Phylogenetic study of the New Caledonian endemic genus Adenodaphne (Lauraceae) confirms its synonymy with Litsea

The genus Adenodaphne is currently considered endemic to New Caledonia, but its distinction from Litsea is questionable based on morphological similarity. An earlier phylogenetic analysis (ITS) including one species of Adenodaphne and two Asian species of Litsea did support their close relationship but did not permit resolution of their generic boundary. We sampled the four species of Adenodaphne currently recognized (11 accessions) and 11 of the 13 endemic species of Litsea currently recognized, plus one undescribed species (24 accessions in total). Based on our extensive herbarium studies, field work, and especially our molecular phylogenetic analyses (ITS) we conclude that Adenodaphne is not distinct from Litsea and that all species of Adenodaphne should be recognized within Litsea, thereby necessitating the creation of two new species synonymies and one nomen novum. As well, Litsea paoueensis is here synonymized with L. deplanchei.

Methods
In this study we generated internal transcribed spacer region (ITS) sequence data for 43 new samples (Litsea, 31; Adenodaphne, 11; Actinodaphne, 1). We selected the ITS region as it has been successfully used across the Lauraceae at different taxonomic levels (Chanderbali et al. 2001; Jian-Feng et al. 2016; Li et al. 2004; Li et al. 2008; Li et al. 2011; Liu et al. 2013; Rohde et al. 2017), and provides the highest level of resolution at the species level (China Plant Bol Group et al. 2011; Liu et al. 2017).

Thirty-three samples were collected in New Caledonia, six during an expedition in Papua New Guinea (see Munzinger et al. 2020), one in New Zealand, and one in Wallis and Futuna. The New Caledonian samples represent the four species of Adenodaphne accepted by Kostermans in the Flore as well as eleven of the thirteen Litsea species that he considered there, plus two individuals from Ouaième, that we could not relate to any Litsea or Adenodaphne species described. We also included ITS sequences from GenBank from published studies that included vouchered specimens, among them that of the type species for the genus Litsea, L. glutinosa (Lour.) C.B.Rob. We did not include Litsea paoueensis, known only from the type Hürlimann 1158, or Litsea imbricata Guillaumin (known only from two collections), both of which we searched for in the field in vain. As well, we excluded L. mackeei Kosterm., which Kostermans (1977) described 3 years after the publication of his treatment in the Flore, as it belongs to the Oleaceae (Munzinger and McPherson 2017). All taxa are listed in Table 1, which includes the code of the herbarium (sensu Thiers 2021) where the vouchers are deposited.

腺蕊木属（Adenodaphne）目前被认为是新喀里多尼亚的特有属，但基于形态相似性，其与木姜子属（Litsea）的分类界限尚存争议。此前一项包含1个腺蕊木属物种与2个亚洲木姜子属物种的系统发育分析（内转录间隔区，internal transcribed spacer，ITS）虽支持二者亲缘关系紧密，却未能厘清二者的属间边界。本研究采样了当前公认的4个腺蕊木属物种（共11份凭证标本），以及当前公认的13个新喀里多尼亚木姜子属物种中的11个，外加1个未描述物种（总计24份标本）。基于广泛的标本馆研究、野外调查，尤其是本次ITS分子系统发育分析结果，我们认定腺蕊木属并非独立于木姜子属的类群，所有腺蕊木属物种均应归入木姜子属，因此需要建立2个新的物种异名组合及1个新替换名。此外，本研究将Paoue木姜子（Litsea paoueensis）归并入德氏木姜子（L. deplanchei）。

材料与方法
本研究为43份新样本生成了内转录间隔区（internal transcribed spacer，ITS）序列数据，其中木姜子属31份、腺蕊木属11份、黄肉楠属（Actinodaphne）1份。选择ITS区域作为分子标记，是因为该区域已在樟科（Lauraceae）不同分类阶元中得到成功应用（Chanderbali等，2001；Jian-Feng等，2016；Li等，2004、2008、2011；Liu等，2013；Rohde等，2017），且在物种水平上具有最高的分辨能力（中国植物志编委会等，2011；Liu等，2017）。
本次采样共获取33份样本：其中33份采自新喀里多尼亚，6份采自巴布亚新几内亚的考察（详见Munzinger等，2020），1份采自新西兰，1份采自瓦利斯和富图纳群岛。新喀里多尼亚的样本涵盖了Kostermans在《Flore》中认可的4个腺蕊木属物种，以及他记载的13个木姜子属物种中的11个，另包含2份采自瓦伊埃姆（Ouaième）的未知标本，暂无法归入任何已知木姜子属或腺蕊木属物种。本研究还纳入了GenBank中已发表研究的ITS序列，其中包括木姜子属模式种*L. glutinosa* (Lour.) C.B.Rob.的凭证标本序列。我们未纳入仅知模式标本Hürlimann 1158的Paoue木姜子（Litsea paoueensis），以及仅知2份馆藏标本的覆瓦木姜子（Litsea imbricata Guillaumin），二者在野外均未采集到。此外，我们排除了Kostermans（1977）在其《Flore》处理发表3年后描述的*L. mackeei* Kosterm.，该物种实际隶属于木犀科（Oleaceae）（Munzinger & McPherson，2017）。所有类群详见表1，表中包含凭证标本存放的标本馆代码（遵循Thiers 2021的定义）。