Comparative Analysis of Epicuticular Lipids in Locusta migratoria and Calliptamus italicus: A Possible Role in Susceptibility to Entomopathogenic Fungi.

Cuticular lipids protect insects from desiccation and may determine resistance to fungal pathogens. Nonetheless, the trade-off between these lipid functions is still poorly understood. The migratory locust Locusta migratoria and the Italian locust Calliptamus italicus have dissimilar hygrothermal preferences: L. migratoria inhabits areas near water bodies with a reed bed, and C. italicus exploits a wide range of habitats and prefers steppes and semideserts with the predominance of sagebrushes. This paper presents significant differences between these species' nymphs in epicuticular lipid composition (according to gas chromatography with mass spectrometry) and in susceptibility to Metarhizium robertsii and Beauveria bassiana. The main differences in lipid composition are shifts to longer chain and branched hydrocarbons (di- and trimethylalkanes) in C. italicus compared to L. migratoria. C. italicus also has a slightly higher n-alkane content. Fatty acids showed low concentrations in the extracts, and L. migratoria has a wider range of fatty acids than C. italicus does. Susceptibility to M. robertsii and the number of conidia adhering to the cuticle proved to be significantly higher in C. italicus, although conidia germination percentages on epicuticular extracts did not differ between the species. We propose that the hydrocarbon composition of C. italicus may be an adaptation to a wide range of habitats including arid ones but may make the C. italicus cuticle more hospitable for fungi.

Distribution and Diversity of Beauveria in Boreal Forests of Northern European Russia.

The distribution and genetic diversity of 91 of Beauveria isolates collected during a long-term survey in boreal forests of northern European Russia was studied. Based on morphological and sequence analysis of TEF and Bloc loci, three Beauveria spp. were identified: B. pseudobassiana, B. bassiana, and B. caledonica, with abundance of 81, 11, and 8%, respectively. Through multilocus sequencing, four haplotypes of B. bassiana and two haplotypes of B. caledonica were detected. Twelve haplotypes of B. pseudobassiana with non-random distribution were identified. Two haplotypes of B. pseudobassiana were the most abundant and widespread occurring across the whole study area, whereas others tended to be more specific to either the north or south of the study area, indicating the presence of different subpopulations. For further analysis of these putative subpopulations, southern and northern areas were separated along the boundary of the Köppen-Geiger climate zones (dfb and dfc), and the genetic structure was examined by analysis of molecular variance and spatial autocorrelation. Molecular evidence of intraspecific recombination of B. pseudobassiana and B. bassiana across northern European Russia area was indicated.