importance of body size in the aquatic compared with the terrestrial realm, and
little has been published explicity on the macroecology of aquatic invertebrates
a deficit that this symposium was designed to rectify.
A species’ dispersal ability has fundamental and far-reaching consequences
for its biogeography, evolutionary persistence and, therefore, its macroecology.
Yet dispersal has not figured heavily in macroecological investigations (Gaston,
2003 ), which almost certainly stems from the lack of good data on actual
dispersal propensity for groups other than vertebrates (e.g. Paradiset al., 1998).
At the same time, dispersal is an emergent property that is likely to be influ-
enced by a combination of traits, which complicates investigations of its role in
ecological terms (Table10.1). It is likely, however, that some of the traits that
influence the dispersal abilities of taxa are likely to be linked to body size and,
hence, that dispersal is a key, emergent trait that may provide a link between
organismal size and distribution (Table10.1).
Dispersal presents a variety of challenges for aquatic organisms, from fresh-
water taxa occupying discrete water bodies surrounded by an inhospitable
terrestrial landscape mosaic to microscopic passive dispersers at the mercy of
large-scale oceanic currents (Finlay & Esteban, this volume). Our aims in this
chapter are, first, to review what is known about how invertebrates disperse in
aquatic habitats, including the ways in which body size and dispersal may
interact and, second, to explore whether there are potential links between
body size, dispersal ability and macroecological patterns (i.e. range size). The
difficulty of obtaining empirical data on the actual dispersal abilities of indiv-
idual aquatic taxa makes investigation of the relationships between body size
and dispersalper seintractable at present. Instead, we concentrate on the
relationship between surrogate measures of dispersal that potentially relate to
body size and range size.
Table 10.1Traits potentially influencing dispersal in
aquatic invertebrates: * indicates those traits most
likely to be linked to body size.
Life history
Production of dispersive stages (e.g. resting eggs, cysts)
Timing of reproduction
Reproductive output
Ecological
Habitat requirements (i.e. specialists vs. generalists)
Metabolic/mechanical
Flight efficiency
BODY SIZE, DISPERSAL AND RANGE SIZE IN AQUATIC INVERTEBRATES 187