51 research outputs found
UHPLC-ESI/TOFMS Determination of Salicylate-like Phenolic Gycosides in Populus tremula Leaves
Associations of salicylate-like phenolic glycosides (PGs) with biological activity have been reported in Salix and Populus trees, but only for a few compounds, and in relation to a limited number of herbivores. By considering the full diversity of PGs, we may improve our ability to recognize genotypes or chemotype groups and enhance our understanding of their ecological function. Here, we present a fast and efficient general method for salicylate determination in leaves of Eurasian aspen that uses ultra-high performance liquid chromatography-electrospray ionization/time-of-flight mass spectrometry (UHPLC-ESI/TOFMS). The time required for the liquid chromatography separations was 13.5 min per sample, compared to around 60 min per sample for most HPLC protocols. In leaf samples from identical P. tremula genotypes with diverse propagation and treatment histories, we identified nine PGs. We found the compound-specific mass chromatograms to be more informative than the UV-visible chromatograms for compound identification and when quantitating samples with large variability in PG content. Signature compounds previously reported for P. tremoloides (tremulacin, tremuloidin, salicin, and salicortin) always were present, and five PGs (2'-O-cinnamoyl-salicortin, 2'-O-acetyl-salicortin, 2'-O-acetyl-salicin, acetyl-tremulacin, and salicyloyl-salicin) were detected for the first time in P. tremula. By using information about the formic acid adduct that appeared for PGs in the LTQ-Orbitrap MS environment, novel compounds like acetyl-tremulacin could be tentatively identified without the use of standards. The novel PGs were consistently either present in genotypes regardless of propagation and damage treatment or were not detectable. In some genotypes, concentrations of 2'-O-acetyl-salicortin and 2'-O-cinnamoyl-salicortin were similar to levels of biologically active PGs in other Salicaceous trees. Our study suggests that we may expect a wide variation in PG content in aspen populations which is of interest both for studies of interactions with herbivores and for mapping population structure
Phylogeny and Biogeography of Hawkmoths (Lepidoptera: Sphingidae): Evidence from Five Nuclear Genes
The 1400 species of hawkmoths (Lepidoptera: Sphingidae) comprise one of most conspicuous and well-studied groups of insects, and provide model systems for diverse biological disciplines. However, a robust phylogenetic framework for the family is currently lacking. Morphology is unable to confidently determine relationships among most groups. As a major step toward understanding relationships of this model group, we have undertaken the first large-scale molecular phylogenetic analysis of hawkmoths representing all subfamilies, tribes and subtribes.The data set consisted of 131 sphingid species and 6793 bp of sequence from five protein-coding nuclear genes. Maximum likelihood and parsimony analyses provided strong support for more than two-thirds of all nodes, including strong signal for or against nearly all of the fifteen current subfamily, tribal and sub-tribal groupings. Monophyly was strongly supported for some of these, including Macroglossinae, Sphinginae, Acherontiini, Ambulycini, Philampelini, Choerocampina, and Hemarina. Other groupings proved para- or polyphyletic, and will need significant redefinition; these include Smerinthinae, Smerinthini, Sphingini, Sphingulini, Dilophonotini, Dilophonotina, Macroglossini, and Macroglossina. The basal divergence, strongly supported, is between Macroglossinae and Smerinthinae+Sphinginae. All genes contribute significantly to the signal from the combined data set, and there is little conflict between genes. Ancestral state reconstruction reveals multiple separate origins of New World and Old World radiations.Our study provides the first comprehensive phylogeny of one of the most conspicuous and well-studied insects. The molecular phylogeny challenges current concepts of Sphingidae based on morphology, and provides a foundation for a new classification. While there are multiple independent origins of New World and Old World radiations, we conclude that broad-scale geographic distribution in hawkmoths is more phylogenetically conserved than previously postulated
Do climate and soil influence phenotypic variability in leaf litter, microbial decomposition and shredder consumption?
We tested the hypothesis that water stress and
soil nutrient availability drive leaf-litter quality for decomposers
and detritivores by relating chemical and physical
leaf-litter properties and decomposability of Alnus glutinosa
and Quercus robur, sampled together with edaphic
parameters, across wide European climatic gradients. By
regressing principal components analysis of leaf traits
[N, P, condensed tannins, lignin, specific leaf area (SLA)]
against environmental and soil parameters, we found that:
(1) In Q. robur the condensed tannin and lignin contents
increased and SLA decreased with precipitation, annual
range of temperature, and soil N content, whereas leaf P
increased with soil P and temperature; (2) In A. glutinosa
leaves N, P, and SLA decreased and condensed tannins
increased with temperature, annual range of temperature,
and decreasing soil P. On the other hand, leaf P and condensed
tannins increased and SLA decreased with minimum
annual precipitation and towards sites with low temperature.
We selected contrasting leaves in terms of quality
to test decomposition and invertebrate consumption. There
were intraspecific differences in microbial decomposition
rates (field, Q. robur) and consumption by shredders (laboratory,
A. glutinosa). We conclude that decomposition rates
across ecosystems could be partially governed by climate
and soil properties, affecting litter quality and therefore decomposers and detritivores. Under scenarios of global
warming and increased nutrients, these results suggest we
can expect species-specific changes in leaf-litter properties
most likely resulting in slow decomposition with increased
variance in temperatures and accelerated decomposition
with P increase.This
research was funded by the IMAR and the FCT through the project
POCI/BIA-BDE/58297/2004
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