Abstract
Plants living above and around caves represent an important, albeit poorly studied, resource within cave ecosystems. The presence of plant material (root-like structures or rhizothemes, saplings, seeds, and seedlings) correlates positively with the biodiversity of the cave dwelling animals as shown for iron-ore caves in Carajás, Pará, Brazil. Plant material collected in caves has proven to be difficult to identify by traditional botanical methods, thus this research aims to provide a qualitative insight into the taxonomy and morphology of rhizothemes and other plant fragments found in the caves. The identification process used a combination of different molecular markers (ITS2, rbcL, and trnH-psbA) followed by a comparison of the sequences obtained against publicly available databases. The rhizothemes were submitted to micromorphological analysis to ascertain their putative root or stem origin and to compare their anatomy with known patterns found in the plant families or genera recovered through molecular matches. All studied samples were Angiosperms, mostly belonging to subclass Rosideae, within four orders: Malpighiales (Euphorbiaceae, Hypericaceae), Sapindales (Anacardiaceae and Sapindaceae), Myrtales (Myrtaceae), Fabales (Fabaceae), and only two belonging to subclass Asteridae, order Gentianales (Apocynaceae). Some of the samples were matched to generic level, with ITS2 being the best marker to identify the fragments because it shows high degree of sequence variation even at specific level and result reliability. All rhizothemes turned out to be roots, and correspondence was found between the existing literature and the individual anatomical patterns for the families and genera retrieved. DNA barcode has proved to be a useful tool to identify plant fragments found in this challenging environment. However, the existence of well curated, authoritatively named collections with ample biological information has proven to be essential to achieve a reliable identification.
Highlights
Human history and cave environments have been entwined for tens of thousands of years, generating a long-term interest that pervades paleontology, archeology, and biology, culminating in the development of speleology, a science totally dedicated to the study of caves (Ruchkys et al, 2015)
The overall objective of this study is to provide a qualitative insight into the taxonomy and morphology of rhizothemes, bringing further information toward the study of the plant diversity and plant-animal interactions, both of value toward the conservation of this unique ecosystem and to inform the current procedures that are followed to ascertain the conservation of the local caves
The plant material was partly fixed in ethanol 70% for micromorphology analysis, and the remaining was stored in a NaCl-saturated solution of 2% CTAB (Rogstad, 1992) for molecular analyses
Summary
Human history and cave environments have been entwined for tens of thousands of years, generating a long-term interest that pervades paleontology, archeology, and biology, culminating in the development of speleology, a science totally dedicated to the study of caves (Ruchkys et al, 2015). While it is only possible to suppress or modify caves if these are found to be of low, medium or even high relevance, maximum relevance caves are to be left untouched alongside with their area of influence. This has resulted in scientific research being dedicated to study aspects that influence the richness of cave fauna, including troglobites, as these organisms are used to establish the biological importance and the level of protection assigned to a given cave (Culver and Pipan, 2009; Trajano and Bichuette, 2010; Souza-Silva et al, 2015; Jaffé et al, 2016). “Geoespeleologia das cavernas em rochas ferríferas da região de Carajás, PA,” in Anais do
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