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Phenols in leaves and bark of Fagus sylvatica as determinants of insect occurrences.

Petrakis PV, Spanos K, Feest A, Daskalakou E - Int J Mol Sci (2011)

Bottom Line: We found 298 insect species associated with beech trees and dead beech wood.While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna.Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Entomology, National Agricultural Research Foundation, Institute for Mediterranean Forest Ecosystem Research, Terma Alkmanos, Athens 11528, Greece; E-Mail: edaskalakou@fria.gr.

ABSTRACT
Beech forests play an important role in temperate and north Mediterranean ecosystems in Greece since they occupy infertile montane soils. In the last glacial maximum, Fagus sylvatica (beech) was confined to Southern Europe where it was dominant and in the last thousand years has expanded its range to dominate central Europe. We sampled four different beech forest types. We found 298 insect species associated with beech trees and dead beech wood. While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna. Insect species that inhabit beech forests are less than one fifth of those species living in oak dominated forests despite the fact that beech is the most abundant central and north European tree. There is a distinct paucity of monophagous species on beech trees and most insect species are shared between co-occurring deciduous tree species and beech. This lack of species is attributed to the vegetation history and secondary plant chemistry. Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees.

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Diagram showing the mean content of total phenols (mg/g) in the six leaf categories for each site. Bars with the same letter on top are not significantly different across sites i.e., those having the same color at p = 0.01.
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f5-ijms-12-02769: Diagram showing the mean content of total phenols (mg/g) in the six leaf categories for each site. Bars with the same letter on top are not significantly different across sites i.e., those having the same color at p = 0.01.

Mentions: The number of insects is expected to depend inversely on the concentration of phenolics [21]. Since phenolic compounds have fluctuating concentrations as precursors of lignin and provide defense mechanisms against insects and fungi [2,5,21], we used the bark and leaf phenolic sum content at each site. An interaction term (site) × (phenol content) was also added to the regression model: (number of insect species) = ct + (phenolic content) + (site). It was found that the number of insect species depends on site effects (F = 5.34; df1 = 3; df2 = 12; p = 0.01) but both the effect of phenolics and the interaction (in a mathematical sense) of each site with the phenolic concentration of beech bark were insignificant. If only leaf categories are taken into account then the phenolic content of leaves is significantly affected by the insect damage, the size and the position of the leaves on the crown (Table 2) (N = 120; r = 0.98; F = 980.23; df1 = 5; df2 = 96; p < 10−4) in each site (F = 2.93; df1 = 3; df2 = 96; p = 0.0035) and the combination of them (F = 11.89; df1 = 15; df2 = 96; p < 10−4). The variation of total leaf phenolics in all categories across sites is given in Figure 5. Without regard to sites but to the groups of Figure 3 the phenolic concentration was highly positively correlated to the number of insects species (N = 20; r = 0.92; F = 14.31; df1 = 1; df2 = 17; p = 0.001). If no grouping was taken into consideration then the regression: (number of insect species) = ct + b (total phenolic content) was significant but the correlation coefficient was positive but low, and the regression coefficient was practically nil (r = 0.27; ct = 118.0; tct = 11.09; b = −0.008; tb = −2.81; p = 0.01).


Phenols in leaves and bark of Fagus sylvatica as determinants of insect occurrences.

Petrakis PV, Spanos K, Feest A, Daskalakou E - Int J Mol Sci (2011)

Diagram showing the mean content of total phenols (mg/g) in the six leaf categories for each site. Bars with the same letter on top are not significantly different across sites i.e., those having the same color at p = 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3116155&req=5

f5-ijms-12-02769: Diagram showing the mean content of total phenols (mg/g) in the six leaf categories for each site. Bars with the same letter on top are not significantly different across sites i.e., those having the same color at p = 0.01.
Mentions: The number of insects is expected to depend inversely on the concentration of phenolics [21]. Since phenolic compounds have fluctuating concentrations as precursors of lignin and provide defense mechanisms against insects and fungi [2,5,21], we used the bark and leaf phenolic sum content at each site. An interaction term (site) × (phenol content) was also added to the regression model: (number of insect species) = ct + (phenolic content) + (site). It was found that the number of insect species depends on site effects (F = 5.34; df1 = 3; df2 = 12; p = 0.01) but both the effect of phenolics and the interaction (in a mathematical sense) of each site with the phenolic concentration of beech bark were insignificant. If only leaf categories are taken into account then the phenolic content of leaves is significantly affected by the insect damage, the size and the position of the leaves on the crown (Table 2) (N = 120; r = 0.98; F = 980.23; df1 = 5; df2 = 96; p < 10−4) in each site (F = 2.93; df1 = 3; df2 = 96; p = 0.0035) and the combination of them (F = 11.89; df1 = 15; df2 = 96; p < 10−4). The variation of total leaf phenolics in all categories across sites is given in Figure 5. Without regard to sites but to the groups of Figure 3 the phenolic concentration was highly positively correlated to the number of insects species (N = 20; r = 0.92; F = 14.31; df1 = 1; df2 = 17; p = 0.001). If no grouping was taken into consideration then the regression: (number of insect species) = ct + b (total phenolic content) was significant but the correlation coefficient was positive but low, and the regression coefficient was practically nil (r = 0.27; ct = 118.0; tct = 11.09; b = −0.008; tb = −2.81; p = 0.01).

Bottom Line: We found 298 insect species associated with beech trees and dead beech wood.While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna.Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Entomology, National Agricultural Research Foundation, Institute for Mediterranean Forest Ecosystem Research, Terma Alkmanos, Athens 11528, Greece; E-Mail: edaskalakou@fria.gr.

ABSTRACT
Beech forests play an important role in temperate and north Mediterranean ecosystems in Greece since they occupy infertile montane soils. In the last glacial maximum, Fagus sylvatica (beech) was confined to Southern Europe where it was dominant and in the last thousand years has expanded its range to dominate central Europe. We sampled four different beech forest types. We found 298 insect species associated with beech trees and dead beech wood. While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna. Insect species that inhabit beech forests are less than one fifth of those species living in oak dominated forests despite the fact that beech is the most abundant central and north European tree. There is a distinct paucity of monophagous species on beech trees and most insect species are shared between co-occurring deciduous tree species and beech. This lack of species is attributed to the vegetation history and secondary plant chemistry. Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees.

Show MeSH
Related in: MedlinePlus