9780521861724htl 1..2

species suggest that analysis of covariance (ANCOVA) may not be the most appro-

priate method of analysis, because of covariation between explanatory variables.

Ecosystem consequences of body size – results

Predicted community metabolism was positively related with total community

biomass (Fig.13.7a). However, there were three unusual communities with

greater than 1 mg biomass per ml of media (this equates to about 0.1% of the

culture volume occupied by organisms), while the remaining communities

2 species

6 species

10 species

14 species

18 species

4

3

5

6

7

(a)

–7 –6 –5 –4

Log 10 (Average cell mass (mg))

Log

(Total density per ml) 10

Expt. 1

Expt. 2

Expt. 3

4

3

5

6

7

(b)

–7 –6 –5 –4

Log 10 (Average cell mass (mg))

Log

10

(Total density per ml)

Figure 13.4Relationships between total density and average cell size of the individuals

in a community in analysis one, coded by (a) species richness and (b) experiment.

2 species

6 species

10 species

14 species

Low temperature

High temperature

(a)

–8.0 –7.5 –7.0 –6.5 –6.0

Log 10 (Average cell mass (mg))

6.0

6.5

7.5

7.0

Log

10

(Total density per ml)

(b)

–8.0 –7.5 –7.0 –6.5 –6.0

Log 10 (Average cell mass (mg))

6.0

6.5

7.5

7.0

Log

10

(Total density per ml)

Figure 13.5Relationships between total density and average cell size of the individuals

in a community in analysis two, coded by (a) species richness and (b) temperature.

256 O.L. PETCHEYET AL.