Phylogeny Explains Variation in The Root Chemistry of Eucalyptus Species

Abstract

Plants are dependent on their root systems for survival, and thus are defended from belowground enemies by a range of strategies, including plant secondary metabolites (PSMs). These compounds vary among species, and an understanding of this variation may provide generality in predicting the susceptibility of forest trees to belowground enemies and the quality of their organic matter input to soil. Here, we investigated phylogenetic patterns in the root chemistry of species within the genus Eucalyptus. Given the known diversity of PSMs in eucalypt foliage, we hypothesized that (i) the range and concentrations of PSMs and carbohydrates in roots vary among Eucalyptus species, and (ii) that phylogenetic relationships explain a significant component of this variation. To test for interspecific variation in root chemistry and the influence of tree phylogeny, we grew 24 Eucalyptus species representing two subgenera (Eucalyptus and Symphyomyrtus) in a common garden for two years. Fine root samples were collected from each species and analyzed for total phenolics, condensed tannins, carbohydrates, terpenes, and formylated phloroglucinol compounds. Compounds displaying significant interspecific variation were mapped onto a molecular phylogeny and tested for phylogenetic signal. Although all targeted groups of compounds were present, we found that phenolics dominated root defenses and that all phenolic traits displayed significant interspecific variation. Further, these compounds displayed a significant phylogenetic signal. Overall, our results suggest that within these representatives of genus Eucalyptus, more closely related species have more similar root chemistry, which may influence their susceptibility to belowground enemies and soil organic matter accrual.

Forest fire may disrupt plant–microbial feedbacks

“…Yet, these studies support our findings by showing that eucalypt species may differentially modify both soil chemical and biotic characteristics, potentially through species varying in traits (i.e., growth rate and chemistry) related to the quantity and quality of organic matter entering soils (Baxendale et al 2014;Orwin et al 2010). In the case of our study, interspecific variation in foliar or root chemical traits (Li and Madden 1995;Senior et al 2016) may have also contributed to differences in soil microbial communities, through influencing the quality of organic matter entering soils or by directly affecting root-microbe interactions.…”

Range-expanding plant species and their belowground neighbours : digging into novel interactions

“…Apparently, and unlike previously shown (Senior et al 2016), root chemistry can be highly variable between closely related plant species. In line with the results of Chapter 3, the results of Chapter 6 therefore show that phylogenetic distance cannot be easily used to estimate differences in chemical profiles between plant species.…”

“…However, the differences in root chemistry between the range-expanding plant species and congeneric natives may nevertheless be linked to phylogeny, as phylogenetic distance has been shown to explain variation in root chemistry among congeners (Senior et al 2016). Based on root chemistry, Centaurea stoebe might therefore be less closely related to C. jacea than G. pyrenaicum is related to G. molle.…”

“…Plant species differentially shape soil communities (Bais et al 2006;Burns et al 2015), for example by producing different root exudates and volatiles (van Dam & Bouwmeester 2016;Venturi & Keel 2016). As phylogenetically closely related plant species are more likely to share such chemical traits than distantly related species (Gilbert & Parker 2016;Senior et al 2016), it may be expected that close relatives condition soil communities more similarly than distantly related species. In turn, natural enemies in the attracted soil communities will likely have comparable effects on closely related plant species (Gilbert & Webb 2007;Parker et al 2015).…”

Phylogenetic trait conservatism predicts patterns of plant‐soil feedback

“…On the island of Tasmania, Australia, eucalypt species typically coexist in mixed stands that tend to include at least one species from each of the two larger eucalypt subgenera, Eucalyptus and Symphyomyrtus (Austin et al 1983, Duff et al 1983). The subgenera differ in root chemistry (Senior et al 2016), and there is also evidence that they differ in their relationships with soil pathogens and mycorrhizae (Podger and Batini 1971). The subgenera differ in root chemistry (Senior et al 2016), and there is also evidence that they differ in their relationships with soil pathogens and mycorrhizae (Podger and Batini 1971).…”