Ng Poh-Kheng, Lin Showe-Mei, Lim Phaik-Eem, Hurtado Anicia Q, Phang Siew-Moi, Yow Yoon-Yen, Sun Zhongmin
Institute of Marine Biology, National Taiwan Ocean University, Keelung, Taiwan, R.O.C.
Institute of Ocean and Earth Sciences, University of Malaya, Kuala Lumpur, Malaysia.
PLoS One. 2017 Jul 31;12(7):e0182176. doi: 10.1371/journal.pone.0182176. eCollection 2017.
Many studies classifying Gracilaria species for the exploitation of agarophytes and the development of the agar industry were conducted before the prevalence of molecular tools, resulting in the description of many species based solely on their morphology. Gracilaria firma and G. changii are among the commercially important agarophytes from the western Pacific; both feature branches with basal constrictions that taper toward acute apices. In this study, we contrasted the morpho-anatomical circumscriptions of the two traditionally described species with molecular data from samples that included representatives of G. changii collected from its type locality. Concerted molecular analyses using the rbcL and cox1 gene sequences, coupled with morphological observations of the collections from the western Pacific, revealed no inherent differences to support the treatment of the two entities as distinct taxa. We propose merging G. changii (a later synonym) into G. firma and recognize G. firma based on thallus branches with abrupt basal constrictions that gradually taper toward acute (or sometimes broken) apices, cystocarps consisting of small gonimoblast cells and inconspicuous multinucleate tubular nutritive cells issuing from gonimoblasts extending into the inner pericarp at the cystocarp floor, as well as deep spermatangial conceptacles of the verrucosa-type. The validation of specimens under different names as a single genetic species is useful to allow communication and knowledge transfer among groups from different fields. This study also revealed considerably low number of haplotypes and nucleotide diversity with apparent phylogeographic patterns for G. firma in the region. Populations from the Philippines and Taiwan were divergent from each other as well as from the populations from Malaysia, Thailand, Singapore and Vietnam. Establishment of baseline data on the genetic diversity of this commercially important agarophyte is relevant in the context of cultivation, as limited genetic diversity may jeopardize the potential for its genetic improvement over time.
在分子工具普及之前，人们进行了许多旨在分类江蓠属物种以用于琼脂植物开发和琼脂产业发展的研究，这导致许多物种仅根据其形态进行描述。真江蓠和张氏江蓠是西太平洋地区重要的商业琼脂植物；两者的特征都是具有基部缢缩的分支，这些分支向尖锐的顶端逐渐变细。在本研究中，我们将这两个传统描述物种的形态解剖界定与来自样本的分子数据进行了对比，样本中包括从张氏江蓠模式产地采集的张氏江蓠代表样本。使用rbcL和cox1基因序列进行的协同分子分析，结合对西太平洋地区采集样本的形态观察，结果表明没有内在差异支持将这两个实体视为不同的分类单元。我们建议将张氏江蓠（一个后来的异名）并入真江蓠，并基于以下特征来识别真江蓠：藻体分支具有突然的基部缢缩，向尖锐（或有时断裂）的顶端逐渐变细，囊果由小的产孢丝细胞组成，以及从产孢丝发出的不明显的多核管状营养细胞延伸到囊果底部的内果皮中，还有疣状类型的深精囊腔。将不同名称的标本验证为单一遗传物种有助于不同领域的群体之间进行交流和知识传递。本研究还揭示了该地区真江蓠的单倍型数量和核苷酸多样性相当低，并且具有明显的系统地理模式。来自菲律宾和台湾的种群彼此不同，也与来自马来西亚、泰国、新加坡和越南的种群不同。在养殖背景下，建立这种重要商业琼脂植物的遗传多样性基线数据是相关的，因为有限的遗传多样性可能会随着时间的推移危及其遗传改良的潜力。
