Table 1.

Selected allelochemical and microbe mediated mechanisms of plant invasion exhibited by well-studied invasive plant species compared to the Brazilian Pepper tree status quo.

Alellochemicals/Soil microbe(s)	Invasive plant involved	Method of action	Brazilian Pepper tree Status quo	Reference
Juglone	Black walnut (Juglans nigra) Secrets Juglone∗	Juglone – selectively inhibits respiration of nearby plants	No known direct allelochemical discovered. Plant extracts inhibit seed germination in native plants∗∗	Jose, 2002∗; Morgan and Overholt, 2005∗∗; Donnelly et al., 2008
Sodium ions	Salt lover (Halogeton glomeratus) Extrudes sodium ion to the environment∗	Alteration of soil microbial and plant communities via increased sodium toxicity	No known or similar mechanism discovered. High phosphate concentrations are associated with BP invaded soils∗∗	Li and Norland, 2001∗∗; Duda et al., 2003∗
8-hydroxy-quinolone	Diffuse knapweed (Centaurea diffusa) Root microbiota benefits plant and secrets antimicrobial∗	Alteration of soil microbial composition via 8-hydroxy–quinolone antibacterial effects	Numerous anti-microbial compounds recovered from BP∗∗. Links to plant invasion are vague.	Singh et al., 1998; Callaway et al., 2004∗; Gomes et al., 2013∗∗
Glucosinates	Garlic mustard (Alliara petiolata) Roots produce glucosinates∗	Alteration of composition of arbuscular mycorrhiza (AM) in soil	No glucosinates recovered from BP yet and no reports on similar mode of action despite clear AM involvement	Callaway et al., 2008∗
Frankia spp.	Firetree (Myrica faya) Recruits nitrogen-fixing bacteria - Frankia spp. ∗	Colonize nitrogen-limited soils, altering plant community structure	Similar studies are scarce for BP. Recruitment of such soil microbial species unknown	Vitousek and Walker, 1989∗
Mycorrhizal fungi	Pine (Pinus spp.) Recruit mycorrhizal fungi∗	Superior resource use mechanism. Improves growth and colonization	Known to recruit Mycorrhizal fungi∗∗. Exhibits efficient resource use mechanisms and nutrient uptake	Richardson et al., 1994∗, Aziz et al., 1995∗∗
Sulfur oxidizing and sulfur reducing bacteria, arbuscular mycorrhizae	Yellow starthistle (Centaurea solstitialis) Recruits beneficial soil organisms∗	Competitive advantage with altered rhizosphere microbiota composition	No such studies have tied sulfur oxidizing or reducing bacteria in BP invasion	Batten et al., 2006∗
Sulfur oxidizing and sulfur reducing bacteria, arbuscular mycorrhiza	Barb goatgrass (Aegilops triuncialis) Recruits beneficial soil organisms∗	Competitive advantage with microbial association and altered rhizosphere microbiota composition	No such studies have tied sulfur oxidizing or reducing bacteria in BP invasion	Batten et al., 2006∗
Glomus geosporum	Forb (Solidago canadensis) Specifically associates with G. geosporum and suppresses the prevalence of a widespread AM – G. mosseae∗	Disruption of soil mycorrhizal community to the detriment of natives.	BP has been shown to recruit G. geosporum AM in soil∗∗ but no studies have demonstrated the detrimental effect on natives if any.	Aziz et al., 1995∗∗; Zhang et al., 2010∗
Rhizobium spp. and Azotobacter spp.	Polygonum avuncular. Inhibits proliferation of Rhizobium spp. and Azotobacter spp.∗	Indirect Allelopathy via reduction of n-fixing rhizobacteria and Azotobacter populations	No such studies have tied the reduction of beneficial rhizobacteria and Azotobacter by BP during invasion	Alsaadawi and Rice, 1982∗

For each row, *well studied mechanisms of other plants and corresponding reference. **Case of BP and the corresponding reference.