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Evolution of orchid mycorrhiza

The Orchidaceae, with ~25 000 species the largest family of plants, have mycorrhizae with unique features.

Supervisors
Vincent Merckx & Sofia Gomes

Contact
vincent.merckx@naturalis.nl, sofia.fernandesgomes@naturalis.nl

Period & duration
2017-2018; 6 months

Study & level
Biology, MSc.

Background & context
The Orchidaceae, with ~25 000 species the largest family of plants, have mycorrhizae with unique features. On the basis of morphological examination and molecular identification, the Orchidaceae generally form mycorrhizae with the Basidiomycota. A few taxa are exceptions, forming symbioses with the Ascomycota. The interactions with fungi have major impacts on the ecology and distribution of orchids and, as a result, may have increased the opportunities for the enormous diversification of the family.

Most orchid species are dependent on mycorrhizal fungi for completion of their life cycle, at least during the early stages of their development. In analogy with plant– animal interactions, the network of orchid–fungus interactions may have either a small number of links among species, indicating an assemblage of ecological specialists, or numerous links, indicating ecological generalists. In the case of orchid species, the architecture of orchid mycorrhizal networks will thus depend on the nature and specificity of the interaction between orchids and their fungi. Previous studies have shown that mycorrhizal specificity may vary considerably between species, ranging from very narrow specificity in nonphotosynthetic and some photosynthetic orchids to broad interactions in other photosynthetic orchids. However, the evolutionary history of species interactions in the Orchidaceae remains largely unexplored.

Objectives & goals
In this project we will investigate the evolution of the interaction between orchids and their mycorrhizal fungi. By reconstructing a comprehensive DNA database of orchids and their sequenced mycorrhizal fungi (Basidiomycota and Ascomycota) we will be able to investigate patterns of interactions, specificity, and mycorrhizal shifts in relation to orchid diversity and mode of life (initial mycohetertrophic, partial mycoheterotrophic, and full mycoheterotrophic).

Methods, tasks, and approach
This research project consists of database-mining, modern phylogenetic approaches to reconstruct plant and fungal evolutionary hypotheses, and analyses of complex interaction patterns. The results will be of interest to a broad scientific audience, and may lead to a scientific publication.

Requirements
None