Saline stress tolerance partly matches with habitat preference in ground-living wolf spiders

Salinity interacts with many physiological functions and therefore probably influences the distribution of terrestrial fauna in tidal flooded salt marshes. The present study tests the hypothesis that the physiological tolerance of stenotopic wolf spiders for saline conditions at least partially determines their occurrence throughout salt-marsh and nonsaline habitats. The duration of survival of three stenotopic wolf spider species (Araneae: Lycosidae) with different habitat preferences is compared in a controlled laboratory experiment. The forest-dwelling Pardosa saltans, the salt-marsh resident Pardosa purbeckensis and its sister species the inland-living Pardosa agrestis are exposed to experimental conditions with different levels of salinity. Individuals (45 males and 20-45 females per treatment) are placed in individual air-tight boxes filled with water-saturated sand. Three levels of salinity are tested: nonsaline (0 parts per thousand), medium saline (33-35 parts per thousand) and highly saline (66-70 parts per thousand). Contents of carbon, hydrogen and nitrogen and the molar ration carbon/nitrogen remain constant over time and do not differ among salinity treatments, indicating that starvation effects on survival, if any, are similar for all treatments. Conversely, body water significantly decreases over time and differs among salinity treatments, in accordance with patterns of survival. Conforming to their habitat preference, the survival of P. saltans and P. agrestis decreases quickly under highly saline conditions. Pardosa purbeckensis, however, has a high survival under both saline and nonsaline conditions. The duration of survival of females is significantly lower than that of males of P. saltans and P. purbeckensis. Durations of survival of ground-living wolf spiders exposed to salinity partly match their habitat distribution but do not explain the restriction of salt-marsh species to saline habitats.