Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA.
Department of Entomology and BEES Program, University of Maryland, College Park, MD, 20742, USA.
New Phytol. 2014 Apr;202(1):247-258. doi: 10.1111/nph.12643. Epub 2013 Dec 24.
To test the extent of herbivory in early terrestrial ecosystems, we examined compression-impression specimens of the late Middle Devonian liverwort Metzgeriothallus sharonae, from the Catskill Delta deposit of eastern New York state. Shale fragments of field-collected specimens were processed by applying liquid nitrocellulose on exposed surfaces. After drying, the film coatings were lifted off and mounted on microscope slides for photography. Unprocessed fragments were photographed under cedarwood oil for enhanced contrast. An extensive repertoire of arthropodan-mediated herbivory was documented, representing three functional feeding groups and nine subordinate plant-arthropod damage types (DTs). The herbivory is the earliest occurrence of external foliage-feeding and galling in the terrestrial fossil record. Our evidence indicates that thallus oil body cells, similar to the terpenoid-containing oil bodies of modern liverworts, were probably involved in the chemical defence of M. sharonae against arthropod herbivores. Based on damage patterns of terrestrial plants and an accompanying but sparse body-fossil record, Devonian arthropodan herbivores were significantly smaller compared to those of the later Palaeozoic. These data collectively suggest that a broad spectrum herbivory may have had a more important role in early terrestrial ecosystems than previously thought.
为了测试早期陆地生态系统中食草作用的程度，我们检查了来自纽约州东部卡特斯代尔三角洲矿床的晚中泥盆世苔类植物 Metzgeriothallus sharonae 的压缩印痕标本。采集的标本的页岩碎片通过在暴露表面施加液态硝化纤维素进行处理。干燥后，将薄膜涂层揭下并安装在显微镜载玻片上进行摄影。未处理的碎片在雪松油下拍摄以增强对比度。记录了广泛的节肢动物介导的食草作用，代表三个功能摄食群和九个下属的植物-节肢动物损伤类型（DT）。这种食草作用是陆地化石记录中最早出现的外部叶食和瘿食。我们的证据表明，类似于现代苔类植物中含萜类化合物的油体，叶状体油体细胞可能参与了 M. sharonae 对节肢动物食草动物的化学防御。基于陆地植物的损伤模式和伴随的但稀疏的身体化石记录，与晚古生代相比，泥盆纪节肢动物食草动物的体型明显更小。这些数据共同表明，广谱食草作用在早期陆地生态系统中的作用可能比以前认为的更为重要。
