9780521861724htl 1..2

actual sizes in the current study concur with Townsendet al.’s ( 1997) suggestion

that time without disturbance would be likely to blur any relationship with

body size. Patterns of body size at a site at any moment in time are likely to

result both from the sum of evolutionary forces (determining maximal size

obtainable) and time since disturbance (determining current body size).

Our predictions that body size would be positively related to algal producti-

vity and substratum grain size were not supported. Indeed our multivariate

analysis indicates, if anything, that body size was smaller in more productive

environments and/or those with coarser substrata, running counter to the

predictions. This highlights the problem of testing single-factor predictions in

All invertebrates

Collector gatherers

Predators Filter Feeders

Shredders

(^6) Grazers
5 4 3 2 1 0 8 7 6 5 4 3 2
Invertebrate body size (mm)^1
0
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
Pasture Tussock Pine Bush Pasture
Land-use type
Tussock Pine Bush
Figure 5.4Averages (with standard error bars in mm) for mean (grey bars), lower (white bars) and
upper (black bars) quartile body lengths of macroinvertebrates from 18 New Zealand
streams in four land-use classes. Bush¼native podocarp forest.
BODY SIZE IN STREAMS 91