Seasonal variations of Collembola (Hexapoda) assemblages in damp riparian habitats
Lek-Ang, Sithan; Deharveng, Louis
Archiv für Hydrobiologie Volume 153 Number 4 (2002), p. 635 - 655
published: Apr 9, 2002
ArtNo. ESP141015304007, Price: 29.00 €
The changes in species richness and abundance of Collembola in two Pyrenean springs (Ruau and La Maure) were evaluated bimonthly on an annual cycle, comparing the hydrophilous and non-hydrophilous population components. Low species richness and high abundance of the hydrophilous component was a constant feature of the studied assemblages. The non-hydrophilous component (forest and meadow litter species) exhibited much higher richness and lower abundance. Seasonal fluctuations in species richness were moderate and highly correlated between the two springs for the non-hydrophilous component (discarding the aberrant April data of Ruau), but not for the hydrophilous component. A high proportion of juveniles was encountered throughout the year. Abundance peaked in June, in association with an increase in juvenile recruitment, and was minimum in August (Ruau) or December (La Maure). The observed biodiversity patterns may result from a combined effect of evolutionary and habitat-dependent factors according to the following hypotheses: (i) hydrophilous Collembola always have a lower diversity than mesophilous ones, which presumably implies that the group tends to speciate less in damp habitats, i.e. at the limit of its ecological range; (ii) the spatial configuration of the damp habitats studied (small patches around springs and narrow strips along streams), as well as the non-saturation of communities due to frequent ecological resets after flooding, determine a high permeability to outside colonizers; (iii) high fertility, in the absence of individual adaptation, acts as a population-level response to constraints imposed by periodical flooding; (iv) water acts as a thermal and humidity buffer making hydrophilous species assemblages less dependent on climatic fluctuations; (v) for the same reason, damp habitats constitute refugia for invertebrates when surrounding environments are affected by drought, warmth or cold. This last feature might give damp habitats a central function in the dynamics of the larger terrestrial ecosystems in which they are nested.