Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

Orchid mycorrhizal detection, based only on fungal isolation from roots, is biased due to difficulties in isolating the respec- tive fungi. Previous investigations have shown that mostly ascomycetes, housed in the sheltered compartment of the vela- men covering the roots of epiphytic orchids, are isolated on agar plates. Roots of 83 individual epiphytic orchid of Stelis hallii, S. superbiens, S. concinna, Stelis sp. and Pleurothallis lilijae were sampled in the Reserva Biológica San Francisco, Southern Ecuador. The velamen was partly removed and root tissue macerated and transferred to Petri dishes containing corn meal agar, malt extract agar and Melin Norkrans modified medium. DNA was extracted from the cultures and the 5.8S-ITS region and partial nrLSU sequenced. Phylogenetic analysis revealed members of 12 orders of ascomycetes associ- ated with the roots of these orchids, a much higher diversity than previously known. Twelve isolates were related to the Helotiales. Our results have uncovered some of the fungal diversity within the velamen of epiphytic orchids; fungi invading, most likely, from tree bark or humus accumulation close to the roots.

Abstract:

In times of climate change and devastation, the conservation of biodiversity is an important issue. The formation of a mycorrhiza plays a very important role. The arbuscular mycorrhiza is a mutualistic symbiosis between fungi and plant roots. The arbuscular mycorrhizal fungi represent a monophyletic group, the Glomeromycota, which probably have a common ancestor with the Asco-and Basidiomycota. The arbuscular mycorrhiza is characterized by an enormous spreading. It is found in all climates. The vast majority of tropical plants form an arbuscular mycorrhiza, including plants in the Páramo, a type of vegetation in the humid tropical high Andes of South America above the treeline. In this study, root material from the Páramo-vegetation in Cajanuma in South Ecuador was examined. The analysis can be divided into two parts, the morphological and genetic analyses. Concerning the morphology the root samples were analysed under the light microscope. In 16 of 20 samples colonization with arbuscular mycorrhizal fungi was detected. Exactly these 16 samples also showed fungi belonging to the group of dark sepatate endophytes (DSE) which are likely representatives of the Ascomycota. In the context of genetic analyses arbuscular mycorrhizal fungi have been analysed with molecular methods sequencing part of the 18S rDNA. For the identification of fungi, which do not belong to the Glomeromycota, a part of the ITS-region of the DNA has been studied and sequenced. The sequences of arbuscular mycorrhizal fungi belong to families of Glomeraceae and Acaulosporaceae. In comparison with other investigations it can be assumed that the Páramo in Cajanuma has its own AMF community. The sequences of the Ascomycota all belong to the order of the Helotiales. By comparing the results to other investigations it could be demonstrated, that the dark septate endophytes survive under several climatic conditions. Furthermore they probably play an important role in the supply of nutrients. In this work, the dark septate endophytes show a greater range of species than the arbuscular mycorrhizal fungi. That possibly indicates a higher diversity in the Ascomycota than in the Glomeroycota in the Páramo-vegetation in Cajanuma. In order to confirm this hypothesis, a far greater data base is required. This data base will be the key to maintaining biodiversity. It ensures a better understanding of fungi and their interactions. Through this understanding, new approaches to protect biodiversity can be created.