Linking Bacterial Rhizosphere Communities of Two Pioneer Species, Brachystegia boehmii and B. spiciformis, to the Ecological Processes of Miombo Woodlands

Miombo is the most extensive ecosystem in southern Africa, being strongly driven by fire, climate, herbivory, and human activity. Soils are major regulating and supporting services, sequestering nearly 50% of the overall carbon and comprising a set of yet unexploited functions. In this study, we used next-generation Illumina sequencing to assess the patterns of bacterial soil diversity in two pioneer Miombo species, Brachystegia boehmii and Brachystegia spiciformis, along a fire gradient, in ferric lixisol and cambic arenosol soils. In total, 21 phyla, 51 classes, 98 orders, 193 families, and 520 genera were found, revealing a considerably high and multifunctional diversity with a strong potential for the production of bioactive compounds and nutrient mobilization. Four abundant genera characterized the core microbiome among plant species, type of soils, or fire regime: Streptomyces, Gaiella, Chthoniobacter, and Bacillus. Nevertheless, bacterial networks revealed a higher potential for mutualistic interactions and transmission of chemical signals among phylotypes from low fire frequency sites than those from high fire frequency sites. Ecological networks also revealed the negative effects of frequent fires on the complexity of microbial communities. Functional predictions revealed the core “house-keeping” metabolisms contributing to the high bacterial diversity found, suggesting its importance to the functionality of this ecosystem.info:eu-repo/semantics/publishedVersio

Plasticity in plant defense and the role of phytochemical dissimilarity in limiting specialist herbivory

Phytochemical diversity is an effective plant defensive attribute, but much more research has focused on genetic and environmental controls of specific defensive compounds than phytochemical diversity per se. Documenting plasticity in phytochemical richness and plant chemical composition as opposed to individual compounds is important for understanding plant defense. This study outlines a multi-site transplant experiment in Cerrado gallery forests in central Brazil, utilizing Piper arboreum (Piperaceae), a prevalent and widespread neotropical shrub. Clones from four distinct populations were planted either at their origin site or in a different forest. Secondary metabolite composition varied between populations initially and then changed after transplanting. Interestingly, clones with chemical profiles that were distinct from the populations where they were introduced experienced reduced specialist chrysomelid herbivory compared to clones that were more chemically similar to the existing P. arboreum populations where they were planted. Specialist Lepidoptera herbivory also declined in clones transplanted to a new forest, but this change could not be ascribed to chemical profiles. In contrast, generalist herbivory was unaffected by chemical dissimilarity and transplanting. This research adds to the expanding body of evidence suggesting that phytochemical diversity is a dynamic trait exerting unique effects on different herbivore guilds

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Costs of defense and a test of the carbon-nutrient balance and growth-differentiation balance hypotheses for two co-occurring classes of plant defense.

One of the goals of chemical ecology is to assess costs of plant defenses. Intraspecific trade-offs between growth and defense are traditionally viewed in the context of the carbon-nutrient balance hypothesis (CNBH) and the growth-differentiation balance hypothesis (GDBH). Broadly, these hypotheses suggest that growth is limited by deficiencies in carbon or nitrogen while rates of photosynthesis remain unchanged, and the subsequent reduced growth results in the more abundant resource being invested in increased defense (mass-balance based allocation). The GDBH further predicts trade-offs in growth and defense should only be observed when resources are abundant. Most support for these hypotheses comes from work with phenolics. We examined trade-offs related to production of two classes of defenses, saponins (triterpenoids) and flavans (phenolics), in Pentaclethra macroloba (Fabaceae), an abundant tree in Costa Rican wet forests. We quantified physiological costs of plant defenses by measuring photosynthetic parameters (which are often assumed to be stable) in addition to biomass. Pentaclethra macroloba were grown in full sunlight or shade under three levels of nitrogen alone or with conspecific neighbors that could potentially alter nutrient availability via competition or facilitation. Biomass and photosynthesis were not affected by nitrogen or competition for seedlings in full sunlight, but they responded positively to nitrogen in shade-grown plants. The trade-off predicted by the GDBH between growth and metabolite production was only present between flavans and biomass in sun-grown plants (abundant resource conditions). Support was also only partial for the CNBH as flavans declined with nitrogen but saponins increased. This suggests saponin production should be considered in terms of detailed biosynthetic pathway models while phenolic production fits mass-balance based allocation models (such as the CNBH). Contrary to expectations based on the two defense hypotheses, trade-offs were found between defenses and photosynthesis, indicating that studies of plant defenses should include direct measures of physiological responses

Dracaena resin

<i>3.2. Volatile compounds in Dracaena resin</i> <p> Our comparison of terpenoid profiles was based on an evaluation of 20 compounds, 13 of which are described in <i>Dracaena</i> resin volatiles for the first time here. These compounds include five monoterpenes, namely <i>α</i> -thujene, <i>α</i> -pinene, camphene, <i>β</i> -pinene, and <i>δ</i> -2-carene, and eight sesquiterepenes, namely (−)-isodauca-6,9-diene, <i>γ</i> -elemene, <i>trans-</i> muurola-3,5-diene, <i>γ</i> -humulene, <i>γ</i> -himachelene, <i>ε</i> - and <i>ω</i> -amorphene, and <i>α</i> -muurolene. Furthermore, this is the first report of the volatile composition of <i>D. serrulata</i> and <i>D. ombet</i> resins. Many terpenoid compounds identified in <i>Dracaena</i> resins are common plant volatiles (El-Sayed, 2012) and have valuable medicinal properties, including anti-carcinogenic, antimalarial, antiulcer, antimicrobial, antiseptic, nematicidal, larvicidal, anti-inflammatory and diuretic properties (Schwab et al. 2008). Nevertheless, the majority of studies on <i>Dracaena</i> are focused on the isolation and identification of flavonoids and sterols (Baumer and Dietemann, 2010; Gupta et al. 2008; Masaoud et al. 1995; Yi et al. 2011), while only a limited number of reports describe the composition of terpenoid volatiles from <i>Dracaena</i> resins. Santos et al. (2011) used SPME-GC-MS to analyze leaf extracts of <i>D. draco</i> (from the Azores, Portugal) and detected 31 components, eight of which were terpenes. Both our work and that of Santos et al. (2011) document the presence of limonene, <i>α</i> -calacorene, and caryophyllene oxide in <i>Dracaena</i> spp. resins. Twenty-six volatiles were also identified from <i>D. cochinchinensis</i> resin extracted in hexane and run on a GC-MS; these include three sesquiterpenes (<b>τ</b> -cadinol, <b>τ</b> -muurolon and α-cadinol; Teng et al. 2015). GC-MS analyses of <i>D. reflexa</i> leaf volatiles revealed 16 terpenoid compounds, 13 of which are monoterpenes and three of which are sesquiterpenes (Gurib-Fakim and Demarne, 1994). Two of the <i>D. reflexa</i> monoterpenes, <i>δ</i> -3-carene and <i>p</i> -cymene, were also identified in the present study. In comparison with previous reports on <i>Dracaena</i> volatile organic compounds (VOCs), our method allows for the identification of a wider spectrum of terpenoids. This may be due to the combination of the analytical approaches we used, including the optimized SPME technique for VOCs collection and our very sensitive GC × GC-MS method.</p> <p>tr ≤ 0.3%.</p> <p> Key: DD - <i>Dracaena draco</i> subsp. <i>draco</i> from Canary Islands, DDA - <i>D. draco</i> subsp. <i>ajgal</i> from Marocco, DO - <i>D. ombet</i> from Ethiopia, DC - <i>D. cinnabari</i> from Socotra, DS - <i>D. serrulata</i> from Oman.</p> <p> a The numbering of the compounds corresponds with Fig. 1.</p> <p> b Abbreviation corresponding to Fig. 2, M1-8 monoterpenes, S1-12 sesquiterpenes.</p> <p> c Typical mass spectrometric fragments confirmed with those published by Adams (2007), and by Joulain and König (1998) for monoterpenes and sesquiterpenes identification, respectively.</p> <p> d Retention indices (RI) on DB-5 column.</p> <p> e Retention time (RT) in seconds on 1st, and 2nd column, respectively. RI ref Reference retention indices as published by f Babushok et al. (2011), g Joulain and König (1998), and h Adams (2007).</p> <i>3.3. Species specificity in Dracaena resins</i> <p> We demonstrated that the composition of terpenoids in <i>Dracaena</i> is species specific. We therefore propose that monoterpene profiles of <i>Dracaena</i> resins may be evaluated in future studies as chemotaxonomic traits that allow for the identification of the species origin of <i>Dracaena</i> resins. In pines, the composition of monoterpenes in cortical oleoresin changes with location and season (Mita et al. 2002). In addition, high variation in the presence/absence of particular volatile compounds was found within <i>Boswellia</i> species (Burseraceae); this variability could have been caused by different environmental features associated with the trees sampled, by differences in the timing of sampling, or by differences in the part of the trees sampled (stem base vs. annual shoots; Maděra et al. 2017). Nonetheless, studies collectively suggest the composition of <i>Dracaena</i> resin is species specific. In previous reports on <i>Dracaena</i> marker determination, Edward et al. (2001) found differences among resin from two species, <i>D. draco</i> and <i>D. cinnabari.</i> Key vibrational spectroscopic marker bands were identified in the Raman spectra of the resins, and they were used for species identification and determination of the geographical origin of samples (Edward et al., 2001). Gonzalez et al. (2004) compared the composition of VOCs in the resin of <i>D. draco</i> and <i>D. tamaranae,</i> finding that the chemical composition of resins from <i>D. draco</i> subsp. <i>draco</i> (Canary Islands and Cape Verde) and <i>D. draco</i> subsp. <i>ajgal</i>. Together with our data and the results of Gonzalez et al. (2004) and Sousa et al. (2008), these findings all demonstrate the chemical composition of <i>Dracaena</i> resin is an accurate and useful species identifier.</p> <p> Currently <i>D. draco</i> is found only in a very restricted area of southern Morocco. It is noteworthy that these Moroccan populations have been designated as their own subspecies, <i>D. draco</i> subsp. <i>ajgal</i>, an indication that the taxon is in the early stages of speciation (Marrero et al. 1998). If chemotypes align with phylogeny, our results would suggest that the most closely related species are <i>D. draco</i> subsp. <i>draco</i> from the Canary Islands and subsp. <i>ajgal</i> from Morocco followed by <i>D. ombet</i> from Ethiopia and <i>D. cinnabari</i> from Socotra. <i>Dracaena serrulata</i> from Oman is the most distinct from the other four. However, Lu and Morden (2014) investigated the phylogenetic relationship among <i>Dracaenoid</i> genera and species using chloroplast DNA loci and have come to different conclusions. According to their results the most closely related species are <i>D. draco</i> and <i>D. serrulata</i>, whereas <i>D. cinnabari</i> and <i>D. ombet</i> form distinct clusters and are also distant from each other. In contrast, morphological work suggests that <i>D. draco</i> is closely related to the Socotra species, <i>D. cinnabari</i> (Marrero et al., 1998). Work with other groups of plants has similarly demonstrated that chemotypes do not always match phylogenies. Becerra (1997) found only a weak relationship between phylogeny and chemical similarity for <i>Bursera</i> species, common trees in the dry forests of Mexico. Likewise, Kursar et al. (2009) found a weak correlation between phylogenetic and chemical distances within the Neotropical tree genus, <i>Inga</i>. Overall chemical similarity between species was also not associated with phylogeny in the genus <i>Protium</i> (Salazar et al., 2018). This lack of phylogenetic signal in the expression of specialised metabolites suggests divergent selection on antiherbivore defences, such that closely related species do not necessarily produce similar defences. This should make it more difficult for herbivores to track hosts over evolutionary time, thereby reducing herbivore pressure on plants and resulting in the evolutionary lability of defensive traits (Endara et al., 2015). Specialised plant metabolites, such as the terpenes studied here, play important ecological and evolutionary roles, most notably in the deterrence of natural enemies. Detailed studies of herbivores and chemical diversity should be undertaken in the genus <i>Dracaena</i> in order to better understand its phytochemical richness and contribute to ecological investigations of chemically mediated plant-insect interactions.</p>Published as part of <i>Vaníčková, Lucie, Pompeiano, Antonio, Maděra, Petr, Massad, Tara Joy & Vahalík, Petr, 2020, Terpenoid profiles of resin in the genus Dracaena are species specific, pp. 1-8 in Phytochemistry (112197) (112197) 170</i> on pages 2-6, DOI: 10.1016/j.phytochem.2019.112197, <a href="http://zenodo.org/record/8292512">http://zenodo.org/record/8292512</a&gt