Molecular ecology and conservation of Mediterranean orchids and their mycorrhizal fungi.

Abstract

• The distribution and abundance of orchid mycorrhizal fungi (OMF) can influence the the establishment and resulting spatial pattern, as well as the population dynamics, of their host plants. Yet, our understanding of these mycorrhizal associations is currently limited by our restricted knowledge of the ecology and spatial distribution of OMF, especially those belonging to the 'rhizoctonia' complex sensu lato. In a recent investigation focusing on Mediterranean grassland orchids, some OMF rhizoctonias were undetected even in the soil beneath their orchid hosts, questioning the view of these fungi as unspecialized soil saprotrophs. Whereas members of the Sebacinales and Ceratobasidiaceae are known to establish mycorrhizal or nonmycorrhizal endophytic associations with non-orchid plants, the ecology of the Tulasnellaceae is largely understudied. The goal of my research is aimed at assessing the impact of the surrounding non-orchid vegetation on the occurrence of OMF in the roots of the orchid host, by comparing the frequence of the fungal symbionts in the roots of naturally grown orchid plants in either undisturbed soil cores or soil cores in which the neighboring non-orchid plants had been manipulated or removed, and to find alternative niches of the fungal symbionts. A second branch of my research is aimed at investigating the ecology, biology and genetic structure of Orchis patens, an endangered mediterranean orchid with a strong disjunct distribution, and its relatives from Orchis mascula group sensu lato. For these species I am investigating the threatening factors, causes of their rarity, such as mycorrhizal association (supposed to be more selective in polyploids) or pollination activity. I also developed nuclear and plastid microsatellites markers to detect genetic variability among different populations, and sequenced and assembled the whole plastomes of 6 Orchis species.