Abiotic conditions rather than resource availability cues determine aerial dispersal behaviour in spiderlings of Dolomedes triton (Araneae: Pisauridae)

Abstract

AbstractMany species respond to risks and benefits of dispersal that vary over the short term through condition-dependent dispersal. We used wind tunnels to investigate how abiotic factors, spiderling age, and indicators of environmental quality affect aerial dispersal behaviour of spiderlings in Dolomedes triton (Walckenaer) (Araneae: Pisauridae), a denizen of temporary habitats. More than half of all spiderlings exhibited preballooning, ballooning, or spanning behaviours. Warm temperatures (>22.5 °C) and low wind speeds (<2.0 m/second) increased aerial dispersal. Aerial dispersal behaviour increased significantly until 5 days after hatch, after which it decreased, coinciding with the onset of active hunting by spiderlings. In contrast, cues about ambient food availability (egg sac number and food limitation of the mother) and potential resource competition or risk of cannibalism (conspecific density) did not affect aerial dispersal propensity. Offspring from different females ballooned in different proportions, except at the peak of dispersal, but a female's reproductive output and propensity of her offspring to balloon were uncorrelated. Thus, it appears that spiderlings of D. triton adopt a fixed strategy of high dispersal rate under optimal abiotic conditions, rather than reducing dispersal in response to cues about local food availability or conspecific density.