Evol Ecol Res 9: 817-827 (2007)     Full PDF if your library subscribes.

Heritability of spider ballooning motivation under different wind velocities

Dries Bonte* and Luc Lens

Terrestrial Ecology Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium

Author to whom all correspondence should be addressed.
e-mail: dries.bonte@ugent.be

ABSTRACT

Background: Ballooning is the main dispersal mode in small spiders, by which individuals are carried by wind currents as spheres attached to thin silk threads. It involves a typical and unique pre-dispersal ‘tiptoe’ behaviour that can easily be observed under laboratory conditions.

Hypotheses: Is the ballooning behaviour of a saltmarsh-inhabiting spider heritable? Do heritability estimates differ under two different environmental conditions (wind velocity)?

Organism: Second-instar offspring from Pardosa purbeckensis (Lycosidae; Araneae).

Site of experiments: Parents were collected in a large and a small saltmarsh. Offspring were tested for behavioural variation under standardized laboratory experiments.

Methods: Ballooning motivation (tiptoe behaviour) was assessed at two wind velocities in wind tunnels. We conducted a quantitative (half-sib) genetic analysis of ballooning motivation and applied threshold models to estimate heritabilities under both wind conditions.

Results: Heritability estimates were 0.17 (standard error = 0.07) at low wind velocities and 0.42 (standard error = 0.21) at high wind velocities. Because of the absence of a genetic correlation among the two wind environments, independent selection on dispersal motivation under different wind velocities must be prevalent.

Keywords: dispersal, Pardosa, saltmarsh, selection, threshold model.

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