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Abstract Detail


McCormick, Melissa [1], Crain, Benjamin [2], Whigham, Dennis [3], Zettler, Lawrence [4].

Diverse mycorrhizal fungi are associated with greater range size and island colonization in Palau orchids.

Identifying the drivers of species distribution is critical for species conservation and for predicting vulnerability of species to changing conditions. Colonization of islands has shaped much of our understanding of the mechanisms that influence species distributions, due to their discrete nature and evolutionary history. Biotic interactions may also drive species distribution, and species that are relatively independent of, or have very general, biotic interactions are expected to have an advantage in island colonization because they do not require co-colonization by other species for growth, reproduction and dispersal. All orchids form an obligatory symbiosis with mycorrhizal fungi to support growth during seed germination and initial seedling development, and this association continues to maturity. We studied orchids in the Republic of Palau and hypothesized that: 1) widespread orchids that had colonized Palau would associate with more diverse fungi than endemic species and 2) orchids that were common on Palau would be able to associate with more fungal taxa than those that were rare. We collected 285 root samples from 29 orchid species that we classified as either globally widespread or endemic and either common or rare within Palau. We cultivated fungi from a subset for conservation purposes. We extracted DNA from each root or fungus, amplified fungal DNA, aligned sequences, and grouped them into OTUs. We tested for differences in mycorrhizal specificity by calculating total OTU richness for each species. We also calculated the percent of roots of each species colonized by a dominant fungus (i.e., the OTU present in the most individuals). This allowed us to distinguish apparent generalists that had a core fungal taxon that characterized the majority of samples, but also had other sporadic, environmentally-determined fungi, found in a few roots, from orchids that were true generalists, associating with a wide range of fungi, with no dominant taxa(on). We compared the number of OTUs associated with each species and the dominance of specific OTUs using ANOVAs. We found a significant difference in mycorrhizal fungal specificity and dominance between endemic and widespread orchids. Widespread orchids, especially those that were abundant, associated with more distinct OTUs and their dominant fungi were less widespread among individuals than for endemic orchids. The idea that fungi might affect orchid distribution on a global scale has been discounted by many, but remote islands may reveal potential for symbionts to limit orchid distribution, as has been suggested for plants and their mycorrhizal fungi as a group.

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Related Links:
A description of the Palau orchid conservation initiative

1 - Smithsonian Institution, SERC, 647 Contees Wharf Rd, Edgewater, MD, 21037, United States
2 - Smithsonian Environmental Research Center, 647 Contees Wharf Rd, Edgewater, Maryland, 21037, United States
3 - Smithsonian Environmental Research Center, 647 Contees Wharf Rd, Edgewater, MD, 21037, United States
4 - Dept Of Biology-Illinois Coll, 1101 W College Ave, Jacksonville, IL, 62650, United States

island biology

Presentation Type: Poster
Session: MYP3, Mycology Posters III
Location: /
Date: Wednesday, July 21st, 2021
Time: 5:00 PM(EDT)
Number: MYP3007
Abstract ID:921
Candidate for Awards:None

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