The toxic unit approach as a risk indicator in honey bees surveillance programmes: A case of study in Apis mellifera iberiensis

The influence of genetic diversity and exposure to xenobiotics on the prevalence of pathogens was studied within the context of a voluntary epidemiological study in Spanish apiaries of Apis mellifera iberiensis, carried out during the spring season of years 2014 and 2015. As such, the evolutionary lineages of the honey bee colonies were identified, a multiresidue analysis of xenobiotics was carried out in beebread and worker bee samples, and the Toxic Unit (TUm) was estimated for each sampled apiary. The relationship between lineages and the most prevalent pathogens (Nosema ceranae, Varroa destructor, trypanosomatids, Black Queen Cell Virus; and Deformed Wing Virus) was analysed with contingency tables, and the possible relationships between TUm and the prevalence of these pathogens were studied by using a factor analysis. The statistical analysis supported the associations between V. destructor and Deformed Wing Virus (DWV), and between N. ceranae and Black Queen Cell Virus (BQCV), but the association between these pathogens and trypanosomatids was not observed. TUm values varied between 5.5 × 10^-6 and 3.65 × 10^-1. When TUm < 3.35 × 10^-4, it was mainly determined by coumaphos, tau-fluvalinate and/or chlorfenvinphos. At higher values, other insecticides also contributed to TUm, although a clear predominance was not seen up to TUm ≥ 1.83 × 10^-2, when it was mainly defined by acrinathrin, spinosad and/or imidacloprid. The possible cumulative effect from the joint action of xenobiotics was >10% in the 63% of the cases. The prevalence of pathogens did not appear to be influenced by the distribution of evolutionary lineages and, while the prevalence of V. destructor was not found to be determined by TUm, there was a trend towards an increasing prevalence of N. ceranae when TUm ≥ 23 10^-4. This study is an example of using TUm approach beyond the field of the ecotoxicology.

High correlation of chemical composition with genotype in cryptic species of the liverwort Aneura pinguis

Chemical constituents of cryptic species detected within the liverwort Aneura pinguis were identified using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Fibre coating with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) was used. A total of 48 samples of A. pinguis were analysed. The studied plants were identified genetically based on barcode DNA sequences and represented three cryptic species (A, B and F) of A. pinguis. Cryptic species A and B are genetically diverse; both represent three evolutionary lineages: A1, A2, A3 and B1, B2, B3, respectively. The cryptic species F that was recently detected is not diverse. The most characteristic compounds in analysed samples were sesquiterpene hydrocarbons (up to 17.7% for A1; 15.7% for A2; 20.6% for A3; 7.7% for B1; 2.0% for B2; 3.7% for B3; 10.2% for F), oxygenated sesquiterpenoids (up to 68.0% for A1; 54.7% for A2; 52.6% for A3; 63.5% for B1; 88.7% for B2; 82.7% for B3; 78.8% for F), and linear aliphatic hydrocarbons (up to 14.8% for A1; 1.1% for A2; 12.1% for A3; 6.9 for B1; 5.2% for B2; 1.1% for B3; 7.0% for F). The dominant compound in the studied samples was pinguisone. The second dominant compound present in the tested plant material was deoxopinguisone, except for lineage B2, where only a small relative concentration of this compound was found. A high content of deoxopinguisone in cryptic species A (lineages A1, A2 and A3) was accompanied by the presence of isopinguisone and methyl norpinguisonate, whereas these two compounds were not detected in cryptic species B (lineages B1 and B3) and F. The chemical compounds detected in the studied samples of A. pinguis were subjected to multivariate statistical analysis. The results showed that the chemical composition depends mainly on the genotype of the plant and slightly on the habitat. However, there was no clear correlation between the volatile compounds and the date of collection of the studied plants.