Reproductive effort typically scales as mass0.75 in unitary organisms (colonies of cells), but less is known about such scaling in colonial organisms (colonies of individuals). I compiled data on worker and reproductive number at maturity for 65 ant species from 12 subfamilies. This analysis is the largest of its kind and contains a range of colony size spanning nearly 5 orders of magnitude in worker number and ca. 3.5 orders of magnitude in number of reproductive ants produced.
Results/Conclusions
I found an interspecific allometry (reproductive number = worker number0.73) whose exponent was significantly less than 1 (p < 0.0001), even after a phylogenetic correction. When I analyzed 15 species for which biomass data were available, I found an interspecific isometry (reproductive biomass = worker biomass0.89) whose exponent was not significantly different from 1 (p = 0.07). Analysis of maximum species biomass values, rather than averages, strengthened this isometry, yielding a slope b = 1.01 that was also not distinguishable from 1 (p = 0.821). Species with larger colony size at reproduction invested in proportionately fewer, but larger male (p < 0.0001) and female (p < 0.0001) reproductive ants. This comparative analysis suggests a tradeoff between the size and number of reproductive ants and provides a framework for studying diverse colony life histories and the mechanisms generating allometries.
