The effect of food supply on the colonisation of barley by aerially dispersing spiders (Araneae)

Abstract

A field experiment was carried out to determine whether different levels of food availability affected the retention rate of ballooning spiders landing in trays of seedling barley plants, half of which were infested with aphids from laboratory cultures. The trays were placed within bases in the field, then collected sequentially and spider numbers assessed in each tray. Deposition trays, containing trapping fluid only, were used to measure ballooning activity throughout the experimental period. The experiment was repeated four times. Overall, ballooning spiders were more likely to be retained in trays where aphid prey were present, with a total of 340 spiders found in the infested trays and 251 in the aphid-free trays, over the four experiments. Most of the spiders found were of the family Linyphiidae. In the second and fourth experiments the increased retention of spiders in the aphid-infested trays was statistically significant. Immature linyphiids alone also showed significantly higher retention in the infested trays in those two experiments and in the fourth experiment were largely responsible for the higher numbers found in the infested trays. There was also a statistically significant trend for a higher retention rate of female spiders, compared to males, in the barley trays than would have been expected from the ratios of females to males caught in the deposition trapping trays alone.

Environmental and genetic background of tiptoe-initiating behaviour in the dwarfspider Erigone atra

“…Relations with individual and maternal fitness characteristics were not found. Our results confirm that tiptoe behaviour in erigonid spiders is strongly influenced by food deprivation (Van Wingerden & Vughts 1974;Legel & Van Wingerden 1980;Weyman & Jepson 1994;). This pattern was found only during the first week of food deprivation, however, and not during food deprivation in the next 2 weeks.…”

Inbreeding depresses short and long distance dispersal in three congeneric spiders

“…I here show that inbreeding can be considered as an additional, yet highly significant, inhibitor of dispersal capacity. The degree of inbreeding induced in this study may be considered irrelevant under natural conditions, given the high local population densities of our study species (Weyman & Jepson, 1994). However, as Erigone spiders belong to the initial pioneers of isolated terrestrial ecosystems or ephemeral habitats (Bell et al.…”

Low propensity for aerial dispersal in specialist spiders from fragmented landscapes

“…Salmon & Horner 1977;Dean & Sterling 1985) and restricted to the juvenile instars from the larger species due to physical constraints (Humphrey 1987). It is triggered by innate responses to acute food shortage (Weyman & Jepson 1994) or to food shortage during juvenile development (Bonte et al 2003a). Developmental temperature also explains a substantial part of the observed individual variation (Bonte et al 2003a).…”