Gametophytes of the Fern Genera Dracoglossum and Lomariopsis (Lomariopsidaceae) and their Phylogenetic Significance
Gametophytes of the Fern Genera Dracoglossum and Lomariopsis (Lomariopsidaceae) and their Phylogenetic Significance
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DOI：
10.1086/705587
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发表时间：
2019-09
影响因子：
2.3
通讯作者：
J. E. Watkins;R. Moran
中科院分区：
文献类型：
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作者：
J. E. Watkins;R. Moran
研究的优先权。分子系统发育研究已解决龙舌藻和Lomariopsis姐妹，即使他们的孢子体是非常不同的形态。我们想检查这两个属的配子体，以确定它们是否支持姐妹关系。方法论我们研究了车前龙舌草和三种Lomariopsis（L.）japurensis，L. maxonii和L. vestita）在哥斯达黎加的三个地点。我们记录了配子体的形式，成熟后的行为，和基板发生（土壤，岩石，或树木）。通过发现仍然附着的幼孢子体叶并追踪它们到容易分配到种的相继较大的叶来鉴定配子体。初步结果。在形态学上，两属的配子体是相同的，除非存在幼孢子体叶，否则难以区分。两者的配子体都是一样的带状，中央加厚，缺口顶端分生组织位于缺口内，并附着在基板上的顶部分支假根。两者的配子体也表现出一种独特的行为：当年轻时，叶状体贴附在基底上，但随着它们成熟，它们的下边缘抬起并远离基底，使配子体仅在上侧附着在基底上。配子囊只发生在配子体上，呈架状。在两属中颈卵器都很常见，但在龙舌草属中没有发现精子器，而在Lomariopsis中只观察到两次。龙舌草属和拟龙藓属配子体的主要区别在于生态学上：龙舌草属生长在溪流中的巨石上，而拟龙藓属作为附生植物生长在树干的下部。虽然龙舌兰和Lomariopsis的孢子体是不同的，我们发现了一个相似之处以前未报道：紫色的叶柄和轴在提琴状阶段。结论.龙舌草属和拟肋草属的配子体在形态上是相同的，并具有一些共同的特征，如带状的叶状体，无毛的表面和边缘，以及顶部分枝的假根。它们在成熟时也有一个不寻常的行为：配子体从贴靠在基质上变成一个下边缘向上抬起的架子状形式。这些特征是派生的，支持两属的姐妹关系。龙舌兰属和Lomariopsis在蕨类植物中是不寻常的，因为孢子体几乎没有提供姐妹关系的证据，而配子体强烈支持它。
Premise of research. Molecular phylogenetic studies have resolved Dracoglossum and Lomariopsis as sister, even though their sporophytes are quite dissimilar morphologically. We wanted to examine the gametophytes of both genera to determine whether they supported the sister relationship. Methodology. We studied wild populations of gametophytes of Dracoglossum plantagineum and three species of Lomariopsis (L. japurensis, L. maxonii, and L. vestita) at three locations in Costa Rica. We recorded gametophyte form, behavior upon maturation, and substrate occurrence (soil, rocks, or trees). Gametophytes were identified by finding young sporophyte leaves still attached and tracing them to successively larger leaves that were readily assignable to species. Pivotal results. Morphologically, the gametophytes of the two genera were identical, being indistinguishable unless young sporophyte leaves were present. Both had gametophytes that were alike by being ribbon shaped, centrally thickened, notched apically with the meristem located within the notch, and attached to the substrate by apically branched rhizoids. Gametophytes of both also exhibited a distinctive behavior: when young, the thalli were appressed to the substrate, but as they matured, their lower edge lifted up and away from the substrate, leaving the gametophyte attached to the substrate only on the upper side. Gametangia occurred only on gametophytes with a shelflike form. In both genera, archegonia were common, but antheridia were not found in Dracoglossum and observed only twice in Lomariopsis. The main difference between the gametophytes of Dracoglossum and Lomariopsis is ecological: Dracoglossum grows on boulders in streams, whereas Lomariopsis grows as an epiphyte on the lower portions of trunks. Although the sporophytes of Dracoglossum and Lomariopsis are dissimilar, we found one likeness previously unreported: purplish petioles and rachises in the fiddlehead stage. Conclusions. The gametophytes of Dracoglossum and Lomariopsis are identical morphologically and share several distinctive characters such as ribbon-shaped thalli, hairless surfaces and margins, and apically branched rhizoids. They also share an uncommon behavior upon maturation: gametophytes change from appressed against the substrate to a shelflike form with the lower margin lifted upward. These characters are derived and support the sister relationship of the two genera. Dracoglossum and Lomariopsis are unusual among ferns in that the sporophyte provides almost no evidence of a sister relationship, whereas the gametophytes strongly support it.