Termite study challenges popular theories of physiology and evolution

The speed with which an organism consumes energy is known as the metabolic rate. It is important because it dictates the speed of energy flows through ecosystems. Often, the total energy of an ecosystem is concentrated (in the form of living matter) in relatively few organisms, such as plants and insects. Thus, it is important to know what determines the metabolic rate of these organisms.

 

Currently, the most popular theory is that the metabolic rate of all living beings is determined by their size, being proportional to the body mass raised to three quarters. This means that the metabolic rate would increase with the size of the organisms, but the larger they were, the lower would be this increase. Thus, 1 g of a large organism would consume less energy than 1 g of a small organism. This theory, known as the "Rule of Kleiber", is the basis of many other theories in physiology, ecology, and evolutionary biology. However, there are suspicions that it is not as universal as it seems.

 

In light of this, researchers from the Laboratory of Systematics and Ecology of Terrestrial Arthropods (LabArtro / INPA) and the Center for Integrated Studies of Amazonian Biodiversity (CENBAM) have analyzed data compiled from the literature of the last seven decades on termites, dominant insects in many tropical ecosystems. The results revealed that the metabolic rate increases faster with size in termites that eat wood than in termites that eat humus, but neither group follows the Kleiber Rule. Because termites are colonial animals, the researchers also investigated how these features are related to the size of their colonies. They found that termites with larger colonies generally also have larger bodies. This finding contradicts most of the theories on the evolution of social insects (such as termites and ants), according to which the evolution of larger societies would occur by "economy" in the size of individuals, allowing the production of a greater number of individuals ). The study suggests that several accepted biological theories currently require extensive revision, possibly because they were built with an overemphasis on mathematical abstractions and little attention to real-world patterns.