Abstract
BackgroundWhile a considerable amount of research has explored plant community composition in primary successional systems, little is known about the microbial communities inhabiting these pioneer plant species. Fungal endophytes are ubiquitous within plants, and may play major roles in early successional ecosystems. Specifically, endophytes have been shown to affect successional processes, as well as alter host stress tolerance and litter decomposition dynamics—both of which are important components in harsh environments where soil organic matter is still scarce.ResultsTo determine possible contributions of fungal endophytes to plant colonization patterns, we surveyed six of the most common woody species on the Pumice Plain of Mount St. Helens (WA, USA; Lawetlat'la in the Cowlitz language; created during the 1980 eruption)—a model primary successional ecosystem—and found low colonization rates (< 15%), low species richness, and low diversity. Furthermore, while endophyte community composition did differ among woody species, we found only marginal evidence of temporal changes in community composition over a single field season (July–September).ConclusionsOur results indicate that even after a post-eruption period of 40 years, foliar endophyte communities still seem to be in the early stages of community development, and that the dominant pioneer riparian species Sitka alder (Alnus viridis ssp. sinuata) and Sitka willow (Salix sitchensis) may be serving as important microbial reservoirs for incoming plant colonizers.
Highlights
While a considerable amount of research has explored plant community composition in primary successional systems, little is known about the microbial communities inhabiting these pioneer plant species
The highest number of operational taxonomic unit (OTU) were isolated from Sitka alder (22), followed by Sitka willow (14), cottonwood (10), Douglas fir (11), western hemlock (7), and noble fir (1)
Frequencies of isolation ranged from 45.13% (OTU01; Arthrinium sp.) to 0.885% for singletons (18 OTUs), averaging 3.12 ± 7.12% over all cultured OTUs
Summary
While a considerable amount of research has explored plant community composition in primary successional systems, little is known about the microbial communities inhabiting these pioneer plant species. The Pumice Plain of Mount St. Helens (Lawetlat’la in the Cowlitz language) has served as a model for studying primary succession since its catastrophic eruption in 1980 [1, 2]. A few years following the eruption, del Moral [3] observed just 3% vegetation cover on an exposed ridge affected by the pyroclastic flows, and by 1995, Lawrence and Ripple [4] estimated that vegetation cover on the Pumice Plain remained at 0–10% cover, with some areas of 11–20% cover. While there have been many studies of primary succession of vascular plants [6,7,8,9] and even their associated mycorrhizae [10,11,12], virtually no information exists on the diversity, temporal variation, and turnover of foliar endophyte communities colonizing these plants
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