Geoscience Reference
In-Depth Information
A
Amphibians
30
a
LM
=
1.3
20
10
5
0
0
2
4
6
8
10
B
5
a
LM
=
2.25
4
3
2
1
a
LM
=
2.68
0
0
2
4
6
8
10
Log
2
(Body Size mm3)
Figure 7
Density-mass relationships for amphibians in the metacommunity of
ponds. (A) The histogram indicates the existence of two modes in the distribution.
Maximum likelihood estimation of scaling for the whole dataset throws a shallow
parameter. (B) Segmented regression identified four scaling regimes and the ML
estimation of parameters for the negative ones indicates the existence of two different
and steeper slopes.
To this end, we empirically evaluated the DMR for a group of freshwater
organisms living in an array of temporal ponds located in eastern Uruguay.
A main source of variation in reported DMRs is the combination of data from
different communities, involving different species pools, available resources,
and environmental conditions. Further, published patterns usually present one
of the alternative statistical and conceptual approaches introduced in the
previous section. In this context, it is difficult to disentangle the relative impor-
tance of the methodological approach from real variation among systems. It
has been suggested that a thoughtful analysis of the DMR at local scale could
be particularly relevant to identify the mechanism involved (
Blackburn et al.,
1990; Russo et al.,2003
). Here we present the five DMR reported in the
literature (see
Table 1
) within a single metacommunity composed of 18 local
