类群相互独立，后者包含多个属以及缺乏或仅具不完全皮层的广义伞藻（Udotea sensu lato）物种。基于在瓦胡岛与毛伊岛开展的野外调查，格氏伞藻的分布深度范围为20米至90米以上，在60–85米的中光层深度达到丰度峰值，于此形成的大面积藻床可为伴生生物多样性提供支撑。