Trace Fossils as the Physical Evidence of Evolution of Insect Behavior

Abstract

This chapter reconstructs the development of ideas and methodology, from the first insect behaviors described to the incorporation of trace fossils in the study of evolution of behavior. The knowledge on the behavior of extinct species of a given group should necessarily contribute to our understanding of its behavioral evolution. Trace fossils are the physical evidence of such behavioral evolution, the only direct record of past behaviors. Despite this had to wait until recent years to gain some acceptance and to be applied. The concept of evolution of behavior and behavioural homologies went through a long history of controversies, which are briefly reviewed in this chapter. Before the last part of the 80s any mention to evolution of behavior in insects implied series of steps from simple to complex behaviors independent from phylogeny. During the late 80s and early 90s cladistics started its methodological integration with studies on evolution of behavior stressing the necessity to base such studies on known phylogenies. By the same time it was discussed the incorporation of fossils to phylogenies, at once by considering only their morphological information, and later, their stratigraphic information through the dating of nodes or the calibration of molecular clocks. In parallel, the ichnological approach of evolution of behavior was to recognize series of trace fossils that reflected increasing morphological complexity over millions of years. This procedure does not consider possible producers and their phylogenies. More recently were proposed some criteria to recognize monophyletic ichnotaxa. The incorporation of trace fossils in phylogenies was only possible after the integration of cladistics with paleontology. In accordance, one of the uses of trace fossils in evolution of behavior may be to attribute ages to nodes in a cladogram, establishing in turn, minimal ages for the appearance of certain behaviors, or to calibrate molecular clocks. Curved bee cells, dung beetle pupation chambers, and sweat bee nests are used as examples of these last approaches.

Dedicated to Jordi de Gibert

“L’insecte accourt enfin aux vivres. Une pilule est confectionnée suivant toutes les règles. Nul apprentissage : du premier essai, la forme sphérique est obtenue comme ne s’en obtient pas de plus régulière après une longue pratique. Un terrier est creusé pour y consommer en paix le pain qui vient d’être pétri. Ici encore le novice est versé à fond dans son art. L’expérience prolongée n’ajoutera rien à ses talents .” (Henri Fabre 1897, Souvenirs Entomologiques, The sacred scarab)

“There are, to be sure, surprisingly numerous examples of what may be called fossilized behavior: tracks, burrows, wounds and tooth marks , even animals fossilized in the act of parturition or copulation. Nevertheless, I know of only one or two rather unimportant examples in which change, actual evolution, of behavior can be observed in such materials” (George G. Simpson 1958, The study of evolution: methods and present status of theory)