Figure 1.
Generalized stoichiometric patterns relating consumer stoichiometry to resource stoichiometry ([2], modified).
Horizontal and vertical axes are any single stoichiometric measure, such as N:P ratio. Dashed lines represent no homeostasis, i.e. a constant change of consumer's stoichiometry proportional to the resource stoichiometry. Continuous lines represent strict homeostasis. Sterner and Elser [2] defined that for an arbitrary point x, y in a plot of consumer versus resource stoichiometry, homeostatic regulation of nutrient content x, y can be diagnosed as a slope less than x/y, down to an expected lower limit of zero.
Figure 2.
Generalized homeostasis patterns relating organisms internal conditions to external conditions.
Regulators maintain their internal composition stable for a certain range of environmental conditions. The homeostasis strength of an organism is defined by the magnitude of the range of environmental conditions over which the internal milieu of the consumer remains stable. Conformers allow the environment to determine their internal composition for a certain range of environmental conditions.
Figure 3.
Equilibrium phytoplankton stoichiometry as a function of nutrient supply stoichiometry in chemostats.
(A) Klausmeier et al. [15] model predicted phytoplankton N: P under three dilution (growth) rates. The solid line represents Rhee's [36] experimental setup, with dilution (growth) rate α = 0.59 d−1. The dashed and dotted lines represent higher dilution rates, α = 0.9 and α = 1.05 d−1, respectively. (B) Dependencies of the molar ratios of N:P of Rhinomonas reticulata cells at a range of inflow N:P ratios under high light (open symbols) and low light (filled symbols). The dashed-line represent the 1∶1 line and error bars represent standard deviation [17]. Since this example is a clear case but there are only very few data points, the solid line is fitted by eye to the data.
Figure 4.
N:C of the fungus Polyporus versicolor as a function of medium N:C, data from Levi and Cowling [19].
The dashed line represents the 1∶1 line. The dashed-dotted line represents the linear regression (the equation is indicated in the graph) used by Sterner and Elser [2]. The solid line represents the three segments piecewise regression applied to the data. R-square and p-value are shown on the plot. Although the ΔAIC (−2.27) indicated that a straight linear regression fits better the data than a piecewise regression, the residuals are not distributed homogenously around the line. We therefore plotted the piecewise regression.
Figure 5.
Haemolymph osmolality of the isopod Idotea chelipes in relation to the medium osmolality.
Data represent means and error bars represent standard deviation of five observations [20]. The dashed line represents the 1∶1 isosmotic line. The solid line represents the three segments piecewise regression applied to the data. R-square and p-value are shown on the plot. Although the ΔAIC (−10.20) indicated that a straight linear regression fits better the data than a piecewise regression, the residuals are not distributed homogenously around the line. We therefore plotted the piecewise regression.
Figure 6.
Relationship between organismal temperature and external temperature.
(A) Relationship of body temperature of the toad Odontophrynus occidentalis and substrate temperature in the dry season [21]. (B) Relationship between torpid subcutaneous temperature in the pichi Zaedyus pichiy and burrow temperature, estimated as the average temperature measured 1 m aboveground for the previous 10 days [23]. Dashed lines represent 1∶1 lines and solid lines represent threesegments piecewise regressions applied to the data. R-square and p-values are shown on the plot. The ΔAIC (16.68 and 16.58) indicated that piecewise regressions fit better the data than a straight line.
Figure 7.
Relationship between consumer and resource nutrient content.
(A) Zinc content in zooplankton and tripton in lakes [29]. The dashed line represents the 1∶1 line and the black line is fitted by eye to the data due to the very low number of data points. (B) C:N of the dinoflagellate Oxyrrhis marina as a function of its prey Rhodomonas salina C:N (unpublished data from Meunier et al.). The dashed line represents the 1∶1 line. Solid lines represent the three segments piecewise regression applied to the data. R-square and p-value are shown on the plot. The ΔAIC (23.97) indicated that a piecewise regression fits better the data than a straight line.