The life-history strategies of riparian spiders (Araneae)

This thesis addresses the life-history strategies of cursorial riparian spiders using field- and laboratory-based research.;Species distributions were compared to important habitat variables with particular reference to disturbance. The nature of a "habitat templet" for riparian spiders was also examined. No 'typical' riparian spider fauna was identified. Most dominant species were opportunistic aeronauts, associated with disturbed habitats. Disturbance accounted for little variation in distributions. This is attributed to all sites being disturbed, with the actual frequency of flooding having little influence. Light penetration, the proportion of sand in the substrate, amount of exposed substrate and leaf-litter depth all significantly influenced the distribution of spiders.;The influence of disturbance on the life-history traits of two congeneric and co-habiting lycosids (Paradosa argicola and P. amentata) was examined using manipulated levels of flooding. This showed that both species have evolved different strategies to cope with the consequences of flooding. P. amentata, a widespread generalist, had more plastic development periods and instar sizes across different treatments. Traits of P. agricola, a habitat specialist, were not plastic and this species has evolved a greater tolerance to flooding.;Examination of the reproductive strategies of P. agricola and P. amentata revealed that both species can adjust their reproductive output. Both species produced smaller clutches later in the season. Offspring of these clutches had larger instars and shorter development periods, which is assumed to increase juvenile survival in conditions of greater environmental stress. No trade-off existed between the numbers and sizes of eggs within clutches. Maternal body size, however, was positively associated with clutch size and weight. Maternal size had no influence on egg sizes.