Plasticity in flood-avoiding behaviour in two congeneric riparian wolf spiders

The ecological effects of disrupted flooding are known to be pernicious for the occurring riparian fauna. As flooding disturbance is argued to structure species assemblages, behavioural aspects may be affected just as well. Generally, eurytopic inhabitants possess a well-developed dispersal ability allowing frequent recolonization, whereas specialized stenotopic species are expected to be adapted to these stress regimes. This study aims at determining whether flooding induces different behavioural responses in two congeneric wolf spider species. Variation in flood-avoiding behaviour was evaluated by means of individual tests performed under different ambient conditions. We considered sheltering behaviour preceding flooding, a direct flight reflex induced by the flood event, an escape reaction away from the rising water and submersion tolerance. Our findings indicated clear flood-avoiding behaviour for both species, yet a higher degree of plasticity in individual behaviour for a riparian wolf spider (Pardosa agricola) in contrast to a generalist species (P. amentata). Nonetheless the former species systematically reacted under different ambient conditions, a generalist shifts responses, displaying a higher degree of between-individual variation. Submersion tolerance was equivalent, emphasizing similar morphological characteristics. We argue habitat specialization and/or experience with local conditions to influence behavioural responses in order to optimize long-term persistence under flood stress. Future studies of behavioural variation should consider temporal variation in species condition, thus employing distinct populations thriving under different local stress regimes. (C) Koninklijke Brill NV, Leiden, 2008