Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Kaur, Jaspreet [1], Linde, Celeste [2], Jacquemyn, Hans [3], Sharma, Jyotsna [1].

Inter-continental comparisons reveal high endemism in orchid mycorrhizal fungal communities.

Background/Question/Methods: Species within the Orchidaceae display patchy distributions and majority of the orchids are highly endemic whereby they are restricted to specific habitats, regions, countries or continents. A few previous studies have revealed that the patchy distribution of orchids corresponds to the patchy distribution of their orchid mycorrhizal fungi (OMF) at local scales (a few meters to kilometers). Provided that, it is possible that the global distribution of orchid species also follows the trends of global distribution of OMF communities. To our knowledge, however, detailed studies analyzing the pan-global distribution of OMF communities are lacking. Given that all orchid species are obligate holo-mycoheterotrophs during seed germination, it is crucial to understand the distribution of OMF at various spatial scales. In this study, we asked if there is an overlap in previously delineated OMF community composition across continents. We hypothesized that each continent represented in the study will host a high proportion of unique OMF compared to OMF shared by two or more continents. To answer this, we first created a database of fungal nuclear ribosomal Internal Transcribed Spacer (ITS) region from orchid roots by gathering sequences generated by 143 peer-reviewed studies. These sequences were clustered into Operational Taxonomic Units (OTUs) at 97% similarity threshold. Finally, OMF communities were compared between continents.
Results/Conclusions: After quality filtering, we obtained a total of 6,857 OMF sequences that represented six continents, 47 countries and 599 orchid taxa. These sequences clustered into 1,360 OTUs. Fungi from the Tulasnellaceae, Ceratobasidiaceae and Sebacinales accounted for 78% of the OMF communities world-wide. The same three taxa also accounted for ≥75% of the OMF communities from Africa, Australia, North America and South America whereas they accounted for only 47% in Asia and Europe. When alpha diversity (i.e. hill numbers derived from Shannon index) was compared between continents, Asia hosted the highest number of effective OMF OTUs followed by Europe, North America, South America, Africa and Australia (Kruskal Wallis P < 0.05). Of the 1,360 total OTUs, 91% were restricted to a single continent. Beta diversity analyses based on Bray-Curtis dissimilarities also detected differences in OMF community composition among six continents (PERMANOVA P < 0.05). The proportion of unique OTUs hosted on each continent was highest for Asia (86%) followed by Europe (80%), South America (81%), Australia (76%), Africa (72%) and North America (72%). Pairs of any two continents shared only 1-18% of their OMF OTUs. A distance-decay analysis also revealed high dissimilarity in OMF communities even at small geographic distances (<1 kilometer). Altogether, our analyses suggest high endemism in OMF communities at small geographic scales to global scale, which could potentially affect the distribution of orchids that are specific towards recruiting mycorrhizal fungi and may restrict their range expansions in future.

1 - Texas Tech University, 2911, 15th st, Bayer Plant Science Bldg., Lubbock, Texas, 79409, United States
2 - Australian National University, Division Of Ecology & Evolution, 46 Sullivans Creek Rd, Research School Of Biology ANU College Of Science , Canberra, ACT, ACT, 2600, Australia
3 - KULeuven, Laboratory For Plant Ecology, Kasteelpark Arenberg 31, Heverlee, 3001, Belgium

Orchid mycorrhizal fungi

Presentation Type: Oral Paper
Number: SYM2007
Abstract ID:445
Candidate for Awards:None

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