Temperature‐associated upper limits to body size in terrestrial poikilotherms

Abstract

We show that the largest tropical species of terrestrial poikilotherms from 25 taxa exceed, in linear body size, the largest representatives of the same taxa from the temperate (e.g. Great Britain) and polar (e.g. Wrangel Island) zones by 3.2 and 5.7 times, respectively. Here we develop a theoretical approach which quantitatively explains the observed body size patterns and relates them to ambient temperature under the assumption that there exists a temperature‐independent critical minimum value of mass‐specific metabolic rate bmin, a fall below which is incompatible with successful biological performance. This value sets an upper limit to linear body size within a taxon. Mass‐specific metabolic rate decreases with increasing body size but, in poikilotherms, grows exponentially with ambient temperature. Such compensation of the size‐related drop in mass‐specific metabolic rate b by higher ambient temperature extends the permitted range of body sizes for which b≥bmin. As a result, the maximum linear body size grows approximately twofold per each ten degrees of increase in ambient temperature. We also discuss why this prediction does not apply to interspecific comparisons of aquatic poikilotherms, for which an opposite trend is to be expected. We quantify in theory the maximum body size patterns recently reported for benthic gammaridean amphipods.

Giant boid snake from the Palaeocene neotropics reveals hotter past equatorial temperatures

“…We solved for the temperature associated with the larger taxon (Titanoboa; Fig. 3) as follows: MAPT = MAT + 3al0 C log 10 (TBL T /TBL E ) logioQio (5) where MAPT is mean annual palaeotemperature (temperature; in equation (4)), MAT is modern mean annual temperature (temperature^ of equation (4)), TBLp is total body length of Titanoboa (I; in equation (4)), TBL E is total body length of Eunectes (L 2 of equation (4)), Q 10 is mass-specific metabolic rate of 2.65 for bold snakes 27 , and i = 0.33 (ref. 0.42 (6) …”

“…We estimated body length for Titanoboa by regressing SVL and TBL measured in millimetres onto postzygapophyseal width measured in millimetres for precloacal vertebrae between 60% and 65% intervals along the precloacal vertebral column for the examined sample of extant boines (n = 21, Supplementary Table 2 (4) where I[ is length of the largest taxon, L 2 is length of the smallest taxon, 10 °C is interval of temperature change associated with metabolic rate change (Qi 0 ; ref. 5), and AT= temperature; -temperature^. We solved for the temperature associated with the larger taxon (Titanoboa; Fig.…”

“…Snakes have body temperatures that are dependant on their ambient environment (poikilothermy), and ambient temperature regulates maximum body size in poikilofhermic vertebrates 4,5 . Palaeotemperature can be predicted from fossils of poikilofhermic taxa using a model for extant taxa 4 that demonstrates that the difference in maximum body size of taxa between two localities is proportional to the difference in ambient temperature for a given mass-specific metabolic rate (see Methods).…”

Temperature-size rule is mediated by thermal plasticity of critical size inDrosophila melanogaster

“…A number of mechanistic hypotheses have been proposed to explain the TSR [8,[13][14][15][16][17][18][19], and each differ in how temperature is thought to affect the developmental and physiological processes that regulate body size. For example, the van der Have and de Jong model of TSR [18] proposes that temperature directly regulates the rate and duration of growth, but the rate of growth is less thermally sensitive than the rate of differentiation, which controls the duration of development and growth.…”

Non-universal interspecific allometric scaling of metabolism

“…The origin and the universality of the scaling exponent of metabolic rates is a subject of great controversies and there are several debates in the literature [16][17][18][19][20][21][22]. In a recent paper [11], we and a colleague proposed an unified theory for the interspecific allometric scaling of metabolism.…”