Collections & Research, Western Australian Museum, 49 Kew St, Welshpool 6106 WA, Australia; Curtin Medical School, Curtin University, Bentley 6102 WA, Australia.
Collections & Research, Western Australian Museum, 49 Kew St, Welshpool 6106 WA, Australia.
Mol Phylogenet Evol. 2021 Aug;161:107179. doi: 10.1016/j.ympev.2021.107179. Epub 2021 Apr 20.
Sponges represent one of the most species-rich hosts for commensal barnacles yet host utilisation and diversity have not been thoroughly examined. This study investigated the diversity and phylogenetic relationships of sponge-inhabiting barnacles within a single, targeted host group, primarily from Western Australian waters. Specimens of the sponge order Dictyoceratida were surveyed and a total of 64 host morphospecies, representing four families, were identified as barnacle hosts during the study. Utilising molecular (COI, 12S) and morphological methods 42 molecular operational taxonomic units (MOTUs) of barnacles, representing Acasta, Archiacasta, Euacasta and Neoacasta were identified. Comparing inter- and intra-MOTU genetic distances showed a barcode gap between 2.5% and 5% for COI, but between 1% and 1.5% in the 12S dataset, thus demonstrating COI as a more reliable barcoding region. These sponge-inhabiting barnacles were demonstrated to show high levels of host specificity with the majority being found in a single sponge species (74%), a single genus (83%) or a single host family (93%). Phylogenetic relationships among the barnacles were reconstructed using mitochondrial (12S, COI) and nuclear (H3, 28S) markers. None of the barnacle genera were recovered as monophyletic. Euacasta was paraphyletic in relation to the remaining Acastinae genera, which were polyphyletic. Six well-supported clades of molecular operational taxonomic units, herein considered to represent species complexes, were recovered, but relationships between them were not well supported. These complexes showed differing patterns of host usage, though most were phylogenetically conserved with sister lineages typically occupying related hosts within the same genus or family of sponge. The results show that host specialists are predominant, and the dynamics of host usage have played a significant role in the evolutionary history of the Acastinae.
海绵是共生藤壶最丰富的宿主之一，但宿主的利用和多样性尚未得到彻底研究。本研究调查了单一目标宿主群体中海绵共生藤壶的多样性和系统发育关系，主要来自西澳大利亚水域。对海绵目 Dictyoceratida 进行了调查，在研究过程中总共鉴定出 64 种海绵宿主，代表四个科。利用分子（COI、12S）和形态学方法，共鉴定出 42 个藤壶分子操作分类单元（MOTU），代表 Acasta、Archiacasta、Euacasta 和 Neoacasta。比较种内和种间 MOTU 遗传距离表明，COI 的 barcode 间隙在 2.5%至 5%之间，而 12S 数据集的 barcode 间隙在 1%至 1.5%之间，因此 COI 是一个更可靠的条形码区域。这些海绵共生藤壶表现出高度的宿主特异性，大多数藤壶仅在单一海绵物种（74%）、单一属（83%）或单一宿主科（93%）中发现。使用线粒体（12S、COI）和核（H3、28S）标记物重建了藤壶的系统发育关系。没有一个藤壶属被重建为单系群。Euacasta 相对于其余的 Acastinae 属是并系的，而其余的属是多系的。恢复了 6 个支持度高的分子操作分类单元支序，本文认为这些支序代表种复合体，但它们之间的关系没有得到很好的支持。这些复合体表现出不同的宿主利用模式，尽管大多数在系统发育上是保守的，姐妹谱系通常占据同一属或海绵科内相关的宿主。研究结果表明，宿主专化是主要的，宿主利用的动态在 Acastinae 的进化历史中发挥了重要作用。
