Spatial distribution of aphids in the canopy of a temperate forest: where can they be found?

摘要

Temperate forest canopies support a high diversity of insects, but in comparison to the tropics, little is known about insect spatial distribution, particularly in terms of vertical stratification. We used an aerial lift platform to sample a temperate floodplain forest canopy during two seasons. We aimed to describe patterns of aphid density and diversity in terms of vertical canopy stratification within a 0.2 ha forest plot. Vertical gradient affected both the density and diversity of aphids. There was no general pattern in aphid distribution that applied to the eight tree species included in our survey. The aphid taxocoenosis was stratified differently on particular tree species and changed during the season. Species composition was better explained by aboveground absolute position (in m), while aphid density was better explained by relative height in the tree (position in the crown). Considering that these factors were significant but that the same statistical models excluding any influence of relative or absolute position provided more robust explanations, we concluded that aphid spatial distribution in temperate forests is difficult to simplify. This likely depends on environmental factors, such as wind direction and strength, that affect aphid flight and landing.