Revista Chilena de Historia Natural 78 (4): 615-622, 2005
RESEARCH ARTICLE
Seed predation in a Mediterranean pasture: can ants modify the floristic
composition of soil seed banks?
Ants may play an important role on vegetation dynamics, especially in
arid and semiarid environments, where they can consume a high proportion of the produced seeds. Although some works have
analysed the influence of seed predation by ants on the density of vegetation in Mediterranean pastures, there are no studies on the
influence of ant activity upon the floristic composition of the vegetation and the soil seed banks in this kind of ecosystem. We have
studied the effect of ant exclusion on the floristic composition of the vegetation and the soil seed bank in a Mediterranean pasture of
central Spain. We sampled the floristic composition of the pasture during 2002 and 2003 springs and also we collected soil seed bank
samples in autumn 2002. Floristic composition of soil seed banks was estimated by means of greenhouse germination.
Cerastium semidecandrum seeds were almost four times more abundant in the plots subjected to ant
exclusion than in those with ant activity. Due to the high spatial heterogeneity shown by soil seed banks, we have corrected the
differences found between the autumn soil seed banks subjected to different ant treatments by using the floristic composition of the
pasture community in the previous spring, as it was the primary source of the seeds collected in autumn. We found significant
differences between the floristic composition of the soil seed banks subjected to ant exclusion and control treatments. However, no
effects where found when the same procedure was used to detect ant effects on the spring adult community, highlighting the necessity
of longer time spans for these pastures to manifest changes taking place at the soil seed bank stage.
Key words:
annual pasture,
ant exclusion, predation, soil seed bank, spatial heterogeneity
