Agriculture Reference
In-Depth Information
Ecological categories
Different life-forms ('Lebensformen') were recognised early by Gisin (1943) on the basis
of morphological characters while Petersen (1980) and Vannier (1978) have supple-
mented these with ecological and physiological characters. Three main groups may be
distinguished: epigeic, hemiedaphic and euedaphic (Table III. 11).
Epiedaphic Collembola (
i.e
., living in the 'Atmobios') live on the plant surfaces and
in the upper litter (L) layer. They are generally large species with long legs, antennae and
furcae; the eyes have numerous ommatidia and they have a dark pigmentation. Because
they live in an unpredictable environment, these species have developed a resistance to
desiccation. These Collembola use high quality nutritional resources which allow them
to sustain a high metabolic rate when changing conditions require increased locomotory
activity. In consequence, they have definite seasonal patterns of activity and reproduc-
tion and their demographic profiles are often of the '
r
' type.
Euedaphic species are adapted to life in the pore space of the H and A horizons where
movement is limited and food is of relatively low quality, although environmental
conditions are more stable. These species are small and unpigmented and their
appendices and ocelli are reduced. Their demographic profiles appear to be of the '
K
' type.
The relationships between demographic strategy and ecological categories of
Collembola are still unclear. Certain epigeic species have a high mortality rate due to
