Low propensity for aerial dispersal in specialist spiders from fragmented landscapes

Abstract

Aerial dispersal by ballooning is a passive flight, by which wind drag generates an upward lift on a silk thread. It is likely to reflect an aerial lottery, in which the absence of flight direction control is a serious cost for long-distance dispersal in a fragmented landscape. For species occurring in one patchily distributed habitat type, dispersal should evolve in a different way from morphological traits, directly linked to active dispersal. Therefore, we expect that if the risk of landing in an unsuitable habitat is lower than the probability of reaching a suitable habitat, selection should benefit a well-developed ballooning behaviour. We investigated interspecific variation in the ballooning-initiating tiptoe behaviour as it is linked to spider dispersal performance. Our results indeed indicate that ballooning performance is negatively related to habitat specialization in spiders from patchy grey dunes, so habitat specialists are characterized by poorly developed dispersal behaviour. These findings are concordant with recent insights that dispersal is selected as risk spreading in generalists, while it is selected against in specialist species.

Geographical variation in wolf spider dispersal behaviour is related to landscape structure

“…Thomas et al 1998;Van Dyck & Matthysen 1999;Hanski et al 2002). Furthermore, our results suggest that selection forces in fragmented habitats can alter within-species dispersal propensity in a similar way as between species (Bonte et al 2003d), indicating that microevolutionary changes in aeronautical behaviour can overrule evolutionary changes at the species level. This is confirmed by similar ranges of ballooning propensity between Pardosa wolf spiders (Richter 1970), compared to variation within P. monticola.…”

“…Under such conditions, average costs of dispersal can be expected to be high and natural selection can be expected to favour philopatry, particularly under high levels of habitat specialization (Den Boer 1970;With et al 1997;Bonte et al 2003d) and/or habitat isolation (Southwood 1962;With et al 1997;Dieckmann et al 1999).…”

“…At present, the genetic component underlying aerial dispersal in wingless arthropods is poorly known, but the presence of genetic variation has been documented in mites (Li & Margolies 1993 and spiders (Bonte et al 2003b). Selection for aerial dispersal has been reported for species occupying rare habitats (but not unstable or predictable ones; Richter 1970) and for generalist species (Bonte et al 2003d). In anemochorous plants, habitat isolation selects against dispersal-related seed traits (Carlquist 1966;Cody & Overton 1996).…”

Integrating across Life‐History Stages: Consequences of Natal Habitat Effects on Dispersal

“…Indi viduals from poor or deteriorating habitats may develop a high motivation to disperse and leave these conditions (McPeek and Holt 1992;Dingle 1996;Coll and Yuval 2004). In contrast, motivation to disperse may also be related to the probability of dispersal being successful (Bonte et al 2003), and very high-quality habitats may produce more individuals capable of successfully dispers ing to new habitats than are produced by low-quality hab itats. Currently, we lack theory on how natal habitat effects on individual characteristics such as body size affect the evolution of conditional strategies.…”

Spatial Association Between a Spider Wasp and Its Host in Fragmented Dune Habitats

“…In addition to earlier studies on the mobile wolf spider Pardosa monticola (Clerck 1757), we here report on the population structure in coastal dune habitats of the specialized fossorial wolf spider Alopecosa fabrilis (Clerck 1757) with limited aerial dispersal abilities (Bonte et al 2003b) and of its main (winged) parasitoid, Arachnospila rufa (Haupt 1927) (Hymenoptera, Pompilidae), knowing to host on larger Alopecosa wolf spiders (Koomen & Peeters 1993;Peeters et al 1994). According to theoretical work, host-parasitoid metapopulations dynamics strongly interfere and occupancy patterns should strongly overlap in case of limited host interpatch dispersal abilities and relatively low infection rates and parasitoid survival rates (Hassel et al 1991;Comins et al 1992;White et al 1996;Hanski 1999).…”