Abstract
Little is known about the rhizosphere microbiome of the Brazilian pepper tree (BP) – a noxious category 1 invasive plant inducing an enormous economic and ecological toll in Florida. Some invasive plants have been shown to drastically change the soil microbiome compared to other native plants. The rhizobacteria community structure of BP, two Florida native plants (Hamelia patens and Bidens alba) and bulk soils were characterized across six geographical sites. Although all 19 well-known and 10 poorly described phyla were observed in all plant rhizospheres, BP contained the least total bacterial abundance (OTUs) with a distinct bacteria community structure and clustering patterns differing significantly (pCOA and PERMANOVA) from the natives and bulk soil. The BP rhizosphere community contained the highest overall Proteobacteria diversity (Shannon’s diversity 3.25) in spite of a twofold reduction in richness of the Gammaproteobacteria. Remarkably, the invasive BP rhizosphere was highly enriched with Alphaproteobacteria, dominated by Rhizobiales, including Rhodoplanes and Bradyrhizobiaceae. Also, the relative abundance of Spartobacteria under BP rhizosphere was more than twice that of native plants and bulk soil; featuring unique members of the family Chthoniobacteraceae (DA101 genus). The trend was different for the family Pedosphaerae in the phylum Verrucomicrobia where the abundance declined under BP (26%) compared to (33–66%) for the H. patens native plant and bulk soil. BP shared the lowest number of unique phylotypes with bulk soil (146) compared to the other native plants with bulk soil (B. alba – 222, H. patens – 520) suggestive of its capacity to overcome biotic resistance. Although there were no specific biomarkers found, taken together, our data suggests that the occurrence of key bacteria groups across multiple taxonomic ranks provides a somewhat consistent profile of the invasive BP rhizo-community. Furthermore, based on the observed prevalence of a bacteria group (Spartobacteria – Chthoniobacteraceae – DA101); we propose that they have a possible role in BP biology. Our results emphasize the need to further investigate the potential value of “unique phylotypes” in the rhizosphere relative to bulk soil as an ecological tool for monitoring plant-cover/invasion history; or even detecting exotic plants with invasion tendencies.
Highlights
The Brazilian pepper tree (BP – Schinus terebinthifolius) is one of the most tenacious, difficult-to-control invasive plants in the Everglades National Park (ENP), exerting devastating ecological and economic impacts in the area
The bacterial community structure of BP in its invasive range was evaluated across six geographic sites using the total genomic DNA from the rhizosphere (n = 6)
Unpaired t-tests between S. terebinthifolius and bulk soil showed no significant difference between the operational taxonomic unit (OTU) means (p = 0.67)
Summary
The Brazilian pepper tree (BP – Schinus terebinthifolius) is one of the most tenacious, difficult-to-control invasive plants in the Everglades National Park (ENP), exerting devastating ecological and economic impacts in the area. In the Florida Everglades, BP is the most widely distributed invasive plant, covering over 30,000 ha, followed by Melaleuca (17,802 ha), and Old World climbing fern – 7,033 ha (Rodgers et al, 2014). With more than 283,000 hectares of south and central Florida dominated by this category one invasive plant (Rodgers et al, 2014), current extensive and expensive control/restoration measures, relying on chemical treatment or mechanical uprooting have been minimally successful (Dawkins and Esiobu, 2016). Unlike Melaleuca (Melaleuca quinquenervia), where current control efforts have been successful in restricting spread, the BP is resistant but has expanded its range to all parts of the Florida Peninsula (Ferriter, 1997). The restoration of native ecology after removal of BP is impeded by the poorly understood BP legacy effect, where soils fail to support the native flora and fauna as expected (Nickerson and Flory, 2015)
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