represents only a small part of their range). In a recent analysis on a subset of the
data collated from the OdonataCentral database Rundleet al. (2007)were able to
demonstrate, for a much fuller analysis, a significant positive relationship
between wing size and range size in North American species of the damselfly
genusEnallagma(Fig.10.3). The recent publication of a phylogeny for these
damselflies (Turgeonet al., 2005) also facilitated an analysis that controlled for
phylogenetic relatedness (Harvey & Pagel, 1991 ). This comparative analysis
confirmed that evolutionary changes in wing size were correlated with those
in range size (Fig.10.3). As in Malmqvist’s (2000) study, and the analysis for
North American dragonflies as a whole, there were no significant relationships1.3 1.5 1.7 1.9
log body length02468log range(a)
1.3 1.5 1.7 1.9
log body length012341.1 1.3 1.5 1.7 1.9
log wing length02468log range(c)
1.1 1.3 1.5 1.7 1.9
log wing length01234(b)log occupancylog occupancy(d)Figure 10.2The relationships of (a) body length (mm) and range size (km^2 ), (b) body
length and occupancy, (c) wing length and range size and (d) wing length and occupancy
in dragonflies (closed circles) and damselflies (open circles) of the USA and Canada.
Range size data were extracted from the OdonataCentral database (Abbott, 2005 )by
downloading distribution maps as JPEG files and then tracing and measuring ranges
using image analysis software. Occupancy data were the number of site records for each
species on this database. Stepwise regressions performed to explore the power of wing
length and body length as predictors of area and occupancy demonstrated significant
models for dragonflies only. For dragonfly range size and occupancy wing length was the
only predictor entered into the model and the lines for these relationships are presented
on the relevant panels: (c) R^2 ¼0.14, y¼1.31xþ3.82, F1,213¼4.0, p¼0.047; (d) R^2 ¼0.19,
y¼0.993xþ0.49, F1,213¼4.17, p¼0.043.BODY SIZE, DISPERSAL AND RANGE SIZE IN AQUATIC INVERTEBRATES 195